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Bill Starr: How to plant Irish potatoes

With all the cold weather we’ve had this winter, it’s hard to believe it’s getting time to think about planting potatoes. Generally, gardeners can plant potatoes when the soil temperature reaches 45 degrees F. but potatoes germinate and emerge when the soil temperature gets about 50 degrees F. This usually happens around Valentine’s Day. This is about the same time that crabgrass starts to germinate.
You need to cut your seed so that each piece of potato has at least two eyes and should weigh 1.5 to 2 ounces. During cutting, discard any potatoes that show dark ring or discoloration inside. Seed should be planted immediately after cutting. Remember to use only certified seed and do not use potatoes from the supermarket.
Some Irish potato varieties you could plant include Kennebec and Irish Cobbler. Early varieties include Red Pontiac and Red LA Soda. In our publication, “Potato Production in the Home Garden” we also list some unusual potato varieties that you may want to try out.
Space the seed eight to 10 inches apart and 4 to 5 inches deep with the cut side down. Later crops should be planted five to six inches deep. The best row spacing is generally 30 to 36 inches wide.
You can plant your potatoes on flat ground, but most people prefer to form a hill around the plant. Hilling will  more room for developing tubers and also help with drainage. I’m going to experiment this year with a different way to grow potatoes; I’ll let you know how it goes.
Irish potatoes can handle soil with low pH with ideal conditions being from 4.8 to 5.4. If the pH is higher than that, then the potatoes can get a disease called scab. You need to get a soil test from your local Extension office to find out your pH.
You also need to be careful with your fertilizer. Too much N will cause delays in tuber growth. Broadcast fertilizer when you form your hills before you plant and incorporate it into the top 6 to 8 inches. Apply a complete fertilizer such as 10-10-10 at a rate of 1.5 pounds per 100 square feet of garden. Once the potatoes are up and growing well, I usually come back with a little additional nitrogen like ammonium nitrate; a little goes a long way. Once the sprouts are out of the ground about 6 inches high, begin hilling soil around them. The use of mulch or straw can be helpful to prevent sunlight from penetrating down to the crop. Potatoes that develop in sunlight will be green and inedible.
Crop rotation is a must with potatoes. Do not plant potatoes in the same area of the garden each year. Do not plant behind tomatoes, potatoes, peppers or eggplant. Try to follow beans, squash or corn.
If you have any questions about Irish potatoes or any other veggies, please contact your local county Extension office. Don’t forget it is getting close to time to put out any pre-emergence herbicide for crabgrass. You may as well do that the same time you plant your potatoes.

Bill Starr is ANR agent and Sumter County Extension coordinator, University of Georgia Cooperative Extension Service. Contact him at 229-924-4476.