Most gardeners that want to raise their own starts from seed will eventually want to buy a light for this effort. A good grow light can be a great investment, both for the gardener and the northerner trying to baby house plants through our cold and dark winters.
Unfortunately, not just any light will do. For example, incandescent lighting is a very poor choice for plant growth. Fortunately, there is a lot of research that has been done on artificial lighting and plant growth.
There are three major types of lighting that are generally acceptable to use for indoor plant lighting. These types are fluorescent, HID or high intensity discharge and LED. We’ll discuss these types of lighting in more detail below.
Photosynthetic Active Radiation & Plant Growth
Research has shown that plants are known to use a specific spectrum, or frequency, of lighting. This spectrum is called PAR or photosynthetic active radiation. This specific light spectrum is what allows the plant to photosynthesize, which is how plants harness light energy to grow. The spectrum ranges from blue (cool) to red (warm) with green and yellow frequencies in between.
Without delving into lighting and specific plant complexities, there are a couple things to know about light spectrum. Generally, the blue spectrum, is great for vegetative phases. The red spectrum is used more heavily in flowering and fruiting phases.
The sun is a very strong source of light. Mimicking the sun indoors can be challenging. Most plants will soak up a lot of light, but too much light can also be detrimental. When we are trying to recreate the outdoor environment indoors, a strong light is often a good thing to have.
Like with most things, you generally get what you pay for. The primary things you want to pay attention to will be overall cost, coverage area, lighting strength for what you want to do and energy (or operational) cost. Secondary factors might be the physical dimensions of the light, future projects you may want to use the light for and personal desires.
Fluorescent Lighting And The Indoor Garden
This is one of the most common types of lighting used for seed starting. Fluorescent lights come in many varieties and sizes that can suit your purpose, from regular light bulbs to long tubes that cover greater area. Any of these varieties will work for plant growth.
There are fluorescent lights that are specifically marketed to gardeners, these are the T5 variety fixtures. The advantage of the T5 over common flourescent bulbs is they have a boosted strength which helps with photosynthesis.
These high output bulbs are stronger than most other types of fluorescent lights, which helps with keeping tight internodal growth and prevents leggy plants.
Multi-bulb fixtures allow you to easily cover large areas, such as seedling trays. You will generally see two, four, six and eight bulb fixtures available on the market. More bulbs provide more greater light strength and greater coverage area.
The advantages of fluorescent lights are generally inexpensive cost, ease of covering larger areas, excellent energy efficiency, little heat generation and sufficient light spectrum for early vegetative growth.
The primary disadvantages are that they are not strong enough to penetrate thick plant canopies, therefore aren’t as good for bringing plants and vegetables to full maturity. Also, the bulbs do not last forever and will need to be replaced semi-often.
LED Lighting And The Indoor Garden:
LED lighting is a relatively young lighting market, but one that shows great promise.
Originally, these lights were prohibitively expensive for most gardeners and were more commonly used by cannabis growers. These days, however, the cost of LED lights has dropped considerably which makes it a more practical consideration for general gardeners.
Early generation LED’s were not really that good. They used small wattage LED’s, which weren’t great at providing light penetration. Manufacturers also weren’t addressing all of our plant’s lighting needs, providing limited spectrum lighting.
Modern multi/full spectrum LED’s are better and 5+ watt LED’s are able to provide much stronger light penetration than earlier generation LED’s.
The advantages of LED lighting is optimal energy efficiency and the ability to customize the provided light spectrum more specifically for the plants. This means that you’re not spending electricity generating light frequencies and heat your plant simply won’t use. Another advantage is long LED’s lifespans, which means you eliminate bulb replacement costs. One of the greatest benefits of modern LED lighting is reduced heat that comes from the light fixture.
The disadvantages of LED’s are generally cost, they tend to be more expensive than other types of lighting. This is usually countered with significant energy savings, however, and often will pay for the difference quite quickly. Modern LED lights can also be quite powerful, meaning you have to take care when using them with seedlings.
Given our very high electricity costs, we have migrated our lighting to LED systems. For us, they provide much greater light to watt ratios than other types of lighting.
Notes About Modern Full Spectrum LED Lighting
You will likely come across terms like “multi spectrum” and “full spectrum” if you are looking at LED’s. The LED industry is moving towards full spectrum LED’s, or natural looking lighting. If you are considering LED, we also recommend full spectrum LED lighting.
There are many purple/blue/red LED’s on the market. This spectrum is not natural to our eyes and can prevent your ability to see plant deficiencies and problems. While these lights will grow plants, the purple color of the lighting can simply be less than desirable. Full spectrum LED’s provide a more natural light and are superior in this regard.
High Intensity Discharge (HID) And The Indoor Garden:
You have seen these types of lights before, they are commonly used in street lamp applications. They provide a very robust amount of light, stronger than any of the above sources of lighting.
There are two major types of HID lights. Metal Halide, which provides a cooler/blue spectrum ideal for early and vegetative growth. HPS, or high pressure sodium, provides a warmer spectrum which is good for flowering and fruiting purposes.
HID lights use what is called a ballast to create the very high energy levels needed to run these lights. Modern digital ballasts include features like the ability to use both metal halide and HPS bulbs, as well as selectable power settings that will allow you to use less energy.
For most gardeners interested in growing starts, the HID light is a bit of overkill. However, they will give some of the best results available. They also tend to more easily cover large areas, such as 4 foot by 4 foot grids, making them an ideal choice for the larger scale gardener. If you also delve into year round production, they could be an ideal choice for you.
HID lights are usually sold by the number of watts, which is essentially how much energy it will draw while running. Common values are 150, 250, 400, 600 and 1000 watt varieties. Bigger is not always better, your specific application and desired footprint coverage will determine the size needed.
Generally, the lower end will cover 2×2 or 3×3 foot spaces, whereas the larger units can cover 4×4 foot and larger. If you are able to get a digital ballast with selectable power settings, it may be desirable to go a bit larger and dial it down for your needs at the time.
The primary advantages of HID lights are superior light penetration, allowing you to grow full maturity plants with ease. They also are highly energy efficient, however, they do not give a “perfect” spectrum for plants and energy is wasted on non-essential light spectrum. HID lights tend to be quite cost effective as well.
The major disadvantages of HID lighting is they tend to draw more energy than other lighting types, meaning your operational costs will be higher. Also, bulb life is much shorter than other lights, which means you will have to replace them far more often. Another common disadvantage is they generate more heat than other lighting types. Sometimes, this additional heat can be an advantage to cool climate gardeners. The larger wattage bulbs, such as 600 and 1000 watt varieties generate a lot of heat, which often means you have to develop cooling methods to evacuate that heat.
It is common to see HID lights used with reflectors, which will help direct the light energy towards your plant. Hood type reflectors are usually great for easier cooling, where ducting can be connected to inline fans to evacuate the heat. Gull wing reflectors are simpler to operate, however, will be more difficult to keep cool.
We have used these types of lights in the past and they are excellent for providing rapid plant growth.
So Many Choices! Just Help Me Choose A Light!
For a sure fire, easy experience – your best bet will be an appropriately sized fluorescent bulb fixture. This will be plug and play, relatively inexpensive and energy efficient. They will be a very reliable workhorse year after year and will get the job done effectively. Buy the size you need, either 2 foot or 4 foot, depending on the length of coverage desired. If you need to cover up to 2 foot of depth, consider a six or more bulb fixture.
However, if you are looking to try to save operational costs, LED is definitely going to be your choice. These have become extremely popular in recent years, which has also brought the pricing down significantly. As we mentioned above, we have transitioned to almost entirely using LED lights in our gardens. Eventually, LED lights will pay for the cost differences of other types of lighting and will benefit you over the long term.