Gardeners' Holidays 2019: Plumfest

Since I first introduced the idea of Gardeners' Holidays back in 2013, I've celebrated the August holiday under a variety of names. For the first couple of years it was Squashmas, a celebration of zucchini, which reaches its peak in early August (assuming the squash vine borers don't kill your plants before that). But in subsequent years, other crops frequently displaced the zucchini, turning August 1 into a celebration of cherries, tomatoes, or cucumbers. And this year, a new crop is taking center stage: plums.

This is a big change from last year, when a combination of brown rot and the depredations of squirrels left us with virtually no plum crop at all. (I think we may have managed to harvest two Opals.) So we decided to get serious about protecting our plums, developing what I think of as the 3-Point Plum Plan: pruning, spraying, and wrapping the trees with paper coated in Tree Tanglefoot to deter the squirrels.

This plan turned out to be a mixed success. Though Brian diligently sprayed the plums every week with the new Serenade spray we bought, many of them still turned brown, withered, and fell off the trees. However, early in the summer, he ran out of the Serenade spray and, rather than buy more (since it didn't seem to be working all that well anyway), he switched back to the copper fungicide we'd used the year before. And this actually seemed to be a lot more effective. It hadn't worked very well the first time, but that was when Brian was attempting to apply it with an ordinary spray bottle, which couldn't reach most parts of the tree. With our new sprayer, which attaches to the hosepipe, he was able to apply the fungicide much more thoroughly. We were still seeing a few plums rot, but a much larger percentage of them were actually surviving long enough to start ripening.

This, of course, was the point at which the squirrels stepped in. Well before the plums were actually ripe enough to pick, they were scampering up the tree to snatch them. We tried girdling the trunks and the largest branches with strips of paper coated in Tree Tanglefoot, and this apparently did catch them a few times, as we found tufts of grey fur sticking to the strips on more than one occasion. But we couldn't block every single branch this way, so those crafty rodents just found new routes to the plums, leaping over and around our improvised barriers to reach the fruit. Often they would leave the half-eaten carcasses of the unripe plums scattered at the base of the tree, as if to taunt us. We quickly concluded that if we waited for the fruits to ripen fully on the tree, we'd never get to taste any of them.

Now, it is apparently possible to pick plums when they're slightly under-ripe and ripen them indoors. But how under-ripe is "slightly"? Despite diligent searching, I couldn't find any information to tell me just what was the earliest stage at which plums could safely be picked. So Brian decided to figure it out by trial and error. He picked a mixed batch of plums—some from the Opal tree, some from the Mount Royal—and set them downstairs in the laundry room (the coolest room in the house) to see if they would ripen.

The red Opal plums, which had been ripest to start with, obligingly ripened right up over the course of the next week or so. So, eventually, Brian went out and picked all the ones that were left on the tree, about 35 plums in total. Compared to last year's pitiful crop, it was a pretty good haul, and the plums were quite tasty, with sweet-tart, juicy yellow flesh. However, the purple Mount Royal plums from this batch were much less cooperative. They stayed obstinately hard for weeks, then suddenly turned to mush apparently overnight. Clearly, they hadn't been ready for picking.

So, about a week and a half ago, he picked a second batch and stored them in the same way, testing them periodically to see if they were actually ripening. This time, it worked out much better. He tried one Thursday morning and found that, while not quite ripe yet, it was almost there—and definitely riper than it had been when he picked it. So he decided they were ready, and went out and picked all the literally low-hanging fruit off the tree. He went out with our big 6-quart mixing bowl, and came back in with it piled high with plums. And that was only the first installment. He went out again that evening with the stepladder and filled the bowl a second time, and he made another trip out just now and climbed up the tree itself to get all the remaining plums that he could reach—maybe another quart or so.

So all told, we've harvested over 13 quarts of plums from the Mount Royal tree alone, plus the 35 Opals. (The plums on our third tree, a Golden Gage, are still green, so we don't know when we'll be able to pick those.) We've already eaten all the Opals, but if we succeed in ripening up all the Mount Royals, we'll have far more than we can possibly eat fresh. Even in the fridge, they'll only keep for about two weeks, and this is definitely more plums than we can consume in two weeks. If we want to enjoy the fruits of our labors, we're going to need some means of preserving them. And since we don't have a chest freezer or a food dehydrator, that probably means canning.

A quick search led me to this recipe/monograph on "awesome plum jam" on Serious Eats, penned by Kenji Lopez-Alt, who certainly should know what he's talking about. The recipe calls for a food mill, but he says earlier that using it is an optional step if you "like a bit more jamminess to your preserves." So we could make the recipe without one and just have chunkier preserves. (We'd also add what he calls the "optional" step of adding lemon juice to make sure the preserves are acidic enough to combat botulism, because we wouldn't want to take chances with that.)

So we've got a suitable recipe; the problem is the canning process itself. We don't have a pressure canner, and our little pressure cooker is too small to handle more than one jar—and even if we do our jars in a water bath, our biggest pot can only accommodate three quart jars or four pint jars at a time. But the biggest problem is that, every time we've tried it, we haven't actually managed to get the jars to seal. Brian thinks it might work better with small jars rather than big ones, so we'll try that, but that means we won't be able to process as many plums at once. So preserving this volume of plums will be quite a process, most likely requiring us to make and can multiple batches over the course of a single weekend. Watch this space for a future post on how that goes.