9 Common Problems With Vegetable Seed Germination

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Later this month, we will be starting up our indoor grow room and will finally get started planting our seeds.  It’s a good time to cover common problems that can affect vegetable seed germination and what you can do about these issues.

Starting your garden from seed is not particularly difficult, but it can present some challenges.  The first part of the whole process is getting the seeds to germinate!

Without further ado, these are the top reasons you might have problems with vegetable and fruit seed germination!

1. Germinating At The Correct Temperature

This is probably one of the most common problems people run into, especially in our cold climate.

All vegetable and fruit seeds have a range of temperatures that they will germinate within.  If you are outside of that range, germination can be difficult or impossible.  Additionally, there is usually an optimal temperature at which you will get the fastest germination rate.

Many people try to germinate their seeds next to a window or maybe a garage, which can often be far too cold for germination.  Or, they might use a heat mat and accidentally exceed the maximum seed germination temperatures.  Both of these can present problems by bringing seeds outside of their preferred germination temperatures.

We recommend keeping your germinating seeds between about 70 and 80 degrees Fahrenheit.  Even a typical ambient temperature of 65-68 degrees is fine.  This is fairly close to the optimal range for most seeds.  If you can maintain this temperature as much as possible, you will have really good success.

As you get further away from the optimal temperature for each seed, the longer germination can take.  An example might be a day or two after planting at the optimal temperature, but it could take many days to weeks the further away from optimal temperatures you are.

2.  Provide The Correct Humidity

For many of us in sub arctic, we experience a fairly dry climate.  Humidity in our homes can be quite low and this isn’t necessarily a good thing for seeds and seedlings.

Seeds, and more importantly seedlings, need some humidity to survive.  When there’s an overall lack of humidity, the seedlings can quickly dry up.  As a result, seedlings can experience a difficult time getting established.

For our garden, we’ve standardized around the 1020 tray system.  This allows us to use commonly available humidity domes that help trap moisture and create the right environment for seeds and seedlings.  The domes also have vents that allow us to dial in the amount of humidity more or less to address our needs.  There are other ways to do this, but the concept is to trap the soil’s moisture as much as possible.  This creates a high humidity environment, which is ideal for seeds and seedlings.

On the flip side, too much moisture can also be a bad thing.  You know you have too much when you see moss or other green stuff grows on your seedling’s soil.  This indicates you need to vent a little bit more, which will help curb moss growth.  It also is a sign that your soil isn’t sterilized, which is a good thing for germinating seeds.

You don’t have to get into exact specifics of certain humidity percentages.  The goal is to simply create a reasonably humid environment for your seeds and seedlings.

3. Your Seeds Are Too Old

Seeds do have a limited amount of time where germination is still ideal.  Past this point, germination rates can start to decline, sometimes quite rapidly.  To make this a little more complicated, there is no universal age when different types of seeds are past their prime.

For the most part, seeds have a lifetime somewhere between one and five years for optimal germination rates.  That’s not to say that your seeds can’t exceed this, by even decades.  But, at a certain point, germination rates will become lower and lower.

You can test your seed viability.  The easiest way to do this is to dampen a paper towel to the point of being moist, but not saturated with water.  Place 10 or so of the seeds you want to test on the paper towel.  Insert the dampened paper towel and seeds into a plastic ziplock bag.  Wait for a few days, or the expected germination time, and check the seeds that have sprouted.  You can calculate the viability percentage by dividing the number of sprouted seeds by the total number of seeds.  This can give you insight into how many seeds you might want to plant at each location to get a viable plant.

We also write the purchase year on all of our seed packets.  While most seed packets have the year on them, it’s convenient to have a consistent labeling technique.  When the age starts to show, we check against seed viability charts.  Sometimes we test the seed’s viability as discussed above.

Some seeds should be purchased annually or bi-annually for best germination rates.  The commonly grown vegetable seeds that fit into this category are typically:

  • Onions
  • Parsnip
  • Corn (1-2 years)
  • Leek (1-2 years)

For detailed information on seed viability, please see our writeup with tables for most vegetables and herbs.

4.  Soil Is Too Moist or Too Dry

Similar to the humidity issues, the moisture of your seed starting soil can greatly impact seed germination rates.

You want your soil to be somewhere between lightly moist and soaked.  Bone dry will be very bad for seeds since the seed sprouts based on contact with water.  Too moist can cause the little seedling to drown before it gets a chance to grow.  You also want a fairly consistent moisture level throughout the soil you are planting in.

The temperature of your growing area and the intensity of your lighting can dramatically impact the soil’s moisture.  Check your seeds and seedlings often to make sure they have sufficient moisture.  Humidity domes, as discussed above, can slow down evaporation rates.

We use a pressurized sprayer to create a fine mist for watering our seedlings.  This works well as it minimizes disturbance of the seeds.  It also is much easier on our hands than a typical bottle sprayer.  We try to assess the soil’s moisture and provide the balance in between soaking wet and lightly moist.

5.  Poor Seed Storage Techniques

Seeds do have a need to be stored correctly.  You don’t need to get into a highly exact storage condition, but there are a few guidelines to follow.

The best storage environment for seeds is a dry, cool and dark place.  By cool, we don’t necessarily mean “refrigerator cool” – but rather ambient room temperature or less.  You definitely want to avoid extremes.  Too hot or too cold can affect seed viability.  You definitely want to avoid freezing temperatures and hot temperatures above 90 degrees Fahrenheit.  Also, avoid highly humid areas as this could inadvertently cause your seeds to sprout.

We recommend storing your garden seeds in either a shoe box or other basic container.  If you have a lot of seeds, we have found that a photo organizer (pictured above) is a great storage method.  This makes it easy to tuck into a cabinet or other storage space that will remain relatively consistent.

6.  Use Of Heavy / Compact Soils

Seedlings are somewhat sensitive to the soil they are being germinated in.  If a soil is too compact, it can negatively affect the germination of the seed.  The seedlings only have so much energy available to them and compact soil can be too much for them to bear.

We generally recommend seeking out a soil geared specifically towards seed germination.  These are often referred to as “seed starting mix” or “seedling mix.”  It is different from general potting soil.  These soil mixes are very good at resisting compaction, retaining moisture and creating an ideal soil environment for starting seeds.

You definitely want to avoid the use of “garden soil” in all cases as this will tend to compact quite heavily.  Potting mix can be used in a pinch, but it’s still less than ideal for most seedlings.

We do have some exceptions to the use of seed starting mix.  For our vining plants, we tend to plant these directly into potting soil.  This is because these plants are more sensitive to transplanting, so we start them in the container they will grow in until we transplant them into our garden.  Examples of these are:

  • Cucumbers
  • Squash (Summer and Winter)
  • Melons

When you plant your seeds, you want a firm – but not compressed – soil above the planted seeds.

7.  Seeds Planted Too Deep

Planting your seeds into the soil at the correct depth is important for high germination rates.  If you plant too deeply, the seedling may struggle to reach the soil’s surface.  If planted to shallow, the seedling may not be able to establish a good, stable root structure.

There is a general guideline that you can follow that gets you “close enough” in most cases.  Most seeds should be planted roughly two-times the seed’s diameter (or width) into the soil.  So, if your seed is 1/16 of an inch, plant about 1/8 of an inch beneath the soil.  If it’s roughly a 1/4 inch, plant at depth of 1/2 inch.

For very small seeds, it’s usually sufficient to just lightly cover the seeds with soil or vermiculite.  Larger seeds, such as beans, can be planted up to an inch beneath the soil.

8.  No Light For Germination

You may have heard that seeds don’t require a source of light to germinate.  That’s true.  But, some seeds do absolutely require light to germinate properly.

That said, there is no requirement to keep your seeds in darkness.  It’s been our experience that germinating under light is not problematic at all.  Unless you have space issues that limit you from providing light to your seedlings, it’s not a bad idea to give it.  Plus, offering light from day one allows the seedlings to transition from germination into growth without further intervention.

Some examples of seeds that require light to germinate are:

  • Dill
  • Ornamental Peppers
  • Lettuce
  • Begonia
  • Columbine
  • Geranium
  • Petunia
  • Impatiens
  • Poppies
  • Snapdragon

9.  Special Seed Requirements

Most seeds don’t have highly specific requirements or specific treatments that are required to get successful germination.  But, some seeds (or specific varieties of plants) do have special requirements.

In general, these special treatments might include one of the following:

  • Scarification, or scoring the seed to make it easier for the seed to germinate.  This simulates seed movement or rough treatment, such as being eaten by an animal.
  • Stratification, or the process of simulating winter by placing seeds in a refrigerator or freezer.
  • Boiling, or the process of simulating extremely hot temperatures such as being on the ground in the baking sun.
  • Radical temperature or humidity changes, simulating natural seasonal changes that might occur if the seed were growing in a natural environment.

In general, if the seeds require a special treatment like this, the seed packet will specifically identify the process that is required.  The seed packet will often provide detailed instructions that involve the amount of time or specific parameters for the treatment.

Fortunately, for most common vegetables and fruits, you don’t have to worry about these special techniques.  If you are growing from collected seed, or some relatively eccentric plants, it’s worth doing a little bit of research to see if any specific treatments are required.

Bonus Tip!  What Isn’t Causing Your Issues!

A somewhat common misconception is that “seed starting mix” doesn’t have the nutritional ability to start your seeds.  While it’s true that seed starting mix is mostly inert and isn’t high in nutrients, it doesn’t have to be!

A seed contains everything the plant needs to get established.  Every seed contains enough reserves for the seed to hatch, a tap root to be established and practically everything up to the first set of true leaves.  Isn’t that amazing?

It is important to transplant out of seed starting mix once the plant does become established.  Common potting soils are good for this purpose as they usually contain enough compost or diluted fertilizer to help the plant get through the early stages of life.  You usually don’t need to worry about fertilizing your plants until they are several weeks to well over a month old.

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