How to Know When to Harvest Potatoes

Tips on how to know when to harvest potatoes. Includes different signs to look for, such as what happens to their foliage and flowers. Also includes information on when to harvest new potatoes versus maincrop varieties.

One of the easiest vegetables to start growing is the humble potato. They’re relatively simple to plant and care for and so fun to dig up! Each plant, on average, can give you around eight to ten potatoes, making them a delicious and worthwhile crop. There are also dozens of different types of potatoes that you can grow. Everything from varieties bred for sweet and tender new potatoes to oblong-shaped fingerling varieties to huge baking potatoes. Then there are the colors! Red potatoes, yellow potatoes, purple potatoes, and multi-colored potatoes. Though most types can be grown similarly, knowing when to harvest potatoes comes down to their type and when you plant them.

Don’t worry, though — growing them is relatively easy, as is knowing when to harvest potatoes. Especially if you know which type of potato it was that you planted. Knowing when it’s time to dig them up is a breeze if you have that information on hand. You either wait for the allocated time or watch the plant for the signs it gives that the potatoes are ready. If you’ve forgotten which type of potatoes you’re growing, you can use these signs to work out when to harvest them.

Two Main Types of Potatoes

The time it takes potato plants to produce a crop is dependent on whether the potato is an early potato variety or a maincrop (storage) variety. Early potatoes need much less time from planting to harvest and grow good crops of thin-skinned new potatoes. You tend to harvest early potatoes in late spring to early summer since they take around eight to fourteen weeks (55-100 days) to harvest. Maincrop varieties take much longer, often around five months.

Within the early category, you have potatoes that grow faster than others. The quickest is ‘first early’ potatoes, which can give you a harvest of new potatoes eight to twelve weeks after planting, depending on the variety. ‘Second early’ potatoes generally take fourteen to sixteen weeks to mature, which is excellent because it staggers the harvest if you plant both first and second earlies in your garden. You can plant them at the same time or wait a couple of weeks to stagger the harvests more. 

In the maincrop category, there are also early maincrops, ready between sixteen and twenty weeks after planting, and ones that need a little more time. Harvesting them is a little different than early varieties and will give you thicker-skinned potatoes that you can bag up and store for months.

When to Harvest First Early Potatoes

My favorite potatoes to grow fit into the first early category. You can plant them two weeks before your last frost date and have a crop two to three months later! First early potatoes are small and tender-skinned and taste incredible in those early days of spring. You can start harvesting them when they’re about the size of an egg or leave them in an extra week or two to plump up to a larger size.

I’ve grown several varieties over the years, including Arran Pilot, Home Guard, Lady Christl, and the only first early potato with red skin (that I’m aware of), Red Duke of York. My hands-down favorite is called Annabelle, a tender new potato with creamy yellow flesh. 

I’m zone 9a and plant first earlies on or around St Patrick’s Day, but I have planted them as early as late-February before. If a frost comes after the potato foliage is up, it can damage them, which is why many people earth up their early potatoes. That means drawing soil or compost up around the plant, even completely covering the foliage. You can also use a row cover to protect potato plants from frost.

Depending on the variety, early potatoes can be ready to harvest in as little as two months. If you’re growing a row of first early potatoes, dig one plant up after that time and see what the yield is like. Otherwise, wait longer, or you can often refer to the flowers the plant produces. Most early potato varieties will produce flowers in June, quite pretty ones too. Many are white, but they come in purple and pink too. Once the flowers start to go over or the unopened flower buds drop, you know that the potatoes are ready to harvest. This will take anywhere from eight to twelve weeks after planting.

 When to Harvest Second Early Potatoes

Second Early potatoes take two to four weeks longer to crop than First Early potatoes and include varieties such as Anya, Charlotte, British Queen, Nadine, and International Kidney (Jersey Royals). This longer cropping time comes in handy in the vegetable garden since it means you can finish eating the first earlies before beginning to harvest second earlies. Second early potatoes take anywhere from twelve to sixteen weeks (three to four months) to harvest but are otherwise the same as first earlies. They often produce flowers and don’t store well, so dig them up and eat them within a week. The tenderness and fresh flavor of early potatoes can fade quickly. Even if stored in the fridge or cupboard.

Second early potatoes generally produce flower buds that sometimes bloom and sometimes don’t. It’s time to dig up your tender, homegrown potatoes when the buds drop or the flowers that do bloom begin to fade. At this point, the leaves will still be green, but some may start fading to yellow. The potato crops from second earlies can be like first earlies in size and tenderness. Leave them growing for longer, and the potatoes can get bigger too! There’s a fine line between big early potatoes with tender skin and big early potatoes with thickened skin, so don’t leave them too long.

When to Harvest Maincrop Potatoes

Maincrop potatoes, also called late-season potatoes, are the larger storage types that we dig, dry, and store for use over the winter. These are thicker-skinned potatoes that we don’t eat the skin of (usually), and they take a lot longer to grow. They can be cooked as baking/jacket potatoes or peeled, fried, roasted, or boiled. In the USA, these include russet potatoes, any storing potato with brown skin and floury white flesh. Maincrop potatoes can have other skin and flesh colors, too! I grow an entirely purple potato called Purple Majesty that stores well, and King Edward, Cara, and Pink Fir Apple (a fingerling potato) are also popular UK maincrop potatoes.

Maincrop potatoes can be planted at the same time or up to a month later as second early potatoes. They need a lot more time to grow to maturity — around 20 weeks. Over the summer, they swell and develop, resulting in harvests large in both size and quantity. You harvest main crops in late summer, typically from August to September, and you know the time is right when the foliage on the plants begins to turn yellow. It will then wilt and dry; eventually, only brown withered leaves and stems will remain. 

Maincrop Potato Foliage Dies Off Naturally

As they begin to die off, you can cut the foliage off an inch or two from the ground or wait until the plants are completely dead and brown. Wait a further two weeks before digging the potatoes from this point. The tubers need this time to develop a thicker skin that will help them last longer in storage.

Maincrop potatoes may also produce flowers and sometimes green berries (toxic, don’t eat), but these will come at the end of summer. If the foliage starts to die back or develop black spots before four months from planting, it may also be a case of potato blight or another potato disease.  If you determine that your potatoes have blight, remove all the foliage and stems and either burn or throw them away. Wait two weeks, then dig the potato tubers up. Throw any away that have black splotches or remain wet after drying.

What do Potato Plants Look Like when Ready to Harvest

If you’re unsure about which type of potato you’re growing or when to harvest potatoes from it, you can do a couple of things. First, watch the foliage and flowering cycle, and second, manually check to see the size of the potatoes at any given time. 

If the potato variety produces flowers, it will be towards the end of its growing season. Keep in mind, though, that not all potato plants will produce flowers. Still, most early potatoes have flowers and those appear in late spring to early summer. If you don’t see blossoms on your plants then, there’s a good chance that the plants aren’t earlies.

Foliage can be a dead giveaway for knowing when potatoes are ready to harvest. Not so much with early varieties, though the lower leaves may start to yellow when ready. With maincrop potatoes, the foliage and stems above the ground will completely die off. It happens from late August to early September, and the plants will wither into brown husks. Be aware that potato blight can cause similar foliage to die off, but it tends to happen earlier than you’d expect.

Still stumped? Another way to check when to harvest potatoes is to dig up an entire plant from the row or gently pull the soil from around the base of the plant. Either will quickly if decent-sized potatoes are waiting under the ground. Potatoes grow relatively shallowly, so you should find some just an inch or two around the base of the plant. Maincrop potatoes don’t produce much more than pebble-sized potatoes until later in the summer. If you use this method, I’d recommend doing this from the twelve-week stage at the earliest, and only if you haven’t spotted flowers on the plant.

How to Harvest Potatoes

There are a few different ways to grow potatoes, and how you harvest them depends on how they’re growing. If you’ve planted them in the ground, use your garden fork to dig them up. Place it a good distance from the plant, about 12-18 inches from the base, and dig from there. Your aim is not to spear any potatoes as you dig since you can’t store damaged potatoes. Set any damaged potatoes aside to eat on that day.

Another way to grow potatoes is under mulch; you’ll sometimes see the method referred to as no-dig potatoes. You set the seed potatoes on the soil’s surface and then cover them with a thick layer of compost or straw. The potato plants grow right up through the mulch, and the potato crop is incredibly easy to harvest. You simply push the mulch aside and harvest your spuds.

Potatoes can also successfully be grown in containers. Some gardeners even prefer growing them that way! You plant one seed potato in a large pot, basket, or container, and when it’s finished growing, you upend the container and harvest your potatoes. Early varieties of potatoes are usually determinate, meaning they only produce a certain number of potatoes at the base of the plant. Some main crop potatoes are indeterminate, though, just like tomatoes. If you keep earthing them up, they’ll continue growing potatoes up their stem. That’s how some people get huge harvests from a single plant. 

Harvest Maincrop Potatoes as Early Potatoes

If you cannot find potatoes specifically bred to be first or second earlies, you can still harvest new potatoes from maincrop varieties. Beginning in July, use your hands to pull the soil or mulch from around a plant. Take just a few baby potatoes from the surface, then cover the plant back over. Taking a few potatoes from each plant won’t hurt it, and the rest of the potatoes can continue growing into big storage potatoes.

Though you can harvest many main-crop potatoes as earlies, or carefully dig a few out after the plant has flowered, I think it’s best to grow types specifically bred to be earlies. They’ll crop earlier and be bred for flavor and texture. I don’t often grow maincrops, but when I do, I tend to leave them to grow into the biggies they’re supposed to.

Storing Early Potatoes

Early potato varieties produce delicious thin-skinned tender potatoes, but unfortunately, they don’t store well. Once you dig them up, you can keep them in a cupboard or the refrigerator, but the flavor is best if you cook them within a week. Alternatively, you can leave first earlies to continue growing in the ground. The potatoes will initially get bigger and still have that tender new potato skin. However, if you leave them in the ground for too long, the skin will thicken, and the flesh texture may change.

If you have too many early potatoes to eat, you can temporarily leave them in the ground. Just be aware that you may need to peel them before cooking them. Alternatively, you can preserve potatoes in a pressure canner. They’re a low-acid vegetable that needs precise handling and canning to make them shelf-safe. Pressure canners are not common in Britain and Europe but are widely used by preserving enthusiasts in North America. 

Storing Maincrop Potatoes

Unlike early potatoes, maincrops are suitable for long-term storage. First, you should inspect the potatoes and choose only undamaged ones for storage. Any that are damaged or have scab should be set aside for eating relatively soon. Then dry them thoroughly (called curing potatoes) before putting them in bags or cardboard boxes for storage. Don’t wash the soil off the potatoes or it will shorten their storage time.

You cure potatoes by spreading them out in a warm, dry place such as a garage or greenhouse. You could even leave them outside in the sun for a few hours, turning them over after one side is dry. Leaving potatoes in the sunlight for a day or two can cause them to turn green, though. Small amounts of green are harmless, but if a potato turns dark green, you want to avoid eating it.

After drying them off for a suitable time, check to see if there are any wet spots. These could be the beginnings of rot or disease. If you find any, set them aside to cook immediately before bagging up the others.

Store potatoes in hessian or paper bags in a cool garage, basement, shed, or a root cellar if you have one. Check them regularly to spot any signs of rot or pests and ensure you eat the best ones first. Someone I know once tried to save the best ones for last, but by the time he got to them, the mice had already had their turn.

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