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When you look in a seed catalog, you may see potatoes described as “main crop”. This has a specific meaning in terms of time to maturity and other factors. So, what are main crop potatoes? Main crop potatoes are varieties that take longer to mature (usually 100 to 160 days, or 14 to 23 weeks). Main crop potatoes are larger than early potatoes, and they keep better in storage. Some main crop potato varieties include Canela Russet, German Butterball, Gold Rush, Kennebec, and Yukon Gem. Of course, there are lots of main crop potato varieties to choose from, in addition to the ones listed above. In this article, we’ll talk about main crop potatoes and answer some common questions about them. We’ll also give some information on selected main crop potato varieties. Let’s get started. What Are Main Crop Potatoes? Main crop potatoes are large potatoes that keep well in storage. Due to their larger size, main crop potatoes generally take a long time to mature (often 110 to 160 days). Main crop potatoes are plants that produce larger tubers later in the growing season. These tubers usually store well. Main crop potatoes are sometimes known as mid potatoes (mid-season potatoes) or late potatoes (late season potatoes). What Is The Difference Between Early & Main Crop Potatoes? Early potatoes (also called early season potatoes) are varieties that mature faster than others. Often, the tubers are ready to harvest in summer. Some early potatoes only take 60 to 80 days to mature. Early potatoes include varieties like Adirondack Blue, Algonquin, Belmonda, Dark Red Norland, Red Gold, and Yukon Gold. Yukon Gold potatoes are an early variety that produces mature tubers sooner. Main crop potatoes are generally larger, store better, and take longer to mature than early potatoes. The table below summarizes the differences between early and main crop potatoes at a glance. TypeEarlyPotatoesMainCropPotatoesNamesearlyseason;earlymid-season;mid;late season;lateDays ToMature60 to 80days (9 to 13 weeks);some upto 90 days100 to 160 days(14 to 23 weeks)SizeVariesMost arelarger thanearly typesSkinThinnerThickerStorageMost do not store as wellCan storelongerthan early typesExamplesAlgonquinBelmondaRed GoldButteCarolaGold RushYukon GemThis table summarizes some of the differences between early season and main crop potato varieties. Main Crop Potato Varieties Here is a list of main crop potato varieties that will give you a start (it is not exhaustive!): Butte Canela Russet Carola German Butterball Gold Rush Green Mountain Kennebec King Harry Purple Peruvian Red Chieftain Russet Burbank Yukon Gem You can find more details on these potato varieties below. Butte This main crop (late season) russet potato variety has tan to brown skin and smooth, buttery, white flesh. The large tubers are good for baking, mashing, and frying. (You can find a recipe for twice baked mashed potatoes here.) Released in 1977, Butte tolerates both scab and late blight. The tubers mature in 110 to 135 days. You can find Butte potatoes from Stark Brothers. Canela Russet This late season heirloom potato variety has tan to brown skin with bright white flesh. It is good for fries or baked potatoes. Canela Russet is high-yielding and stores well. The tubers can grow up to 2 pounds, and harvest is 100 to 130 days after planting. You can find Canela Russet potatoes from Gurney’s. Carola This German main crop potato variety has yellow skin and yellow flesh. The large tubers are good for boiling, baking, mashing, and scalloping. Carola stores well and maintains the taste and texture of new potatoes, even after months in storage. Resists scab and other diseases. You can find Carola potatoes from Gurney’s. German Butterball This potato has light brown or yellow skin and yellow flesh. True to its name, the flesh is buttery and smooth, yet dry – perfect for roasting or frying in the winter. German Butterball potatoes have light brown skin and yellow flesh that is buttery and smooth.Image courtesy of user: Idealites via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:German_butterball.jpg This variety boasts high yields and it stores well. It has resistance to scab, but is susceptible to Rhizoctonia. You can find German Butterball potatoes from Fedco Seeds. Gold Rush This mid-season potato variety is a russet variety with thick, rough, brown skin and white flesh. It is perfect for making baked potatoes. The tubers store well and resist hollow heart. The plant itself has moderate resistance to Verticillium wilt, blackspot, and scab. You can find Gold Rush seed potatoes on the Johnny’s Selected Seeds website. Green Mountain This main crop potato variety (mid to late season) is an old one. Its tubers are oblong with white skin and white flesh, good for frying, baking, and boiling. Green Mountain produces a good yield and stores well. Unfortunately, it is susceptible to scab and late blight. You can find Green Mountain potatoes from Grand Teton Organics. Kennebec This potato variety is quite productive, with thin tan skin and smooth white flesh. It is good for frying, baking, or boiling. One downside is their thin skin, which makes them bruise easily. Kennebec potatoes are very productive. The tubers have tan skin and white flesh, but thin skin that bruises easily. Kennebec boasts high yields and disease resistance (including late blight). It matures in 80 to 100 days. You can find Kennebec potatoes from Renee’s Garden. King Harry This main crop russet potato variety (from Cornell University) is a unique one. Its tubers are round with tan skin and white flesh. King Henry has pest resistance due to sticky leaf hairs that deter insects. It also has some resistance to Colorado Potato Beetle. You can find King Henry potatoes from Hudson Valley Seed. Purple Peruvian This main crop potato variety is an heirloom from the Andes Mountains (where potatoes got their start many years ago!) Its tubers are smaller than other main crop potatoes, but they still boast dark purple skin and light purple flesh. Purple Peruvian potatoes are smaller than other main crop pottaoes, but they boast dark purple skin, light purple flesh, as well as resistance to heat and drought.Image courtesy of user Stephen Lea via Wikimedia Commons: https://commons.wikimedia.org/wiki/File:PurplePeruvianPotatoes.jpg Purple Peruvian resists both heat and drought. The skin is thin, so you won’t need to peel them unless you want to. You can find Purple Peruvian potatoes from Hudson Valley Seed. You can also learn about other purple potato varieties here. Red Chieftain This mid-season potato has thin pinkish-red skin and firm, moist, white flesh. It is good for boiling, or for use as new potatoes (harvested before maturity). It has better flavor than Dark Red Norland (and stores better). It also resists late blight. You can find Red Chieftain potatoes from High Mowing Seeds. Russet Burbank This thick-skinned heirloom potato variety has tan to brown skin with dry, white flesh that makes it ideal for baking, frying, or mashing. It takes 120 days to mature, but it’s worth the wait, which is probably why it is one of the most popular in the U.S. Russet Burbank potatoes have thick brown skin and white flesh. Often called the Idaho Baking Potato, the tubers are large and oblong, storing well in the long term, even during the winter. You can find Burbank Russet potatoes from Gurney’s. Yukon Gem This mid-season potato has light tan skin and buttery light yellow to white flesh, good for baking, boiling, or frying. The tubers are round or oval – excellent flavor (same as Yukon Gold). Developed by North Dakota State University, it stores very well and also resists both scab and late blight. You can find Yukon Gem from High Mowing Seeds. How Far Apart To Plant Main Crop Potatoes? A good rule is to leave 1 foot (12 inches or 30 centimeters) between main crop potatoes. This spacing will maximize the number of plants you get, while minimizing the chance of disease and competition between plants (due to overcrowding). Leave 12 inches (or a little more) between potato plants to avoid overcrowding, which leads to competition and disease. If you want larger tubers, you can leave a little more space to give plants more room to breathe (perhaps 15 inches, although this means only 80% as many potato plants in the same space). Remember to leave 3 feet (36 inches or 91 centimeters) between rows of potato plants. This will give you room to move between rows during the season so you can water, check for pests, and hill up potatoes. Can I Plant Main Crop Potatoes In Bags? You can plant main crop potatoes in bags, but remember that you will need a larger grow bag. Main crop potatoes tend to produce large tubers, so they will need more space in the soil to grow to full size. Make sure that your grow bag is large enough for main crop potatoes. Also, remember that you will need enough space in the bag for each plant (12 inches between plants). For example, in this 16 inch diameter grow bag, you could plant 3 seed potatoes (4 might be pushing it). Of course, you can also try out containers with sides that open for easy harvest, like the ones here. (Or, you can just pour the contents of the bag over a sifter to separate the tubers from the soil!) When Should I Plant Main Crop Potatoes? A good general rule is to plant main crop potatoes “as soon as the soil can be worked”. Basically, this means that the soil has thawed enough that you can actually dig in it (without breaking your shovel)! It’s also nice if the snow is already gone from the ground! However, you can still clear away a place to plant potatoes if the ground is thawed and you are convinced there will be no more frost. If you want to be more precise, wait until 2 weeks after last frost to plant potatoes. Wait until 2 weeks after your last frost date to plant main crop potatoes in spring. (You can find your last frost date here). For example, the last frost date in Boston, MA is April 8. Going forward 2 weeks (+14 days) puts us at April 22. So, we can plant potatoes around April 22 in the Boston area without too much worry over frost. (If frost does threaten your potato plants, you can learn how to protect them here). How Long Do Main Crop Potatoes Take To Mature? Main crop potatoes can take 100 to 160 days (14 to 23 weeks) to mature. However, many fall somewhere in the range of 120 to 135 days (4 to 4.5 months). Main crop potatoes usually take 100 to 160 days to mature. Most fall into the range of 120 to 135 days. The days to maturity for main crop potatoes depends on the variety (along with growing conditions). When To Harvest Main Crop Potatoes There are two ways to know when to harvest main crop potatoes: 1. The first and most direct way is to look and dig. Look at the potato plant: are the vines turning yellow and dying back? If, so, dig into the ground under a potato plant. If the tubers look large and the skin is thick, they are ready to harvest (thin skins will rub off easily with your finger). 2. The second way is to keep a record of planting dates and times to maturity on your calendar. For example, let’s say you plant Kennebec potatoes on April 22 in Boston. Kennebec takes 100 to 120 days to maturity, so you would expect mature tubers between July 31 (100 days after April 22) and August 20 (120 days after April 22). Use a planting calendar to keep track of when you planted your potatoes. Work forward (using days to maturity) to get an estimate for your harvest date. How Long Can I Leave Main Crop Potatoes In The Ground? You can leave main crop potatoes in the ground for 1 to 2 weeks after maturity. This is a little longer than early season potatoes, due to the thicker skins on main crop potatoes. The longer you leave potatoes in the ground, the higher the chance that they will fall prey to: Disease Rot Pests (insect or animal) When you harvest potato tubers, don’t leave them out in the sun. Put them in a shaded spot to avoid green potatoes. Keep harvested potatoes out of the sun (and use hilling while growing) to avoid green tubers.Image courtesy of user:Rasbak via:Wikimedia Commons: https://commons.wikimedia.org/wiki/File:Groene_aardappels_%27Dor%C3%A9%27_(Solanum_tuberosum_%27Dor%C3%A9%27).jpg To store potatoes for a longer time period, stop watering the plants just before harvest. Let the vines die back completely, and then dig out the potatoes gently (gloves work well to avoid cutting or piercing them with a shovel or pitchfork). Keep the tubers out of sunlight, and clean them with a soft brush (no washing). Use up damaged potatoes for eating first. Cure the potatoes for 7 to 10 days, and then store at 40 to 45 degrees Fahrenheit in a cool, dark, humid place. (You can learn more about how to store potatoes for the long term here). Conclusion Now you know what main crop potatoes are and when to expect a harvest. You also have information on several varieties that you can choose from. You can get an idea of how many potatoes to expect per plant here. You can learn about red potato varieties here. You can learn about yellow potato varieties here. You can learn all about summer planting here.