Potatoes are starch-storing tubers, and a staple crop that has a decent storage life. This means that whenever you harvest them, if you store them correctly, you’ll have homegrown potatoes for cooking for up to six months.
But how do you know when your potatoes are ready for harvest? If you want small, “new” potatoes, you can harvest them 7-8 weeks after planting. Otherwise, let the potato grow and wait for the foliage to die back. The timeframe will depend on the variety you have planted, but it’s a good rule of thumb to follow.
How Do You Know When Your Potatoes Are Ready to Harvest?
Generally, home gardeners harvest their potatoes late in the growing season. The key to when they are ready for harvest is in the foliage and flowers.
When to Harvest New Potatoes
Delicious, little new potatoes will be ready to harvest about 2-3 weeks after the plants stop flowering. This will be about 7-8 weeks after you planted them.
The skins of new potatoes are tender and you don’t have to peel them. You’ll be able to tell because the skins underground are thin and will rub off easily.
When to Harvest Mature Potatoes
If you want mature potatoes from your potato plants, they’ll last longer if you toughen them up for storage before you harvest them. Once they start to flower, give them very little water and leave the potatoes in the ground to continue growing.
You can harvest your fully grown potatoes when the tops of the plants have died back completely. But, it’s best to dig up a test plant to make sure that the potatoes are indeed mature.
Their skins will be thick and they won’t rub off easily like the skin of new potatoes. If the skin is still thin, leave the potatoes in the ground for a week or so longer.
It’s also good practice to harvest fully grown potatoes on a warm, dry day.
Another factor you must consider is that you need to get them out of the ground before the first hard frost. If they are left in the ground, they will freeze and you will lose some if not all of your crop.
What Happens If You Don’t Harvest Potatoes?
If potatoes are left in the ground long term, and you live in a cold climate where the ground freezes, the tubers will die. If the soil is wet, the potatoes are likely to rot.
If you live in a warm, dry climate, this is one of those garden crops that will sprout again in spring. But potatoes that were left in the ground may not be edible.
Oregon State University’s Extension Services experts advise that you should only eat them if the tubers are still firm and the skin isn’t green. They also warn that potato sprouts can be toxic.
The Michigan State University’s Extension horticulturist, Cindy Tong, warns that not only do green potatoes taste bitter, they can also cause diarrhea and vomiting.
How to Grow Potatoes From Last Year’s Crop
Certified seed potatoes are disease-free as per the United States Department of Agriculture (USDA) certification standards. Of course, seed potatoes aren’t seeds as such, but rather the potato eyes that sprout.
If you have grown your potatoes from certified potato plants, you can save some of them for planting growing and harvesting next year. Store them in a cool dark place so that they don’t sprout too soon.
About 3-4 weeks before it’s planting time again, move your seed potatoes to a warm place and cover with moist paper towels. The potatoes are ready to plant when they sprout. Simply cut into 2 ounces (56 g) segments, each with a sprout – and plant them. You will find some guidelines here.
Commercial producers of seed potatoes leave potatoes in the ground until they are fully mature. After harvesting, they leave them to cure for a couple of weeks to allow their skins to harden.
This is what we do after harvesting all mature potato varieties, although some varieties store better than others. In general, yellow and white varieties store better than the thinner-skinned red types.
How to Harvest Potatoes?
In a word, harvest your potatoes carefully! If you cut into potatoes while you are harvesting, you will damage them and they won’t last very long in storage.
It’s best to use a garden fork rather than a spade because it’s less likely to do any damage. If you do damage potatoes in the ground, eat those first.
Step 1: Dig Them Out
If the ground is soft and loose, you can probably pull them out of the ground with gloved hands. Otherwise, dig around the plant carefully with your garden fork, and lift the whole plant out of the ground.
Step 2: Let Them Cure
Leave them in a dark, dry, well-ventilated environment where the temperature is between 50 and 60°F (10 and 15.5°C) for 10-14 days.
As mentioned above, this allows the skin to harden. It also lets minor bruises and cuts heal. Most importantly, it will lengthen the storage life of your homegrown potatoes.
Step 3: Prepare Potatoes for Storage
Brush the soil off the potatoes. Don’t wash them as this can encourage mold and reduce their storage life.
If the soil was moist when you harvested them, let the potatoes air-dry before packing them away into storage.
Step 4: Store Your Potatoes
If you’ve got a root cellar, that’s the best place to store your mature potatoes. Otherwise, find another cool dark area like a garage or basement that will allow for longer storage life.
It’s important to keep them away from too much light otherwise they might turn green and you’ll have to discard them. Remember that the longer potatoes are in home storage the more likely they will be to sprout.
Store them loose in baskets or pack into perforated or mesh bags. Don’t put them into airtight containers or plastic bags.
How to Harvest New Potatoes
You can harvest all the new potatoes on your plant, or just pull a few off the plant.
If you want them all, dig down about 6-12 inches (15-30.5 cm) and pull out the plant. Otherwise, dig gently around the edges with a garden fork, and lift the potatoes to the surface. Take what you want and then replant the rest of the potatoes in the ground.
Don’t leave new potatoes to cure.
You might be able to harvest a second crop of new potatoes. Otherwise, you can leave them for longer, and harvest the rest when they are mature.
Should You Wash Potatoes after Harvesting?
You can wash potatoes after you’ve harvested them, as long as you are going to eat them soon. If you are planning to store potatoes (or some of them) for any length of time, then don’t wash them. All you do is brush off the excess soil.
New potatoes are best eaten within a few days of harvesting. But they will last for a week or so. Ideally, you shouldn’t wash them until you are ready to cook them. If you do wash them, keep them in the refrigerator.
Can You Eat Potatoes Immediately after Harvesting?
Yes, you can eat potatoes immediately after harvesting. In fact, that’s when they are at their best, especially little new potatoes.
But many home gardeners grow mature potatoes and store them for those cold winter months when stew and soups go down so well.
Cindy Tong from the University of Minnesota Extension recommends storing them in a cool place with a temperature of between 42 and 50°F (5.5 and 10°C). It should be dark, with 90% relative humidity – so not too dry.
This is warmer than the average root cellar and more humid than a refrigerator. So, give it a try.
Potatoes aren’t difficult to grow, and they will reward you with a staple vegetable that will last through the cool, winter months.
The question of when to harvest potatoes depends mainly on whether you want new potatoes or mature potatoes that you can store. Of course, you can have the best of both worlds and harvest some new potatoes, leaving the rest to mature for a later harvest.
It will also depend on when you planted your potatoes and when (and if) you expect the first hard frost. But ultimately, the key lies in the foliage and flowers of your potato plants.
New potatoes are ready to harvest 14-21 days after the plants have stopped flowering. Potatoes that are grown to maturity, and for storage, are ready to harvest once the foliage has died back.
This article has lots of gardening tips that will help you decide exactly when to harvest your homegrown potatoes. We have also shared tips on how to harvest your potatoes and how to store them.
Now, you can do some research on different ways of cooking potatoes. But whether you opt for a good old-fashioned potato and leek soup, mashed potatoes to serve with steak or sausages, or a nouvelle cuisine dish, we bet that you’re going to enjoy eating the fruits of your labor.