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The life cycle of a potato (Solanum tuberosum) consists of five distinct stages:
- Sprout development
- Vegetative growth
- Tuber formation
- Tuber maturity
- Plant maturation
The entire growth cycle happens in a single season. Potato plants are sensitive to frost, but even in hotter climates, these plants die off in a single year and have to be replanted the following spring from seed potatoes, which are potato tubers that have been preserved and chitted, ready for planting.
Potato plants grow from seed to ready to harvest in around 100 days. You can harvest new potatoes from around 70 days, but need to wait 80 to 130 days to achieve the full yield of large potatoes. Remember, you’ll only get between 1 and 5 pounds of new potatoes for every pound of seed potatoes you plant. But if you wait, you’ll get between 15 and 20 pounds of mature potatoes for every pound you plant.
Let’s take a look at the growth cycle of potatoes. Understanding the growth stages and what things can affect that cycle can help you achieve healthier plants and bigger harvests.
Stage 1: Sprout Development
Sprout development is the very first stage of potato plant growth. The seed potato has “eyes” on it, and from there the new sprouts emerge. This is known as chitting. While it’s not technically necessary to chit before planting, you stand a better chance of getting the potatoes to grow instead of rot if you take the time to chit them before planting. Therefore, most people consider it an essential part of preparing seed potatoes for planting.
These sprouts are often pale with a green to light purple tip at first. You’ll likely have seen this type of potato growth on the old potatoes that have sprouted at the back of your cupboard.
Did you know you can plant those old sprouted potatoes?
Although you may think these white, delicate sprouts are roots, they’re not. They are the stems that shoot upward and form the above-ground foliage. Once suitably sprouted, it’s time to plant the potatoes so that they’re ready for their second life stage.
Stage 2: Roots, Stems and Leaves Appear
Once chitted and planted, potato plants start to form roots and stolons. Stolons are underground stems that the tubers will form on. The chitted stems push upward, breaking through the soil and form leaves and primary stems above ground. This is known as the vegetative growth stage.
During this rapid developmental period, the growing tuberous plant takes its food, including sugars and nutrients, from the seed potato it’s attached to. It cannot begin to photosynthesize until the leaves form and open, and so can use the sunlight to begin the photosynthesizing process, turning the sun’s energy into nourishment.
Stage 3: Tubers Begin Forming
Known as the tuber initiation phase, stage three is when the potato plant starts developing tubers on the stolons below the ground. The young tubers are little more than small nodules at this point, and their growth is slow. They’re really not big enough to eat yet.
Tuber initiation lasts until shortly before potato flowers appear. So, by the end of the initiation phase, you could be harvesting some small baby potatoes, although you won’t get the most bang for your buck if you harvest potatoes at this stage.
Stage 4: Tubers Swell
Tuber bulking occurs at this point. You may see flowers form, too, depending on the potato variety. Then the potato plant stops producing new leaves and flowers and concentrates on tuber growth, swelling the size of the tubers, where nutrients, water, and sugars are stored for the new growth cycle.
The potato tubers grow rapidly, increasing in size and weight. But wait! Don’t harvest potatoes just yet. Be patient for just a little while longer.
Stage 5: Potato Plant Reaches Maturity
As the potato plant grows to maturity, each potato tuber has achieved its full size, so plant growth above and below ground slows and eventually stops. If present plant flowers have already dropped, and fruits have formed which are now dropping, too.
Once mature, the potato plant starts to dry up. It loses its color, drops its leaves, and starts to die back as it completes its growth cycle and returns to the soil surface where it gets worked back into the earth to nourish the next generation.
It’s at this point that you can harvest potatoes. They won’t grow anymore and can no longer produce tubers, as the parent plant is dead. So get in there and dig! Here’s the time where you can reap the rewards of all the effort you put into growing potatoes.
Dig them up, cure them for a few days, then store them in a dark, dry, cool place until you want to eat them or plant them.
Things That Affect the Potato Plant Life Cycle
There are a range of things that can affect the life cycle of the potato plant. While the potato will try to fulfil its growth cycle, no matter what (hence the sprouted potatoes at the back of your cupboard), there are lots of variables that affect plant healthy, yield, and life cycle performance.
Soil Moisture Levels, Structure, and Nutrient Content
The quality of your soil has a huge impact on the life cycle of a potato as well as the performance and yield of a potato plant.
While potato plants do use the parent seed potato for nutrients and sugars during the early days, and they do photosynthesize for energy, they still need a ready supply of nutrients to be present in the soil, or they can die, experience stunting, or just not produce a good crop.
If you’re going to plant potatoes, you need to make sure the soil is free-draining but that you provide enough water throughout the season to sustain the plant and allow for proper water and nutrient uptake, and enough water for the plant to divert some to the growing tubers to help swell them before harvest.
Compact, heavy, and clay soils can also be challenging for potatoes. Grow them in loose, loamy soil wherever possible. Or, at the very least, use straw mulch, manure, or other organic matter to help improve soil structure year-on-year.
Ideally, plant potatoes in nutrient-rich sandy soil, with a slightly acidic pH of 6 to 6.5. If you don’t know the makeup of your soil or you think there may be a problem, get a cheap soil test kit so you can make the right amendments.
Potato Plants Are Sensitive to Air and Soil Temperature
Potato plants are tender and sensitive to soil and air temperatures. So be mindful when planning to grow potatoes. Remember that you need at least 100 days for mature potatoes before the first frost, or they won’t achieve maximum growth.
You can plant chitted potatoes when the ground reaches around 40°F (5°C), just a week or two before the last spring frost predicted in your area. Just be ready to protect any emerging plants with a cloche or a frost blanket if you get an unexpected late frost.
Early spring planted potatoes should be ready to harvest well before the first frosts and, if you plant sucessionally, you should have quite a few sewings of different potato varieties to harvest well into fall.
If you’ve still got actively maturing plants at the end of the growing season, when it looks like there’s going to be a freeze, you can cover the plant by adding an extra layer of straw mulch to keep the soil warm, and use a frost blanket or similar insulating protection around the potato plant rows if you want to give those tubers a few more days to reach maximum size.
Blight
Potato blight is a devastating, fast-spreading fungal disease that can decimate a potato crop in just a few days. And it lives in the soil for years, so potato grows desperately try to avoid it. It’s commonly introduced by people trying to grow grocery store potatoes, hence I only recommend growing those in containers, as it’s easier to keep blight from infecting your whole garden that way.
Early blight and late blight, while caused by different fungal pathogens, have the same catastrophic effect on potato plants, and there’s no way to stop it. If you’ve got a blight infection, you’ll see gray-brown spots on the potato leaves that quickly spread, engulfing the leaf with a type of wet rot that causes the leaves to die off. Lesions can also appear on the stems.
Picking off leaves with minimal symptoms can slow the progress of the disease long enough for the potato tubers to swell enough to make them worth harvesting. However, if more than 25 percent of the plant is infected, you should cut it off at the base and burn it or put it out for curbside collection. Whatever you do, don’t compost it!
Once the infected foliage is removed, you can dig up the tubers and use them. It’s not advisable to store tubers from infected plants because there’s a good chance the tubers are also infected. They’re perfectly safe to eat, but they might not store well and can pass the infection on to other potatoes.
The blight fungus can also infect tubers and the soil if they’re washed off the plant and onto the soil surface during watering or heavy rain. So be vigilant and pay close attention to your potato plants.
Potato Pests
Wherever you live, potatoes are at the mercy of a whole bunch of critters. For those of us who grow naturally and organically, choosing the right companion plants, attracting predatory insects, and picking the little blighters off by hand are usually the most effective forms of control. Because they’re in the same family, companion plants for peppers are also good choices for interplanting with potatoes.
Here’s a brief roundup of some of the most common and problematic potato pests.
Colorado Potato Beetles
Colorado potato beetles are one of the most notorious pests of potatoes. They can sweep through a crop and cause huge damage in no time. And, because they’ve been so heavily sprayed with pesticides to try and eradicate them, they’re resistant to just about every toxic chemical on the market.
Potato beetle larvae are red-bodied, with black dots on their sides and black heads and legs. Adults are oval, 3/8 of an inch long, and are yellow-orange with black stripes.
Control involves getting out among the potato plants and picking them off, attracting lacewings and ladybugs, and using repeated applications of neem leaf or oil spray (ONLY if you don’t have cats as neem oil is toxic to them).
Flea Beetles
Flea beetles are a pain in the ass for most edible crops, including broccoli, cabbage, potatoes, spinach, lettuce, melons, and more. Black, bluish, or bronze-hued, these tiny pests chomp irregular holes in leaves, causing so much damage that plant growth is stunted and yield decreases.
Because flea beetles like to hide in dead organic matter, aside from companion planting and predatory insects, one of the best control methods is to keep your growing area clean of litter and plant debris, and to control weeds. You can also use a plant that they love, like radishes, as a trap crop.
Aphids
Controlling aphids naturally is difficult, but since they can’t reliably be controlled by chemical treatments, there’s little other choice. Aphids are common and eat all kinds of plants, as well as potatoes. While small infestations aren’t problematic, in large numbers, they can stunt your potato growth and reduce yield.
Unfortunately, ants farm aphids for their sweet honeydew, which can increase aphid numbers and worsen the damage they do. You’ll need to employ a variety of techniques to keep on top of aphids, including washing them off, using a mixture of Doctor Bronner’s castile soap and water, controlling the ants (naturally), companion planting, and other natural methods to stay on top of the problem.
Cutworms
The larvae of the cutworm moth, cutworms are ravenous little critters that feed on all kinds of vegetable crops. Young plants are the most at risk, as the cutworms literally cut the tops off the emerging plants, effectively killing them.
Controlling cutworms involves looking at the undersides of leaves and picking the worms off. Either crush them in your fingers or drown them in soapy water. Gross but effective. To try to prevent their appearance, leave a border of four feet of dry soil around at-risk crops as the larvae don’t like dry conditions. They are only a significant problem, usually, in spring, when potatoes and other plants have tender stems that are easily cut.
Potato Leaf Hopper
Potato leafhoppers don’t just feast on potatoes (solanum tuberosum), they go after other crops, too, including alfalfa, and feed on the sap within the phloem. Unfortunately, they do a huge amount of damage to plant cells and also inject their saliva which acts on potato plants to reduce photosynthate movement, which significantly reduces crop yield.
Natural cultural control methods are the most effective, and include the introduction of predatory insects, including wasps, lacewings, and ladybugs. You can also pick off and drown the bugs as soon as you spot them. They have a distinctive appearance, being bright lime green, about an eighth of an inch long, with a broad head and big white eyes.
Wireworms
The larvae of the click beetle, wireworms are a scourge for potato growers. These nasty little wormy pests tunnel into potato tubers, leaving holes and tunnels behind that can open the door to rot and disease, not to mention other pests. Potatoes subjected to wireworm damage can’t be stored, because they’re full of holes and may still contain the wireworms.
Hilling Potato Plants
Hilling potato plants won’t directly affect the lifecycle of the plants, but it does help with certain issues, including reducing the risk of blight infecting the growing tubers. Hilling, or earthing up, also provides insulation, helps with moisture retention, and reduces sun damage.
Growing too close to the surface, exposed tubers suffer damage from sunlight and turn green, so they’re no longer safe to eat. Hilling helps to prevent this.
While all parts of the potato plant, including the tubers, contain a chemical called solanine, green tubers contain huge amounts, just like the fruit and leaves, rendering them poisonous and not at all safe to eat.
Never, ever eat green potatoes, nor any part of the potato plant, including stems, leaves, and sprouts. Only ever eat cooked, healthy potato tubers.
Tips to Increase Your Potato Harvest
There are lots of ways to increase your potato harvest. But here are some of my favorite quick tips that are easy to implement:
- Chit potatoes to give them the best start
- Get the timing right
- Leave enough space when planting potatoes
- Choose the Right Potato Varieties
- Test the soil and amend pH and nutrients if necessary
- Choose the Right Location
- Earth them up as they grow
- Be on the lookout for pests and diseases
- Wait until the tops die before harvesting
FAQs
It can take around 70 days to grow new potatoes, but for a full harvest of larger potatoes, plan for 80 to 120 days, depending on the variety.
Potatoes are annuals. They complete all stages of their growing cycle in a single year. Even in warmer climates, potato plants have a single season life cycle.
Unless you’re in a particularly dry location, no, potatoes shouldn’t need watering every day. To encourage deep roots, deeper stolons, and therefore potentially more tubers, only water deeply once or twice per week. Your potatoes need 1 to 2 inches of water per week and should be watered when the soil is moderately but not completely dry.
To fulfil the potential of their growth cycle and to produce the largest number of good-sized tubers, potatoes should get at least 6 hours per day of full sun.
Once potatoes reach the maturation stage, when their leaves start to yellow and die back, stop watering. At this stage, the plant is no longer actively growing, so can’t use the water. Plus, ideally, the ground should be dry when you harvest the potatoes, otherwise they’re more likely to rot in storage.
No, potatoes do not come back the next year. The old seed potato is used up by the new potato plant and, at the end of the growing cycle, the plant dies. However, if you don’t manage to harvest every last little potato from the plant, the following year, you may notice you have one or two volunteer potato plants growing. And that’s perfectly fine, as long as they don’t show signs of blight.
Yes, you’ll need to plant fresh seed potatoes every year. Potatoes are annuals, so their life cycle only lasts for growing season. And remember you’ll need to practice crop rotation, too, planting your potatoes in a new spot each year to avoid nutrient depletion and lower the risk of pests and diseases.