MANHATTAN, Kan. – Savvy gardeners know that St. Patrick’s Day is the traditional date for planting seed potatoes. But Kansas State University horticulture expert Ward Upham said March 17 isn’t a hard-set rule for planting in Kansas.
“Actually, any time from mid- to late-March is fine for potato planting,” Upham said.
The key, he adds, is that gardeners buy seed potatoes, rather than potatoes for cooking. “Seed potatoes are certified disease free and have plenty of starch to sprout as quickly as soil temperatures allow,” Upham said.
“Most seed potatoes can be cut into four pieces, though large potatoes may yield more, and small potatoes less. Each seed piece should be between 1.5 and 2 ounces; and will have more than one eye.”
As a rule of thumb, each pound of potatoes yields 8-10 pieces. Upham said the seed potatoes should be cut 2-3 days before planting so that freshly cut surfaces have a chance to suberize – or toughen – and form a protective coating. “Storing seed in a warm location during suberization will speed the process,” he said.
Plant each seed piece 1-2 inches deep and 8-12 inches apart in rows.
Upham said seed potatoes emerge slowly. “It is often mid- to late April before new plants poke their way through the soil,” he said. “As the potatoes grow, pull soil up to the base of the plants. New potatoes are borne above the planted seed piece, and it is important to keep sunlight from hitting the new potatoes.”
Potatoes that have been exposed to too much sun will turn green and produce a poisonous substance called solanine. Upham said keeping the potatoes covered will prevent this.
Upham and his colleagues in K-State’s Department of Horticulture and Natural Resources produce a weekly Horticulture Newsletter with tips for maintaining home landscapes. The newsletter is available to view online or can be delivered by email each week.
— Pat Melgares, K-State Research and Extension news service