Most staples are laborious to get from the ground to a form that you can use in the kitchen. Wheat, for example, takes a lot of work to dry and thresh and grind into flour. Potatoes, by comparison, are not only easy but the harvest can be as fun as finding treasure.
What follows is what I’ve learned about when and how to grow potatoes in Southern California, after having grown them for many years in different yards in the region.
When to plant
The best planting time is February. But I think of potatoes as having two seasons here — one is August into early September for a late fall or early winter harvest, and the other is February for a late spring harvest.
While I’ve certainly gotten good crops out of planting in August, I’ve gotten consistently better crops from February, for a couple reasons. Growing from February takes advantage of the rainy season, so less watering is necessary. February planting also requires less attention to the plants generally. For example, my last August crop suffered from spider mites because I used drip irrigation and there was no rain to wash the foliage off and I failed to bring the hose out to give the plants a shower frequently (mites infest dry, dusty foliage).
What’s a “seed” potato? It’s just a potato, really, except that it is intended to be used for planting instead of eating. You can buy potatoes that were grown specifically to be used as seed.
Or you can buy potatoes at the grocery store or farmers market, go home and stick it in the ground and thereby have turned it into a seed potato. When I do this, I try to buy organic because they are probably tougher tubers, not having been protected and pampered through their growing life by the more powerful fungicides and insectides that conventional farmers use.
Many sources claim it’s vital to use seed potatoes that are certified disease-free, but for so long I’ve grown some of those alongside potatoes that I bought from the grocery store, as well as potatoes taken from a previous harvest of my own and used as seed. And I’ve never noticed a significant difference in plant performance or tuber yield.
I’ve also found the claim of needing to chit, or pre-sprout, or “green sprout,” the eyes on the seed potatoes overemphasized. When I plant a seed potato with eyes a half-inch long compared to a seed potato with eyes that haven’t sprouted, they both grow well. The seed potato with half-inch eyes just emerges sooner, that’s all.
I suspect that it might be more important to chit seed potatoes in colder climates since those growers are more likely to plant into colder, wetter soil, which makes it more likely that the potato will rot in the ground before growing. Here in Southern California, the soil temperature rarely gets below 50, and in most years it does not stay consistently wet because we don’t get that much rain.
An exception may be if you’re planting into heavy (clay) soil. That is not ideal potato-growing soil. If I were planting into clay, I would wait until my seed potatoes were showing growth. (I would also not plant deep.)
A unique challenge for us Southern California gardeners is that seed potatoes are often not available for purchase when it’s our ideal planting time (February or August). Seed potatoes are usually not available for purchase until March, and they’re sold out in summer, and then some nurseries get new stock in November or December.
What to do? Either plant a bit late, in March, when the seed potatoes arrive. Or, buy the new stock around December and keep it until February; you can even plant it before February if your garden never gets frost, but be aware that potato foliage is very sensitive to cold temperatures. Or use seed potatoes from the grocery store, which are almost always available. Over time you might also curate your own seed potatoes from previous plantings.
How to plant
When planting, you only need to bury the seed potatoes so their eyes are covered. It’s not necessary to bury them any deeper. I used to bury them deeper, but it never improved yields and it only made me dig deeper to harvest the potatoes. I now usually plant the potatoes so there’s about two inches of dirt covering them. (One exception is for August planting, which I’ll explain below.)
You’ll notice that I didn’t cut up my seed potatoes above, as is often suggested. Mostly, I don’t do it because it’s more work, but sometimes I do it if I don’t have enough whole seed potatoes for the space I want to plant.
Until plants emerge, the soil around the seed potatoes only needs to be slightly moist. In other words, don’t keep it saturated. I’ve made that mistake in the past and rotted the seed potatoes.
For the August planting window, many times I’ve had good results planting right at the base of recently harvested corn. This has become a regular rotation in my garden. In the spring, I plant corn one foot apart, and then in August after the corn harvest, I plant a potato near the base of each corn stalk — so, also one foot apart. The results have always been good. Potatoes seem to like following corn.
Another reason that this seems to work well is that the corn has been shading the soil during the heat of summer and potatoes don’t like to grow in very warm soil. Think of the places we associate with potatoes: Ireland, Idaho, Peru up in the Andes. They are all cool locations. So for that August planting, if I don’t put the potatoes under corn, then I usually bury them a little deeper than two inches because the soil is cooler down there.
I also often plant my August potatoes under fruit trees rather than in a garden bed because it’s cooler there and it saves space. When I say “under” I mean they’re usually tucked just under the south edge of the tree’s canopy.
(See my post, “Growing vegetables under fruit trees.”)
Over the course of the plants’ three to four months of life, it’s usually necessary to mound up a little dirt or lay some mulch or compost around the base of the plant because the potatoes develop there and you don’t want them to be exposed to the sun. If the potatoes are exposed to the sun, they turn green.
I usually heap up some dirt or mulch on them twice — once when the plants are around six inches tall, and then again when the plants are about a foot tall. If I see a tuber showing at the base of a plant at any time, I’ll cover it immediately.
These days I use in-line drip emitter tubing where the emitters put out 0.5 gallons per hour and are spaced one foot apart. I plant each seed potato one foot apart so there’s one emitter per plant. At first, I wasn’t sure this would saturate a big enough area in my sandy loam soil, but it works just fine. While small, potato plants don’t need much water. But once the plants are about a foot tall, I give them approximately as much as most other vegetable plants of the same size.
At the beginning of each of my drip lines I have a shut-off valve so I can quit watering the whole row of potatoes once the plants are full sized and the leaves are starting to yellow. (Sometimes, potato plants flower before their foliage begins to yellow.) That’s the indicator for harvest time: the potato plant foliage starts dying.
Harvesting is easier when you can dry out the soil around the potatoes for at least a week or two prior. The tubers then pop out of the dirt very cleanly — no cakey mud on them that needs to be scrubbed off.
If you really want to eat some potatoes before the plant’s leaves have started yellowing and dying, you can. Harvesting early like this is called harvesting “new” potatoes. The tubers will be smaller and more delicate, and the skin will peel off easily so be gentle.
Not all potato plants flower, but if one does, that indicates that the tubers are probably at least the size of ping pong balls.
From a February planting, most potato varieties will be totally mature and ready for harvest in late May or early June. From an August or early September planting, they might be ready around Christmas.
Storing the harvest
Potatoes like to be stored in soil-like conditions. That means cool, humid, dark.
If harvesting in winter, you can actually leave the tubers in the ground for weeks and “store” them there. I’ve done this many times.
For the May/June harvest, it’s harder to keep the tubers from sprouting for more than a month or so. Putting them in paper bags in the fridge works, if you have room. Putting them in a cupboard on or near the ground is second best.
Potatoes may not keep as long and as easily as wheat, but at least they’re easier to harvest and eat!
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