Growing potatoes is rewarding, inexpensive, and fun. These tuber plants can be grown on a large scale, for commercial purposes, or in a backyard garden. Gardeners may opt to plant them in an in-ground garden or a container, but how long can you leave them in the ground?
In cold or moderate climates, potatoes can stay in the ground until late fall or early winter when the soil freezes. Conversely, in warmer areas, they run the risk of sprouting. Potatoes can typically stay in the soil for two weeks after the foliage dies but can go longer under the right conditions.
This article explores the conditions of harvesting potatoes. Read on to learn how long you can leave them in the ground.
Potato Growth Cycle
Before you can think about how long you should leave your potatoes (Solanum tuberosum) in the ground, you need to understand their growth cycle.
From planting to harvesting potatoes, the whole process takes about 3 to 4 months. It begins with the seed potato tubers, which form sprouts from buds often referred to as “eyes.” These sprouts then grow into stems and leaves of potato plants.
As the plants grow, they gather more sunlight and begin to develop potato tubers underground, typically before blooming flowers. The tubers finally grow into their mature size, and the plant’s leaves start to die.
When the plant’s foliage dies down completely, the tubers are ready to harvest.
Harvesting is the most satisfying part of growing potatoes. You get to uproot the succulent tubers and see the results of your work for the past 90 days. This part is so fun that even the kids will want to join in. It’s like digging up treasure you can eat!
However, you need to know when to harvest them because the potatoes won’t mature if you harvest them too early. On the other hand, if you take too long to harvest, the potatoes might begin sprouting.
When to Harvest Potatoes
The right time to harvest potatoes depends on why you need them.
For example, if you want to reap the tubers for winter storage (known as main crop potatoes), you should observe the weather and the plant for signs. Wait for the plant’s foliage to die completely before you can start harvesting.
You should also factor in the temperature of both the air and soil. In areas where the air is cool without frost in fall, soil temperature will dictate when you can harvest your tuber. Typically, your soil should be above 45 °F (7.22 °C) for you to harvest main crop potatoes.
Maincrop potatoes need to develop a tough skin for longer storage. As a result, you should only harvest them when you’re sure that the tuber is mature enough.
On the other hand, the timing is different if you want to harvest potatoes for dinner. Digging up potatoes for dinner is much easier.
These are known as new potatoes and don’t need to mature fully. You just need to wait until late in the season 50 to 55 days after planting and take only the tubers you need. The first sign you need to look out for is the blooming flowers.
For a long harvest of new potatoes, stagger your seed potato plantings or mix late and early-maturing varieties. This way, you can enjoy fresh potatoes from late spring to early fall.
How to Harvest the Potatoes
Now that you know when to harvest potatoes, you need to know how to do it right. The harvesting process must also be meticulous to avoid damaging the precious tubers. It’ll also be determined by whether you’re harvesting new potatoes or maincrop potatoes.
New potatoes are small and tender and do not store well. These should be harvested and eaten right away. You can harvest them using a garden fork or shovel, and if you’re careful, you can replant the plant’s small tubers to grow.
However, if you’re harvesting potatoes for storage, wait until all the foliage has died before you start harvesting. Then, dig up a few tubers to test maturity.
If the potatoes’ skins are still thin and light, they’re still “new” and not ready for storage. To encourage faster maturity, cut off the stems and leave the tubers for a few days without water.
When the tubers are mature enough, follow these few simple steps to dig them up:
- Push a garden fork or spade about 6 inches (15 cm) from the base of the plant.
- Lift the plant with the fork and shake off the soil.
- Gather the potatoes and dispose of any that have green skin. (This indicates a toxin called solanine.)
- Lift the loose soil near the potato with the spade or garden fork to discover any tubers you might have missed.
- Discard the foliage and the original potato seed to prevent diseases.
The tubers are now ready for storage. However, unlike new potatoes, you shouldn’t wash main crop potatoes after harvesting. While it’s hard to resist the temptation, washing the potatoes introduces moisture to their skins, which is not good for storage.
I recommend watching my YouTube video below if you’re a visual learner. I’ll visually walk you through how long you can leave potatoes in the ground and the telltale signs you need to look out for during this period.
Factors That Affect How Long Potatoes Can Stay in the Soil
Generally speaking, leaving your potatoes in the ground after the foliage dies is not recommended, especially for long-term storage. Leaving them under a layer of soil that will probably become wet might either cause them to rot or encourage sprouting. Both of these results aren’t good for your produce.
You can leave the tubers in the ground for up to two weeks after the potato foliage begins to die. If you take longer than that, the tubers might start sprouting if the soil temperature and moisture support it. Otherwise, they’ll start rotting.
Anecdotal evidence proves that you can leave potatoes in the ground for much longer. However, what works for other farmers might not work the same for you.
If you want to know whether or not you can keep your potatoes in the soil longer, you can refer to the following factors to consider below:
Under perfect conditions, you can leave your potatoes in the ground all year round and expect new growth every growing season. However, not all areas share the same climate, and your region’s climate can determine how well and how long your ground can store potatoes.
The temperature conditions required for growing and storing potatoes in the ground are quite simple:
- Soil temperatures of 55-65 °F (13-18 °C) for 10-21 days for germination.
- Warm air temperatures of 60-70 °F (15.6-21 °C) for 60-90 days for tuber development.
- Soil temperatures of 40-50 °F (4-10 °C) for ground storage.
Cold (USDA Zones 1-5)
In cold regions with freezing winters, it’s best to take the tubers out of the ground before they freeze. However, some people had success leaving the potatoes underground over winter with adequate mulch.
This may be because potatoes are typically buried deep into the ground—about 4-6 inches (10-15 cm) deep. USDA zones 11 and 12 typically have frost depths of zero, whereas that for zones 1-10 can vary significantly.
Frost depths, also known as frost lines, are the measure of how deep the soil freezes in winter. Having a low frost depth means your potatoes are safe from the freeze. With about 2-4 inches (5-10 cm) of mulch and dry winter conditions, potatoes will have better chances of enduring the winter.
Temperate or Moderate (USDA Zones 6-9)
If you live in a temperate region with mild winters, it’s usually safe to keep the potatoes in the ground over winter, especially if you have dry winters and low frost depth. If the soil conditions remain suitable for growth, your ground-stored potatoes may sprout again in spring.
Warm or Hot (USDA Zones 10-12)
In warmer regions, farmers typically grow potatoes in early spring and harvest by summertime. The hot summer will then cause the tubers to enter dormancy. However, warm fall temperatures may give your potatoes the false signal that it’s time to break out of dormancy and begin sprouting. Unfortunately, the crops will die at the first fall frost.
Even if your region doesn’t reach freezing temperatures, fluctuating temperatures dipping below 55 °F (13 °C) during fall development will result in poor-quality yields or plant death. In worse cases, your tubers may even become mushy or rot, especially when you keep the soil moist.
As discussed, potatoes take 3-4 months to mature and be ready for harvest. If you live in a cooler region and started planting potatoes in late spring, you’ll most likely harvest them by late summer or early fall.
You can delay your harvest because the high temperatures will force the tubers to go dormant. By fall, the tubers will have a hard time breaking out of dormancy because the soil temperature will be too low for the potatoes to germinate. Therefore, they will remain dormant.
Amount of Rainfall
One crucial factor to consider when keeping potatoes in the ground for storage is the amount of rainfall in your area. Light rains that soak only the top 3 inches (7.6 cm) of the soil shouldn’t be a cause for alarm. However, heavy rains can saturate the soil deeply enough to reach your potato tubers.
With such an amount of moisture, your potatoes run the risk of sprouting or rotting. Therefore, you should dig the tubers out 2-3 days after the rain and air-dry them in onion bags for winter storage.
Pro-tip: Never wash your newly harvested potatoes to avoid unnecessary moisture that can invite harmful microbes during storage.
Soil Pests and Pathogens
Another important factor that affects how long potatoes can safely stay in the ground is the presence or absence of soil pests and pathogens.
You can inspect the harvested potatoes for signs of pest infestation or disease. If they show bite marks or discoloration (black or green spots), then it’s best not to keep your potatoes in the ground for too long after the foliage dies.
Digging out your potatoes and growing new plants or cover crops in the fall will help eliminate or reduce problems with diseases or nematodes.
Storing Potatoes in the Ground
Once you’ve determined that your environmental conditions are suitable for storing the potatoes in the ground—or if you simply want to give it a try—you’ll have better chances at success by keeping the following steps in mind:
- Mark the spots where your potatoes are. This will make it easier to distinguish your potato patch from neighboring plants, especially if the hilling flattened while you harvested the other tubers.
- Avoid watering the soil near your potatoes. Typically, potato rows should be 2-3 feet (60-90 cm) apart from one another and from other plants in your farm or garden. If the neighboring plants are still growing and need adequate water, ensure to water only their root zone and avoid getting your potatoes wet.
- Install pest or animal repellents when necessary. Field mice, voles, and rabbits are only a few of the animals that will try to feed on your potatoes left in the ground. You can place physical barriers around your potatoes, such as gopher or vole cages. You can also grow marigolds around your potato rows as trap plants for nematodes.
- Add 2-4 inches (5-10 cm) of mulch as the nighttime temperatures drop below 45 °F (7 °C).
How to Store Harvested Potatoes
Storage is another important aspect of growing potatoes. If you store the tubers in the right conditions, they can last for weeks or even months. However, if you expose them to elements like moisture or heat, they will sprout or rot.
Store in a Cool Place
When stored between 43 and 50 °F (6-10 °C), raw potatoes can go for many months without spoiling. This temperature is slightly higher than refrigeration and can be achieved with basements, cool cellars, sheds, or garages.
These conditions discourage the formation of sprouts, a strong sign of spoilage. As a matter of fact, studies show that potatoes stored in cool conditions had four times the shelf life of potatoes stored under normal conditions.
Further research revealed that potatoes stored in cool conditions retain their vitamin C content longer than those stored at room temperature. Therefore, keeping potatoes at cool temperatures, slightly above refrigeration, is a great way to maintain their vitamin C content and extend their shelf life.
Keep Away From Other Produce
Many fruits and vegetables emit ethylene gas as they ripen. The gas helps them soften and increases their sugar content.
However, if you expose potatoes to the gas, they will soften and sprout much faster. Therefore, avoid storing potatoes near ripening vegetables and fruits, especially tomatoes, bananas, onions, and apples.
Although there are no scientific studies to show how far potatoes should be kept from fruits and vegetables, storing them on the other end of a dark room should be enough.
Place in an Open Paper Bag or Bowl
Potatoes need good air circulation to avoid the accumulation of moisture. The best way to achieve this is by placing them in an open airbag or bowl. Don’t store them in an enclosed container with no ventilation, such as lidded glassware or a zipped bag.
With no air circulation, moisture from the tubers will accumulate in the container, promoting the growth of bacteria and mold.
Don’t Store Potatoes in a Freezer or Refrigerator
Although cool temperatures are ideal for potato storage, freezing or refrigeration is not. Freezing potatoes can cause cold-induced sweetening.
This is when some of the starch is converted into reducing sugars. These sugars can form carcinogenic chemicals known as acrylamides when the tubers are fried or exposed to very high cooking temperatures.
If you’re curious, check out my article on how to harvest and store the most popular fruits and vegetables: How to Harvest and Store Your Fruits and Vegetables
Keep Some Plants to Use as Seeds
If you plan on replanting potatoes, you can set aside some tubers to use as “seeds.” Then, a few weeks before planting season, bring the potatoes to a warm sunny area and cover them with moistened paper towels or moist burlap. Soon, the potatoes’ eyes will begin to sprout shoots.
When it’s time to plant, you can cut big potatoes into two segments so that each part has a shoot. In a few months, each sprout will produce an entire hill.
Common Related Questions
Will Potatoes Grow Back After the Plant Dies?
Potatoes will grow back, but they won’t keep growing immediately after the plant dies. When the foliage dies back, the tubers will enter a dormant stage for about 4-8 weeks as they generate enough energy for new growth. The dormancy period can extend much longer if the conditions aren’t ideal for growth.
Potatoes are cool-weather crops and require soil temperatures to be steadily between 55 and 65 °F (13 and 18 °C) to germinate. In the summer, as the temperatures rise over 68 °F (20 °C), the tubers slow down or stop developing.
Can You Eat Potatoes That Have Been in the Ground All Year?
You can eat potatoes that have been stored in the ground all year as long as there are no discolorations or bite marks. Green spots on potatoes indicate the presence of the toxin solanine, whereas bite marks indicate nematode infestation. Also, make sure the tubers are firm and not mushy.
In addition, always choose potatoes without sprouts. If they’re showing early signs of sprouting, you can eat them after you remove the buds or eyes. If too many eyes have sprouted about a quarter inch (0.63 cm) big, you might as well leave the potato in the ground to grow into a new plant.
To Sum It Up
Leaving potatoes in the ground is not recommended. However, the tubers can stay in the soil for up to two weeks after the foliage dies without spoilage. In moderate climates, the potatoes can even stay up to late fall or early winter without sprouting.
If your area has dry winters, potatoes can even stay in the ground over winter as long as there’s up to 4 inches (10 cm) of mulch to insulate the soil.