Propagation and seed heat mats are an important part of the growers toolbox. It’s easy for beginner gardeners to forget about the temperature of their grow media and how it affects the plant’s root system. Usually, forgetting about the temperature of your grow media won’t cause any notable issues for adult plants that already have a strong root system in place.
Unfortunately, this isn’t the case for seeds, seedlings, and cuttings that have barely developed a root system, if one at all. Even worst, young plants don’t have anywhere near the light demand that adult plants do. As such, this requirement for less light will translate into less heat building on and warming the grow medium.
Why Heat is Critical to Seed Germination
The temperature of the grow media will play a vital role in both the success and time seeds germinate at. In fact, many vegetables and fruits have an optimal temperature for germinating that is quite high.
Beets, peppers, eggplant, tomatoes, cabbage, and radishes are just a few that have an optimal temperature of 85°F. Corn, cucumbers, squash, watermelon, and beans all prefer an optimal temperature of 95°F – you’re most likely not keeping the temperature in your house anywhere near that, nor will your propagation lights come close to warming up the grow media to said temperature.
Fortunately for gardeners, especially ones of the outdoor variety, seeds have a much lower practical temperature they can germinate at, however, this results in poorer success rates and reduced germination speed.
Set Your Plants Up For Long-Term success: Pros of Seedling Heat Mats
Why getting a seedling heat mat is a good idea:
- Most seedling mats will raise temperature 10 to 20 degrees over ambient temperature providing the perfect environment for your roots to take off.
- Seedling mats are affordable and durable – they will ultimately save you money with each successful propagation after successful propagation.
- They come in a variety of sizes working with your preferred propagation setup.
- They provide the root zone with an optimal temperature that decreases production time and increases germination rates.
- They give outdoor growers, who experience a colder spring or an environment that experiences harsh temperature fluctuations, the ability to germinate in their greenhouses earlier in the year, and give them the choice to have their propagation setup outside.
Cons of Seedling Heat Mats
The benefits outweigh the cons by a significant amount, however, there are two issues you need to watch out for:
- First, heating mats tend to dry out the grow media faster – experience gardeners will not find this to be an issue as they’ve developed an eye for telling if the media is properly watered. But it’s common for new gardeners to over and underwater in the beginning, so more diligence is recommended when using a heating mat.
- Second, it’s always a smart idea to have a way to monitor the temperature. Remember, these heating mats can raise temperatures 20 degrees above ambient temperatures and this can burn seeds, especially if they have a low optimal temperature such as spinach, lettuce, and parsley.