I am new(ish) to gardening, and last season attempted to do all my own starts instead of purchasing them. I admittedly did not plan well, started late, and didn't utilize my space.

This year, being much more organized I'm starting much earlier and have a better set up. I'm going to using heat mats with a soil thermostat, and LED lights along with the standard trays and dome.

The kicker is in the interest of space, I'm doing it in the garage. I live in the Bothell area, and am worried about my plants post germination. So the question would be, for some of the plants that I will need to start fairly soon like peppers and tomatoes, can I continue to use the heat mats to help protect the plants while being in the garage? My garage is insulated but it does drop below 50 at night. My plan would be to continue to use the mats but regulate the temp of the soil to much lower than germination temps, until the ambient temp in the garage is warm enough to maintain temps above 50.

First..

Second sounds like you have nice heat mats. Would you share which brand you purchased? I have a couple el cheapos and one broke the second time I plugged the mat in. I'm wondering if you'd get enough heat for the tomato plants if you tented them with the lights inside. I get that the lights are LEDs but my LEDs still put off some heat. My experience with starting tomato plants is growing in my basement on shelves with LED strip lighting. I start the seeds on the heat mat and then prick them out into cell trays. The temp stays above 60 most likely. When I leave the heat mat under the seedlings, the added heat has a tendency to dry out the soil so you need to really keep an eye on the soil moisture.

I think you do need some heat after germination because temps below 50 will stunt tomato plants. I'm not sure how you would provide this. I'm not sure leaving them on heat mats would be a good idea. I do like Thomases idea. He gives good advice.

thommesM said:First..

Second sounds like you have nice heat mats. Would you share which brand you purchased? I have a couple el cheapos and one broke the second time I plugged the mat in. I'm wondering if you'd get enough heat for the tomato plants if you tented them with the lights inside. I get that the lights are LEDs but my LEDs still put off some heat. My experience with starting tomato plants is growing in my basement on shelves with LED strip lighting. I start the seeds on the heat mat and then prick them out into cell trays. The temp stays above 60 most likely. When I leave the heat mat under the seedlings, the added heat has a tendency to dry out the soil so you need to really keep an eye on the soil moisture.

Well I don't know if they're good or not??? They had good reviews and the size was right. They are MET mats and I am using VivoHome thermostats.

Tenting is a good idea. I think I can make something up to test out. Thank you!!!

Good luck! Keep us posted on your progress.

BearDog1906 said:

Well I don't know if they're good or not??? They had good reviews and the size was right. They are MET mats and I am using VivoHome thermostats.

Tenting is a good idea. I think I can make something up to test out. Thank you!!!

If it has a thermostat, the heat mat is good in my book. Two thoughts on the tenting idea. Maybe you could use the heat mat as a heater for the tent. I personally wouldn't keep the plants on top of the mat in order to retain soil moisture. (I don't like watering every day or even twice a day) The other thought is to keep whatever you make the tent out of away from the light for safety concerns.

Good luck!

I was watching YouTube and a survival video came on. An idea struck me and I thought I'd offer it up. If you do consider making some sort of tent for protection of your tomato plants, you might consider making the tent out of an emergency foil blanket. The silver shiny mylar? material would reflect the light and heat.

Tenting is a good idea - but as you are using LED lights they - unlike incandescent or fluorescents do not produce any heat. Thus, it would seem that tenting would only increase the ambient temperature if the heat mats were in use, and who knows by how much. Or, perhaps you incorporate a separate incandescent bulb into the mix for warmth vs light.

For what it's worth; I germinate my seeds either in an unheated greenhouse or, for things like peppers, on heated mats and then move them to the greenhouse once the first set of true leaves have formed. Nighttime temperatures in the greenhouse frequently fall into the mid - upper forties. I have not noticed tomatoes being stunted with such cruel treatment.
Finally, I would suggest choosing varieties suitable to your cooler and shorter growing season and start the seeds a bit later. I cannot speak to their flavour but varieties such as early Cascade were developed for your PNW climate.

I always think that starting seeds too early is a bigger problem than starting them a bit too late - seeds germinated a bit late and grown more healthily will catch up faster than you think once planted out into warm soil and sunshine.

Good Luck.

I have LED lights. No seeds started yet but I'm using my setup to help along some new succulents. My basement was dropping to 58-60 at night so I decided to put the greenhouse cover on the setup. Even though the lights are LED it stayed warmer inside than the rest of the basement. So your lights might keep the temp above 50, depending on how cold it gets.

The LED lights will produce some heat, especially if they're purpose-built grow-lights (they have the big heat sinks on them). I've found that even LED tubes that replace florescent tubes in shoplight fixtures produce some heat. A cheap setup would be to buy two or three panels of 3/4" rigid insulation and build a closet with a clear plastic curtain on the front. A single 40W incandescent bulb would heat it nicely. But remember that once the tomatoes germinate they like cool temperatures. Around 60F is often suggested. I really wouldn't want to keep them on the heating mats due to possibly encouraging rampant root growth that could make them root bound before they're ready to go to their "forever home".

Also, I quit using heat mats last year after walking in and finding my germinating tomato seeds about to roast. The mat was one of the import "stick a name on it" thin black mats that was supposedly thermostatically controlled. But, just to be safe I put a "stick a name on it" thermostat inline for a failsafe. I quit using them all and the seedlings did great! Just keep a watch on them.