At Home Microgreens we use the default seedling heat mat temperature setting when germinating microgreens. There are some exceptions, and we’ll discuss those later in the article.
There are many reasons why we use a seedling heat mat when we germinate microgreens seeds.
First off, consistently warm temperatures improve seed germination. That fact is indisputable.
Vegetable seeds and most microgreens are either vegetables or herbs, that germinate over a wide range of temperatures. The range extends higher than average room temperature.
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Since we grow microgreens in our home, the microgreens seeds we sow need a warmer local boost to speed up the germination rate.
Do you need a heat mat?
Not really, but they will help germination rates if your house is cooler, even during the summer if you use air conditioning below 75 degrees (f).
Before discussing the best seedling heat mat temperature, we should show you what heat mat we use with great success.
We use the seedling heat mat when we want our pizza dough to rise.
Vivosun Heat Mat
The seedling heat mat we use the Vivosun Waterproof Seedling Heat Mat.
Although the Vivosun comes in quite a few different sizes, we purchase the 10-inch by 20.75-inch mat. We find that two of these mats work well on each of our microgreen shelves and conveniently, Vivosun sells a two-pack on Amazon, which lowers the price by about $1.50 a mat.
Not that heat mats are expensive by any means, at $12 each, these are a good deal.
We’ve used these mats for two years and haven’t had any issues. We love them!
The Vivosun has several different heat mats. These are shown at the bottom of the article and include affiliate links to Amazon. As an affiliate, we will receive a small commission at no additional cost to you.
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Seedling Heat Mat Temperature
Well, the short answer is we don’t set our heat mats to any specific temperature.
The Vivosun seedling heat mat temperature stays between 10 and 20 degrees (f) above the ambient air temperature. At least that is what the marketing material mentions.
In our experience, the temperature of the heat mat never gets too high when ambient room temperatures are in the 70s or lower. Obviously, during the summer months, we don’t use the heat mats.
Here’s How We Adjust the Seedling Heat Mat Temperature
In the northeast, there are really three temperature seasons.
- Winter = Cold
- Summer = Hot
- Spring & Fall = Warm days and cold nights
During the winter months, our room temperature is always too cold for good microgreen germination. Even if you keep your house in the low 70s and don’t lower the thermostat during the night a secondary heat source helps germination.
In the winter months, we keep the Vivosun seedling heat mat on 24/7. We even keep it on under the microgreens as they’re growing.
More on the topic of keeping the heat mat on under growing microgreens later.
We put germinating planting trays right on the heat mats since we don’t water them until they’ve germinated. Then we place them in watering trays or 10 by 20 trays.
Believe it or not, we don’t run air conditioning in the house during the summer. Only during long hot spells or when the humidity is unbearable with no breeze.
The house is in the high 70’s or warmer (sometimes way warmer!) even with the windows open at night.
We unplug the heat mats and leave them off all of the time.
Spring and Fall
During these two seasons, the weather here is variable. So it’s a little bit of work to get the temperatures right.
Most days the outside temperatures are warm, especially near the microgreen shelf since it’s near a southeast-facing window and the sun hits the shelves. But at night, it can get cold.
We leave the windows open all day and night except during the freezing cold nights.
So there is a significant temperature fluctuation between day and night. During the day, the trays could get too warm, and at night too cold. Remember, constant warm temperatures are better for seed germination
But we’ve found an easy solution to the variable temperatures.
We plug all of our Vivosun seedling heat mats into a power strip connected to a timer. We currently have six Vivosun heat mats on our microgreen shelving system and the power strip can handle all of them.
We use timers to turn on the power to seedling heat mats during the evening when the days are warmer but the nights are colder.
Don’t worry, each heating mat only uses about 18 watts, so there’s no worry of overloading the power strip. We don’t even notice a change in our electric bill when the heat mats are on.
The timer turns the power strip on at night and off in the morning. We adjust the timer as the nighttime temperatures increase during the summer and lengthen the time as winter approaches.
If You Want Control or a Set Temperature
If you want to control the temperature, you can still use the Vivosun seedling heat mat.
Vivosun has a temperature controller that sticks a sensor to the heat mat. The sensor adjusts the wattage to keep the mat at the temperature you set the controller to.
Naturally, the heat mat can’t cool, so when you’ve reached your temperature setting, power is shut off to the heat mat.
We See No Need For The Expense
If you have only one seedling heat mat, the controller might be a good idea, but since we have six mats, we think our system works well enough.
Maybe one temperature controller set to the coldest mat and connected to the power strip might work to turn on all six mats and control the temperature effectively.
We’re not sure, but the system we have works well enough, even if not 100% efficient.
At some point, we may test the Vivosun Controller and give it a review. If you use one, drop a comment and let us know what you think.
Leaving The Heat Mat On After Germination
We were curious about what other microgreen growers do with their heat mats after the seeds have germinated.
The survey says: Turn them off.
What do we do: Leave them on.
Notice that the planting trays are in a 1 by 20 tray or a watering tray. Don’t water microgreens sitting directly on the heating mat. Even if the mat says it’s waterproof.
The growers contend that the warmth under the microgreens makes them grow too fast and become leggy.
We agree with that point.
Not an Issue with the Home Grower
However, here’s why it isn’t a big deal to leave trays of microgreens on the heating mat.
Growers, those that are selling microgreens, have timetables for each tray. They know how long it will take them to reach harvest height and how many greens they need on any particular day. Any variation, whether, a larger harvest or ugly leggy microgreens is not good for their business.
For us home growers, it’s not a big deal, if the microgreens are to a point where they’re getting leggy we harvest and store them in the refrigerator.
For that reason, we leave our heat mats set on our seasonal settings and grow our microgreens on the mats. We’ve never had any problems.
What Not To Do On Heat Mats
Here are some tips that will increase the longevity of your heat mats.
Keep the Heat Mats Flat
Don’t let your heat mat hang over the edge of your growing surface.
The heat mat has very thin wires embedded in the sturdy plastic coating of the mat. Bending the mat, especially at tight angles will increase the probability of those wires breaking.
If you can’t store the mats flat, loosely roll them up and use the drawstring bag that comes with the Vivosun heat mat to store them. Don’t roll the mat any tighter than the bag.
No matter what, don’t fold the mats.
Don’t Cut Anything On The Mat
See above. Don’t risk breaking or cutting the wires in the plastic.
Don’t Place Leaking or Dripping Trays on Mats
The Vivosun mats state they’re waterproof. Don’t test that out. It’s not worth the risk with electricity flowing through the mats.
The watering tray is under the Home Microgreens planting tray. Don’t let water leak on your heating mat.
We aren’t saying to not water over the heat mats. Instead, don’t let the trays drip out onto the heat mat.
As you can see in the last two images, the planting trays are in containment trays. If we spill water on the heat mats when filling the watering trays, we wipe them off right afterward.
What Else Watering Trays Do
Another thing that watering trays do is keep the roots that grow through the planting tray holes away from the direct heat (not that the mats get hot at all, to begin with).
The watering tray provides a bit of insulation from the heat. The roots won’t get quite as warm this way since there is air in the bottom of the watering tray or at least ridges on the 10 by 20 trays that keep conductive heat from the roots.
We highly recommend the Vivosun Seeding Heat Mat.
The heat mats are a big help when the ambient air temperature is below 75 degrees. We also believe that our germination rate is much higher with heat under the trays.
Besides a little extra watering when the microgreens are growing the heat mats give us no issues.
At $12 or so, a heat mat or two is an excellent investment for growing microgreens at home.
What’s your opinion? Leave a comment below.
Have a Question?
If you have any questions about the information in this post or microgreens in general please leave a comment below or reach out to me using the Ask a Question page.
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