The Best Seedling Heat Mat & Thermostat

The heat and temperature of seedlings is so important when you are starting seeds indoors. While each plant and variety have different ideal growing conditions, most seeds need to be started in a warm environment.

A seedling heat mat combined with a digital thermostat is a great option since the soil outside is too cold when we need to plant seeds.

best seedling heat mats

I tried growing seeds in containers outside, but it took almost 3 weeks to even see a sprout above the soil. Then I discovered seedling heat mats (aka seed propagation mats) and realized I needed to get a little smarter with how I was growing veggies in the winter.

Here are some of the best seedling heat mats and thermostats you can buy for growing plants indoors and/or starting seeds.

The Best Seedling Heat Mats & Thermostats

1. Hydrofarm Jump Start Seedling Heat Mat

Hydrofarm Jump Start MT10009, 107 Watt UL Certified Heat Mat, 48 x 20.75
$55.21
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09/18/2021 03:02 am GMT

The Hydrofarm has an almost 5 star rating and their items seem to be well received.

  • Warms root area 10-20˚F over ambient temperature to improve germination rates to increase success of seedlings and cuttings
  • Double insulated and most uniform heated surface on the market
  • Exclusively made in North America with American made materials
  • The only fully listed UL Listed seedling heat mat on the market

2. Vivosun Seedling Heat Mat with Thermostat

VIVOSUN 48"x20.75" Seedling Heat Mat and Digital Thermostat
$45.99
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09/18/2021 12:13 am GMT

The Vivosun Heat Mats get as close to 5 stars as I’ve seen on these reviews. While some people experience issues (as they will with any product), the vast majority are really happy with a seedling heat mat from them.

I bought two of these and the mats and thermostats seem to work great so far – I’ll post more product info once I test it more. But the shipping was super fast and customer service seems very responsive.

  • VIVOSUN says they go beyond the MET standards, with a fortified connection between mats and power cord, water-resistance that enables safe scrubbing and a 1-year warranty.
  • The controller maintains a stable temperature between 68-108°F (20-42°C) for professional horticultural systems; the sensor probe delivers accurate readings in both cool and warm environments.
  • You can set the temperature or change the display between Fahrenheit/Celsius.

3. Super Sprouter Seedling Heat Mat

Super Sprouter Premium Propagation Kit with Heat Mat, Tray, 7" Dome & T5 Light
$80.77
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09/17/2021 02:22 pm GMT

This one is kind of like the “big daddy” when it comes to buying a seedling heat mat. It comes as part of a seed starter kit with a few bells and whistles that aren’t exactly necessary, but they can be a big help especially if you’re new to seed starting.

  • The Super Sprouter comes with a 7 in Vented Humidity Dome and built in light track channels
  • Has an 18 inch high output T5 fluorescent grow light that is UL listed
  • Comes with a Double Thick 10 x 20 inch seedling tray with no holes
  • Art of Propagation booklet with expert advice for starting seedlings and cuttings


4. Viagrow Seed Propagating Seedling Heat Mat

Viagrow 20.5 in. x 8.5 in. Seed Propagating Seedling Heat Mat
$23.99
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09/18/2021 01:15 am GMT
  • Warms root area 10-20 above room temperature
  • Speeds germination and encourages strong root growth
  • Fits snugly under a standard size seed tray
  • MET approved and extreme temperature tested
  • Viagrow Heat Mat is 120 Volts, 60Hz, and 20 Watts.
  • Simply set the temperature probe, plug-in the controller, and use the large 3-button interface to choose your desired temperature setting. Digital display supports units in both Fahrenheit and Celsius.
  • LED heating and power indicator lights allow you to see the controller’s status even in total darkness. Controller features a convenient hanging tab, and a bright, easy-to-read display inside a tough plastic housing.
  • It comes with a temperature probe and grounded 3-prong plug that measure an extended 6 feet in length, designed to suit almost any application you can imagine.
  • The BN-Link Durable Seedling Hydroponic Heating Pad provides consistent, uniform heating at temperatures around 68°F to 86°F (20°F to 30°F), which are the perfect temperatures for seed starting and cutting propagation.
  • Not only is the BN-Link Durable Seedling Hydroponic Heating Pad built to last with its durable, water-resistant material, the Heating Mat also remains elastic and flexible. Perfect for most conditions indoors/outdoors. Each unit comes with BN-Link’s strong 15-month warranty.

6. Seed Factor Seedling Heat Mat

Seedfactor, MET Certified Seedling Heat Mat (2-Pack)
$21.99
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09/18/2021 02:44 am GMT

This one also gets almost 5 stars and has great ratings.

  • MET safety certified
  • Comply with UL 499
  • Ensures the root area of seedlings remains between 70℉ and 85℉ to ensure growth and increased germination
  • Available in 4 sizes:
    • Mini:3.5 x 21, Watt: 7.3W
    • Small: 10 x 20, Watt: 17.5W
    • Medium: 20 x 20, Watt: 45W
    • Large: 48 x 20, Watt: 100W

These are not the only options for you in terms of propagation mats, but they do get great reviews and work quite well for starting seeds indoors.

I recently just picked up 3 of these so I’ll be posting my in-depth reviews and more information later, but so far each of these heat mats works great.

While you can purchase seed heat mats up at a big box store like Walmart, Lowes or Home Depot, make sure you check reviews online before purchasing.

Some “fly by night” companies make heat mats that don’t really stand up with the test of time well.

Why Should You Germinate Seeds With Heat Mats?

By using a mat, you’re able to give your plant the heat source and warmth it needs to grow. Combine that with water, light and oxygen, and you’re telling your seed it’s time to start the germination process.

Without a heat mat, you’re slowing down the process and won’t have great results.

I started some arugula this winter season using a plastic container as a mini-greenhouse. When I started, the weather was warmer (50s) so it only took 1 week to see some growth, but the weather cooled down so much that a month later they were close to the same size. Clearly, I needed this information before 🙂

Using a heat mat to increase seed germination rates is a great way to make sure your seeds actually grow. They need pretty consistent temp levels to get started, especially if you want to speed up their growth.

A seedling heat mat allows you to make sure this process is happening. For the price point, I think it’s well worth it.

What to Look For in Heat Mats

Waterproof

You’re going to want a plant heating mat that is waterproof since we’re going to be watering seed and you’ll inevitably get some sort of moisture or water on it. You can check the product information and make sure it has this, but almost any mat you find will (as long as it has at least 4 stars).

Thermostat

The thermostat piece of this is HUGE. If you look at the reviews online, you’ll see that some people have great experiences with their orders and give it 5 stars, while others end up with a heating mat that doesn’t heat up enough or cooked the root zone because it got so hot.

This happened to me when I just got lazy and didn’t plug in the thermostat – rookie mistake.

By getting heating mats with a digital thermostat controller you’ll be able to stabilize this a bit more than just flying blind.

Here are some common questions people ask about when buying a heat mat:

Should You Get a Seedling Heat Mat With a Thermostat?

While buying a product with a thermostat is not necessary, it is ideal. A lot of companies, even those with great reviews often have a few products that can overheat or under heat your plants. Without a thermometer/controller, you might not realize the change in temperature until it’s too late.

If you can, spend the extra $10 on a thermometer for temperature control so you can allow your seeds to germinate at the right pace and they don’t heat up too much.

What Size Seedling Heat Mat Should You Get?

This is going to depend on your seed starting setup and how many plants you’re looking to grow. I like the 10×20 size because it fits most seed starting trays and flats.

Some of the more common sizes of heat mats:

  • 10 x 20 inches
  • 20 x 20 inches
  • 48 x 20 inches

If you’re a microgreens grower, make sure you get one big enough to cover the larger trays you’ll likely be using.

What is the Ideal Temperature to Germinate Seeds?

According to Iowa State University research, “most seeds germinate when the soil temperature is between 68 and 86 degrees Fahrenheit.

If you’re not sure about a specific plants optimum soil temp, 75 degrees is a pretty safe bet. That’s well above room temp for the average home.

Thankfully we can use a seedling heat mat to keep the temperatures of our root zone at a steady place.

Every plant has a slightly different ideal range for germination to take place. By getting your seedlings as close as you can to the ideal degree, you’ll be speeding along the germination process.

Here are some common plants with their “optimum soil temperature for germination”, as compiled by the University of Florida:

PlantOptimum
Germination
Temperature
(Fahrenheit)
Asparagus75 degrees
Beet85 degrees
Broccoli85 degrees
Cabbage85 degrees
Carrot80 degrees
Cauliflower80 degrees
Celery70 degrees
Cucumber95 degrees
Eggplant85 degrees
Endive75 degrees
Lettuce75 degrees
Lima Bean80 degrees
Muskmelon95 degrees
Okra95 degrees
Onion80 degrees
Parsley85 degrees
Parsnip70 degrees
Pea75 degrees
Pepper85 degrees
Pumpkin95 degrees
Radish80 degrees
Snap Bean85 degrees
Spinach70 degrees
Squash95 degrees
Sweet Corn85 degrees
Swiss Chard85 degrees
Tomato80 degrees
Turnip80 degrees
Watermelon95 degrees

Do I Leave the Heat Mat on All the Time?

How long should seedlings stay on the heat mat?

When you’re starting seeds and trying to grow seedlings, you’re going to want to keep the heat mat on 24/7 to make sure it doesn’t get too cold and stunt the germination process or kill your plants.

After about 10 days, as long as your plants aren’t in 30 degree weather, you can start to taper down the temperature so they become more hardy and will be ready to move outside.

Are There Alternatives to Using a Heat Mat?

There are always alternatives. The question is, how well do they work?

You can place your plants on appliances that stay warm (radiator, etc.), but if the temperature varies too much you could end up with a plant heating up too high. On the other hand, if the appliance isn’t warm enough, you’ll stunt the growth of your plants.

You don’t necessarily want to heat the entire plant, just the bottom where the root zone is, so heating with a light or lamp would not be ideal (although you will need a light source for your seed).

Can you use a heating pad for seedlings? You definitely can, but some heating pads don’t have a temp gauge, so make sure you don’t overheat them.

To keep seed germination on track, you really want to keep the temperature control in that sweet spot by using a temperature controller.

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