hot cap

[Sly boots 9]

What is a hot cap? Is it like a plastic bag over the plant?

[Blues Ma]

Can be little paper domes to protect from night frosts and stretch your growing season. Gotta take 'em off when the sun comes up tho or the plants will cook.  

[Janice]

They have been around for years, but are pretty much a dome formed with a wire frame and waxed paper formed around that and enough of an extra fringe around the edges so you can plop the cap over the transplant, and then scoop some dirt up on that "fringe" to hold it in place. They're used to protect transplants from being frosted, and when put out early in the spring when the sun is weaker or it's cloudy a good deal of the time, they're also used like a little green house to allow earlier planting. But like greenhouses, they get hot fast under sunshine, so they're usually put over the plant you want to protect at night,then taken off in the daytime.. at least in the home gardens.

I have seen whole fields with hot caps over the transplants, but I think they were melons..and they left them on the plants ..until they were safe from frost..no on and off there!

Janice

[Bill]

I've seen the other two (at this point) replies. I want to add that locally to me (Detroit, MI) hot caps are sold as clear plastic domes (their actual shape is sort of squarish) with a generously sized vent hole in the top. There is no need to remove them during the day. These run a little on the expensive side at (IIRC) about 75 cents each in packs of 4, but they look like they will last several seasons so the price may well be justified.

I bought a couple dozen this year and they seemed to work as advertised. I set my tomatoes out April 15 and didn't lose any until I (erroneously) believed a NOAA weather report that stated a low of 34 deg F for the night.

Maybe it never went below that where they took their measurements, but I lost half my Druzba tomatoes and a couple of each of the other varieties to frost. From now on, no more taking chances. If the advertised low is below

40, I'm leaving the hot caps on.

Bill

[Pat Kiewicz]

Be wary of frost any time predicted low is less than 40 degrees and the sky is clear. Be especially worried if the DEW POINT is at or near 32 degrees. Get REALLY WORRIED if there is no wind. Radiative cooling can produce patchy frost even when the official, measured low is higher than 32 degrees.