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Potatoes

When to Plant

Potatoes prefer cool weather.

In Northern regions, some gardeners will plant the first crop of early-maturing potatoes in early to mid-April, 6 to 8 weeks before the average last frost date or as soon as the soil can be worked; they can survive some cool weather but the threat of frost is a gamble. If there is a threat of frost at night, temporarily cover any sprouted foliage with mulch or an artificial covering such as old sheets or plastic containers (and be sure to remember to remove the coverings in the morning).

  • To avoid frost, consider starting potatoes 0 to 2 weeks after your last spring frost. You may plant earlier, as soon as soil can be worked, but be aware that some crops may be ruined by a frost or overly wet soil.

  • The soil, not the calendar, will tell you when it's time to plant. The temperature of the soil should—ideally—be at least 50°F (10°C). The soil should also not be so wet that it sticks together and is hard to work. Let it dry out a bit first. Like other seeds, potato seed pieces will rot if planted in ground that's too wet.

In Southern regions, potatoes can be grown as a winter crop and planting times range from September to February. Where winters are relatively mild, you can plant a fall crop in September. In central Florida, gardeners plant potatoes in January; and in Georgia they plant in February.

Choosing a Planting Site

  • Potatoes grow best in cool, well-drained, loose soil that is about 45° to 55°F (7° to 13°C). 

  • Choose a location that gets full sun—at least 6 hours of sunlight each day.

  • Grow potatoes in rows spaced about 3 feet apart.

  • With a hoe or round-point shovel, dig a trench about 6 inches wide and 8 inches deep, tapering the bottom to about 3 inches wide.

  • Spread and mix in fully-rotted manure or organic compost in the bottom of the trench before planting.

How to Plant

  • In each trench, place a seed potato piece (cut side down) every 12 to 14 inches and cover with 3 to 4 inches of soil.

  • If your garden soil is very rocky, put the seed potato pieces directly on the ground. Sprinkle with a mix of soil and compost. Cover them with straw or leaves, hilling the material up as the potatoes grow.

  • The best starters are seed potatoes. Do not confuse seed potatoes with potato seeds or grocery produce! Select seed potatoes which have protruding eyes (buds). 

  • Use a clean, sharp paring knife to cut large potatoes into pieces that are roughly the size of a golf ball, making sure that there are at least 2 eyes on each piece. (Potatoes that are smaller than a hen’s egg should be planted whole.)

  • If you are cutting up potato pieces yourself, do so 1 to 2 days ahead of planting. This will give them the chance to "heal" and form a protective layer over the cut surface, improving both moisture retention and rot resistance.

  • 12 to 16 days after planting, when sprouts appear, use a hoe to gently fill in the trench with another 3 to 4 inches of soil, leaving a few inches of the plants exposed. Repeat in several weeks, leaving the soil mounded up 4 to 5 inches above ground level.

  • After the potato plants have emerged, add organic mulch between the rows to conserve moisture, help with weed control, and cool the soil.

How to Grow

A critical part of growing potatoes is to not let their tubers (i.e., the potato crop) be exposed to sunlight for too long. Exposed tubers will turn green and produce a toxic compound called solanine, which makes them bitter, inedible, and potentially nausea-inducing.

To combat this, we employ a technique called hilling.

Hilling is simple: As a potato plant grows, it produces a main stem with leaves and flowers aboveground. Meanwhile, underground, tubers form on secondary stems that branch off from the main stem. In order to prevent shallow tubers from being exposed to sunlight and to encourage the plant to keep producing more tubers, a few inches of soil are periodically "hilled" up around the base of the stem. This is typically done three to four times during the season.

Tips

  • Do the hilling in the morning, when plants are at their tallest. During the heat of the day, plants start drooping.

  • Maintain even moisture, especially from the time when sprouts appear until several weeks after they blossom. The plants need 1 to 2 inches of water per week. If you water too much right after planting and not enough as the potatoes begin to form, the tubers can become misshapen.

  • The last hilling should be done before the potato plants bloom, when the aboveground part of the plant is at least a foot tall. Hoe the dirt up around the base of the plant in order to cover the tubers as well as to support the plant.

  • Practice yearly crop rotation with potatoes.

Pests/Diseases

  • Potato Scab: Most likely caused by a high soil pH. Remember: Potatoes like acidic soil (do not plant in soil with a pH higher than 5.2). Dust seed potatoes with sulfur before planting. Some readers suggest adding pine straw on top of the potatoes when planting for natural anti-bacterial elements.

  • Colorado potato beetles need to be hand-picked and predatory birds will often eat them. While they’re in the nymph state, they can be controlled with diatomaceous earth (food grade) which is a non-toxic way to control pests in the garden. If they continue to be a problem, a few sprays of Spinosad, an organic pesticide, will get rid of the beetles. Always use products at dawn or dusk to avoid harming beneficial insects.

  • Aphids

  • Flea Beetles

  • Early/Late Blight

How to Harvest

  • Regular potatoes are ready to harvest when the foliage begins to die back. (See each variety for days to maturity.) The tops of the plants need to have completely died before you begin harvesting.

    • "New potatoes," which are potatoes that are purposefully harvested early for their smaller size and tender skin, will be ready for harvest 2 to 3 weeks after the plants stop flowering. New potatoes should not be cured and should be eaten within a few days of harvest, as they will not keep for much longer than that.

  • Toughen up potatoes for storage before harvest by not watering them much after mid-August.

  • Dig up a test hill to see how mature the potatoes are. The skins of mature potatoes are thick and firmly attached to the flesh. If the skins are thin and rub off easily, your potatoes are still too new and should be left in the ground for a few more days.

  • Potatoes can tolerate light frost, but when the first hard frost is expected, it’s time to get out the shovels and start digging potatoes.

  • Cut the brown foliage off and leave the potatoes for 10 to 14 more days before you harvest. This allows the potatoes to develop a thick enough skin. Don't wait too long, though, or the potatoes may rot (especially in moisture-laden soil).

  • Dig potatoes up on a dry day. Dig up gently, being careful not to damage the tubers. Avoid cutting or bruising potato skin. Damaged potatoes will rot during storage and should be used as soon as possible. The soil should not be compact, so digging should be easy.

  • If the soil is very wet, let the potatoes air-dry as much as possible before putting them in bags or baskets.

  • Don’t leave the potatoes that you have dug in the sun for long after they have been dug up from your garden, otherwise your potatoes may turn green. Green potatoes have a bitter taste due to the presence of solanine, and if enough is eaten, can cause vomiting and diarrhea. Small spots can be trimmed off, but if there is significant greening, throw the potato out.