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Potato Growth Stages and Growing Quick Tips

Potatoes growing in straw mulch

There are five potato growth stages: sprout development, vegetative growth, tuber growth, tuber bulking, and maturation.

Potatoes are commonly grown from the eyes of other potatoes, not from seeds. Potatoes used to grow new potatoes are called seed potatoes. Seed potatoes are small tubers, also called baby potatoes. Commercial seed potatoes are specifically grown to be free from disease and to provide consistent and healthy plants. Commercial seed potato growing regions usually have cold winters that kill pests and summers with long hours of sunlight each day for optimum growth.

Potato growth stages
Potato plant growth cycle. Stages of growth from left to right are sprout development below ground, vegetative growth above ground, tuber growth, tuber bulking, and tuber maturation.

Potato growth stages

When a seed potato is planted, the potato growth stages begin. Here are the fie potato growth stages

Stage 1: Sprout Development. The eyes of the potato develop sprouts. The sprouts grow and emerge from the soil. Sprouts and stems rise from the ground two to six weeks after planting depending on the climate.

Stage 2: Vegetative Growth and Photosynthesis. Photosynthesis begins in the leaves and stems above ground. Stolons (underground stems) develop underground. The plant prepares to store nutrients in tubers.

Stage 3: Tuber Growth. Tubers begin forming on the end of stolons; the stolon tips swell and tubers begin to form. Above ground, shoots develop ahead of flowers. Stolons usually swell before the plant flowers. (Because the “root” of the potato plant is a stem, not really a root, potatoes are considered tubers.) Tuber development begins 5 to 6 weeks after sprouts emerge from the soil.

Stage 4: Tuber Bulking. Tubers enlarge. Sugars and starches accumulate in the newly formed tubers. Optimal soil moisture and temperature as well as the availability of soil nutrients are very important for a good yield.

Stage 5: Maturation. The tubers reach full size. The leaves and stems above ground begin to dry out and die. Tuber skins harden. When the top of the plant dries out and dies, tubers are ready for harvesting. The harvest of mature tubers can begin 10 to 26 or more weeks after planting (70 to 120 days) depending on the variety. However, potato tubers can be harvested at any size they are edible.

Potato seed starting is further explained in Potato Seed Starting.

Potato growth of tubers
A potato plant lifted from the soil with developing and mature tubers.

Potato growth challenges

Keeping tubers buried is critical for their development. Sometimes new tubers may start growing at the surface of the soil. Exposed tubers should be buried ahead of harvest. Exposure to light leads to an undesirable greening of the skins and the development of solanine as a protection from the sun’s rays, growers cover surface tubers. Solanine is an alkaloid found in potatoes and other Solanaceae family plants. If ingested, solanine can cause poisoning in humans and animals. “Hilling up” or “earthing up”—the piling of additional soil around the base of the plant as it grows—inhibits the development of solanine. An alternative to “earthing up” is the covering of plants with straw or other mulches.

Home gardeners often grow potatoes from a piece of potato with two or three eyes, commonly in a hill of mounded soil or in a grow bag or containers. Commercial growers plant potatoes as a row crop.

Potatoes are sensitive to heavy frosts, which damage them in the ground. Even cold weather makes potatoes more susceptible to bruising and possibly later rotting.

Potato plant planting and growth are further explained in How to Plant, Grow, and Harvest Potatoes.

Potato tubers ready for harvest
Potato tubers ready for harvest

Potato growing quick tips

Planting: In cold winter regions, plant seed potatoes in spring as soon as the soil can be worked. For a summer crop where the soil temperature does not climb above 85°F (20°C), plant 2-3 weeks before the last frost. For a fall crop, plant in late spring. In mild-winter regions, plant in late winter—4 to 6 weeks before the last frost—for a summer crop. Plant in late summer for a winter-into-spring crop. Potatoes are tolerant of cool soil and late frost. Set seed potatoes 2-4” (5-10 cm) deep and 12-18” (30-45 cm) apart in all directions. Plant in soil rich in compost and rotted manure.

Growing: When plants are 12” (30 cm) tall, draw soil up around them—called “hilling”—so just a few inches (5 cm) of the plant is seen. Hilling will protect potatoes from sunburn and from turning green. Grow potatoes in full sun. Keep the soil just moist. Add a side-dressing of high phosphorus fertilizer to the soil after 1 month of growth.

Harvesting: Potatoes planted in early spring will be ready for harvest in 90-110 days; planted in late spring, 100-120 days; planted in late summer or fall, 110-140 days. Dig early for “new potatoes” when plants begin to bloom and fade; dig for mature, full-size potatoes when the vines yellow and die. To harden the potato skin before harvest, stop watering 2 weeks before harvest; cut away the top foliage 10 days before harvest. Carefully lift potatoes with a garden fork, staring 8-10” (20-25 cm) away from the plant, then work closer t the vine. Brush but do not wash clinging soil from tubers. Store potatoes in a dry, dark, well-ventilated place for up to 6 months.

For more detailed articles on potatoes click on Potatoes.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. Harvesttotable.com has more than 10 million visitors each year.

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