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Can I Plant Potatoes Now? Soil Temperature Decides

Calendar dates mislead. The soil temperature that matters, how late is too late by variety group, and when a second autumn crop is realistic.

By Salma 2 min read Save to Pinterest — opens Pinterest in a new tab
Four wicker baskets of seed potatoes with pale sprouts, standing on grass
Photo: Pavlofox, Pixabay Content License, via Pixabay
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The useful answer is not a date. It is a soil temperature, and in most gardens the bed in full sun reaches it a fortnight before the bed by the fence.

Is it too late? Count backwards

GroupWeeks to harvestPlant by
First early10–1212 weeks before first frost
Second early13–1515 weeks before
Maincrop18–2020 weeks before

If you are inside those windows, plant. If you are past them, an early variety still gives a small crop, and bags that can be moved under cover buy a few extra weeks.

Maincrop planted late is the one to skip — it will not bulk up and the ground is tied up for months.

A soil thermometer beats every planting calendar

Push it four inches down and read it in the morning for three or four consecutive days. When it holds at 45F or above and the soil is not sodden, plant.

Aspect and soil type shift this by weeks within a single garden — a light sandy bed in sun warms far ahead of heavy clay in shade.

Autumn and Christmas crops

  • Specially prepared seed sold in late summer, grown in bags
  • Moved into a frost-free greenhouse or porch as the weather turns
  • Works in mild regions and under cover; fails in open ground in a cold climate
  • Tubers left in cold wet soil rot rather than keeping, so lift rather than storing in the ground

Chitting, briefly

  • Worth it for first earlies, marginal for maincrop
  • Cool and bright, eyes upward, for a few weeks
  • Short stubby green shoots are what you want
  • Warm and dark gives long pale shoots that snap off at planting — worse than not chitting

Common questions

When can I plant potatoes?

When soil at four inches deep has reached about 45 to 50F and is not waterlogged, which in most temperate regions means two to four weeks before the last expected frost for first earlies, and progressively later for maincrop. The calendar date is a poor guide because soil warms at very different rates by region, aspect and soil type — a light sandy bed reaches planting temperature weeks before heavy clay in the same garden.

Is it too late to plant potatoes?

Count backwards from your first expected autumn frost. First earlies need roughly 10 to 12 weeks from planting to a usable crop, second earlies 13 to 15, and maincrop 18 to 20. If you have fewer weeks than that remaining, you can still plant an early variety and accept small tubers, or grow them in bags that can be moved under cover to extend the season. Maincrop planted late rarely bulks up properly.

Can I plant potatoes in autumn?

In mild regions, yes, for a Christmas crop — specially prepared seed potatoes sold for the purpose are planted in late summer and grown in bags moved into a frost-free greenhouse or porch as the weather turns. In open ground in a cold climate it does not work: the plants are killed by frost before tubers bulk, and tubers left in cold wet soil rot rather than keeping.

What soil temperature do potatoes need?

About 45 to 50F at planting depth for reliable sprouting. Below 45F the seed potato sits dormant in cold soil and is at real risk of rotting, especially in wet ground, and nothing is gained by planting earlier. A cheap soil thermometer pushed four inches down and read in the morning for a few consecutive days is more useful than any planting calendar.

Should I chit potatoes before planting?

For first earlies it helps and gains you a week or two; for maincrop it makes little difference. Chitting means standing seed potatoes in a cool bright place for a few weeks until short stubby green shoots form, eyes upward. Keep them cool and bright — warm and dark produces long pale shoots that snap off during planting and are worse than no chitting at all.

Can I plant supermarket potatoes?

You can, and it is a poor idea. Supermarket tubers are often treated with sprout suppressant, they carry no guarantee of being virus-free, and potato virus and eelworm persist in soil for years once introduced. Certified seed potatoes cost more per kilo and are screened for exactly the problems you do not want in a bed you will keep using.

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