Sweet potatoes in Seattle? Yep, it can be done. At Seattle Urban Farm Co. we love pushing the boundaries of what can be grown in our region, so for the past two seasons we have been growing sweet potatoes in our unheated greenhouse. We are thrilled to report we have had tons of success!
Originating in the tropical regions of Central and South America, Sweet potatoes (Ipomoea batatas) are more closely related to the morning glory flower than true potatoes. In fact, as you will see when growing the crop, the leaves and vines strongly resemble those of the ornamental (and invasive) morning glory. The flowers also look just like morning glory, but these agricultural cultivars do not always flower in temperate climates like ours. Since sweet potatoes evolved in warm, humid climates, they can be a challenge in our region, so any warming assistance you can provide, such as a greenhouse, row cover or cold frame will help improve yields and speed up plant growth.
Interestingly, sweet potatoes are most often planted from "slips", which are cuttings of adventitious roots from another plant or tuber. It is possible to grow your own sweet potato slips by simply sticking an organic sweet potato tuber in a glass of water and waiting. However, this process can take quite a long time, so most growers order slips from seed companies for spring planting.
Consider placing an order for slips now, even though they don't ship or get planted outside until later in the spring, its a good idea to order early to make sure stock doesn't sell out. We recommend the variety Beauregard.
Once your slips arrives, plant them 3-4" deep in raised beds 10-18" apart in rows 36-60" apart. Keep well irrigated until plants are established. Sweet potatoes actually require little attention- we basically just planted them a lightly fertilized planting bed and crossed our fingers!
Good luck!