Tenting with clear plastic only gives 1 or 2 degrees protection. You do need to either add heat inside, or use something a lot thicker. Old blankets and quilts are better. A couple of layers, with a dead air space in between, will help, too, if you can do that. If you do use tarps or plastic, be sure they are elevated off the majority of the plant, or the frost goes right through them.

A different option is to spray everything down with water just before dark, and then do it again in the wee hours of the morning. That helps, because water releases heat as it freezes, and ice is an insulator. If you do that, though, a word of advice based on experience -- drain your hoses and take them inside with you after you spray in the evening, or they will be too frozen to use in the morning hours.

Good luck. I'm pretty much resigned to just losing stuff. I looked at Asian Pear blooms yesterday, I'd say about 1/4 of them were black inside, the trees are in full bloom. If it holds at 28/29 tonight, some might squeak through. If it goes lower, adios.

I think this is going to be a very bad year for fruit production in the midwest/northeast. 90 in March, 20s in April. Just as I feared.

Cover and heat is best in most cases. But beware of leaving clear poly on during sunny days. I killed the fruit once that way by excessive heat.

You might consider PVC or thin wall conduit for the support unless you have something already on hand.

I believe tenting gives more protection than that if you do a good job of sealing it at the base so heat from the ground is captured. I know I get more like 5 to 6 degrees improvement in my tall unheated greenhouse.

I'm using old blankets, sheets, etc... I try to stay away from plastic.

One option I'm throwing around is butchering a few of these apricots back... Since I lose all the fruit uncovered, I might as well prune the heck out of them (they need it bad...lots of long wood with fruit only at the ends of the branches)... and then cover them. I'm going to start collecting blankets today...next week looks brutal.

I'm building a whole cover for the cherries. I'm not losing them.

My greenhouse covered with double layer inflated poly only gives a few degrees of protection without heat. On a clear night in winter it's almost none. But now it's warming to 88F by day and that gives about 3-5F protection at night. That's all I've seen on pretty good temperature sensors.

denninmi, fruitnut ,harvestman , Thank you all for your help.

I do have several 2x 4 8' wood on hand which I plan to use. My plan is to staple a sheet of 2 ml. clear plastic on the wood, all the way to the ground to catch some groud heat. The ground is warmed up despire the freeze air temporature. Then I staple the plastic all the way up , only leave just about an inch to the top for heat to escape in the sunny day . This will protect the plant from the wind and get warm in the day. I do have a old movers blanket that I can put it to the teepee too. But I don't have enough to cover all.

So far I got the lowest at 36 at nigth which will not be problem for the young fruit. but tomorrow night will be in upper 20s, at least this was forecasted, which is the big problem. I still keep my fingers crossed that weather man might say lower 30s in my suburb tomorrow. The lowest temporature does not last very long at night so raise few degree of temporature might do the trick.

Spread water also help depends how low and how long the temporature will go. If the temporature does not go down too far, I can go to Walmart to get 3-4 large gabage can putting around the tree. Then fill all the gabage cans with warm water in later evening for it to release heat during coldest night. Garage can is about 3 ' tall and my fruit tree is about 4-5' so the water heat should be able to reach the top. This should work well if all the gabage cans are inside a teepee. Welocme anyone might want comment/add on this method.

Thanks for remind the PVC pipe contruction. it is very clever way. You can put one together fairly fast and easy, and take it down when it is not in use, and does not take up much space. I read something like that and visited a website, and saw some drawings for various projects. I haven't figured out what willl be the most optimal structure shape to build that will accomadate a smaller tree now and a bigger tree in few years. I am not talking about the height, I can also swap a 10 ' tall PCV to replace 5' tall one.. I am talking about the branches. Don't want a strange looking , huge monster in the yard that neigbors might raise issue, but large enough to cover most of the branches. Also PVC pipe is light weight, If the structure is too large, it increase the chances of catching the wind , might be blowed away even with bricks to hold it down. I don't know where you folks live. Where I live, anything permnant will need a permit so the PVC structure has to be temporary, removable.

I know I will be very busy tonight. THG, I am off tomrrow for Good Friday.

Frank, how far along are your cots?

Some are the size of a dime...it doesn't matter because they'll all be dead by next week at this time, unless I can figure out how to protect them.

I build my teepee covered with 4 mil plasticsheet Thursday night. We did had frost last night but the lowest temporature only went down to 34 degree around 5:00am.I don'tthink I have major frost damage but there are more frosty nights left in the season,The teepee defintely helped.

It must have been colder here than in WI. I have not seen any cot trees yet, but it was a regular 25F, 3 hr freeze.

I wish there were better data on how much cold developing fruits can take.

ltilton:

The data on freeze damage from MSU, I'm sure you've seen it, is excellent and in my extensive experience with spring freezes, very close to real world. Don't know how you could ask for more.

ltilton-

I think it depends somewhat on how long you spend under 28F.

I was 31F here this morning...but I'm worried big time about next week. I plan on building a high tunnel over my sweet cherries this weekend.

I'm in Madison and I didn't see any frost. Luckily my trees are on a hill so I think they're still okay. But next week isn't looking good right now with three nights below freezing in a row. My apricots are just past petal fall with tiny fruits, my plums are almost to petal fall, my peach was in full bloom but had been open for a few days. I'm ignoring the cherries as my Lapin is too young anyway and Danube never gives enough to do anything with.

Athena-

Sparta, Volk Field and Black River Falls all were at 21F this morning. I see MSN was 26F, but I think the airport sits away from the city in a colder site. My yard isn't great (flat), but I'm not the lowest spot in the neighborhood. I was down to 27F a few years back in April and didn't have much damage.

I think next week Tues/Weds looks the bad night here. Winds should go calm at some point and that is when temps can plummet.

fruitnut - the MSU chart doesn't go past petal fall and shuck split.

Frank - the Madison airport is on the other side of town from me and is usually colder. The local abc station said it was 30 degrees at 5am and they're much closer to me. I think I would have seen more frost at the bottom of the hill if it had been much colder than that.

The local paper did have a great article about what the larger vineyards and orchards are doing. They're looking at possibly losing thousands of dollars.

Here is a link that might be useful: Fighting frost with fire

ltilton:

On my chart the last stage is post bloom. I've had damage as warm as 30F at that stage. But a degree or two can easily be measurement error.

As the tree leafs out, one does start getting protection from the foliage overhead. That helps on those quick radiation freezes that are common late in the year.

Here is a link that might be useful: MSU freeze chart

One easy trick I stumbled upon was to build the simple teepee with wire or tomato cages or anything you have on hand and then drape a tarp (plastic or fabricc)over the teepee and extend it out in all directions away from the plant. If you have bushes or small trees in a row and really big tarp just drape it up and over what you can and then lay the rest of it flat against the ground. The soil will give off heat at night and the heat will collect in the tents made by the small trees. There can still be some frost damage where the leaves touch the plastic but it is amazing how much green you can save.

fruitnut - my question is, is the post bloom damage threshold the same from petal fall to harvest size? As the fruits develop and grow larger, are they more vulnerable to frost? Or not?

Thru the spring freeze period the green fruit is all about the same. I've had it frozen out at one inch size. Some damage at 30F. Near total lose at 28F. It's all about the same after the blossoms open. Before the blossoms open they are much more freeze tolerant. And before they open the blossoms can actually reharden. The increase in frost tolerance is brought on by a couple days in the 30s and 40s before dropping lower. The rehardening is likely brought on by a decrease in water content brought on by cold just above freezing.

Sounds like the tart cherry crop in Michigan is about toast. Some farmer said last year he harvested 300,000lbs and this year he probably won't harvest anything.

Fruitnut, The MSU freeze chart is very helpful. Thanks for posting it.

Was just checking hx and see we got down to 27F a couple days ago. Does the damage show immediately? I didn't see any damage to mine.

Damage shows immediately if you cut into the fruit. There can be some damage that doesn't show until later. But if it were of any real significance it should show up within minutes or hours after thawing.

Thanks fruitnut, but we are still in the blossom stage here. Will a freeze cause visible damage to blossoms?