Who doesn’t love a good tuber, whether it’s the sweetness of baked sweet potatoes or the crispy-hot goodness of french fries?
In Southern California, tubers can be grown quite easily. We asked experts for their tips on how to grow potatoes as well as sweet potatoes.
In Southern California, potatoes can generally be grown in both the early spring and fall. Some gardeners plant potatoes around February for a summertime harvest, and again around August for a fall harvest.
Maddison MacDonald is the potato tissue culture technician for the Seed Savers Exchange, a nonprofit dedicated to the preservation of heirloom seeds based in Decorah, Iowa. She’s responsible for maintaining the health of 700 potato varieties and 70 sweet potato varieties and helps grow out the potatoes and sweet potatoes that the Seed Savers Exchange offers yearly.
Potato plants grow from the eyes, or sprouts located along a potato, so one of the common ways for gardeners to grow potato plants is to order seed potatoes that are specifically meant to be planted so their eyes can grow potato plants.
MacDonald said that after ordering seed potatoes, gardeners should give them a chance to sprout by putting them in a warmer area out of direct sunlight where temperatures are 65 to 70 degrees in a process known as chitting. The seed potatoes can then be cut everywhere an eye develops and each of those eyes can then be planted.
Michael Washburn, preservation director for the Seed Savers Exchange, said it’s important to prepare garden beds ahead of time before putting in seed potatoes. He recommends putting in a mixture of compost and potash into the ground a few months before the potatoes go in.
The potato eyes can be planted 10-12 inches apart in furrows – trench-like rows – and the furrows themselves should be 32-36 inches apart.
Once potato plants have gotten to be 6-12 inches tall, gardeners will want to mound dirt around their stems so that only 2-4 inches of the plant is above dirt. Once the plant has grown to be about 6 inches above the ground again, gardeners will want to mound dirt up to the top of the plant once more.
Washburn said that on average, potatoes will be ready after about 90 days, but could be ready in more or less time. Some “new,” or immature potatoes could be harvested around 60 days.
Despite not being fully mature, people will harvest new potatoes often because they like the flavor.
“They’ve got a very thin skin on them and they’re going to be a lot more tender,” Washburn said.
Whether you’re storing potatoes for later consumption or trying to hold onto seed potatoes for future planting, cool, dark, humid places with lots of air circulation are important.
MacDonald says the Seed Savers Exchange keeps potatoes in a cellar at temperatures between 38 and 40 degrees Fahrenheit and humidity levels between 80 to 90 degrees. She said those conditions can help to keep potatoes in good shape for 6 months or more.
People who don’t have a root cellar can try keeping their potatoes in a basket or a burlap sack. Washburn suggested that to create some humidity they might try to have some water nearby or perhaps use a humidifier, but says gardeners will have to evaluate whether they want to use that kind of energy.
MacDonald says another option could be that if gardeners have a small, separate chest fridge, they could adjust the temperature in that and place the potatoes in it with some wet rags.
But no matter the method, it’s important to keep potatoes away from light.
“You just want complete darkness because it’s that light that sparks them to want to grow,” Washburn said.
Sweet potatoes
Sarah Alvernaz, the general manager of sales at the Merced County-based California Sweet Potato Growers, said sweet potatoes are actually a member of the morning glory family. Unlike a potato which can be grown by planting an eye in the ground, sweet potatoes are grown by planting rooted plants, called slips. The swollen feeder roots of the plants are what become the sweet potatoes people eat. It takes between 90-120 days from planting to harvest to get full-sized sweet potatoes.
Sweet potatoes prefer sandy and well-draining soil as well as warm temperatures. Plants should be planted 10-12 inches apart, and soil should be moist before they go in. The best time to plant them is in May and June, Alvernaz said. She said it is possible to start a little later than that – in say July or August – but the sweet potatoes will need to be taken out before the weather cools and the risk of frost sets in, meaning that gardeners who start later might find that their sweet potatoes are smaller in size than they would have been if planted earlier.
Plant and seed retailers that ship nationally, such as Baker Creek Heirloom Seed Company, Burpee and Gurney’s Seed & Nursery Company, sell sweet potato slips, but gardeners can often start their own slips from something like a grocery store sweet potato. There are a wide variety of methods for how to do that and tutorials can be found online but they often involve putting the potatoes in dark or warm conditions to make them sprout.
Once sweet potatoes are in the ground, it’s best for them to be watered daily with drip irrigation, Alvernaz said.
Toward the end of the growing season there may be some signs that sweet potatoes are ready (the leaves might start to yellow, for example), but Alvernaz said the best way to know is to simply start digging underneath the plants to see how big the potatoes have gotten. She said this can be done around the 100-day mark.
Once sweet potatoes are the right size, Alvernaz said the California Sweet Potato Growers turn off the water and leave them in the ground for about 10-14 days for the sugars to settle and for the sweet potatoes to have a more concentrated flavor.
After harvest, sweet potatoes can be stored in a place with good airflow and temperatures around 55 degrees, but Alvernaz warns to not put them in the fridge.
“They’ll actually get what’s called chill injury, where they’ll turn woody and black on the inside,” she said.
Sweet potatoes can be kept in storage for about 10 months, but expect that they may change a little bit by the end of the 10-month period. They may have experienced some shrinkage, but they should still be good.
Alvernaz also says not to worry if your sweet potato begins sprouting. It doesn’t mean the sweet potato has turned toxic.
“If your potatoes start to sprout, knock them off,” she said. “You can still cook them and still have good quality meat under there.”
