Freezing Our Blossoms Off

Remember when it was in the 80s for two weeks and everything burst into bloom while I was at the beach?

Well, yesterday the temperatures plummeted, and in our backyard the low hit 25 degrees. That wasn't just a kiss of 25 and a quick warm-up when the sun came up, either. It was down to 32 at sunset, so it was at or below freezing for at least 12 hours last night.

Did I mention winds from the north gusting to 40 mph?

We knew it was coming (well, except for the winds, although given the windy weather history here, I suppose we should have expected that as well), so I was researching how to protect our tender fruit trees over the weekend. Because they are big (well, in general — ours aren't actually all that big yet), fruit trees are harder to protect than other tender plants that are low to the ground and can just get covered up. For example, our cold frame is easy:


Notice, though, that this time we used some leftover bricks as weights so the glass wouldn't blow away and smash like before.

For the trees, though, the first step is to figure out which trees were in danger. Further evidence of the greatness of Penn State? This excellent chart detailing all the stages of blossom development and the kill temperatures of each:


If you are at all interested in an orchard of your own, check out the link above to the full Pennsylvania Fruit Tree Production Guide.

Anyway, based on this information, our apricot in full blossom is vulnerable at 27 degrees:


Also, our heirloom apple that has one grafted section in "first pink" is vulnerable at 28 degrees:


The rest of the trees, though, didn't make the danger list (provided the forecast was correct). And honestly, I'm not sure what the howling winds add to that kill-temp equation.

But I do know that all that wind made it pretty effing miserable to try to cover up our plants yesterday afternoon. In fact, we were only able to cover one, because the wind was turning the covers into a wall that would push branches over, and we were afraid the branches would break under the stress. In the long run, that would be worse than one lost crop.

Here's what we ended up with:


The apricot was too tall to cover effectively, and the cover pressing in with every gust of wind would have knocked off most of the blossoms anyway. It got Christmas tree lights wound among the blossoms on every branch. The idea here (and I am not the first person to try this — Google it) is that the lights will give off just enough heat to keep the air around the blossoms a degree or two warmer. This is a game of degrees, so we're hoping it helped.


In addition to the lights, the apricot, along with the peaches and nectarines in the background, are surrounded by milk jugs filled with hot water. The idea here is that the bottles radiate heat in the space around the tree. Again, not much, but another degree or two of warmth should help. Each tree was also watered thoroughly yesterday afternoon, because moist earth will hold its heat better too. Would all this work better if the trees were covered to hold in that extra heat? Of course. But it couldn't be done in yesterday's conditions, so we are hoping for the best.


As for the apple tree, it is smaller, and Kirk built a mini-PVC hoop house around it, connecting the pipes with a four-way connector. We weighted the plastic with extra bricks and kept our fingers crossed that it would hold up in the wind.


Inside the hoop is a staked outdoor spotlight, which has a pretty powerful bulb. We're hoping that it helps keep the space in the plastic just warm enough to keep the blossoms from freezing. We also had to be careful to weight all the plastic near the light so it wouldn't blow onto the bulb and burn our tree down. That would be somewhat counterproductive.

This took over an hour of work in less than comfortable conditions. It may not work — I'm pretty sure the wind whipped away most (if not all) of the heat trapped by the hot water bottles around the uncovered trees. When I left the house this morning it was still 25 degrees, and the sun wasn't yet up. Kirk left the apple tented (though turned off the light and opened a vent in the plastic), and the apricot lights were left on for the day. I will check the damage when I get home this afternoon.

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