Sweet Potatoes in New York? Of Course!
By Steve Reiners, Professor and Chair, Horticulture Section, Cornell University, Cornell AgriTech. This is part of a series of columns that he wrote about vegetable gardening during the pandemic that ran Spring-Summer 2020. Read more articles from 2020 | Read later articles in this series.
May 29, 2020
Say sweet potato and people think of a heat-loving crop grown in the Deep South. Rightfully so, as the crop is native to tropical Central and South America. But more and more people in the Finger Lakes are realizing that great sweet potatoes can be grown right here. The good news is that they are easy to grow, have attractive foliage, are plagued by few pests, and are packed with vitamins, minerals, and antioxidants.
First let’s clear up some confusion. The word yam and sweet potato are often used interchangeably. The true yam is a large tropical root completely unrelated to sweet potatoes. It’s not something we could grow here, as it requires a frost-free season of seven months.
In the 1930’s, moist, orange-fleshed sweet potatoes were introduced into the U.S. To differentiate them from the familiar, dryer, white-fleshed sweet potatoes that dominated the market, producers and shippers coined the term yam. Unlike the question of a tomato being a fruit or a vegetable, the Supreme Court has never settled the yam/sweet potato debate.
Variety selection
Since sweet potatoes are originally from the tropics, they can’t be planted until the soil has warmed, which after the heat this week is not a problem. So that makes right now the ideal time to plant. Following a few simple directions can make sweet potatoes a garden favorite.
First, choose a variety that will grow well in our short season. Varieties that have done well for us at Cornell AgriTech include Covington and Carolina Ruby, both red-skinned with orange flesh, and O’Henry with white skin and yellow flesh. Unfortunately, you may be limited by a variety’s local availability.
Planting
To get the “slips” or sprouts needed for your garden, commercial growers place last year’s sweet potatoes in a moist soil in a warm greenhouse. Sprouts emerge off the potato, similar to the growth you see from the eyes of white potatoes. When sprouts are 6 to 8 inches long, they’re pulled off the buried root, bundled together and shipped north, as most of the slip producers are in North Carolina. The slips may look terrible, almost dead. But once planted, they will experience a rebirth.
I used to recommend planting sweet potatoes in black plastic mulch to warm the soil. But the best crop I ever grew was grown on a raised bed in bare ground. Plant one slip up to their bottom leaves, 12 to 15 inches apart, and keep well-watered until you see the plants recover and start to grow. Then just sit back and let them go. Water as needed and sidedress with a little fertilizer a couple of times during the year.
Harvest
By mid- to late-September, they should be ready for harvest. Make sure you harvest before the first fall frost. Carefully dig under the plants with a pitchfork and remove the roots.
Sweet potatoes can be eaten fresh. But if storing the roots, they must be “cured” first. Put them in a warm, humid room, close to 80F, for 10 to 14 days. After curing, put them in a relatively cool (55 to 60F), humid environment like a basement. Do not refrigerate them or place them in a cold room as they will soften and rot. Properly cured and stored, they will keep for months.
In the garden this week, keep the weeds under control. When vegetables are small they are most vulnerable to weed competition. Dry weather requires a good watering so apply at least a third of an inch of water this weekend if it does not rain. In a 100 square foot bed, that would be 20 gallons of water.
Remember to harvest the older leaves of your salad crops rather than taking the whole plant. New leaves will emerge, and you’ll get more production. Finally, don’t forget to get beans planted. My personal favorites are Italian types like Romanos or Romas.