Tips for growing potatoes in the southwest

by Jacqueline A. Soule

No one knows for sure how the potato got from the Andes to Ireland. The potato was firmly rooted in the Irish soil and culture for centuries before disaster struck.

In 1846-47, Ireland had an unseasonably cool, wet year and an opportunistic fungus caused the rot of millions of tons of potatoes, the deaths of thousands of humans and the emigration of tens of thousands. Known as the Great Potato Famine, it may be the only major human catastrophe named for a plant.

Whether you say potato or pah-tah-to, you most likely think of Ireland as this vegetable's birthplace. In fact, potatoes originated halfway around the world from the Emerald Isle in the Andes mountains of South America.

Several thousand years ago, early Incan tribes learned that wild potatoes are a life-sustaining storehouse of energy and nutrients. Utilizing an environment with lower humidity and alkaline soils — similar to the Southwest — they subsequently domesticated more than 100 varieties.

Per unit of land, potatoes provide more protein and calories than any other food crop. The tasty tubers also store a number of important vitamins and minerals found just below the skin.

Potatoes grow best in early spring and late fall when the days are warm and the nights are cool. Although the potato is a cool-season crop and the edible part of the plant is underground, the tops of the plant will not withstand frost. Thus, you have to time your potato planting just right.

You need to get them into the ground as early as possible to get the most crop you can before either summer heat or winter cold kills the plants.

In Phoenix and San Antonio, March is an ideal time to plant potatoes, or try again in late September. In Denver and Albuquerque, March is the month to order potatoes for planting in mid- to late April.

Soil: Potatoes do best in a loose, well-drained, acidic soil. Since Southwestern soils are alkaline, add ample compost to the planting area to help acidify the soil. Poorly drained soils or heavily alkaline soils can cause low yields and undersized, rough tubers.

Fertilizer: Potatoes need fertilizer in their early stage of growth, thus apply most of the fertilizer before planting. Use a complete, balanced fertilizer. If you miss pre-planting application, wait until sprouts have leafed out to fertilize.

Light: Potatoes require at least six hours of full sun each day.

Water: For best yields, keep soil evenly damp, not wet. Allow some drying between waterings.

Start: Cut seed potatoes that are larger than a chicken egg into pieces about 1 inch across. Each piece should have at least one "eye," the bud where the stem will grow.

Two eyes are better. Egg-sized and smaller tubers can be planted whole. Once cut, seed potato pieces need to heal or cure for a few days before planting, otherwise they may rot in the ground.

Select: Buy certified disease-free seed potatoes from garden centers or through online or mail-order catalogs for best results. Avoid planting potatoes from the supermarket because they are often less vigorous and more prone to disease.

Jacqueline A. Soule, Ph.D., is a botanist, writer and educator. A member of the Garden Writers Association, she writes gardening columns for a number of newspapers throughout the Southwest. A self-avowed "Darwinistic" gardener, Jacqueline prefers plants that need as little care as possible while providing color, texture and movement in the landscape.

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