Planting sweet and Irish Potatoes

Don't confuse sweet potatoes with Irish potatoes

Bill Sevier: Ask a Master Gardener

Saturday, March 25, 2017

Q: I would like to grow some sweet potatoes, or yams. Are they grown the same way as Irish potatoes? John, Tulsa

A: No, they are not grown the same way as Irish potatoes, and sweet potatoes are not actually yams.

There is so much confusion about these potatoes and yams that it is worthwhile to try to sort it out.

The only thing Irish potatoes and sweet potatoes have in common is that they are both grown underground and are great sources of food worldwide. Both are nutritious.

Sweet potatoes, which are grown widely, are tasty and have several vitamins, beta-carotene and abundant antioxidants. The Irish potato, also nutritious, was the chief source of food in Ireland until the mid-1800s when a potato disease (blight) devastated the crops. Almost 1 million Irish people starved and another million emigrated to Canada and the U.S.

Sweet potatoes are a tropical warm-season plant and botanically are true roots. They are planted in early June after the soil warms as “slips” — which are small plants grown from the surface of a mature sweet potato. These parent potatoes are either partially immersed in water or shallowly planted in moist sandy beds where the small plants, or slips, develop on the potato. They are removed and planted individually. The process is a bit more involved but can be done by anyone. Full instructions are outlined in OSU Fact Sheet HLA-6022, available at tulsamastergardeners.org.

Irish potatoes, on the other hand, are cool-season crops, which should be planted mid-February through mid-March. These potatoes are not roots but underground stem-tubers. Like above-ground stems, they have buds from which a new plant may grow. To grow this type of potato, a whole potato is cut into generous sized sections, called seed pieces, which contain two or more of these buds or “eyes.” After planting, new plants grow from the eyes. It is best to use only potatoes sold for seed pieces; those in the market may have been treated to prevent sprouting.

Both types of potatoes require a long growing season, the sweet potato 3-4 months and the Irish potato about 2-3 months.

A misconception about sweet potatoes concerns “yams.” Most of us have eaten, or at least heard of, candied yams, a traditional Thanksgiving food for some. However, candied yams are not actually yams. Yams are tropical root crops grown in South America and Africa. They are not at all related botanically to the sweet potato. The term yam originated to distinguish certain types of orange sweet potato and is a corruption of an African word for the actual yam.

One question that Master Gardeners are often asked is whether ornamental sweet potatoes such as the cultivar “Margarita” are edible. The answer is that they are edible, but it is said that they do not have a pleasant taste. However, interestingly, is that not only do they have an attractive vine, for which they are grown, but also most have unique purple potato skins.

Garden tips

All cool-season vegetables, strawberries, asparagus and other small fruit may be planted this month.

Established broadleaf weeds can easily be controlled in lawns at this time with postemergent broadleaf herbicides. These herbicides are most effective in spring and fall when weeds are rapidly growing.

Cut down dead pine trees as soon as possible. Most of these trees died of pine wilt disease due to a nematode infection. The infection is spread by the pine sawyer beetle, and dead pines are a source of infection carried by these beetles.