A light frost isn't going to be a problem for leeks or beets. A hard freeze may damage the beets (well, the leaves) but not a frost. I wouldn't worry about them.

Rodney

That's what I thought, but the plants aren't very large -- probably another month before harvest on the beets.

No you shouldn't just leave it in place. The purpose of them is to trap heat and keep the plants from freezing. So on a sunny day they still trap heat - too much in many cases - and can cook the plants. Air temps outside the cover may only be in the 50-60s but inside it quickly rises into the 80-90s or even more. You will need to either remove it or, depending on how you have it applied, work to vent it open somehow.

Dave

Typically frost blankets - like Remay or harvest cloth or fleece as the Brits call it - only offer a few degrees of cold protection, usually less than 15 degrees. But because it is fully porous/breathable, it does not heat up if left in place. It also does not block sunlight or rain. I would disagree that it cannot be left in place. It is often utilized in this manner to extend the growing season. It is essentially the same as row covers, which are used earlier in the season to keep insect pests off of young seedlings.

But if you are not facing ongoing cold nighttime temps and the potential for frosts, you really do not need to leave in place.

If it’s a predicted frost hard enough to damage my crops, I will just lay the cover directly on top of the plants, weighed down around the edges with logs, rocks, etc. It’s easily just rolled back in the morning. I also do this for deer protection during the growing season. Now, a low tunnel can be handy if the temperatures will drop cold enough to need it, say, below 20, as it provides even more insulation. Leeks are so hardy though, and I’ve read of many people overwintering them without cover as far north as zone 5. Never tried it myself. Beets are pretty cold tolerant for me as well. If it’s just a frost I doubt you’ll need cover. This is for fabric cover. As for leaving it on during the day, I do it no problem unless it’s just warm outside. I would not do this with plastic however...

Here, we may pick up a light frost or two beforehand, but the first real frost is predicted on Tuesday morning. I’ll probably just be leaving everything uncovered.

More to the point, if beets hit a hard freeze, and foliage is damaged, they'll come back readily. Overheating is really about sunlight. If it's cloudy, it will be pretty much the same temp under the cover as outside the cover. So be especially careful on sunny days.

I find that the frost cover is very WET after a frosty night. I hate to dry it, but would rather leave it in place if that is ok.

This is the breathable fabric-type cover, not plastic.

"This is the breathable fabric-type cover, not plastic."

That's fine - never use plastic - but you have to understand that the fabric stuff comes in at least 10 different weights (thicknesses) so no one rule can apply to all without knowing the specific product and weight used. Your degree of sun exposure is also a big variable. That's why I said it is best to uncover.

Usually the label directions will provide some guidance but if that is not available then you will have to experiment a bit to find what works best. You can either incorporate a MIN/MAX thermometer under the cover or you are going to have to do frequent checks on the crop for several days.

If you could incorporate hoop supports as with a low tunnel then it is easy to simply open the ends for venting during the day without removing the whole cover. Another alternative that sometimes woks is to cut some slits/flaps that can opened during the day for venting and then just flipped closed at night. All it takes is one exceptionally warm day in the sun to kill the crop so it is your choice as to how much effort you want to put into it.

Dave