Garden
When to Harvest
When to Harvest Potatoes: Two Crops, One Plant
Depends which crop you want. New potatoes are ready about seven to eight weeks after planting, once the plants flower. For storage potatoes, wait until the tops die back — then wait two more weeks before digging, which is what thickens the skin so they keep.
Which potato are you asking about?
A potato plant grows two crops and they are ready months apart. Almost every page on this subject answers for one of them without saying which, which is why the advice you find never quite matches the plant in front of you.
University of Minnesota Extension puts both in two consecutive sentences: "You can dig new potatoes about seven to eight weeks after planting. Harvest mature tubers after plants have dried."
Those are not two opinions about one harvest. They are two harvests. New potatoes are small, thin-skinned, dug while the plant is still green and growing, and eaten within days. Storage potatoes are what is left if you leave the plant alone until it dies. You can take some of each from the same row — every new potato you dig now is one that will not be in the ground in September, and that is the whole trade.
New potatoes: about seven weeks, and the flowers are the cue
Minnesota's timing is "about seven to eight weeks after planting", and that lines up with the plant doing something you can see: flowering. Our own growth-stage record puts potato flowering at 42 to 56 days from planting, which is the same window described two ways.
Utah State frames it as a choice rather than a date: "Harvest potatoes as soon as tubers begin forming (new potatoes) or as they mature." So if the plants are flowering, there are potatoes down there, and you may go and get some.
Our own habit, which none of our sources spells out: feel for them rather than digging the plant up. Work a hand into the side of the ridge, take what you find, and leave the plant standing. Utah State's framing implies it — harvesting "as soon as tubers begin forming" is not a one-off event — but the technique is ours, not theirs.
New potatoes do not store, and that follows from the sources rather than being stated by them. Everything below about storage turns on the skin setting, and a new potato is by definition one dug before that happened. Which is exactly what makes it good, and exactly why it belongs in this week's dinners rather than in a sack in the cellar.
When are potatoes ready to harvest for storage?
This is the answer most people are looking for, and it has one step in it that almost nobody mentions.
- Wait for the tops to die back. Utah State is direct about the trigger: dig storage potatoes after the vines have died. Minnesota says the same thing as harvest mature tubers after plants have dried. Not yellowing. Dead.
- Then wait two more weeks, and do nothing at all. Maryland: if you plan to store potatoes, leave tubers in the ground for two weeks after plants die back. This will allow them to develop a thickened skin. The plant is finished; the potato is not.
- Dig on a dry day. Maryland again, and it is one short sentence — do not dig potatoes if the soil is wet. Wet soil at lifting means dirt packed onto damp skins going into storage, which is the start of most rot.
- Brush them, do not wash them. Minnesota: gently brush any dried soil off the tubers, but do not wash them. Water on a freshly lifted potato undoes the two weeks you just spent waiting for the skin.
The two weeks are the part worth remembering. Maryland's own words: "If you plan to store potatoes, leave tubers in the ground for 2 weeks after plants die back. This will allow them to develop a thickened skin." Two weeks of doing nothing, underground, after the plant is already dead.
Our own record puts the main crop at 90 to 120 days from planting, which agrees with Maryland's "Days to maturity: 90 - 120". Use it to know roughly which month to start watching the tops, not as a countdown.
Why the skin matters more than the potato
It is worth being clear about what those two weeks buy, because it is the difference between potatoes that keep until spring and potatoes that go soft by November.
An unset skin rubs off. Not dramatically — you will barely notice it as you tip them into a sack. But every scuffed patch is an opening, and a bag of potatoes in the dark is a good environment for anything that gets in through one. That reasoning is ours; what is sourced is the instruction and its purpose. Maryland gives the two weeks and says plainly what they are for — "to develop a thickened skin" — and Minnesota describes curing as letting "the skin to set and any wounds to heal." Both are protecting the same surface.
Which is also why the digging matters. Maryland: "Don't dig potatoes if the soil is wet." And Minnesota: "Gently brush any dried soil off the tubers, but do not wash them." Both instructions are protecting the same thing.
Curing, and the numbers do not agree
After lifting, storage potatoes get a spell somewhere warm and humid to finish setting and to heal any spade damage. Our three sources all say to do it and none of them agrees on how long.
Maryland: "Storage potatoes are cured for 10 to 14 days at 50°F to 60°F and high humidity to heal over wounds and cuts." Utah State: "cure them for 2-3 weeks, and then store the tubers in the dark at 40-45ºF." Minnesota: "allow ten days or more for them to cure completely", in an area that lets "the skin to set and any wounds to heal".
Ten days to three weeks, and the temperatures differ too. Rather than average three answers into a fourth that nobody published, take the purpose: the skin finishes setting and cuts heal over. Minnesota adds the one condition all three imply — "Keep them under cover or in the dark" — because light is what turns a potato green.
Then storage proper, and here they part company again: Minnesota says "dark, cold, moist conditions (32-40°F and 95%" humidity; Maryland says "Medium cool (40°- 50°F), moist (90% RH) conditions; 6 to 8 months." A cool dark cellar satisfies both approximately, which is probably the honest summary of a spread that wide.
One more from Minnesota, and it is the step that saves the sack: "Check over the potatoes, removing any that are soft or shriveled. Eat those soon."
What goes wrong underground while you wait
Two things decide the potatoes you get, and both happen out of sight.
Water, at the wrong moment. Minnesota: "During the enlargement of the tubers, moisture stress can cause knobby or hollow potatoes, and can prevent the plant from producing new tubers." Knobby or hollow is a specific and memorable pair — if you have ever cut into a potato and found a cavity, that is a dry spell during bulking, months ago, and there was nothing to see at the time.
And spacing, decided back in spring. Maryland: "If you would like to mainly harvest new potatoes, space plants 9" apart. If large storage potatoes are your goal space plants as far as 20" apart." The harvest you are asking about today was partly settled in April, which is a slightly annoying thing to learn in August and a useful thing to know next spring. If you are growing them in a bucket, the same trade applies in a smaller space.
Three signs, one window
Potato is unusual in our records: at its harvest window it carries three expected signs, not one. Lower leaves going yellow, tops falling over, and the skin going dry and papery — and all three have a job attached to them rather than being descriptions.
That is the whole reason this section of the site exists. Across the 152 crops we hold growth-stage records for, lower leaves going yellow shows up at 33 different crop-and-stage combinations. Fourteen of them mean go and dig. Nineteen mean nothing whatsoever — mostly perennials putting themselves to bed for the winter.
The sign does not tell you anything on its own. The stage does. It is the same argument as the garlic page, where an identical yellow leaf is a clock, and it is why a page can tell you what to look for and still not tell you what it means.
Potato harvest questions people actually ask
When are potatoes ready to harvest?
For new potatoes, about seven to eight weeks after planting, once the plants are flowering. For storage potatoes, once the tops have died back completely — and then two weeks after that, which Maryland says is what lets them develop a thickened skin.
Can I leave potatoes in the ground too long?
The two-week wait after die-back is deliberate and our sources give it as two weeks rather than as an open-ended one. None of them says what happens if you leave them much longer, so we will not either — what they do say is not to dig in wet soil, so if the two weeks end in a wet spell, wait for a dry day rather than for nothing in particular.
Why are my potatoes hollow inside?
Almost always water. Minnesota: during the enlargement of the tubers, moisture stress can cause knobby or hollow potatoes. It happened months before you cut into it, underground, with nothing visible at the time — which is why consistent watering during bulking matters more than it feels like it should.
Should I wash potatoes before storing them?
No. Minnesota is explicit: gently brush any dried soil off the tubers, but do not wash them. Washing undoes the skin-setting you waited two weeks for, and a damp potato going into a dark sack is the start of most storage rot.
Sources
Every planting date, depth, and temperature on this page traces to these university extension guides. Where they differ, the ranges above hold the whole spread.
- University of Minnesota Extension — Growing potatoes in home gardens
- University of Maryland Extension — Potatoes
- Utah State University Extension — Potatoes in the Garden
We are building GardenTrack to know what stage each plant is at, so a collapsed potato top reads as a two-week timer rather than a plant that died on you — the app is in beta now, invite-only.