Every year that we’ve gardened here in Interior Alaska, we’ve gained more knowledge about just how far you can push cold climate gardening.

Any time you push the boundaries, though, there is bound to be a push back.

We’re going to talk about some of the methods we use to push the limits, but also ensure we protect our gardens against frosts and our cold climate.

Raising Garden Starts In One Of The Harshest Environments

One of the things we wanted to learn this year was just how far we could push our environment for raising garden starts.  We wanted to get our garden starts outside earlier than we ever have in order to maximize our precious indoor garden space.

We are fortunate to have a really nice indoor gardening space.  This has simply been one of our financial priorities as our gardens provide a good portion of the food we eat every year.  That said, no matter how much you invest, your indoor garden space will always be limited.

We wanted to explore techniques that we could use to increase the overall capacity of our indoor garden.  Also, we were interested in leveraging our climate to the maximum extent possible.

This post is the culmination of much of that research.

Understand Cold Hardy Versus Frost Sensitive Plants

We’ve extensively discussed this before, but it’s vital for the cold climate gardener to know which plants will tolerate colder temperatures and those that won’t.  When you know which plants can tolerate what temperatures, it allows you to get some of your plants outside much earlier than others.

For most cold hardy and frost tolerant plants, we are allowing our plants outside up to six weeks before last frost.  During these six weeks, we are closely watching temperatures and the expected weather forecasts.  When temperatures dip into the mid-30’s, we are certain to bring even the cold hardy plants back inside.  However, above that, they can sit outside day and night once they’ve been hardened off.

For frost intolerant plants, we are much more careful.  These won’t be placed outside until temperatures are around 45 degrees or more.  Once your frost sensitive plants are fairly well established, you can push that down to about 40 degrees.  As with the former example, we bring out plants back inside when evening temperatures are expected to be anywhere in the 30’s.

The one exception is those warm loving plants.  We don’t even think about keeping these outside unless the temperatures are expected to be above 50 degrees.  If evening temperatures are expected to dip below 50 degrees, these plants are escorted back inside for the evening.  You simply can’t push these too far in our cold climate.

Organize Your Plants By Their Cold Tolerance

With the above knowledge, we recommend organizing your plants by their cold tolerance.  We use the 1020 tray system and suitable inserts or pots that allow us to do this easily.

We try to aim for a single tray to have plants of only one type of cold tolerance.  This will allow you to treat all of those plants appropriately without having to re-organize them every time.  This organization also helps you prioritize which plants you will harden off before others.

An additional organization technique that is helpful is to organize by general plant maturity.  More mature plants will fare better at cooler temperatures than less mature plants.  Again, this allows you to easily treat a single tray of plants in a similar fashion.

This can be a little bit challenging to keep track of as your grow room reaches capacity.  We solved this by purchasing a different color of 1020 tray that allows us to quickly and easily identify our frost tolerant plants.  While we know what our plants look like, this is also acts as a bit of a fail safe for us.  (Are there any black trays outside?  Bring those in!)

Watch What Your Plants Are Telling You

We aren’t some kooky plant whisperers here.  That said, plants will tell you that they don’t like something by exhibiting visible symptoms.

When a plant is stressed out by cold temperatures, it will tell you by the way it looks.  When you see the signs of stress, you are probably pushing things too much.

With cold hardy plants, we know that they will show some signs of stress as soon as they are exposed to particularly cool temperatures.  However, we’ve also seen them bounce back quite well despite this.  There’s a point where too much is too much, so treat your plants well and they will reward you.

The point is don’t push things too far.  If your plants are showing some signs of cold stress, bring them back inside for a day or so.  Let them warm back up, recover, and then perhaps try again on a bit nicer of a day.

Pushing The Boundaries Of Cold Tolerance

If you’re a new gardener, we don’t recommend pushing the limits.  It’s more important for you to be successful your first few seasons.

You might have noticed that, this year, we started the process of hardening off some of our cold hardy plants in mid April.  A full six weeks before last frost!

The reason we want to do this is that we strongly prefer our plants to be under the (free) sun whenever possible.  The sun is much better at growing plants than anything we can use to simulate it.  Getting (some) of our plants outside also frees up indoor space to grow other plants.

During the six weeks before last frost, we closely monitor the expected daily temperatures.  Based on our knowledge of what plants can tolerate, we will leave our plants outside at any opportunity we can get.  For much of the month before last frost, most of our cold tolerant plants have been entirely outside unless conditions are not suitable.

This does means we do a lot of shuffling of our plants during this time.

It can’t be stressed enough how careful we are when doing this.  We have hyper local meteorological information available to us.  Through a calibrated weather station in our backyard, we know exactly what the temperatures is where we keep our plants.

If there is at all a risk to our plants, we mitigate that risk by bringing them inside.  If we have the slightest bit of uncertainty, we bring our plants inside.  We are not interested in sacrificing our plants to try and get an “edge” on the growing season.

The Indoor Garden Shuffle

As we’ve mentioned, we are pushing the limits to allow us to grow more plants in a limited amount of space.  We are intentionally oversubscribing the indoor growing space that we have.  At some point, we don’t have enough room under artificial lighting to handle all the plants we have.

We manage this problem in a couple of different ways.

The first is by staggering our planting schedule slightly to ensure that our indoor grow rooms can generally keep up with indoor grow room demand.

We know exactly how much room we have and try to give some thought to what we’re going to need at a given time.  This comes with practice and we modify our planting schedule based on what we learn about our space.

For example, we grow a lot of brassicas because they do very well in our climate and we love to eat them.  But, we don’t plant all our brassicas at the same time because it would put too much demand on our grow room.  We stagger our brassica plantings by a week each.  For example, Brussels sprouts, then broccoli, then kale, then cabbage.

The second technique we leverage is that plants we are trying to get outdoors simply don’t get indoor lighting when we bring them back inside for weather reasons.  We bring them outside in the morning, then just put them anywhere we have room in the late evenings.  The kitchen counter or on top of the dryer is just fine.

With this technique you do run some risk.  It’s a problem if we are in a position where outdoor temperatures are simply too low during the day AND we don’t have indoor space for them.  In this case, any light will do.  A day or two without high quality lighting isn’t going to severely impact your plants.  If low temperatures come in for several days, we might alternate our plants under artificial lighting.

Having Two Indoor Growing Spaces Is Better Than One

One of the most helpful things we’ve done is having two separate indoor growing spaces.  This allows us to organize our indoor growing space based on our immediate needs.

We use our indoor grow tent for seed starting and maintaining our warm weather crops practically all the way to transplant dates.  This tent has very high quality indoor lighting that allows us to grow amazing garden starts.  We also keep plants that we just up-potted in this tent to allow them a couple of days to recover.

Our second grow space is just a temporary table that we set up just for the purposes of the “indoor garden shuffle” mentioned above.  It has quality lighting as well, but not quite as good as our indoor tent.

This second space allows very easy access to our plants as we are constantly bringing (most of) these plants indoors and outdoors on a regular basis.  We think of this as our “hardening off” table, of sorts.  If the weather outside is just not supportive of our plants being outside, they will stay on this table for that day.  It’s also acts as our “overflow” space for when we have so many plants going that our grow tent just isn’t enough.

These two indoor grow spaces offer us something like a “production line” for our plants.  It allows for us to  have a fairly clear process on how plants will be processed through our grow rooms and eventually transitioned outside.

Plant In The Ground Only Once It’s Safe

In the interior of Alaska, our spring is usually devious.  It’s very common during the month of May to get at least a few days where temperatures really get quite pleasant.  It’s very tempting to start planting your garden at this point.

Don’t!

Fool’s Spring is very real in the subarctic.  Despite these trends to spontaneously warm up in early to mid May, it’s extremely likely temperatures will dive back down into the low 30’s at some point.

We almost always play it quite safe and wait until at least Memorial Day weekend to put our plants in the ground.  This only applies to our cold hardy and frost tolerant plants, however.  Also, we look at the 10 day forecast over this weekend to make sure dips into the low 30’s aren’t expected.  In some years, the 10 day weather forecast looks really good almost two weeks before last frost.  We sometimes consider planting our cold hardy plants out at this point.

For frost sensitive plants, we typically wait until our last frost date, at a minimum.  Again, we check the 10 day forecast for unseasonable dips and will hold off if unseasonable dips are below 40 degrees are expected.  If, however, the forecast looks good on Memorial Day weekend, we often push it and plant even our frost sensitive plants.  (See below for our backup plan!)

For warm loving plants, these won’t see their permanent outdoor locations until at least two weeks after last frost.  An unexpected frost will permanently impact these plants.  Thus, we don’t take any chances.  Evening temperatures must be consistently over 50 degrees for us to consider planting these types of plants.

Have A Backup Plan For Unexpected Frosts!

No matter what you do, if you’re planting your plants around last frost, someday you will experience a problem.  We’ve seen snow well past our last frost date.  We’ve seen more late frosts than should be expected from a “so called” average last frost.

Frost cloth is a valuable thing to have in your garden kit.  It’s an insurance plan for when things don’t quite work out as planned.  It will protect your plants against the unexpected frosts, should they occur.

We recommend having a roll of frost cloth for emergency purposes.  This is sometimes called a floating row cover.  If you don’t have actual frost cloth, a simple light colored sheet will offer similar protection.

If an unexpected snow or late frost is expected, priority should be given to cover your frost sensitive plants.  These super late frosts are usually only expected over the evenings, so you’ll need to cover them in the early evening and remove the cloth once the danger has passed.  You often don’t get much notice about these late frosts, so it always pays to keep an eye on the weather.

The application of frost cloth isn’t a super technical process.  It’s just a matter of draping the frost cloth over the plants.  You’re trying to protect from frost settling on the plant’s leaves.  You don’t have to tuck the frost cloth in or even ensure that every possible avenue for frost is eliminated.  Close enough is good enough in our experience.

Direct Sowed Vegetables Are A Safe Bet For Early Planting

Practically all direct sowed vegetables share a common trait.  Almost all of them can generally be quite frost tolerant and often are cold hardy.

Additionally, some greens do well with direct sowing and will exhibit similar cold tolerance.  Plants such as leaf lettuce, arugula, mizuna, and spinach are all fast growing greens that can be direct sowed.

If it works into your plan, you can often look at seeding most direct sowed vegetables up to two weeks prior to last frost.  These seeds will germinate in cooler soils, but will only do so when conditions are right for them.

Once you get about two weeks to last frost, take a look at the 10 day forecast.  If temperatures are expected to be above freezing for the considerable future, it’s safe to put your direct sows in the ground.  It’s unlikely at this point that significant, hard frosts are going to occur at this point in time.  If snow or freezing temperatures are predicted, however, hold off on your direct sow until this passes.

When you can get your direct sows into the ground a bit early, you’re adding time for them to mature more fully later in the season.  These extra two weeks can often make a pretty good difference in getting an early harvest off plants such as peas, too.

Additionally, some of these vegetables don’t like summer’s warm temperatures.  Plants such as radish, spinach and arugula have a limited window where they like to grow before warmer temperatures cause them to bolt.  Consider succession planting these varieties in the very early season.  Make hay while the sun’s shining, as it were!

Cold Climate Growing Is Challenging And Exciting!

The early gardening season is one of the most exciting times with so many things going on!

We are constantly learning how far we can push things and have been surprised by what we’ve been able to do.  The subarctic is quite unique as you don’t have a gradual run-up from winter to summer.  It’s far more immediate and you can take advantage of that in your gardening.

We hope that you’ve learned a thing or two about techniques you can use to increase your production, better utilize your growing space and deal with cold climate challenges.

If you have anything further to add on this topic, feel free to slap a comment down below!

Phew!  We made it through April.  And we have some nice plants to show for it.

With our final April plantings completed, it’s time to start looking at May!  The garden is still only getting started!

May is always an exciting month for us.  This is when the snow finally recedes and more importantly, the soil starts to become workable.  We can begin direct sowing some of our crops right into our gardens!  How exciting!

May is definitely the point of no return for planting most things that should have been sowed in April.  We wouldn’t recommend sowing anything now that should have been sowed in March, there just isn’t enough time left.

The Scope Of May Gardening Within Interior Alaska

May’s Planting Tasks

There’s just a little bit of indoor seeding left.  For May’s indoor planting, we are left with the fastest growing plants of them all.  Cucumbers!

The biggest change is that we can begin direct sowing our root crops right into the garden once we get about two weeks or less to last frost.  We gauge this by the weather and wait for low temperatures to consistently be above freezing.  We try to get most of our root crops planted so we have more time later in the month when we need to be planting the rest of our transplants.

The Up-Potting Will Eventually End, We Promise

One of our primary tasks for may is continuing all the transplanting from our seed trays into their semi-permanent transplant pot.  We are looking forward to kicking all the seeding trays out of the grow room and just having more mature plants!  We absolutely need every square inch that our four seedling trays are currently using.

Fertilize Our Garden Starts

While we grow our garden starts in high quality soil, it’s still usually a good idea to supplement your plants with a fertilizer.  Once your plants have their 2nd set of true leaves, they’re ready for fertilizer.  We like to use a water soluble fertilizer at roughly 1/4 strength to help maintain vigorous growth.

Continue Hardening Off All Our Plants

We will be hardening off almost all our plants in preparation of planting them outdoors.  Some of our most cold hardy crops will live outside once evening temperatures are consistently above freezing.  Our warm weather crops will be hardened off as well, but we’ll continue to bring them inside until a week or two after last frost.

Prepare The Gardens!  It Is Time!

One of the largest tasks for May is preparing our gardens for the year.  We are aiming to try to get the bulk of our plants in the ground by our last frost date, or June 1st!  Sometimes we try to squeak them in Memorial Day weekend.

Our primary garden preparations include cleaning up anything that we didn’t get to last fall.  Many times, we find it easier to let the cold temperatures kill off our plants so they are easier to remove in the spring.

We’re also adding compost to all of our beds and preparing our beds with fertilizer, azomite and possibly more greensand.  We’ll be tilling the top layer at our community garden to incorporate the compost and make planting a little easier.  We have found our soil “cakes” pretty bad there and a light tilling is a beneficial practice.

Finally, we’ll be preparing our container gardens.  Preparing our containers is always a lot of work, but a worthwhile effort for the northern gardener.  Our plan calls for the production of quite a bit more soil this year as we are expanding our container gardens even further this year.  Our migration to sub-irrigated buckets means we can not only grow more, but also put less demand on our off grid water systems.

The Interior Alaska Planting Schedule For May

May features a pretty light planting schedule overall with only a single indoor planting scheduled.  The remainder is direct sowed, right into the garden!

For things that are direct sowed, we are paying attention to the weather.  If late snows or unseasonably cold temperatures are in the forecast, we’ll hold off until these are relatively clear.  We’re looking for most nights being above freezing, but a few little dips to near freezing temperatures aren’t of major concern.

5/4/2020

• Cucumber
• Melon (Marginal crop, we are trialing Minnesota Midgets this year)
• Sunflower
• Canary Bird Vine
• Mignoette
• Nemophila
• Sunflower
• Sweet Alyssum
• Zinnia
• Forget Me Nots

Direct Sow Between 5/18/2020 to 6/5/2020

• Beets
• Carrot
• Onion
• Parsnip
• Peas
• Potatoes
• Radish (often succession planted)
• Spinach (often succession planted)
• Turnip

Our Grow Rooms Are Getting TIGHT!

With our final plantings, our grow room is officially bursting at capacity.  Even as experienced gardeners that know how fast the indoor space goes, we always experience some challenges every year.

We started putting some of our cold hardy plants out into our small, temperature controlled greenhouse in mid April.  Throughout most of May, we will be trying to transition our hardiest plants outdoors as soon as we can.  We do this in a few phases, since our greenhouse is quite small and only capable of handling seven 1020 trays at a time.

We’re not yet ready to put our cold hardy plants in the ground.  We wait until at least Memorial Day weekend.  But, we will keep our cold hardy plants outside in their trays when evenings are expected to be above freezing.  We usually keep them close to the house, so they get some radiant heat.  If sub freezing temperatures are expected, we’ll just bring our plants inside at night and put them out the next day.  It’s low tech, but it works.

For all frost sensitive plants, we will harden these off during warmer days in May, typically those above 60 degrees.  However, these plants will continue to be raised indoors until outdoor temperatures are suitable for them to live outside.  Since they will be hardened off, we can keep them outside when evening low temperatures are expected to be above 50 degrees.  We usually like to have these plants in the ground by June 5th, except for peppers which stay indoors until mid June.

Garden Projects Can Finally Get Started!

We have a few garden related projects that we are planning on trying to accomplish this year.

The first project is building a soil sterilizer out of a 55 gallon drum.  We will put up a post on how we build this unit, but the goal is to round out our home grown compost production with full sterilization capabilities.  You could say that we are “less than careful” with our compost and we get a lot of seeds (from weeds, flowers and plants) in our compost.  Our goal is to neutralize these with our soil sterilizer just in case hot composting didn’t get to it.  It will also help with the long term management of our container garden soil, allowing us to kill off any bad stuff that gets in from re-using it every year.

The second garden project we are planning for this year is building our permanent greenhouse!  We are so excited about this!  We have our design figured out, we have saved up the cash for it and we honestly can’t wait!  The goal is for a 10×12 greenhouse that will primarily be used to grow our warm weather crops.  We will also use it next season as a second layer for our garden start production.  This has been years in the making, so we are thrilled to finally be at this point!

This year, we are also planning on replacing the mulch (we use weed fabric) at our Fairbanks Community Garden.  Our current weed fabric was the “cheap” stuff and now that it’s on its fourth garden year, it’s a little worse for wear.  We have a few plans to make it better and more suitable to our growing space.  Our plan is to replace it with a higher grade 20-year fabric in the hopes that we can get it to last a good 6-10 years.

Here at Frosty Garden, we make a lot of our own soil.  Making your own garden soil is a really easy process.  At a certain scale, it’s also much less expensive than commercial soil bags you can purchase at the store.  Here we’ll teach you our techniques and methods.

When you understand the components of a good garden mix, it can open a lot of doors for you.  You will know how to improve almost any soil that you might be working with.

When Should You Consider Making Your Own Garden Soil?

The bottom line, whether you buy soil or make your own, it’s not the most inexpensive of endeavors.  As it turns out, “cheaper than dirt” isn’t very cheap at all!

The honest truth is if you only need a few cubic feet of soil, you are much better off just buying the soil you need.  You will end up spending far more on the components to make your own soil than you would those few bags purchased from the garden store.

If you need a lot of soil, either for a container garden or to fill a raised bed, that’s the point when making your own soil might be worth both the time and the money.  In these applications, you often need quite a bit of soil, which translates to quite a few bags of potting mix.

A general guideline you can use is if you would be spending more than $100 in potting mix bags, you probably should consider making your own.  The materials to build your own soil, in sufficient bulk, will usually be similar at that point.  When you make your own, you can get a lot more of it for the same amount of money.

What Characteristics Make For A Good Potting Soil?

There are some characteristics that you want to see in a good quality potting soil or garden mix.  In general, a quality soil that will help your plants thrive has the following characteristics:

• Plenty of nutrients for your plants initial growth
• Drains water well / Non-clumping
• Retains moisture
• Healthy pH for plants

Good quality potting soil will compress together and hold its shape without breaking apart.  It should also crumble apart with only a minor amount of pressure applied.

What you definitely don’t want to do is dig up a bunch of dirt from your yard and try to use that in your garden!  Your average dirt will have almost none of the above characteristics and will offer you more troubles than it’s worth.

Additionally, what is commonly known as “garden soil” is also not good for the purposes of growing plants.  Garden soil can be used as an element in a soil mix, but it shouldn’t be used exclusively.

What Are The Major Components Of Potting Mix?

As mentioned above, you are looking for certain characteristics in your potting mix.  We’ll go through these one by one and give some examples of materials that you can use to create those characteristics.

Nutrients

• Compost
• Worm castings
• Fertilizer
• Slow release fertilizers
• Azomite
• Greensand

Non Clumping & Drains Water Well

• Sphagnum peat moss (less sustainable)
• Coco coir (more sustainable)
• Vermiculite
• Perlite
• Sand
• Composted wood chips
• Rice hulls
• Brewing grains (in limited quantity)

Moisture Retention

• Sphagnum peat moss (less sustainable)
• Coco coir (more sustainable)
• Vermiculite
• Greensand
• Compost

Soil Acidity or pH

• Garden lime

As you might have noticed, some materials provide multiple benefits.  These are particularly good ingredients to use!

Don’t Worry Too Much About Soil pH!

We were hesitant to mention pH, simply because that can turn a lot of people off from making their own soil.  “It sounds complicated!”, they’ll say.  We agree.

Here’s the thing.  Plants are quite good at growing in soil that has a fairly wide pH.  Will they grow a little bit better with the perfect pH?  Sure.  Will they also grow just fine if the pH is a little off?  Yes they will.  You have a pretty wide range to work in if you’re growing common garden vegetables.

With the ingredients we discuss here, the main one you have to worry about is sphagnum peat moss.  It has a lot of benefits.  It will provide bulk, it breaks down slowly, it retains moisture and it doesn’t interfere with good soil drainage.  But, peat moss is naturally acidic and will therefore tilt your DIY soil towards acidity.

If you use peat moss in your garden mix, it will be beneficial to correct that acidity by raising the pH of the soil.  If you want to correct the pH, you can do so by adding dolomitic lime, more commonly called garden lime.  You can also find calcitic lime, which is basically the same thing with more calcium.  There are two types out there, powdered form and granular form.  Powered forms will tend to correct the pH more quickly, whereas granular does so more slowly and is also generally considered safer to use.

In general, consider adding the following amounts of garden lime:

• 1 Tbsp per gallon (4 liters) of soil mix, or
• 1 (heaping) cup per 15 gallons (60 liters) of soil mix, or
• 3 (heaping) cups per 50 gallons (200 liters) of soil mix

Other than that, you don’t really have to worry about pH.  In many cases, you could probably even skip this step and still be just fine!  Again, this is about trying to get optimal pH and not about just getting plants to grow.

Remember, There Is No Perfect Recipe

There are many ways to go about formulating your own potting mix and garden soil.  There isn’t just one perfect recipe.

We would encourage you to work with ingredients that you have access to.  What do we mean by this?  If you have access to cheap compost, that should be a primary ingredient.  If you have access to free sand or composted wood chips, use that!  Have a local peat moss seller, use them!  If you can’t find one particular ingredient, use something else that provides the same benefit.  If you have more of something, use more of it!

There is a lot of room for experimentation in making your own soil.  That’s certainly one of the benefits of DIY potting soil.  You can make it with what you want and to have the characteristics you want.

Example DIY Garden Soil Mix Recipes

Here are a few of the garden soil recipes that we know about.  We use the “part system” so you can decide what quantity you want to make.  That way, you can base it on gallons, liters, buckets, bushels, or dump trucks for quantities.

As you will see, there are a lot of different ways to go about making various soil mixes!  Also, for all recipes, coco coir can always be substituted for peat moss if desired.

Mel’s Mix from Square Foot Gardening

• 1 part compost (from 5 different sources)
• 1 part vermiculite
• 1 part peat moss or coco coir
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Frosty Garden’s “Secret Weapon” Potting Soil:

• 2 parts compost (typically homegrown or even humanure)
• 1 part peat moss (locally sourced when possible)
• 1/2 part vermiculite
• 1/2 part perlite
• Greensand per manufacturer recommendation
• Biolive per manufacturer recommendation
• Azomite per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

General Potting Soil

• 1 part peat moss or coco coir
• 1 part compost
• 1/2 part perlite
• Fertilizer per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

DIY Potting Soil

• 2 parts peat moss or coco coir
• 2 parts vermiculite
• 1 part compost
• Fertilizer per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Homestead Potting Soil

• 2 parts peat moss or coco coir
• 1 part compost
• 1/2 part vermiculite
• 1/2 part worm castings
• Fertilizer per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Garden Soil Based Potting Mix

• 1 part peat moss or coco coir
• 1 part garden soil
• 1 part compost
• 3/4 part perlite
• Fertilizer per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Houseplant Mix

• 2 parts peat moss or coco coir
• 1 part perlite
• 1/16 part sand (approximately 3/4 cup per gallon of mix)
• Fertilizer per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Cactus Mix

• 3 parts peat moss or coco coir
• 2 parts sand
• 1 part perlite
• 1 part vermiculite
• Fertilizer per manufacturer recommendation
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)

Seedling Mix*

• 2 parts coco coir
• 2 parts vermiculite
• 1 part sand
• Garden lime, if using peat moss (~1Tbsp per gallon of mix)
• See below for notes on seedling mixes

Techniques For Mixing Up Your Garden Soil

If you want to make just a few gallons at a time, we have found using a wheelbarrow to mix the ingredients as a good method.  This is obviously a bit limited as you can only mix an amount that will fit in your wheelbarrow.

If you want to make up larger amounts, we recommend laying out your ingredients on a tarp.  You can mix up the ingredients by hand and also use the edges of the tarp to help mix your materials together.  We have used this technique to mix up to about 50 gallons of mix at a time and it works great.  Yes, you get dirty.  This is what gardening is about.

If we had access to a concrete mixer, we would strongly consider using it to help make up soil.  That would make short work of soil building!

What About Making Your Own Seedling Mix?

One of the most important characteristics of seedling mix is that it’s relatively sterile.    This can be difficult for the home gardener to achieve, but it can be done.  The recipe we provided above should be relatively sterile, but it’s not guaranteed.

In general, we would advise most gardeners to purchase seedling mix instead of making their own.  Most commercially available seedling mixes are pre-sterilized.  Seedling mix is also often not needed in extremely high quantities, either.  We buy our seedling mix and we have every one of the needed ingredients on hand.  We go through a large bag every two years, so it’s not really worth our time to make it.

If you want to sterilize your soil, steam is the best technique to use.  What we recommend is heating your soil with steam to about 140-160 degrees and holding that temperature for at least 15 minutes.  There are other techniques out there, but this is the safest method that will ensure good results.

Should You Build High Quality Potting Soil For Raised Beds?

We think this is a good question and the answer is that it’s entirely up to you.  It can be quite costly to purchase all the supporting materials to fill such a volume.

We made our own soil for our beds (using our “secret weapon” described above) and can tell you that we spent several hundred dollars on the soil for our beds.  We looked at it as a long term investment and wanted our beds to produce intensively for years to come.  Our raised beds produce every kind of fruit or vegetable incredibly well, so it was worth it for us.

What we can tell you is that we’ve seen people experience a number of troubles with trying to fill beds inexpensively.  Several vendors around interior Alaska sell what they call “garden soil” and the quality of that soil vastly varies.  Some is just dirt they dug out of the ground, others do make some effort to create a more appropriate garden mix with a mix of dirt and peat moss.  In every case, the garden soil product can be greatly improved.

What we’d encourage you to do is consider the concepts that we discuss in this post that make for good garden mixes.  That garden soil can certainly be a quality component of your total garden bed!  It might be best to combine other ingredients to make a really nice, quality garden bed soil.  If we were going this route, this is the starting point I would use:

Bulk Garden Bed Mix

• 2 parts garden soil
• 1 part  compost
• 1 part perlite
• 1/2 part sand

If we were looking to improve the above recipe even further?  I would strongly consider adding one part of peat moss or coco coir into the mix to resist clumping and also increase water retention capabilities.  I might also consider adding some vermiculite as well to improve drainage and water retention.  If we were planning to grow intensively in that bed, I would definitely increase the compost up to two parts.

How Much Soil Do You Need To Make?

Warning:  MATH!

It’s a good idea to figure out how much soil you will actually need.  This will help you when planning out how much material to purchase for your project.

In our experience, figuring things out basically by cubic foot has been the most accurate method that we’ve found.  (You can do this in metric, too, but the math will be slightly different.)  Most of the products we discuss are sold by the cubic foot, also making this very easy.

Here are some reference numbers that you might find helpful:

• 1 gallon container:  0.13 cubic feet
• 5 gallon bucket:  0.69 cubic feet
• 10 gallon grow bag:  1.3 cubic feet
• Raised bed:  Length (ft) x width (ft) x (height (in) / 12)

You can determine how much of each material that you need.  For our example, we’ll assume you are filling a 4 foot x 10 foot x 1 foot raised bed and you’re using “Frosty Garden’s Secret Weapon” soil mix:

First, figure out how many cubic feet of total soil mix you would need:

• 4 foot x 10 foot x (12 inch / 12) = 40 cubic feet

Then, determine the recipe’s total number of parts:

• 2 parts compost + 1 part peat moss + 1/2 part vermiculite + 1/2 part perlite
• Simple addition gets us to 4 total parts in the recipe

For each material, divide the total cubic foot volume needed by the total number of parts in the recipe, and then multiply by the parts needed of each material:

• Compost:  (40 cubic feet / 4 parts) x 2 parts compost = ~20 cubic feet
• Peat Moss:  (40 cubic feet / 4 parts) x 1 part peat moss = ~10 cubic feet
• Vermiculite:  (40 cubic feet / 4 parts) x .5 part vermiculite = ~5 cubic feet
• Perlite:  (40 cubic feet / 4 parts) x .5 part perlite = ~5 cubic feet
• Total:  40 cubic feet!

In the event you are ordering materials by the cubic yard, you can figure that out too!  Simply divide the total cubic feet needed by 27 to get the number of cubic yards.  In our example above, we need exactly 1 cubic yard of compost!

Go Forth And Make Your Own Garden Mix!

We hope that this post has been insightful.  If you are looking to build out a garden bed or start a good sized container garden, making your own soil is a great way to get more bang for your buck.

If you have any questions or if we missed something, feel free to slap a comment below!

If you’ve spent any time around gardeners, you’ve heard terms like “frost tolerant” or “warm weather crops.”  This post seeks to demystify those terms and also teach you which specific plants fall into which category.

The four major categories that we will discuss are cold hardy, frost tolerant, frost sensitive and warm loving plants.  For the cold climate grower, these concepts are one of the most important things to understand.

Why Are Some Plants More Frost Tolerant Than Others?

This is a really good question to start with!

Frost occurs when outdoor temperatures hover around the freezing point and moisture on the plants or in the ambient air freezes.  Frost can cause cellular damage to plants that don’t have sufficient protections from it.

The generally accepted reason for some plants to have more frost tolerance than others is due to having higher levels of sugars built up in their leaves.  Sugar water will freeze at a lower temperature than plain water will.  This allows the more frost tolerant plants to avoid actually freezing and thus also avoid cellular damage caused by freezing.

There are two types of cold hardiness that are recognized by most gardeners.  These two levels essentially describe the level of cold tolerance that the vegetables have.  Similarly, for plants that won’t tolerate frost at all there are also two levels of tolerance.  Those which are just sensitive to frost and those that really require warmer temperatures at all times.

What Are Cold Hardy Garden Plants?

Cold hardy plants are the most capable of them all when it comes to cold tolerance.  A mature plant can withstand actual freezing temperatures (32F/0C) for a period of time and even temperatures below freezing.  Cold hardy plants can also handle light to moderate frost without being harmed.  Another way of saying this is these plants can tolerate a hard frost.

When To Plant Cold Hardy Vegetables

Plants which are cold hardy can often be planted outside before any others.  Once outdoor low temperatures are consistently at or above 32F, you can consider leaving these plants outside.  This is typically going to be 3-4 weeks before last frost, or roughly early May in the Interior of Alaska.  Of course, you need to be sure to ensure these plants are hardened off well before doing so.

We do still advise being able to bring your cold hardy vegetables back indoors (or into a greenhouse) in the event that an temperature dip below freezing is expected.  Young plants are still susceptible to freezing temperatures.  We typically plant cold hardy plants in our garden anywhere from two weeks before last frost all the way up to last frost.

For the root vegetables, these can be direct sowed up to two weeks before the last frost date.

When To Harvest Cold Hardy Vegetables

Cold hardy vegetables can also be the last plants you can harvest in the fall, at least if they haven’t flowered or bolted yet.  We are often able to harvest these plants well past first frost and up to the point where the cold really starts to set in.

This is advantageous as we are often quite busy with preservation during harvest season.  These varieties are the ones you can put off just a little bit longer, if needed.  Don’t wait too long, though, as they aren’t invincible!

Notes About Cold Hardy Vegetables

A few of these can also be planted in late summer, allowing for a second harvest.  These are typically very fast growers, such as spinach, lettuce and mustard greens.  If you want to do this, think about planting these about 15-30 days before the first frost for best results.  You can often harvest after the first few frosts and get some extra fresh veggies.

Carrots will actually improve in flavor if you allow them to withstand some levels of frost.  It’s always a good idea to harvest these late in the season after you’ve seen a few frosts or you are in the final stages of your garden clean up.

It should be noted that with the root vegetables in this category, you can keep the plants in the ground well past your last frost date.  While we don’t advise keeping them in the ground all winter, some people do so and harvest when they are needed.  We advise a full harvest and storage in appropriate conditions or the use of preservation techniques.

When it comes to most lettuce-like greens on this list, you can also direct sow these in your garden up to two weeks before last frost.  The best measurement is when the soil is workable and absent of ice.  They will germinate in the cool soils and will sprout when conditions are right for them.  These direct sowed plants will also be more vigorous than indoor grown and transplanted varieties.

A List Of Cold Hardy Vegetables:

• Arugula
• Asparagus
• Beets
• Broccoli
• Brussels Sprouts
• Cabbage
• Carrots
• Collards
• Endive
• Garlic
• Kale
• Kohlrabi
• Leeks
• Lettuce (most varieties)
• Mustard Greens
• Onions (Seeds, sets, bunching)
• Parsnips
• Potatoes
• Rhubarb
• Rutabaga
• Spinach
• Turnips

What Are Frost Tolerant Plants?

The next level of cold hardiness is simply frost tolerance.  These plants are a little bit more sensitive than truly cold hardy plants.  There is enough of a cold tolerance difference to classify them just a little differently in our book.

Frost tolerant plants are those that will, as described, tolerate fairly light frosts.  The biggest difference between these plants and cold hardy varieties is that these don’t tolerate freezing temperatures quite as well.  Some varieties can withstand short periods of freezing temperatures without trouble.

When To Plant Frost Tolerant Vegetables

Frost tolerant plants can be placed outside once temperatures are consistently above freezing, but frosts may still be prevalent.  This is often a week or two before the last frost, or about mid-May in the Interior of Alaska.

As with cold hardy plants, we recommend bringing young plants inside (or in a greenhouse) in the event of a dip into freezing temperatures .  We typically plant our frost tolerant plants in our garden a week before last frost and up to last frost.

When To Harvest Frost Tolerant Vegetables

As with cold hardy plants, these are often plants that you can hold off on harvesting until after the first frost, if needed.  We try to harvest most of these at or around the last frost time, but often prioritize them more than truly cold hardy varieties.

Notes About Frost Tolerant Vegetables

While these plants are frost tolerant, be careful about exposure to freezing temperatures when the plants are young.  Whether you are setting the plants outside or putting them in the ground, be somewhat sensitive that these plants are not extremely cold hardy.

With radishes, you can get some late season harvests in.  Planting radishes about 3 to 4 weeks before first frost and even up to first frost can allow for some nice, quick garden snacks quite late in the season.  Radishes are typically very fast growers, reaching maturity in 3-4 weeks.

Artichokes do surprisingly well within the Interior of Alaska.  Our cool temperatures lend well to the plant’s requirement to spend a couple of weeks below 50 degrees for a good fruit set.  Artichokes in sub-irrigated containers have performed quite well for us.

A List Of Frost Tolerant Vegetables:

• Artichoke
• Bok Choy
• Cauliflower
• Celeriac
• Celery
• Chard
• Chinese Cabbage
• Peas
• Radish
• Radicchio
• Peas (Garden variety)

What Are Frost Sensitive Plants?

There is a tolerance level that sits between frost tolerant and warm loving.  These are best described as frost sensitive plants.

These varieties feature very little frost tolerance and could be expected to be severely injured or even will die once frost hits them.  They do often tolerate somewhat cool temperatures, at least down to the low 40’s or high 30’s where frosts aren’t also present.

When To Plant Frost Sensitive Vegetables

With these varieties, we typically wait until at least our last frost date plant them outside.  Sometimes we will wait until a week or so after last frost, just to be safe.  While we are hardening them off, we look for days that will be in the 40’s or above.  These are also varieties that we will try to protect with frost cloth in the event a late frost comes up in the early season.

When To Harvest Frost Sensitive Vegetables

When we go about our harvest strategy, these are always at the top of our list to get out of the garden as soon as possible.  While you can sometimes wait for the first frost to kill off the plant, we are aiming for harvest usually right around first frost.  We won’t often try to put frost cloth on them late in the season, mostly because growth and maturation of fruit is almost at a standstill in cool temperatures.

Notes About Frost Sensitive Vegetables

A defining characteristic of these plants is that frost sensitive plants always require some degree of warm temperature soil to germinate.  The seeds of these plants will not germinate well, or at all, in cold or even cool soils.

These plants are strong candidates to be placed or planted in a greenhouse, if you have one.  They will appreciate the extra warmth in most cases.

Additionally, with tomatoes, some varieties are exceptionally tolerant of cooler temperatures.  While they don’t like freezing temperatures, we’ve seen a number of varieties get well into the 30’s before showing signs of cold stress.  It’s important to note that this characteristic isn’t universal among tomatoes and is usually only found in the hardiest of varieties.

A List Of Frost Sensitive Vegetables:

• Snap Pea
• Sweet Corn
• Tomatoes
• Beans
• Most herbs (Parsley is frost tolerant)
• With few exceptions, most flowers are frost sensitive.  Exceptions include perennial flowers that are naturally cold hardy.

What Are Warm Loving Plants?

There are some varieties of vegetables that simply prefer warmer temperatures.  We sometimes refer to these as “warm climate crops” as well.

Warm loving plants are usually sensitive to temperatures below about 50 degrees.  Temperatures below this can injure the plant, severely reduce growth rates or sometimes even harm productivity.

When To Plant Warm Loving Vegetables

When we are in the process of hardening off these plants, we try to aim for days in the mid-50’s and above.  We don’t leave them outside at night unless the temperatures are expected to maintain above 50 degrees.  As for planting, we often will wait until at least last frost to put them in our garden.

With peppers specifically, we wait until almost a week or two after last frost to plant them in our garden.  It’s very important to maintain flexibility with these plants and allow them to be brought inside if conditions warrant.

When To Harvest Warm Loving Vegetables

As for harvesting, as with frost sensitive plants, these are always the first to get harvested.  We try to aim for before or right after at the first frost to harvest them.  While most of these will maintain their fruit reasonably well, even after a frost, don’t wait too long as the fruit will quickly be damaged.  As with frost sensitive plants, we don’t bother putting frost cloth on these in late season as growth has virtually stopped once cooler temperatures appear.

Notes About Warm Loving Vegetables

As you might imagine, when it comes to warm loving plants, there aren’t many “fast growers” that can get you vegetables fast.  Most all warm weather plants require at least 2-3 months past the transplant date to reach full maturity.

These varieties will often perform at their best when brought into a greenhouse.  When they are warm, they will grow as fast as they can and mature their fruit and vegetables more quickly.  Additionally, anything you can do to keep the soil warm for these plants will be rewarded in better production.

At least here in the subarctic, we find that we have to finesse our peppers into full maturity.  While we often have some peppers that are fully ripe at or before harvest time, many are not.  We’ve found it to be a good practice to return peppers into our indoor grow room for full maturation.  This process usually happens within days upon bringing them inside, radically improving our harvest rates.

A List Of Warm Loving Vegetables:

• Cucumbers
• Eggplants
• Peppers
• Pumpkins
• Summer Squash
• Winter Squash
• Sweet Potato
• All Melons (Marginal subarctic crop)

Final Notes On Hardiness & Frost Tolerance

One thing that is important is that hardiness against the cold can vary slightly.  There are a number of complex factors that go into this.

The most relevant aspect to cold tolerance is often the exact variety, or cultivar, that you are growing.  You might find one type of lettuce that can barely withstand a frost and others that will tolerate a hard frost.

Additionally, crops with curled/wavy/textured leaves will usually feature more frost tolerance than those with smooth or flat leaves.  This partially relates to the ability for frost to penetrate the plant, but also the curls will create very small micro climates that help the plant survive colder temperatures better.

In closing, we’ll remind you that young plants don’t have nearly as much frost tolerance as their full grown varieties.  It’s always important to keep an eye on the weather in the early season and don’t push things too fast.  We know that it’s exciting when the weather starts to warm up!  If you’re a new gardener, play it safe and just plant everything around the last frost date.