Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden.
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After rice and wheat, potatoes are the third most significant food crop worldwide. Depending on the variety, crops can take 10 to 20 weeks to grow.
Several factors contribute to the time it takes to grow potatoes, but you can generally harvest after 90 days, though some more than 200 varieties can take as long as 140 days. Average yields are between 5 and 20 potatoes per plant, a much greater nutritional return than most crops.
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Growing Potato Plants
Potatoes (Solanum tuberosum) do not root vegetables (like yams) but are sub-surface tuberous stems (roots can’t produce shoots). The plant’s roots are moderate and grow to a depth of 18 and 24 inches. Compared to other crops, potatoes are one of the most water-efficient plants.
There are a huge variety of hybrids, generally divided into seven groups, though farmers group them into three categories – Russet, specialties (which include the colors), and chippers.
Types of Potatoes
Baking varieties are starchy and have a high dry-matter content, while boiling varieties are low in dry matter and are referred to as “waxy.” It takes a long time to develop a variety; each offers consumers skin thickness, flesh color, shape, and size options.
The most common potato varieties used for chipping have brown skins, white flesh, and a spherical form, making them easy to cut in any direction.
The waxy Norland Reds and starchy Russets are two examples. Yukon Gold is a potato variety that falls somewhere between the two extremes.
A further classification is based on the season growth time and storage abilities. Potatoes are divided into early-season potatoes (summer harvest) and late-season varieties (fall harvest).
How Long Does It Take to Develop Seed Potato Varieties?
According to Colorado State University’s San Luis Valley Research Center, hundreds of hybrid potato varieties are created yearly, creating true potato seed, which looks like a tomato seed but is much smaller.
These seeds develop into potato plants that yield little, unique tubers different from their parents. Each hybrid has a unique form, cooking properties, pest resistance, and disease resilience profile.
Around 80,000 seedling tubers are grown yearly in the University greenhouse for field testing. About 800 (1%) of these make it through the first year’s tests and the second year’s evaluations. Each year, rigorous field and quality tests eliminate weaker potato plants.
After eight years of culling, the surviving potato varieties are given to growers and consumers for further testing – usually for a further three years. By the time the selected potato variety is given a name, 14 years have passed, and about 200,000 seedling tubers preceded its selection.
How to Plant Potatoes
Bed Preparation
Before growing our potato crop, we should consider some ground rules – our soil. Ideally, we want well-drained soil rich in organic matter to start with. If we add composted manure, we will need to leave the site standing over winter before planting potatoes in spring. This reduces the risk of potato scab, a common potato disease.
As good gardeners, we have our soil tested every three years to know our soil’s capacities. For potato plants, we’re particularly interested in the cation exchange capacity (CEC), potassium (K), and manganese (Mn) levels. The CEC is essential because soil generally has ample potassium, but it’s unavailable to potato plants unless the soil has an organic matter to boost CEC.
Planting Potatoes
Ideally, we want to plant potatoes in soil temperatures between 60 and 70 °F (15 and 21 °C) but below 80 °F (27 °C). Tubers will not form if the soil temperature is too high. While a raised bed improves drainage, it also can cause soil temperatures to rise faster, so keep an eye on that.
Potatoes are grown from small potato tubers, also called seed pieces. Potato rows should be 34 to 36 inches apart and tubers about 10 inches apart and between 1 and 3 inches deep, depending on the variety.
Always try to get B-size certified seed that weighs just under two ounces. While you can cut seeds, doing so increases the risk of tuber-borne diseases.
Don’t Use Grocery Store Potatoes
You can’t use store-bought potatoes because they have been treated with maleic hydrazide to prevent sprouting and extend shelf life. Pair the chits with ripe fruit to boost sprouting on untreated seed potatoes. As the fruit ripens, it releases ethylene, a hormone that also boosts sprouting.
If you’re using your stock, select them from high-yielding hills and choose well-shaped, smooth, and disease and injury-free tubers. Store seed stock in sterilized crates to avoid any contamination. Seed potatoes should be around 2 ounces in weight.
Larger seed potatoes can be cut into several pieces, each about two ounces. Cut areas should be allowed to form a callus before planting them cut-side down. Each piece should have an eye bud).
To develop buds, you can chit your tubers in a cool (50 °F (10 °C)) room paired with a ripe banana or apple slices.
Fertilizer Applications
We’re not going to apply nitrogen or phosphorus before planting, but we’ll adjust the potassium levels per the soil test recommendations.
If our pH is above 5.8, we might need to add some manganese, which we can include in the starter fertilizer or as two foliar spray applications during active growth.
Side-dress nitrogen as tubers starts emerging from the soil. Remember that potatoes are stems, so as the seed potatoes start sticking from the soil, you can cover them to prevent greening and the development of chlorophyll and solanine.
The latter is bitter-tasting and poisonous.
Green Manure
After applying composted manure in the fall, plant some winter legumes (crimson clover or hairy vetch) to boost nitrogen levels. Legumes have a symbiotic relationship with rhizobial bacteria that capture and “fix” nitrogen in the soil, making side-dressing unnecessary.
What Does it Take to Grow Potatoes?
Many gardeners give their potato crop a head start by growing potatoes in a raised bed. Plant potatoes by following the steps outlined above. When the first shoot appears, hill up the soil around it until it is about six inches deep.
Make sure the growing point isn’t covered. Raised beds make harvesting easier and allow you to grow potatoes less susceptible to root rot caused by wet soils. It also gives you easy access to baby potatoes and makes harvesting potatoes much easier.
As you may know, I love growing potatoes in containers. Potato plants grow well in containers as long as you provide adequate drainage. Check out my 7 Reasons To Grow Potatoes In Containers To Double Your Harvests article.
Potatoes grow well in soil that drains well yet can retain moisture. Ideally, potatoes grow well if given about two inches of water per week. Mulching can conserve moisture, slow weed growth, and keep the soil cool.
Planting Potatoes in Straw
If you want perfectly shaped, easy-to-harvest potatoes, you might grow potatoes in straw. Grow potatoes as described above, but only one inch deep. When the shoot emerges, place straw 4-6” deep around the plants and between the rows, ensuring leaves have access to light.
The potatoes form above the soil surface under the straw, while the straw conserves moisture and keeps the potatoes cool. This gives easy access to baby, new, and mature potatoes. Harvesting potatoes from under the straw is the easiest way possible.
Special Care Times
When potato plants flower and set fruit, just like tomatoes and peppers. Flowering is an indicator that the tubers are setting, an indicator that you should keep a close eye on watering routines and soil moisture. The potato flowers serve no other purpose (for you), so channel the energy they may use to the baby potatoes by cutting them off.
Mature Potatoes
Potatoes mature once the foliage starts dying back. Fully mature potatoes store better, but small potatoes taste better – steamed with butter and salt. Yum. Some gardeners actively cut the potato plant back to accelerate maturity.
How To Harvest Potatoes
Potatoes can be dug from the sides of hills by hand for continual harvest for fresh market sale, but they do not keep as well as mature potatoes. New potatoes can also be harvested in sections at a time, but take care not to harm the plant.
Early-season varieties mature in 50-70 days but do not store well. Late-season potato varieties mature in 90-120 days and store well.
Potatoes harvested before full maturity are called “new potatoes.” Harvest these small potatoes about a month before full maturity, usually about six weeks after the plant has flowered.
Early-season varieties are usually preferred for new potatoes. If harvesting in late fall, let the vines die with the first frost to boost sweetness, then harvest about two weeks later but before a hard freeze. You can expect a yield of around 30 pounds (13.6 kg) per ten-foot (3 m) row.
Possible Challenges
Potato scab is a serious disease and can be prevented by lowering the soil pH to below 5.8. The best option is to select disease-resistant varieties. Adding organic matter and boosting CEC is also advisable. Do this by composting the bed in the fall for an early spring planting.
Late blight, which also affects tomatoes, can devastate a potato planting, killing the plants in two weeks if conditions are right.
Early blight can be a problem in hot, humid weather. It usually infects older leaves on older plants causing dark circular spots.
The Colorado potato beetles feed on the Solanaceae family (potatoes, tomato, eggplant, and pepper). Remove by hand-picking adults. Bt insecticides specific for Colorado potato beetles are available and effective when larvae are small.
A hollow heart, forming a cavity at the center of the tuber, results from uneven growth caused by uneven soil moisture.
In Closing – How Long Does It Take to Grow Potatoes?
Potatoes can be grown in less than two months or as long as four months. Early-season potato varieties mature between 50 and 70 days and are great as new potatoes but store poorly. Late-season potato varieties mature between three and four months but offer the advantage of being able to be stored for extended periods.
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