Irish Potato Solanum tuberosum

Potatoes are herbaceous perennials by nature, they are grown as annuals for harvesting. They can grow up 2 feet tall and maybe erect or sprawling with branching stems. The plant produces stolon's that bear edible underground tubers. All green parts of the potato plant are inedible because they contain a toxin known as solanine. This toxin can be found in the sprouts, stems, leaves, berries, and the green skin of the tuber. Potatoes are cultivated for their starchy tubers and are the fourth most important food crop.

Potatoes are native to South America in parts of Argentina, Bolivia, Chile, and Peru. It is now widely cultivated and major producers include China, Germany, India, Russia, and the United States. 

The genus name, Solanum, is the Latin word, solamen, which means "comforting or soothing." The species name, tuberosum, means "tuber."

Thousands of cultivars exist in varying textures, sizes, and colors that are suited for a variety of culinary uses.  Russet potatoes are most commonly found in stores and restaurants. They are better suited for the climate of the western United States and do not grow well in the eastern states.  For North Carolina's climate and soil, some of the most reliable cultivars include thinner skinned potatoes such as ‘Yukon Gold’, ‘Kennebec’, and ‘Red Pontiac’.

Potatoes grow best in full sun and well-drained, sandy, and acidic soil.  The optimal pH is between 4.8 and 5.4.  Poorly drained soil may cause tubers to rot, and acidic soil helps to prevent bacterial scabs.  Light soil, if consistently moist, can help the plant grow large, evenly shaped potatoes.

The plant's underground tubers may be round, oblate, or elliptic and the colors range from white, red, or purple. They may measure 1 to 4 inches in diameter. The leaves have 6 to 8 pairs of leaflets. The flowers may bloom in colors of white, pink, purple, or blue during the summer and fall. The yellow-green to green berries are also sometimes produced and contain many seeds.

Potatoes are most often grown from "seed potatoes"– small tubers or pieces of tubers that sprout into a new plant.  Buying certified disease-free seeds can help prevent problems such as Potato late blight. The grocery potatoes are often treated with sprout inhibitors and therefore may not be reliable for growing.  Before planting, cut seed potatoes so each piece has at least two eyes and let sit outside for a day to let the cut end scab over.  Plant seed pieces 5-6 in apart with the eyes facing up.  Raised beds provide good drainage and containers or grow bags can be suitable for growth so long as they are at least 2 ft deep and hold at least 30 gallons.  As they grow, pile soil or mulch up around the base of the plant. This encourages the growth of more tubers along with the submerged parts of the stem.  Do this once the plants are one foot tall and once or twice more throughout the season.  Potatoes may be grown in trenches to make the process of hilling easier.  Tubers will turn green and produce toxic compounds if not sufficiently covered. 

In NC, try to have potatoes planted sometime between mid-February and the end of March; they can tolerate a bit of frost.  Potatoes can either be harvested mature when the tubers are fully grown and/or the plant has dried up around June. They may also be harvested early as "new" potatoes once the plants begin to flower.  These young potatoes still have thin, delicate skins and are considered a delicacy.  New potatoes can be harvested about 7-8 weeks after planting.  Mature potatoes can take 3-4 months before they are ready for harvest.

Seasons of interest:

Blooms:  Summer and Fall   Fruits:  Summer and Fall     Tubers: Summer, Fall, and Early Winter

Quick ID Hints:

• underground edible tubers
• green erect, branching, smooth to sparsely hairy stems
• dark green leaves, pinnately compound, 6 to 8 leaflets, sparsely to densely hairy
• white, pink, purple, or blue flower blooms with yellow stamens
• green or yellowish-green berries about 0.5 inches in diameter sometimes appear

Insects, Diseases, and Other Plant Problems:  Potatoes are susceptible to the Colorado potato beetles, flea beetles, wireworms, and leafhoppers which can result in poor crop yields. Colorado potato beetles lay masses of yellow eggs and the larvae defoliate plants.

 Potato late blight will rot tubers and render them inedible. Viral, bacterial, and fungal diseases potential problems. If this occurs, it is best to remove and destroy the diseased plants.

Proper crop rotation, clean garden tools, and using disease-resistant cultivars will reduce pests and diseases which ultimately improves crop yields. 

VIDEO Created by Elisabeth Meyer for "Vegetables, Herbs, Fruits, and Nuts" a plant identification course offered in partnership with Longwood Gardens.