Heat mats needed?

[TacticalSpeed]

Are heat mats really necessary when growing seedlings indoors? If so, is also having a thermostat for each mat overkill?

 

[Chuck]

For tomatoes and peppers heat mats are VERY important when growing seedlings. If you can KEEP your soil temperature between 70F-85F you will be successful. But if your soil temps vary much out of this range you won't. Below 65F it slows germination a lot and 95F+ will basically stop germination. Once the seeds have sprouted and before the first true leaves appear a steady temperature is also important. I grow approximately 1500 tomato and pepper plants every year and a thermostat is not necessary where I have my seed tables. If you keep your ambient temperature around a low of 65F you will not need a thermostat. The soil temps in my seed cells never get above 85F. This year the outside temps dropped to 17F and my soil temps dropped to 71F. You must have a good soil thermometer. Keep a couple of seed cells filled with soil and watered the same as your seeded cells and take temps from these. Sticking a thermometer probe into a seeded cell can destroy a plant embryo and a seedlings roots. My seed tables are on an enclosed patio and the only heat is from a little tower heater.

 

[Meadowlark]

Are heat mats really necessary when growing seedlings indoors? If so, is also having a thermostat for each mat overkill?

The heat maps I use are set at 80 deg F. Thermometer never needed.

Are they necessary? No, but...

If you are willing to accept lower germination rate (sometimes significantly lower and even zero) and willing to accept slower germination times sometimes extending the time by several days and willing to lose seedlings at a rate far higher than otherwise, then they are not necessary.

 

[pepper2.0]

Personally I've never used a heat mat, they didn't even exist back when my dad was gardening and he never had a problem sprouting his seeds. I just keep the room at a comfortable temp and don't let it sway much, never had a batch of seeds not germinate and grow to a decent size to plant in the garden.. maybe one or two seeds out of 40 sort of thing don't pop. Just my opinion but I think a lot of the over priced garden stuff they sell these days is not needed unless growing tropic stuff that shouldn't be growing in a particular climate.

 

[oneeye]

In a commercial greenhouse, we used heating mats for Tomato, peppers, and many others. We used a "1020 tray" that contains 100 cells per tray. Used a vacuum seeder and put them on heating mates under T5 fluorescent lights on tables inside a big greenhouse. The greenhouses stayed full of plant trays. We had a 98% successful germination rate.

On the other hand, I plant a lot of seeds and never use a mat today. I put my cups under a 4ft four bulb T8 shop light on a shelf and use a timer. I have 100% success if the seed is good. I need to keep the germination area warm for at least 12 hrs a day and the light does that. It's okay for the temps to drop during the night as long as you regain your daytime heat. These peppers love the heat from the lights. These will be going to an indoor garden for a month and grow into plants and then outdoors in a few months.

 

[Oliver Buckle]

When I started I used to put seeds in a plastic tub with tissue in the airing cupboard, then the airing cupboard disappeared when we got a gas boiler. Then I built a box with a 40 watt incandescent bulb under in and put them on top, then they started making all new low led bulbs, and I got a heat mat. If the electric supply went I would put them in the corner of the hearth, not too near the stove. In other words, no, you can get by without one, and I reckon if push came to shove I could get by without any heating, they would just be a bit slower and later. After all, plants do grow naturally from seeds in the outdoors and if you give them a good start by digging and raking you get a good germination rate with most things, some even hate being germinated and transplanted unless you are very careful, I have had some right twisty carrots thinking I would help them along.

 

[Anniekay]

Are heat mats really necessary when growing seedlings indoors? If so, is also having a thermostat for each mat overkill?

I've never bothered with heat mats and my tomatoes, peppers and all grow very well without. My indoor thermostat is set at 68 degrees and that's plenty warm enough for germinating anything.

No heat mat and they are so big and full I'm running out of height with my grow light !!

 

[YumYum]

I've got a heat mat. I use it sometimes but most of the times I don't need it since it is warm enough in the house. Those heat mats only heat something like 10 degrees above ambient temp but I'd still want to use my thermostat with it. I've also used a heating pad on low and it surely does need a thermostat because it will cook them if you don't.

Some of the very hot pepper seeds could benefit from a heat mat since they take longer to germinate than the others. I don't grow those so really couldn't say how much.

 

[pepper2.0]

I'd like if someone could explain how a heat mat works. I figure if you set the thermostat to X degrees, and the room stays at that temp with maybe a couple degrees difference here and there, wouldn't the soil pretty much stay at the set temp of the room? If a heat mat keeps the soil at "x" temp, why not just set the house or room temp to that? For most plants like tomatoes it doesn't need to be crazy warm and usually there is a grow lamp right above it going a slight bit more heat to the top of the soil, the seed isn't usually planted very deep anyway.

I can totally see it being needed for some plants that require a lot of heat but not for average garden plants like tomatoes. If I am missing something I wish someone would explain, but that is how my mind see's it. And even if they require a lot more heat, why not just turn up the thermostat in that grow room? The residual heat in the room will keep the heater from running constantly.

 

[oneeye]

In a commercial greenhouse, we used heating mats for Tomato, peppers, and many others. We used a "1020 tray" that contains 100 cells per tray. Used a vacuum seeder and put them on heating mates under T5 fluorescent lights on tables inside a big greenhouse. The greenhouses stayed full of plant trays. We had a 98% successful germination rate.

On the other hand, I plant a lot of seeds and never use a mat today. I put my cups under a 4ft four bulb T8 shop light on a shelf and use a timer. I have 100% success if the seed is good. I need to keep the germination area warm for at least 12 hrs a day and the light does that. It's okay for the temps to drop during the night as long as you regain your daytime heat. These peppers love the heat from the lights. These will be going to an indoor garden for a month and grow into plants and then outdoors in a few months.

View attachment 106813

I worked as a laborer. The planting times were very important to match the photoperiod with the outdoor planting season. I had so much fun in those days I sure miss them. I can't hardly do a damn thang anymore.

 

[TacticalSpeed]

I've got a heat mat. I use it sometimes but most of the times I don't need it since it is warm enough in the house. Those heat mats only heat something like 10 degrees above ambient temp but I'd still want to use my thermostat with it. I've also used a heating pad on low and it surely does need a thermostat because it will cook them if you don't.

Some of the very hot pepper seeds could benefit from a heat mat since they take longer to germinate than the others. I don't grow those so really couldn't say how much.

I will be doing this in the basement. Finished basement, but still much cooler than the rest of the house

 

[Chuck]

https://sacmg.ucanr.edu/files/164220.pdf

 

[oneeye]

https://sacmg.ucanr.edu/files/164220.pdf

Wow, very valuable information. All my questions on temps were answered. Thanks, Chuck.

 

[Oliver Buckle]

https://sacmg.ucanr.edu/files/164220.pdf

The optimum is interesting, but looking at the max. and min. there is not much one would be likely to fail with.

 

[Chuck]

The optimum is interesting, but looking at the max. and min. there is not much one would be likely to fail with.

I have never had the opportunity to observe the max but I have on the min, many times. There are a lot of variables involved but I can say this. If you plant seeds at the min it is POSSIBLE that they will sprout but it is more likely that they will rot. When you are growing seedlings to sell you want every seed to germinate so it is ridiculous not to do everything one can to ensure the highest rate of germination possible and a heat mat does this. In my setup I do not need a thermostat. A quick glance at my soil thermometer and if getting too warm I just flick a light switch and they all turn off. I also have individual rocker switches on each heat mat and light for even more control of everything.