Gardeners' Holidays 2024: Harvest Home

Usually, the crop we're most excited about in September is the tomatoes. And they are doing pretty well this year; to date, we've harvested 9 big Pineapples, 61 Premios, 66 San Marzanos, and 490 little Sun Golds. But all summer rolled into fall, we found ourselves focusing more on a new crop: the potatoes Brian planted this spring in our old rain barrel. The plants, which were green and healthy at midsummer, began turning yellow and dry in August, and Brian figured he'd harvest them once the foliage was completely gone. But a little quick research showed that they're actually ready to harvest a couple of weeks after they start yellowing. In short, they were now as ready as they were going to get, and we might as well go for it.

After scooping all the mulch off the top of the plant and setting it aside, Brian began digging into the dirt itself, transferring it into an empty trash can as he went. And just a few inches in, he saw the first little tuber peeping out of the dirt. Unfortunately, it was green on top, meaning it probably wouldn't be safe to eat. (The green itself comes from chlorophyll, but it's a sign that the spud may also contain high levels of solanine, which is poisonous.) But we took it as a sign that there was probably plenty more where that came from.

Sadly, this was not the case. As he kept digging deeper and deeper into the barrel, he found almost no further spuds. Brian burrowed right down to the layer of rocks he'd put in the bottom of the barrel for drainage and unearthed only a scanty handful of potatoes—far less than we'd harvested from our 5-gallon buckets in 2020. The total weight of spuds we produced was probably less than that of the seed potatoes we put in.

So what had we done wrong? Why had such lush, healthy green potato vines produced so few usable tubers? We put this question to the Internet, which told us that the most likely culprit was over-fertilization—particularly the over-application of nitrogen at the time the potato vines were in flower. But that didn't make sense, since the only fertilizer we'd added to the potato barrel was a single bag of aged manure that we mixed in at planting time. Other possible explanations—poor soil, insufficient sunlight, too little water—also didn't fit the data. The plants had gone into rich, crumbly soil; we'd given them plenty of water; and their patio location provided a good 6 to 8 hours of daily sunlight. And the plants themselves looked healthy and vigorous, with no signs of disease or pest infestation.

But after a few dead ends like this, I hit on a site called Growing Produce. The author said her neighbor had a situation exactly like ours: his potato plants "looked great all summer, with vigorous and healthy tops," but produced "only a few small tubers." She immediately diagnosed the problem: His spuds were grown in containers, which "can yield poor results when high daytime temperatures warm the soil." The high temperatures "promote leaf growth at the expense of tubers," resulting in lush plants that are scarce o' tatties. According to the article, "The optimal temperature for tuber growth is said to be about 59°F, while for leaf it’s about 75°F." And according to my home energy use spreadsheet (yes, of course I track our home energy use on a spreadsheet. Are you really surprised?), the average daily temperature throughout June, July, and August of this year was consistently over 75—much more conducive to healthy leaves than abundant spuds.

In short, this potato-barrel experiment was probably doomed from the start. We might conceivably have better results growing potatoes in the ground where the soil would stay cooler, perhaps in the sloped part of the yard where they'd have a big thermal mass to protect them. But we'd have to plant them early, and there's still a chance that too much heat or too much rain would ruin the crop. We might give it one more try just for the hell of it, but we won't be getting our hopes up.

Fortunately, we have other crops in the garden that definitely won't be letting us down. Along with our trusty tomatoes, there are plenty of green beans, peppers, and, surprisingly, zucchini. Normally these summer plants are entirely played out by the time fall comes around, but this year they're still growing, spilling over the edges of the beds and into the paths, and producing healthy squash. And if we still want potatoes, our new local supermarket (which just opened this weekend, about 18 months after the old one shut down) has them on sale for just 30 cents a pound.