When to harvest potatoes
By Muzamil Ali · Last updated
When to harvest potatoes: dig new potatoes 7 to 8 weeks after planting, and storage potatoes once vines die back and skins set. Dig, cure, and store.
The vines are yellowing, the flowers are long gone, and the question every potato grower asks in late summer is the same: when to harvest potatoes, and how do you know the ones underground are actually ready? Dig too early and you get small tubers with skins so thin they peel in your hand and rot in storage. Dig too late and a hard frost, or weeks of wet soil, can do the damage instead. The good news is that when to harvest potatoes is not a guess — university extension services agree on the signs for when to harvest potatoes, and a two-minute skin test on a single plant settles it.
When to harvest potatoes: the short answer
There are two different harvests, and they follow different rules. New potatoes are dug young, while the vines are still green, for eating right away. Storage potatoes are dug mature, after the vines die back, for keeping through winter. Knowing which harvest you are doing is the first step in when to harvest potatoes, because a new potato dug at the right time and a storage potato dug at the right time look nothing alike underground.
| Harvest | When | Skin test | Use |
|---|---|---|---|
| New potatoes | About 7 to 8 weeks after planting | Skins thin and rub off easily — expected | Eat within days; refrigerate, use within ten days |
| Storage potatoes | After vines die back, about two weeks dead | Skins firm and stay attached when rubbed | Cure, then store for months |
Our potato growing guide covers planting and care, and this guide picks up where it leaves off: the harvest decision itself.
Signs that storage potatoes are ready
Storage potatoes are the main harvest, and extension services give the same sequence of signs for when to harvest potatoes for storage.
Vines dying back
The first sign is above ground. Iowa State University Extension says potatoes grown for storage should be harvested after the vines have died and the crop is mature. Nebraska Extension in Lancaster County is more precise: begin harvest after the vines have died back naturally on their own and have been dead for about two weeks. Oregon State University Extension gives the same preparation advice — reduce watering in mid-August and allow vines to die back completely before harvesting. Let the plant finish on its own schedule; vines killed early by disease or cut down early do not give the same result as vines that died back naturally.
The skin-set test
The deciding test is the skin. Dig up one or two hills after the plants have died, as Iowa State University Extension directs, and rub a tuber with your finger. If the skin is thin and rubs off easily, the potatoes are not fully mature and will not store well — allow the crop to mature in the soil for several more days before harvesting the rest. Nebraska Extension in Lancaster County gives the same test in the same words: mature skins remain firmly attached when rubbed, and thin skins that rub off mean the crop is not fully mature. Oregon State University Extension puts a number on the wait: if the skin rubs off easily, wait another week before harvesting. This one test is the most reliable answer to when to harvest potatoes, because it measures the tubers themselves rather than the calendar.
Days from planting
The calendar is a useful cross-check, not the decision. Iowa State University Extension says most potato cultivars mature 90 to 120 days after planting. So a crop planted in mid-April would be expected to mature from mid-July to mid-August, but a cool summer, a late variety, or a dry spell can all shift that window. Use the days-to-maturity figure on the seed packet as a reminder to start checking, then let the vine dieback and the skin test make the call. When the calendar and the skin test disagree, trust the skin test.
When to harvest potatoes as new potatoes
New potatoes play by the opposite rule: you dig them deliberately early. Nebraska Extension in Lancaster County says new potatoes are young tubers harvested before their skin has thickened and become tough, and that tubers typically reach a good size for harvest as new potatoes about 7 to 8 weeks after planting. Dig a few at that point to check size, and if you are happy with it, proceed with harvest.
Iowa State University Extension gives a size rule rather than a date: new potatoes can be dug when the tubers are more than 1 1/2 inches in diameter, while the vines are still lush and green. The trade-off is storage. New potatoes have thin skins and do not store well, so Iowa State University Extension says to refrigerate new potatoes and use them within ten days. Nebraska Extension in Lancaster County adds a practical detail for the dig itself: potatoes form above the seed potato originally planted, so dig down about 12 inches with a spading fork and turn the whole plant upside down to reach the small tubers without damaging them. Harvest plants as needed, or all at once — either way, new potatoes are for the kitchen this week, not the cellar this winter.
How to dig without damaging the crop
How you dig matters as much as when to harvest potatoes, because a bruised or cut tuber will not store. Choose a warm, dry day to harvest, as Nebraska Extension in Lancaster County advises, and dig with a spading fork, keeping far enough away from the main plant to avoid bruising, skinning, or cutting the tubers. Iowa State University Extension gives the same warning: when harvesting potatoes, avoid bruising, skinning, or cutting the tubers.
Gently brush off the majority of soil, but do not wash the tubers. Nebraska Extension in Lancaster County is blunt about why: washing decreases storage life and increases the potential for rots. Oregon State University Extension allows one exception — in fine, sticky clay soil you may need to rinse the tubers — but adds that in either case the potatoes must be completely dry before storing, and to minimize exposure to light during cleaning. Sort as you dig: damaged potatoes should be used for fresh eating as soon as possible, per Nebraska Extension in Lancaster County, because damaged potatoes are likely to rot in storage. Iowa State University Extension says the same: damaged potatoes should be used as soon as possible.
Frost, and how late is too late
Late-season growers worry most about frost, and here the extension guidance on when to harvest potatoes is reassuring up to a point. Nebraska Extension in Lancaster County says potatoes can tolerate a light frost of 30 to 32°F while still in the ground, but heavier frost will affect potato quality and shorten their storage life. Freezing temperatures cause the potato flesh to turn gray or black. So a light frost is not a reason to panic-dig, but it is a reason to finish the harvest promptly: the tubers left in the ground after a hard freeze lose quality even if they look fine on the outside.
The same rule applies after harvest. Iowa State University Extension says not to allow potatoes to freeze, and Nebraska Extension in Lancaster County says the same — do not allow potatoes to freeze. An unheated garage that drops below freezing on a cold night is not a storage site, even if it was perfect in October. If a hard freeze is forecast and the vines are already dead, dig before it arrives rather than after.
Curing: the two weeks that make storage work
Curing is the step most home growers skip, and it is the step that makes long storage possible after you decide when to harvest potatoes. Before placing potatoes in storage, the tubers should be cured, per Nebraska Extension in Lancaster County: cure at 45 to 60°F and high relative humidity (85 to 95 percent) for two weeks. During curing, minor cuts and bruises heal and the skin thickens. Iowa State University Extension gives a narrower range within the same window — 50 to 60°F and 85 to 90 percent relative humidity for two weeks — with the same purpose: the curing period allows minor cuts and bruises to heal, and thickening of the skin also occurs.
Oregon State University Extension gives a shorter version of the same process: cure newly harvested and cleaned potatoes in a dark, well-ventilated space with moderate temperatures and high humidity for 7 to 10 days, which helps extend storage life. Whichever range you follow, the conditions are the same in kind: dark, ventilated, cool, and humid — not a sunny porch, not a sealed plastic bin, and not a warm kitchen. Perforated plastic bags help hold the humidity during curing, per Nebraska Extension in Lancaster County. After curing, sort again and discard any soft, shriveled, or blemished tubers, since Nebraska Extension in Lancaster County warns that these may spoil in storage and destroy much of the crop. Iowa State University Extension says the same: discard soft or shriveled tubers, because they may spoil in storage and cause other potatoes to spoil.
Storing potatoes through winter
Once cured, potatoes want cold, dark, humid, and still. Iowa State University Extension says to store potatoes at 40°F and 90 percent relative humidity in a dark location, and its winter-storage guide puts the same point at 40°F and 90 to 95 percent relative humidity. Nebraska Extension in Lancaster County gives 40 to 45°F and 90 percent relative humidity, in perforated plastic produce bags to hold the humidity. Oregon State University Extension gives 40 to 46°F for table use, in perforated plastic bags or well-ventilated containers, and notes that tubers are about 80 percent water, so high humidity is essential to prevent shriveling.
How long they last, and what shortens it
When stored appropriately, the average storage life for potatoes is 5 to 8 months, per Iowa State University Extension. Oregon State University Extension agrees for the best case: mature, late-season potatoes can remain in good condition for seven to eight months at 40 to 46°F, but at temperatures above 46°F storage life drops to two to three months, with sprouting and shriveling. Nebraska Extension in Lancaster County gives the same warning at a slightly lower threshold: if storage temperatures are above 45°F, the potatoes will start to sprout after two or three months.
Too cold is also a problem
Do not over-chill them. Iowa State University Extension says that when stored below 38°F, potatoes develop a sugary, sweet taste, though sugary potatoes can be restored to their natural flavor by placing them at room temperature for a few days before use. Nebraska Extension in Lancaster County puts the threshold at 40°F: below 40°F, potatoes develop a sugary, sweet taste, again restorable with a few days at room temperature. Oregon State University Extension warns against temperatures below 38°F for a different reason — sugar buildup that makes darker, oilier fried products. Either way, a refrigerator set at normal fridge temperature is colder than ideal for long storage; Iowa State University Extension suggests an extra refrigerator set a few degrees warmer than normal, an unheated spare room, a cool basement, or an insulated garage.
What not to store them with
Two storage mistakes are easy to avoid once you know them. First, light: store in a dark location, per all three sources, because potatoes turn green when exposed to light, and Oregon State University Extension warns that excessive greening often signals solanine and those tubers should be discarded. Second, fruit: do not store potatoes with apples or other fruit, per Iowa State University Extension, because ripening fruit gives off ethylene gas, which promotes sprouting. Nebraska Extension in Lancaster County and Iowa State University Extension both add that stored potatoes should be checked during the season, and any tuber that starts to decay should come out before it spoils its neighbors. Possible storage locations in the home, per Iowa State University Extension, include an extra refrigerator set a few degrees warmer than normal, an unheated spare room, a cool basement, or an insulated garage — the same short list Nebraska Extension in Lancaster County gives, with a cool garage or basement as the best site for most homes.
A worked example: one row, two harvests
The figures above also answer a practical planning question: how much does a row actually give, and when does each harvest fall? Iowa State University Extension says the average yield with good management practices should be 20 to 30 pounds per 10-foot row. That is a measured extension figure, and the arithmetic from it is straightforward: a 20-foot row at that rate gives 40 to 60 pounds, split between the two harvests if you dig some early.
Take a crop planted in mid-April, the usual central-Iowa timing Iowa State University Extension gives for planting as soon as the ground can be worked in spring. New potatoes at 7 to 8 weeks after planting fall in early to mid-June, dug while the vines are still green and eaten within ten days, per the Nebraska and Iowa rules above. Storage potatoes at 90 to 120 days after planting fall from mid-July to mid-August, dug after the vines have died and been dead about two weeks, per Nebraska Extension in Lancaster County, and confirmed by the skin test. Then two weeks of curing at 50 to 60°F and 85 to 90 percent humidity, per Iowa State University Extension, and storage at about 40°F and 90 percent humidity for 5 to 8 months — which, from an August harvest, carries the crop into winter and early spring. That is the whole calendar for when to harvest potatoes, from one planting date, with every step sourced rather than guessed.
What not to do
A few mistakes undo an otherwise good crop, and extension sources name them plainly:
- Do not dig on the calendar alone. The skin test decides when to harvest potatoes for storage. Thin skins that rub off mean the crop is not mature, per Iowa State University Extension and Nebraska Extension in Lancaster County alike.
- Do not wash storage potatoes. Washing decreases storage life and increases rot, per Nebraska Extension in Lancaster County. Brush soil off and let them dry completely.
- Do not store damaged tubers. Cuts, bruises, and soft spots rot first and spread decay, per Oregon State University Extension, which says to use potatoes with cuts, bad spots, or signs of disease within the first month.
Storage mistakes to avoid
- Do not store in light. Light turns potatoes green, per all three sources, and excessive greening signals solanine, per Oregon State University Extension.
- Do not store with fruit. Ethylene from ripening apples and other fruit promotes sprouting, per Iowa State University Extension.
- Do not plant sprouted or shriveled tubers next spring. Oregon State University Extension warns against it because of potential disease issues, especially viruses, and says to plant only certified, healthy seed potatoes whenever possible.
- Do not let them freeze. Freezing turns the flesh gray or black in the ground, per Nebraska Extension in Lancaster County, and ruins stored tubers, per Iowa State University Extension.
When to harvest potatoes comes down to two checks and one habit: vines dead and skins set for storage, vines green and tubers past 1 1/2 inches for new potatoes, and curing before anything goes into storage. Get those right, and a mid-April planting can still be feeding the kitchen in February. Our when to plant garlic guide covers the next fall planting job, and our planting date calculator works out the dates for your area.
Sources
- Iowa State University Extension and Outreach — Growing Potatoes in the Home Garden (new-potato size and 10-day use, 90–120-day maturity, skin test, digging damage, curing at 50–60°F and 85–90% humidity for two weeks, storage at 40°F, yield of 20–30 pounds per 10-foot row)
- Iowa State University Extension and Outreach — Storing Winter Storage Vegetables (curing at 50–60°F and 85–90% humidity for two weeks, storage at 40°F and 90–95% humidity, 5–8-month storage life, sprouting above 50°F, sugary taste below 40°F, ethylene from fruit)
- Nebraska Extension in Lancaster County — Potatoes: Harvesting & Storage (new potatoes at 7–8 weeks, digging 12 inches with a spading fork, vines dead about two weeks, skin test, light frost 30–32°F, no washing, curing at 45–60°F and 85–95% humidity for two weeks, storage at 40–45°F and 90% humidity)
- Oregon State University Extension Service — Best practices for harvesting and storing homegrown potatoes (reduce watering in mid-August, wait another week if skins rub off, curing 7–10 days dark and ventilated, storage at 40–46°F, 7–8 months for mature late-season potatoes, 2–3 months above 46°F, greening and solanine, certified seed potatoes)