Potatoes are typically categorized into three main categories according to their days to maturity. They are classed as: early, mid-season, and maincrop potatoes. They may also be referred to as earlies, second earlies, and long-season or maincrop potatoes. While early and mid-season potatoes are typically harvested and eaten as new potatoes, late-season or maincrop potatoes are harvested and stored for the winter.
Potato types and varieties
Potatoes are generally grouped into three categories according to their days to maturity, but no hard and fast rule defines each group. Nurseries, seed companies, and even produce stands may list the same potato as either early or mid-season and some may even be labeled as long season.
But there are some generally accepted guidelines.
Early potatoes mature in 60 to 80 days, says HGTV. These potatoes are harvested and eaten as new potatoes. The tubers are generally small with thin skins. While flavor differs among cultivars, new potatoes have firm, waxy flesh that is sweeter than long-season potatoes.
Like all potatoes, early potatoes can be planted as soon as the soil can be worked in the spring, preferably when the soil temp reaches 40 degrees, says Cornell University. Potatoes planted in cold, wet soil may rot and take longer to sprout. Under ideal weather conditions, sprouts appear in two to four weeks.
Early potatoes are ready to harvest for new potatoes in June or July, depending on the variety and your region.
Some examples of early potatoes to try are:
- Red Norland
- Irish Cobbler
- Adirondack Blue
Mid-season potatoes mature in 80 to 95 days. They are typically eaten as new potatoes and do not store well. Most are slightly larger than early potatoes and have tougher skin but have similar flavor and texture, but again flavor and texture differ according to the cultivar.
Mid-season potatoes are ready to harvest a few weeks after early potatoes, generally in July. Mid-season potatoes are also planted in the spring once the soil warms to 40 degrees.
Some popular mid-season potatoes include:
- Gold Rush
- Ida Rose
Maincrop or late potatoes mature in 95 to 130 days (or more) depending on the cultivar. These potatoes are harvested in the fall in September or October when the foliage dies back. Maincrop potatoes are stored for the winter.
Maincrop potatoes have thick skins, are starchy, and are generally large tubers. They can be used for baking, fries, or mashed potatoes. They are also used in soups, stews, and casseroles.
Maincrop potatoes are planted in the spring when the soil warms to 40 degrees and the soil is dry enough to work.
Some common late-season (maincrop) potatoes include:
- Fingerling Salad
- Russet Norkotah
- German Butterball
- Canela Russet
When to harvest early potatoes
Potato plants begin tuber formation at the time when the plants begin to flower. That means you can generally begin harvesting tender, new potatoes in June or July – depending on the variety and your region. Harvesting can usually begin two to three weeks after the plants bloom. Visually the plant will be green, upright and strong, it may still have some of its flowers. The potatoes should be at least the size of eggs.
In many regions, new potatoes and peas are considered a delicacy for July 4th, but whether they are ready by then depends on both the weather and your growing region.
To check if your early potatoes are big enough to harvest, gently dig into the soil beneath the plants and check for tubers. If they are not big enough for your liking, replace the soil and wait another week or two before checking again.
While some prefer to pull the entire plant and harvest new potatoes, it isn’t always necessary. You can easily remove the largest potatoes from the plant and firm the soil back around the potato plant to let the smaller potatoes continue to grow.
When to harvest mid-season potatoes
Midseason potatoes mature two to three weeks after early potatoes, which is from July onwards, but you can use the onset of blooming as your guide to when the potatoes are almost ready to begin harvest. Young potatoes are generally large enough to dig and eat about two weeks after the plants bloom. Visually the potato plant may still be green and standing – similar to early varieties.
Waiting a few weeks longer will give the tubers time to mature. Eating them as new potatoes or letting them grow depends on your preferences. New potatoes (from early, mid, or late-season potatoes) have a distinctive sweet flavour and dense, waxy flesh, while more mature potatoes develop a starchy texture and flavour.
Check the size of the potatoes by digging into the soil with your hands before pulling the plants, as dates to maturity are only a guide. Your mid-season potatoes may reach full size earlier or later than expected.
When to harvest maincrop potatoes
Maincrop potatoes are the last type of potato to be harvested. Maincrop potatoes are usually harvested in September or October. The tops will have fully ripened, visually, the stems will have lost all their leaves, turned colour from green to yellow, then white, and will be laying flat on the surface of the soil.
Maincrop potatoes are normally allowed to fully ripen before harvest – although if the potatoes are starting to grow too big you can remove the tops to stop them from growing any further. Ripening usually begins from September onwards although it can continue until October.
An important part of harvesting maincrop potatoes for storage is skin-set. Skin-set is the toughening of the outer skin of the potato which takes about two weeks to happen when the potato has finished growing. This will occur whether you force the potato to stop growing eg; removing the tops or spraying a desiccant spray known as “burning off” the potatoes, or if the potatoes ripen naturally and the tops die off – so remember to allow time for this before you harvest.
How to harvest your potatoes
Potatoes are harvested for storage once the tops die back in the fall. Mature potatoes have a thick skin and can be stored for months once they are harvested and cured.
Harvest your potatoes during dry weather when the soil is dry. Potatoes harvested in wet soil are more susceptible to rotting and disease and are more difficult to clean. Dry soil brushes off the tubers easily and makes curing and storing them easier.
Pull the tops of the potatoes. Many tubers will lift free of the soil when you pull the tops. Shake the tops to remove excess soil and discard them in the compost bin.
Use a garden fork, garden spade, or a garden hoe to harvest the remaining tubers. A garden fork or spade may be necessary if the tubers are spread out and anchored deeply in the soil. Use care to allow a wide berth around the cluster of potatoes as you lift and turn them with the garden fork. Likewise, you can use a garden hoe to gently nudge the potatoes from the soil.
If you have only a few potatoes to harvest at a time, digging with a fork or spade is fine. If you have a lot of potatoes to harvest you may need a more mechanical way to dig your potatoes, like using a potato harvester. These come in varying shapes and sizes – from a single-row spinner fitted to a small tractor to a four-row self-propelled harvester.
Storing Your Potatoes
Fully mature maincrop potatoes can be stored for several months in the basement or other cool, dark area, but immature potatoes need to be used within a few days to maintain their flavor and texture.
However, you do need to cure your potatoes before you put them into long-term storage. Brush the soil from the tubers and allow them to dry in a shaded area for a few hours. Move them to a cool, dark area with a humidity level between 85 and 90 percent for two weeks to cure, says Iowa State University Extension.
Curing thickens the skin and heals any cuts or nicks from harvesting.
Store them for the winter in slatted wooden boxes or on shelves in a dark, well-ventilated area where temperatures remain between 45 and 50 degrees with a humidity level of about 90 percent.
Growing early, mid-season, and maincrop potatoes in the home garden will provide your family with fresh potatoes all summer. Early and mid-season potatoes provide delicious new potatoes in June and July onwards, while maincrop potatoes can be harvested from September onwards and stored all winter. Keep in mind that the specific cultivar grown also affects the flavor and texture of the potatoes. Check out this video summary of when to harvest potatoes -Enjoy!