Using a heating mat during germination is one of the easiest ways to ensure effective germination, and that all of the seeds you’ve planted will sprout into healthy seedlings. It might be fair to consider a heating mat as optional, as some gardeners do, given that there are alternate techniques for germinating available. When you consider the immense gains to be had from using these affordable and durable heating mats, however, it becomes clear why they are anything but optional in the best greenhouses in operation.
In fact, the same could be said for the majority of gardening techniques. From the humble indoor patch of cilantro to the thousands upon thousands of agricultural farmland being cultivated, there are two ways to go about it all.
Namely, the easy way and the hard way, right?
Sure there are techniques for propagation and cultivation that have proven timeless in their ability to keep a world full of people with access to healthy and tasty food, but modern innovations have made some facets of gardening much, much easier than they might have once been. And while knowing how to do things the hard way certainly holds a certain value, saving time and money through efficiency and efficacy have value as well.
Most of us learned in Kindergarten that we could put some seeds in a damp paper towel and tuck it away, and in a day or two the seed will have cracked open to reveal an eager sprout. This is many a child’s first encounter with creating a living thing (seemingly from nothing), and for some of us, it makes quite the impression.
Sprouting a green bean or a daisy in a dixie cup is one thing, but running a successful indoor hydroponic system will go much more smoothly by implementing more modern methods throughout the plants’ stages of growth. And there is, perhaps, no more suitable place to begin than at the germination stage.
Before we get ahead of ourselves, let’s take a quick look at some of the equipment that commercial greenhouses and home hydroponic growers are using, to great success.
7 Best Heat Mats for Seedlings
VIVOSUN Durable Waterproof Seedling Heat Mat Warm Hydroponic Heating Pad 10″ x 20.75″ MET Standard
This is one of the best-selling and best-reviewed heating mats available. The 10” x 20.75” dimension is designed to accommodate the most popular size of germination tray on the market. The vast majority of propagation domes are available in this industry-standard size, as well.
VIVOSUN 10″x20.75″ Seedling Heat Mat and Digital Thermostat Combo Set MET Standard
This features the same high-quality mat as above but also includes a digital thermostat to ensure optimal temp. ranges during germination and sprouting. Some species of plant require different conditions to be within their optimal range, making the regular monitoring of temperature and humidity an important task.
iPower GLHTMTL-A 48″ x 20″ Waterproof Durable Seedling Heat Mat Warm Hydroponic Plant for Indoor Gardening Germination Starting, Black
iPower has remained alongside Vivosun in terms of popularity and positive feedback; this product is a much larger mat that can be used to heat larger germination trays or multiple standard-sized trays. The more realistic application for the larger mat, however, is in bigger propagation domes and cloning trays. Just as the warmth the heating mat provides acts as a catalyst during germination and hastens the process, certain plants will react the same during the early stages of growth while cloning.
iPower GLHTMTCTRLHTMTL 48″ x 20″ Warm Hydroponic Seedling Heat Mat and Digital Thermostat Control Combo Set for Plant Germination, 48″x 20″, Black
Similar to the offering by Vivosun, the larger iPower mat is also available with an included digital thermostat controller. Because clone trays are often stacked in an enclosed, climate-controlled space in indoor hydroponic gardens, using a large heating mat on each tray requires more careful monitoring than smaller alternatives. The larger mats will distribute heat more evenly to the trays than using multiple small mats will, but your garden will always benefit from your continued awareness of temperature and humidity conditions. Collectively, any number of heating mats can impact the ambient temperature, particularly in an enclosed space like a cloning closet or grow tent, making the inclusion of monitoring that much more important.
3″x20″ Wrap Around Kombucha Fermentation Heating Pad Strip or Windowsill Seed Starting Heating Mat Heat Pad, Use for Seedlings, Herb Gardens, Plant Germination, Cloning, Brewing (1-Unit)
Originally designed for aiding in the brewing and fermenting of individual jars of kimchi and kombucha, these wrap-around thermal heating strips can be used for a variety of other indoor-gardening applications. From speeding up the rooting of jar-propagated clones to accelerating the overall growth of aquaponic plants or clippings, or even speeding up the cultivation of a mycelium network, these heating strips will bring enormous benefit to any gardener that uses gallon-sized mason jars as an implement. At 3” x 20” the strip is intended to wrap around a 1-gallon jar snugly, and radiate warmth evenly all the way around. Also included is an adhesive temperature strip for ensuring the actual temperature of the jar’s contents during operation.
iPower 2-Pack 40-108 Degrees Fahrenheit Digital Heat Mat Thermostat Controller for Seed Rooting, Germination, Reptiles, Fermentation and Brewing, 2 Pack Black
This is a 2-pack of the digital heat mat controllers by iPower; they are made to work best with iPower heating mats but are designed to be universally accommodating to all heating mats. You should really have a controller for each heating mat you use, and most hydroponic gardens find that they can’t have too many mats! This affordable 2-pack makes it easier for indoor gardeners to get only the equipment they need, without wasting money on items they might already have.
iPower GLHTMTCTRLHUMDHTMTS 10″ x 20.5″ Hydroponic Seedling Heat Mat and Digital Thermostat Control and Humidity Monitor Indoor Thermometer Combo Set for Plant Germination, Black
This is iPower’s standard-sized heating mat, which includes the standard digital temperature controller that comes with the combo pack, as well as a nice-looking digital display for monitoring. The display shows pertinent info in large, bold digits, making walk-through monitoring of temp. and humidity a breeze. This kit is ideal for the indoor gardener that is just getting started with putting a proper germination kit together, as it takes care of the heating mat, controller, and monitoring in one swoop.
Heating Mat Standard Sizes:
- 10” x 20.5”
- 20” x 20”
- 48” x 20”
Do I need a heat mat for seedlings?
In truth, nobody needs a heating mat to grow seedlings, or seedlings into healthy plants. The folks over at GardenMyths go into more detail, but essentially heating pads can potentially bring two main benefits to your garden; shorter germination time and a higher germination success rate.
Of course, whether these factors are worth it to you personally is something we could never hope to predict. A substantial number of indoor gardeners swear by the use of heating mats, and most commercial growers see definite value in shaving days off of germination and cloning stages. After all, the faster a batch of plants moves from one stage to the next, the sooner you can start the next batch.
Inexpensive Alternatives to Heating Mats
Still, there are some of us that would like to see for ourselves whether it’s worth it to us, before investing any amount of money. Sometimes it isn’t about the costs, but the principle.
Fortunately, there are a number of affordable alternatives to the more popular items like those we’ve discussed here. Namely, the mainstream alternatives to store-bought heating mats are:
This is likely the most common alternative method of providing heat to germinating seeds, with roots in old-school wisdom from seasoned indoor gardeners. While the trend towards making appliances ever smaller, slimmer, and more energy-efficient could make this route more challenging than it once was, resourceful-minded growers should be able to find something that works. Televisions, freezers/refrigerators, desktop PCs, and desk or table lamps all radiate some amount of heat, which can be used to emulate the function of a heating mat. Just take care not to let any moisture come in contact with electrical appliances.
DIY Light Box
Another popular alternative that is picking up traction with the modern generation of indoor hydroponic growers is the DIY Light Box. The light box is reminiscent to “well-heaters” that the older generation might be more familiar with. It’s basically a box built to dimensions that accommodate the tray or trays you want to germinate. Inside the box are mounted enough incandescent lights to radiate heat inside the box, which in turn warms up and radiates its own heat into the trays and the ambient air around it.
Jump Start JSHC48 Soil Heating Cable, 48-Feet, Black
Using heat cables like these, you can heat a layer of sand that can be used as a bed for as many germinating plants as you can fit in your garden – more, even! The PennState Extension website provides us with a reliable and in-depth explanation of the process, as well as the specific materials you’ll need for a professional-quality assembly.
And it would be a grievous error to omit the increasingly popular method of using old (non-LED) Christmas lights to provide a cheap and readily available replacement to heating mats. Most people lay the lights in a spiral on the bottom of a tote and add enough sand to cover them. The lights will warm up the sand, and germination trays that are set in the sand will, in turn, be warmed.
The same folks at PennState also describe how a natural composting blend can generate its own heat, which can be harnessed and used to help aid germination. As the researchers point out, however, this method will require a little more scrutiny and maintenance over other methods.
How hot does a seedling mat get?
Most mats that do not include a temperature controller will get anywhere between 65°F and 86°F, which is generally considered the “sweet spot” for germination. Some digitally-controlled heating mats can be made to get as hot as 100°F, making a good-quality controller and reliable monitoring vital to your garden’s health.
How do you use a heating mat for seed germination?
Before getting started, check the ideal germinating temperature for the type of plants you are aiming to grow. Most seeds will germinate at 65°F or warmer and in a dark place – but some varieties require temperatures as high as 80°F and even light in some cases!
Generally, you’ll lay the mat down on a flat, solid surface and then place your germinating tray directly on the mat. The mat will need to be placed within reach of an electrical outlet; if using extension cords be certain they are properly rated for the voltage and conditions.
Keep the mat under the germination tray or propagation dome and set the controller to the desired temperature setting. We can’t recommend using a heating mat without a controller, as you could bake your plants without even realizing it. It’s also not a bad idea to include some means of monitoring the temperature and humidity from a device that is separate from the controller. This will provide not only the most precision but also safety against a controller malfunction.
How long should seedlings stay on the heat mat?
After you’ve placed your mat, plugged it in, and positioned the germinating tray on top of it, you typically won’t have to wait long. Some seeds will begin sprouting with 24-48 hours, while other plants can take 10 days or longer to sprout.
Whatever the case, its a good idea to remove sprouted plants from the heating pad once they’ve germinated. The extra warmth will cause the soil to dry out more quickly, and the new sprouts will be thirsty. The warmth can also lead to the accelerated, but disproportionate growth of the seedling also known as “stretching”. This can result in weak stems that prove unable to support their own weight.
Ultimately, the real answer is that seedlings should come off the mat once they’ve germinated.
Should you cover seed trays?
There are two really good reasons to use a cover when germinating seeds in a tray. The first is also the main reason that most gardeners do it – the cover creates a mini-greenhouse that traps humidity and warmth inside, helping to keep the medium from drying out while still remaining warm enough to germinate successfully.
The second reason is one that sometimes evades consideration by newer gardeners, but once you’ve lost a healthy batch of newborn seedlings to some pest or other malady, you’ll never forget again. Covering seed trays not only keeps moisture and heat in, but it does a pretty good job of keeping plant-eating insects, rodents, and mites out.
Ultimately, there are quite a few benefits that come along with implementing heating pads. While there are other ways to accomplish the same thing, the modern waterproof heating mat along with a digital controller is affordable and hard to beat. Sitting a tray on your TV might work for the hobbyist, but as your hydroponic garden becomes larger and more professional in both quality of build and presentation, heating mats provide the ideal solution to germination at any scale.
As always, we hope you’ve found the information here to be informative and helpful. It’s all in the effort to keep you growing like the pros. Thanks for reading, and we look forward to seeing you next time!