MSU Extension

Once the potatoes have cured, remove any that are shriveled or seem soft lest they cause spoilage in the remaining healthy tubers.

How And When To Harvest Potatoes

You’ve planted early, hilled carefully, cultivated and fertilized. Your potato plants are full and healthy. Now you’re wondering when to harvest potatoes you’ve so carefully tended. Knowing how to harvest potatoes will help you will help you get the greatest benefit from your crop.

About Potatoes

Potatoes are one of America’s favorite veggies, with each person consuming 125 pounds (11 kg) of the tubers per year! Available in sizes from tiny fingerlings to larger Russets perfect for baking, potatoes come in all sizes and colors.

Potatoes require little maintenance once planted. This cool weather crop is ideally suited for northern climates, but can also be grown as a winter crop down south.

Seed potatoes can be planted 2-4 weeks before the last frost date for your area, either directly in the garden or in buckets, bags, pots or even straw. Planting in some type of container makes for easier harvesting of potatoes, and is also a great solution for those with limited space.

If you are planting directly into the garden, you will need to hill up around the tubers as they grow. This simply means mounding soil periodically around the base of the plant, making sure the tubers are underground. If they are exposed to sunlight, they turn green and produce solanine,

How Long Until Potatoes Are Ready?

Early season potatoes mature in 60-80 days. Because of their thinner skins, this type of potato can only be stored for about 3 weeks.

Mid-season potatoes or second earlies are ready to be picked 80-100 days after planting. These potatoes store for up to a month.

Later season potatoes can be harvested after 100-130 days. They can be stored for 2-3 months.

How to Tell When to Pick Potatoes

There are a couple of indicators marking potato maturity and readiness for harvest. The first thing to look for is the vigor of the plants. When potatoes are almost mature enough to harvest, the plants have a tendency to begin to yellow and wilt. If you see this, it’s time to stop watering and wait for a week or two. After that time has passed the potatoes are likely ready to harvest.

Another indicator of potato readiness is to dig up a hill and have a look. Dig up a hill after the plant looks practically dead and/or the type of potato you’re growing has passed its date to maturity. Pick up a potato and rub your thumb on it. If it has thin skin that can easily be rubbed off, it’s a new potato. These can be picked and eaten, but they won’t store well. Leave the rest of the plants for a few more days to mature.

How to Harvest Potatoes

When you’ve ascertained the tubers are ready, use a garden fork or spade and as gently as possible lift the soil beginning at the outside edge of the plant until the potatoes are exposed. Take care not to damage the tubers, because this will open them up to bacteria and lead to rot. If you do accidentally fork a potato, use it immediately.

Harvesting Potatoes Grown in Bags

If you are growing your potatoes in a bag, wait until the foliage has yellowed and is dying back and then harvest your tubers. Simply dump the entirety of the bag onto a tarp. With your hands, dig through the soil and extract the potatoes. In a good year, expect to harvest about 7 pounds (3 kg) of potatoes.

How to Avoid Bruising

Bruising of potatoes is a more common occurrence in commercially harvested fields due to mechanical harvesters but it can still occur in the home garden. Again, be as gentle as possible with the tubers to avoid bruising which shortens shelf life by exposing them to diseases.

Curing Potatoes

Prior to storing potatoes for any length of time it is important to allow them to cure. Curing simply means placing the tubers in an area of between 45-60 F (7-16 C) with a relative humidity of 85-95% for two weeks.

What does this do? Curing potatoes is an important step that promotes skin thickening and healing of minor cuts and bruises.

Once the potatoes have cured, remove any that are shriveled or seem soft lest they cause spoilage in the remaining healthy tubers.

Should I Wash Potatoes Before Storing?

Never wash potatoes before storing them. Just gently rub excess soil from the tubers with your hands before curing the potatoes. If you wash them, they will be too wet which can facilitate molds and mildews; fungal diseases.

How to Store Potatoes

Store potatoes in a dark area with a temperature of 38-40 F (3-4 C) and a relative humidity of 90-95%. If temperatures are too warm, the tubers will sprout; if temps are too cool, they develop a sweet flavor.

Never allow the potatoes to freeze. Do not store in sealed, closed bags. Instead opt to leave them open in a box or container or in perforated bags so they get air flow.

Never store potatoes with apples or other fruit which produce ethylene gas that will promote sprouting.

Green Potatoes

As mentioned, when sunlight hits potato tubers, they turn green and produce a toxic compound. Even if you’ve been vigilant about hilling, sometimes one or two will slip by you and become green. Potatoes can even turn green during storage if they are stored where there is sunlight.

If the potato is mostly green, it’s best to discard it. But if there are just small green areas, pare them out with a knife and then the remainder of the tuber can be safely eaten.

MSU Extension

Knowing when to harvest homegrown potatoes and how to handle them after harvest helps gardeners end up with the maximum amount of potatoes possible to store for those cold winter months.

Potatoes are definitely one of America’s favorite vegetables. Did you know that each year we eat about 125 pounds of potatoes per person? Potatoes are a staple food and many home gardeners plant potatoes to store them for the fall and winter months. Knowing how to take care of your homegrown potatoes is important so that they store well.

Michigan State University Extension has these tips for winter storage of homegrown potatoes:

• Toughen up potatoes for storage before harvest by not watering them much after they flower.
• Let the potato plants and the weather tell you when to harvest them. Wait until the tops of the vines have completely died before you begin harvesting. When the vines are dead, it is a sure sign the potatoes have finished growing and are ready to be harvested.

Potatoes are tubers, and you want your plant to store as much of that flavorful starch as possible.

• 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.
• 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 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.
• 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. An interesting place you might not be aware of is the potato museum in Washington, D. C. that contains lots of history, information and artifacts relating to potatoes including antique harvesting tools.
• As you dig, be careful not to scrape, bruise or cut the potatoes. Damaged potatoes will rot during storage and should be used as soon as possible.
• After harvesting, potatoes must be cured. Let them sit in temperatures of 45 to 60 degrees Fahrenheit for about two weeks. This will give the skins time to harden and minor injuries to seal.
• After the potatoes have been dug, brush the soil off. Do not wash potatoes until you’re ready to use them. Washing can easily reduce the storage life and encourage mold.
• Store potatoes in a cool, dark area after harvesting. Too much light will turn them green.

Sometimes before harvesting some potatoes become exposed to the sun because they are just barely underground and not covered with soil. Keep soil over the potatoes to prevent sunlight from turning them green. If you want new potatoes, which are small, immature potatoes about 1 to 2 inches in size, harvest them just before their vines die. Remember though that the more baby potatoes you dig, the fewer full-sized ones you will have for later in the season.

After you decide when to dig up potatoes, get the whole family involved. Equipped with a small basket, even the smallest child can share in this fun and rewarding experience.

To learn even more about potatoes, go to MSU Extension’s Michigan Fresh website. This site has a wide variety of fact sheets that will help you use, store and preserve fresh, locally grown fruits and vegetables. You will also find information on flowers and ornamentals.