Basic but workable. Here's a method from a Countryside Magazine from the 1970s. Get two sheets of Tuff-R 4' by 8' insulation. It's a foam insulation with aluminum foil on both sides. Take one sheet and score it into 2' sections so you can fold it into a box. Cut two inside ends to fit inside the box with cutouts at center top to allow a standard 4' florescent light fixture with grow lights to rest in the top. You need florescent lights to generate the heat as well as light. Cut second set of ends to fit the ends of the box and make a cutout on one side to insert the light fixture. Leaving one long side to open as a door, duct tape all seams, tape over the light end and tape the edges of the door. I've been able to hold 94 degrees F in a cold drafty basement and sprout tomato seedling in 3 days. Keep a jar of water inside for humidity. You can also do the same thing with an old upright freezer turned on it's side but I haven't tried that personally.
I will be using peat moss and last fallen leaves as bed for the sprouts/plant roots to hold moisture, prevent early weeds and give the plants a bit of extra warmth against the deeply cold soil from this winter. This should also give us a second crop of salad tomatoes, small peppers, maybe some more beans. Brussels sprouts (really good when fresh!) are hardy and grow late anyway. Nothing like picking fresh sprouts in a snow-buried garden in late January! Sauteed in butter and garlic...Mmmmm!!! Nice winter treat! Garlic will winter over in the soil. Mrs Alton wants to plant lavender this year so I'm going to try my hand at oil extraction for an essential oil which we use anyway.
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