The Top 3 Seedling Heat Mats & Thermostats in 2022

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By: Chenell - Lead Writer and Gardening Advocate
Published:

The heat and temperature of the soil are 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. Considering that typically when we are starting seeds it’s in the dead of winter, and even with the heat on, your growing space is probably colder than other times of the year.

A heat mat provides a constant (and a uniform heat) to help with germinating seeds.

I tried growing seeds without a heat mat, but it took almost 3 weeks to even see a sprout. Then I discovered heat mats (aka seed propagation mats) and realized I needed to get a little smarter with how I was growing veggies in the winter.

I did some research and bought a bunch of heat mats to see which ones are actually good, which ones are alright and which to avoid.

The Best Seedling Heat Mats & Thermostats

Here are some of the best heat mats I’ve found to help make sure your seeds have the right ambient temperature for getting started.

1. Vivosun Heat Mat with Thermostat

Vivosun has become my go-to company for heat mats because they’re just reliable. They just work. And other people seem to think so as well.

Vivosun Heat Mats get as close to 5 stars as I’ve seen in online reviews. While some people experience issues (as they will with any product), I have only had great experiences with these.

I bought two six of these (yes, 6) and the mats and thermostats seem to work great so far. The shipping was super fast and customer service seems very responsive.

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I got a few in both the 10″x20″ sizes initially and then realized that I could save money by just getting the larger size. The 20″x48″ is large enough to keep a full grow room shelf at the optimal temperature.

The box my Vivosun heat mat came in

This is hands down my favorite heat mat, and even though I bought the others on this list as well, I don’t use them because I know this seedling heating mat brand is TOP NOTCH.

The thermostat is a lot more intuitive to use than other brands as well. You can set these between 68-108°F (20-42°C). And yes, you can change it between Fahrenheit and Celsius with just the touch of a button.

They also come with a reusable storage bag so you can clean up and stay organized after the season is over.

Pros:

Super durable

Comes in multiple sizes

Great customer service and 1-year warranty

Easy-to-use thermostat

Cons:

One of the most expensive options

3. Super Sprouter Seedling Heat Mat

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.

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Pros:

Good for those just getting started

Comes with a humidity dome (albeit a flimsy one) and a T5 grow light

Comes with a pretty detailed “getting started with germination” type of booklet

Cons:

The tray it comes with is kind of “meh” and not super durable

Does not come with a thermostat

The SuperSprouter kit is not going to be a solution for years and years. Some of the components are a little cheap and flimsy, but it’s great for someone just getting started who doesn’t know if they’re going to stick with starting seeds every year.

However, if you have any inkling that you will, I’d go with something a little more durable.

  • 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.
  • 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.

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 lesser-known brands heat mats 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 to 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 (in the 50’s) 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 When Buying a Heat Mat

Here are a few things you’re going to want to look for when you buy a heat mat, whether it’s for commercial use or not.

Waterproof

You’re going to want a plant heating mat that is waterproof since we’re going to be watering the seed. Trust me when I say that you will 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 Included

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 underheat 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.

How Hot Do Seedling Heat Mats Get?

Heat mats generally hold their temperatures at a temperature of 68-86℉ (20-30℃), but can go as high as 105℉.

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 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 consistent temperature.

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 hardier 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.

How to Use a Seedling Heat Mat

Now that you know what are the best heat mats, here’s how you can use them to grow your plants. These work great for all kinds of plants like:

  • Vegetables
  • Flowers
  • Succulents
  • Houseplants
  • Cacti
  • Herbs

When starting seeds, add your soil or growing medium to a seed starting tray. This might be a soilless mix with perlite or vermiculite, peat moss, or something like rockwool if you’re going to grow hydroponically.

I like to leave the heat mat under the soil for a few hours to warm it up enough. You can then start sowing your seeds and this warmed up soil will help speed up the process of them becoming tender seedlings.

Make sure you remove the heat mat from underneath the plant once germination happens. Otherwise, your plants can get leggy and grow too fast to have strong stems.

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AUTHOR, CHIEF GUACAMOLE CONNOISSEUR

Hi - I'm Chenell! I lived in the city for almost a decade, but after moving to the suburbs in 2020, I decided the logical millennial thing to do was to learn how to grow my own avocado toast. That's what this site is all about. 🥑

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