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Anyone REALLY save fruit crop from freeze w/ frost blankets?

Posted by fabaceae_native (My Page) on
Fri, May 17, 13 at 15:26

I'm starting to think that covering a blooming fruit tree during a late spring freeze is just wishful thinking.

The only time it has 'worked' for me was when the temps did not go too low, in which case everything that was not covered fruited anyway (read: covering was useless).

This year I covered a miniature peach tree in bloom (that had awesome peaches last year) with a tripod and three frost blankets with a space heater underneath. I have absolutely no doubt that this setup kept the tree well above the ambient temp, and although the blossoms did not show any damage right away, they have since shriveled and fallen, with no sign of fruit set.

Don't get me wrong, I'm not trying to refute the fact that covering offers some protection, and I've definitely seen it work for tender foliage of various species, but with fruit trees perhaps the temp gain is so minimal that it is practically useless.

I'd like to hear some hard evidence for this either way...

Follow-Up Postings:

RE: Anyone REALLY save fruit crop from freeze w/ frost blankets?

  • Posted by fruitnut z7b-8a,4500ft SW TX (My Page) on
    Fri, May 17, 13 at 16:12

I saved persimmon with a tarp and 1500 watt heater against 24F. This is a pretty big tree, about 7ft wide and tall. So it takes a big tarp. Two nearby unprotected trees lost all fruit and leaves.

I saved grapes from the same freeze by covering and heat.

Saved 15 inch tall sweetcorn by heavy covering without heat. A very few leaves were frost marked. Was covered with cardboard, blankets, and refectix insulation, three layers overhead and two on the sides. It would have taken very heavy and many layers frost blanket to save this crop from 24F.

Wrapped one jujube graft breaking bud with three layers of row cover. It was killed by ~28F and hasn't sprouted back. Other jujube grafts covered with heavy black barrels survived 28F but not 24F later on. It took blankets and another layer to save those.

I think the frost blanket by itself is effective only on low growing veggies with warm soil close at hand. I think fruit trees are too high to benefit much from frost blanket.

An air tight covering has usually worked for me with sufficient heat inside. 750-1500 watts for medium size tree and 100-250 watts on a small tree.

RE: Anyone REALLY save fruit crop from freeze w/ frost blankets?

I saved my figs a few nights ago with tarps and no frame. You need to have the covering spread out below to capture rising heat from the ground. Because I didn't use a frame I lost anything touching the tarps. Uncovered figs a few yards away (nursery trees) were fried.

RE: Anyone REALLY save fruit crop from freeze w/ frost blankets?

You both have pretty much confirmed my suspicions, while also providing the evidence that it is possible. Now I'm not sure if I will continue to try covering my peach and apricot trees, unless maybe the temp is not expected to go much below the critical point. Maybe I'll try a tarp where I use the heater method next time.

RE: Anyone REALLY save fruit crop from freeze w/ frost blankets?

Air movement is used to protect orange trees from moderately low temperatures. My mother believed that old-fashioned Christmas lights with no cover saved her apricots some years.

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