Garden
When to Plant
When to Plant Potatoes: The Crop That Doesn't Wait
Potatoes don't wait for the last frost, because a frost doesn't kill them — Iowa State says frosted tops regrow in ten to fourteen days and you don't replant. What they wait for is soil at 50°F. Buy a soil thermometer, not a calendar, and plant three to five inches deep.
Everything you know about spring planting is about tender plants
The last frost date runs every spring planting guide ever written, and for good reason: it is the day the freezing nights stop, and a freezing night kills a tomato outright.
A potato is not a tomato. University of Maryland Extension records it plainly — "Hardiness: Half-hardy annual. They can withstand light frosts, but not heavy frosts or freezing." Withstands is doing the work in that sentence: light frost, not a freeze.
Half-hardy is a real category and it changes the whole calendar. Utah State does not hedge about what that means in practice: potatoes "should be planted in the garden 2-3 weeks before the last frost." Before. Not after, not on it.
If that sounds reckless it is because almost everything else you have ever planted would die doing it. This one will not, and the next section is why.
What a frost actually does to a potato
Iowa State University Extension gives the whole answer in four sentences, and most pages quote the first one and stop.
"Freezing temperatures (below 32°F) will damage potato shoots. Symptoms may vary from blackening of the leaf margins (minor damage) to death of all aboveground growth (severe damage)."
That is the bad news and it is real — a hard night can take the whole top of the plant. Then the part almost nobody prints: "Fortunately, severely damaged potatoes will send up new growth within 10 to 14 days. There is no need to replant the potatoes."
A frost does not end a potato crop. It costs it two weeks. The plant you can see is not the plant that matters — the seed piece and the developing tubers are underground, insulated by soil, and they send up a new top. That is the difference between planting early and gambling.
It is a cost, not a nothing. Two weeks of growth in spring is two weeks off the end of the season, and Iowa State's own range tops out at "death of all aboveground growth", which is not a light thing to shrug at. But a setback you recover from and a crop you lose are not the same decision, and the pages that treat potatoes like tomatoes are pricing the wrong one.
The real trigger is 50°F soil
If the frost date is not the constraint, something else is. Utah State: "Potato should be planted when soils are at least 50ºF."
Soil temperature and air temperature come apart in spring, which is exactly when you need to know. A run of mild afternoons warms the air quickly and the soil slowly, so the week that feels like planting weather is usually a week or two ahead of the ground. Seed pieces in cold wet soil do not wait patiently; they rot.
So buy a soil thermometer. They cost less than a packet of seed potatoes. Push it in to the depth you are planting at — three to five inches, not the surface — and read it in the morning rather than the afternoon, so you are getting the soil's baseline rather than its best moment of the day.
Maryland gives a calendar band for context, and it is worth reading as a range rather than an instruction: seed pieces go in "from March 15 to May 1 depending on your location". Six weeks of "depending on your location" is the honest width of a calendar answer, which is the argument for measuring instead.
And your zone tells you neither
A hardiness zone is one measurement: the average coldest night of your winter. It is the right tool for deciding whether a fig will survive in your garden and the wrong tool for every question on this page.
It does not know your soil temperature in April, and it does not know when your spring freezes stop — we measured how far apart two gardens in one zone can be, and it is weeks. If you are not sure what your zone even is or what it is for, that has its own page.
For potatoes the zone is doubly beside the point, because the one thing it does describe — hard winter cold — is the one thing this crop is not waiting on.
How deep, and why the number moves
Depth is the other thing that changes with when you plant, and no page we found says why the number you are given keeps shifting.
| When you are planting | Depth | Who says so |
|---|---|---|
| Early — the two to three weeks before your last frost | 3 to 5 inches. | Maryland |
| Later in spring, into warmer soil | 5 to 6 inches. | Maryland |
| General figure, not split by timing | 4 to 6 inches. | Utah State |
What the difference is for
Maryland gives the split without explaining it, so this reading is ours rather than theirs: a shallower seed piece in cold soil comes up sooner, and a deeper one in warm soil sits under more insulation. Early plantings want to get moving; later ones want protection from a soil surface that is about to get hot and dry. What is sourced is the pair of numbers and which one goes with which season — "Plant potatoes in furrows cut side down, 3- to 5-inches deep. Later crops should be planted 5- to 6-inches deep."
Utah State's "4-6 inches deep" sits across both and does not split by timing. Anywhere in that overlap is inside every source we hold.
What happens next
Shoots come up, you hill soil around them — Utah State says to do it "within 4 weeks of planting" — and then the crop spends three or four months underground doing the part you cannot watch.
The other end of it has its own answer, and it is not the one most people expect: a potato plant carries two crops months apart, and for the storage crop the last step is two weeks of doing nothing after the tops have died.
Potato planting questions people actually ask
Can potatoes survive a frost?
The tops can be damaged; the crop usually survives. Iowa State: freezing temperatures below 32°F damage potato shoots, from blackened leaf margins up to death of all aboveground growth — and severely damaged plants send up new growth within ten to fourteen days, with no need to replant.
Can you plant potatoes before the last frost?
Yes, and Utah State says to: potatoes should be planted two to three weeks before the last frost. They are a half-hardy annual rather than a tender one. The condition that matters is soil temperature — at least 50°F — not the frost date.
What soil temperature do potatoes need?
At least 50°F, per Utah State. Measure at planting depth rather than the surface, and in the morning rather than the afternoon. Soil warms more slowly than air in spring, so the first week that feels like planting weather is usually ahead of the ground.
How deep should I plant seed potatoes?
Three to five inches for an early planting and five to six for a later one, per Maryland; Utah State gives four to six across the board. Anywhere in the four-to-five-inch overlap is inside every source we hold, cut side down.
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.
- Iowa State University Extension and Outreach — Cold and Freeze Damage to Garden Plants
- Utah State University Extension — Potatoes in the Garden
- University of Maryland Extension — Potatoes
We are building GardenTrack to know which of your plants are waiting on a frost date and which are waiting on the soil, because they are not the same list — the app is in beta now, invite-only.