Can I Use A Regular Heating Pad For Seedlings?

By Paul Smart •  Updated: 02/20/22 •  8 min read

Can I Use A Regular Heating Pad For Seedlings? If you live in a relatively cold climate and are an avid gardener getting your seeds going early in the season is an absolute must, particularly if you live in regions where the growing seasons are relatively short. So, if you need to get your seedlings going can you use a regular heat pad for seedlings or do you need to use a specific seed propagation tray to get the best out of your seedlings?

You can use a regular heat pad for seedlings if it is one that is waterproof as there will be a little bit of water about due to the need to water the seedlings on a regular basis. However, when using a heating pad it is important to use a seed tray with a humidity dome to make sure that you maintain a moist environment that is suited to the growth of the plants.

Additionally, some heating mats can create temperatures that are suited a little too hot in some cases for growing seedlings. To see the effects of this check out an experiment I conducted in the video below.

However, while heat pads are quite suitable for the job in some cases provided that they can resist moisture and are not too hot my preferred option is to use a heated seed tray for a couple of reasons; the first is that the seed tray is designed specifically to hold one seed tray and has a plastic base which can stop water from leaking out onto the mat which generally makes the whole set up a little bit neater inside your house.

The second reason I prefer a specific heated propagation tray is that it contains a seed tray with the humidity dome which overall will generally be slightly cheaper than buying individual components to create a similar propagation setup.

If you are considering purchasing a heated propagation tray the one that we would recommend is the ipower germination kit which comes with a base tray seedling insert and the humidity domes.

The advantage of having a separate base tray and the seedling insert separate two-fold. Firstly, it allows the seed tray inserts to be replaced on a regular basis which will ensure that it maximizes the life of the unit. The second key advantage of having a base tray is that it can be partially filled with water to ensure that the seeds remain moist and reduce the need to water as regularly. To see the latest price on Amazon click on the link below. 

Get Off To An Early Start With A Heated Propagation Tray

The only advantage that using a regular heat pad has is there are certain products available that come with a thermostat attached which will provide a greater degree of control over the temperature at which your seedlings germinate. However, these versions of the heat mats do cost around double what the basic unit costs. The obvious is question of how important is the precise temperature at which you grow the seeds? 

What Temperature Do These Devices Operate At?

Most heat mats produce temperatures around about 59 to 77°F (15 to 25°C) degrees however this does vary a little bit depending upon the particular brand that you select to purchase. However, the ipower heated propagation tray runs at a slightly higher temperature of about 104°F (40°C). 

This is advantageous because it means that you can keep water in the base of the seed tray and retain a temperature that is likely to be a little bit lower around the 59 to 77°F (15 to 25°C) depending upon the particular conditions where you live.

What Is The Ideal Temperature To Germinate Seeds In?

There are a number of factors that can influence the ideal temperature at which seeds germinate which can include things like the amount of water present and the soil conditions however the University of California has put together a detailed list of vegetables and the preferred temperatures that they recommend based on their research.

However, as a general rule, most vegetable seedlings germinate between temperatures of 40 to 95F, however, there are some plants that do germinate at significantly lower temperatures than this which include things like lettuce, onions, and spinach. A comprehensive list of the University of California recommended germination temperatures is provided in the table below.

CropsMinimum (°F)Ideal Range (°F)Maximum (°F)
Beans, Lima60 75-85 85
Beans, Snap60 75-85 95
Chard, Swiss40 65-8595
Corn50 65-95105
Cucumbers60 65-85105
Eggplant60 75-8595
Garlic32 65-8595
Leeks32 65-8595
Muskmelon (Cantaloupe)60 75-85105
Onions32 65-85 95
Parsley40 65-85 95
Parsnips32 65-7585
Peas40 65-7585
Peppers60 65-7595
Pumpkin60 85-95105
Radishes40 65-85 95
Spinach32 65-7575
Tomatoes50 65-85 95
Note: Celery requires diffuse light and a night temperature from 10° to 15°F lower than the day temperature
for good germination. Optimal conditions are 85°F day, 70°F night with diffuse light and high moisture.

How To Make The Most Of Your Heated Propagation Space?

The heated propagation space that you have is extremely limited so there are several things that you can do to make the most of it. The first thing that we would highly recommend is that you utilize a well-known technique called multi sowing which is promoted heavily by the well-known gardener Charles Dowding. 

In this technique, he recommends planting certain crops in clumps rather than as individual plants which is what is most commonly recommended. This method is suitable for some vegetables but not all which include things such as onions, beets, and leeks to name a few. The number of seeds that can be planted in a clump will depend upon the particular vegetable as planting too many together will result in small vegetables. The number of seeds that is recommended per vegetable by Charles Dowding is provided in the table below.

VegetableSeeds per clumpDesired plants per clump
Basil3 or 42 or 3
Chard for salad/ to cook4/23-5/1-2
Chervil, coriander, dill, parsley32
Fennel, Florence31 or 2
Kale for salad43
Leek5 or 62 to 4
Onion for bulbs6 or 74 or 5
Onion for salad8 or 106 or 8
Oriental leaves to cook21
Oriental leaves for salad43
Peas for pods2 or 31 or 2
Peas for shoots4 or 53 or 4
Radish5 or 64 or 5
Rocket, salad and wild3 or 42 or 3
Spinach for salad43 or 4
Turnip53 or 4

Apart from maximizing the space multi sowing has a couple of other advantages which include Increasing the yield in a given area and also generally quicker to plant out into the garden compared to conventional methods. To see an example of this technique being used we recommend that you watch the video below by Charles Dowding.

The second thing that is highly recommended in cases where multi-sowing is not appropriate is to plant 2 to 3 seeds per cell to ensure that every single cell in your heated tray has at least one plant in it.

The third thing that we would recommend that you do is select only those plants which do require high levels of heat to germinate to put into the seed trays. Vegetables such as onions or leeks germinate at relatively low temperatures so the benefit gained is much lower than more heat-sensitive plants such as tomatoes or peppers.

Vegetables such as onions can germinate at temperatures near freezing which means that placing them into seed tray that is unheated but indoors will often be enough to get your seedlings started in the depth of winter.

The fourth recommendation we have is to try to select, where practical, vegetables that germinate relatively quickly to place into the heated seed tray only for a short period of time to simply get the plants going. They can be moved to an indoor space that is still heated but not as warm. There are a number of vegetables that are relatively slow to germinate, it is advisable to avoid planting them unless they are an absolute favorite vegetable in the heated space as they will prevent a range of other crops from being planted during this time.

To give a thorough understanding of how temperature influences the germination rate a table has been provided below which shows the number of days it takes for a particular vegetable to germinate at a given temperature. 

It is important to note that this table shows that the rate of germination can be significantly increased with temperature which means that the higher temperatures achieved by the ipower heated propagation tray will be quite advantageous in maximizing the output from your heated space.

Crops32°F 41°F 50°F 59°F 68°F 77°F 86°F 95°F 104°F
Beans, Lima0.030.517.
Beans, Snap0.
Corn, Sweet0.00.021.612.
Notes: 0.00 = little or no germination
— = not tested

I hope you found this article useful and have great success with your vegetable garden. If you have any questions or comments please leave them in the section below.

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Paul Smart