![\"Cold](\"https:\/\/www.tomgrimshaw.com\/tomsblog\/wp-content\/uploads\/2026\/04\/Cold_Frame.jpg\")
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A cold frame is a bottomless box with a salvaged window on top. No electricity. No heater. About fifteen dollars in lumber and a window someone threw away.<\/p>\n
The glass traps solar heat and raises the temperature inside enough to start crops six weeks before last frost and keep them going six weeks past first frost. Three extra months of food from a box you can build in an afternoon.<\/p>\n
The whole thing is four boards screwed together with the back taller than the front so the glass slopes toward the sun. The window sits on top \u2014 hinged or just resting there. The box sits directly on soil. That’s the entire build.<\/p>\n
What grows inside one:
\n– Lettuce \u2014 cut-and-come-again greens starting in early March
\n– Spinach \u2014 stays cool enough that it won’t bolt
\n– Radish \u2014 ready in under a month, sow a new row every two weeks
\n– Kale \u2014 frost actually sweetens the flavor
\n– Carrots \u2014 slow but protected from freezing soil<\/p>\n
The one thing that kills seedlings in a cold frame isn’t cold \u2014 it’s heat. On sunny days the interior climbs fast. Prop the window open with a stick when it’s warm and close it at sunset.<\/p>\n
Four boards, one window, twenty screws. Your cold climate neighbors are still waiting for late spring.<\/p>\n","protected":false},"excerpt":{"rendered":"
A cold frame is a bottomless box with a salvaged window on top. No electricity. No heater. About fifteen dollars in lumber and a window someone threw away. The glass traps solar heat and raises the temperature inside enough to start crops six weeks before last frost and keep them going six weeks past first … <\/p>\n