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Mailbag: How hot is too hot for seed germination?

Dear Jessica,
I returned to Long Island a couple of months ago to help out at home, where my mother is the primary caregiver for my father, who is in the later stages of Parkinson's disease. My brother lives in the house next door to my parents, and he has given me free rein to plant a vegetable garden there. I have wanted to plant a garden there for a couple of years, as cooking has been a hobby of mine since I was a kid. Five years ago I started making my own barbecue sauces, then the next year I was canning my own jam, then chutneys, pickles, rubs, curing my own salmon, etc.
I have started bell, poblano and jalapeno peppers from seed using Jiffy's seed-starting pellet kits. I planted my first peppers on St. Patrick's Day, and I have kept the flats on top of my hot-water heater in our furnace room. Since then, I have started tomatoes, along with a few other vegetables and some flowers (snap dragons, etc.). The hot-water heater is warm to the touch, which leads me to believe that it is over 100 degrees. It's not scalding, but I would say the temperature is cozy. Is this an ideal environment for seeds to germinate? They are protected with the bottom tray as well as the majority of the height of the saturated soil pellet. Moisture is kept in by the well-fitting clear plastic lid.  People specifically buy heat pads to keep under the flats.  I'm just wondering if this is too hot, and what you'd suggest as an alternative.
-- John Menacho
Hi, John.
One hundred degrees is way too hot for seeds to germinate, and may very well kill them. The ideal temperature for germination is 78 degrees, which is how warm the commercially available seedling heating mats get. You might consider placing them elsewhere in the boiler room, but not directly on top of the heater.
Good luck -- and consider joining my Great Long Island Tomato Challenge this summer when those tomato seedlings produce fruit. Watch the column for details.
Best to you and your family,

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