The first time I visited “the farm that would later become Terra Firma” was early February of 1992. Among the other activities that were happening that day, the crew was planting potatoes: dropping the cut pieces of potato (aka: “seed”) in the ground and covering them with soil. It was a warm, sunny and dry day. A few days after I visited, it began to rain and basically didn’t stop for the rest of the month. By the time I started work at the farm in March, those “seed potatoes” had rotted in the cold, wet soil. The crop had failed due to wet weather.
For many years after, we would wait to plant potatoes until mid-February or later, depending on the weather forecast. Wet weather is not the only threat to potatoes: the leaves of potato plants are sensitive to frost, so you can’t plant them too early or they can be killed by freeze after they emerge from the soil. And potato seed is expensive and only available for a short time each year in the spring. Losing an entire field to the weather means not just losing money, but not having enough — or any — potatoes to sell that year.
Fast forward almost 30 years to 2021. We started planting potatoes this year the first week of February, and it has barely rained since. In fact, we’ve been irrigating the potatoes since the day after they were planted, almost continuously. With three full months of warm, dry weather, the potatoes sprouted and grew quickly. I’ve been digging up a handful of spuds to eat here and there for a month now — checking the crops is part of my job but also has side benefits. Last week, we mowed a few of the earlier maturing varieties and today we are harvesting them and sending them along in your CSA boxes.
This is the earliest date we’ve ever harvested potatoes at Terra Firma. It’s partially due to the varieties: today we are harvesting Red Norland, which we have not grown in twenty years. The yellow potatoes that we mostly grow mature a few weeks later. But it’s also due to conscious adaptation to climate change.
Since that failed potato crop in 1992, the weather has changed dramatically. We used to plant potatoes through March and into April, and harvest abundant yields into August. But in the last ten years, planting later than February has not produced good results. Potatoes don’t like hot weather at all.
Potato plants will stop producing tubers completely when the soil temperature reaches 85 degrees. That routinely happens here now by mid-June. We can slow it down somewhat by wetting the soil frequently with sprinklers, but once it gets really hot the only difference that makes is that the potatoes “steam” instead baking. Soil temperatures don’t rise dramatically when you get one or two hot days. It takes weeks in a row of hot, sunny weather without clouds and rain. We never had much true “spring” weather here, but in the last ten years hot, sunny weather has been arriving sooner and winter ending earlier. This is shortening our window to grow potatoes successfully. By getting them all planted in early February, it gives the plants a little more time to produce tubers before the soil heats up too much. Next year, I’m going to work with our seed supplier to try to procure some just after New year’s and try to get them planted even sooner.
This year, we will likely finish our potato harvest completely by the 4th of July. The spuds store nicely in the cooler and you should see them in your boxes into October. Beyond that, we’ve been working with small growers on the coast and in the foothills whose weather is more conducive to growing potatoes later in the year. They have been growing potatoes that they harvest in the fall that we’ll be putting in your CSA boxes until early winter.
At some point in the rapidly warming future, we may decide that our shrinking window to grow potatoes has finally shut completely. Until then, we will do our best to grow a nice crop of spuds every spring.