The Q&A Archives: Growing organic potatoes

Question: I'd like some advice on how to successfully plant and grow organic potatoes in Florida, U.S.A

Answer: Potatoes are a pretty easy vegetable crop to grow, but they aren?t the easiest to grow using organic methods. That?s because they are prone to quite a few insect pests and diseases that can be a challenge to manage organically. They also require relatively high levels of available nutrients in order to obtain good yields.

It Starts with Seed. Organically grown ?seed? potatoes are considerably more expensive than their conventional cousins. The national organic standards require the use of organic seed (and vegetative propagules like tubers) unless they are ?commercially unavailable?

There are so many potato varieties to choose from. A few that are common in organic markets are Chieftain, Norland, Superior, Yukon Gold, Carola, Yellow Finn, Russian Banana, All Blue, and Caribe, but many other varieties are grown.

Soil management. As with most crops, adding organic matter can improve soil quality for potato production. However, with potatoes, if the organic matter is too fresh it may lead to soil borne diseases like scab and Rhizoctonia.

Pest Management. Mechanical weed control is relatively easy in potatoes, because they are hilled. But don?t delay; cultivate shortly after the plants emerge, then hill frequently, at no more than 2-week intervals, until the canopy closes. This usually keeps weeds from getting a foothold.

Traditionally potatoes are grown in rows. The potato seeds are planted every 15 in., with the rows spaced 2 1/2 to 3 ft. apart. If space is limited or if you would only like to grow a small crop of potatoes, you may prefer to plant one or two potato mounds. Each 3-4 foot diameter mound can support 6 to 8 potato plants.

Planting in rows
Dig a shallow trench about 4 inches wide and 6-8 inches deep. The spacing at which you place the seed pieces will determine the harvested potato size. For most household uses, you will want to plant your potato seeds 15 inches apart in this trench. If you'd like a quick crop of "baby" potatoes for soups and stews, you can plant the seeds 4 inches apart, and begin harvesting them as soon as they reach the desired size.

Place the potato seeds into the trench (cut side down) and then cover them with 3-4 inches of soil. (Do not fill the trench in completely!) Depending on the soil temperature, the sprouts will begin to emerge in about 2 weeks. At this time add another 3-4 inches of soil.

Your crop of potatoes will form between the seed piece and the surface of the soil. For this reason, when the stems are about 8 inches high, you once again add enough soil to bring the level half way up the stem of the plant. Another hilling will be needed 2-3 weeks later, at which time you again add soil half way up the stem of the plant. After these initial hillings, it is only necessary to add an inch or two of soil to the hill each week or so, to ensure there is enough soil above the forming potatoes that they don't push out of the hill and get exposed to light.

This hilling process is necessary to create sufficient space for the potatoes to develop large tubers, and an abundant crop. Don't get carried away with hilling though... If you cover up too much of the foliage, you may end up reducing your final crop yield.

Mound planting
The basic procedure for planting potatoes in mounds is the same as for planting in rows. The difference here is that you can grow your crop in a more confined area, or take advantage of an otherwise unused area of the garden.

Cultivate and loosen the soil where your potato mound will be. Designate the approximate perimeter of your planting circle (3-4 feet diameter). Space 6-8 potato seeds evenly around your circle, and cover with the initial 4 inches of soil. Continue the same procedures as you would for planting in rows.

Watering and care
For the maximum crop, keep your potato vines well watered throughout the summer, but especially during the period when they are in flower, and immediately thereafter. This is the time when the plant is creating the new tubers, and water is critical. Water early in the day so that the foliage has time to dry completely before evening. (Wet foliage can make your plants more susceptible to several potato diseases.) When foliage turns yellow and dies back, discontinue watering to allow the tubers to "mature" for a week or two before harvesting.

Once the vines have passed the critical watering stage while in flower, they will tolerate a certain amount of drought. According to some studies, non-irrigated potatoes are less watery and more healthful. However, potato plants which are not watered regularly will produce a much smaller crop.

The Potato Harvest
Your may begin to harvest your potatoes 2 to 3-weeks after the plants have finished flowering. At this time you will only find small "baby" potatoes if you were to dig up a plant. Potatoes can be harvested any time after this, by gently loosening the soil, reaching under the plant, and removing the largest tubers, leaving the smaller ones to continue growing.

If you want late potatoes for storage, wait 2-3 weeks after the foliage dies back. Carefully begin digging a foot or so outside of the row or mound. Remove the potatoes as you find them. (Be careful not to bruise or cut the tubers with your spade!) If the weather is dry, allow the potatoes to lay on the soil surface, unwashed, for 2-3 days so they can dry. If the weather is wet, or rain is expected, move the harvest to a cool, dry area (like a garage or basement) for the drying period. This drying step is necessary to mature the potato skin, which will protect the potato during storage.

Don't grow potatoes in the same soil more than once in three years. Many diseases and insect pests will survive and remain in this area, in spite of your best eradication efforts!

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