Potato Growing Calendar: Spring and Late Summer Crops

A potato crop is a three month block

Potatoes take roughly 90 to 100 days from planting to lifting, so they do not occupy the ground all year. Plant in early spring and lift in early summer, or plant in late summer and lift in early winter. Thinking in three month blocks makes planning much easier.

For that reason, follow the crop by counting days from planting rather than by the month. Days since emergence and the height of the plants are far more reliable guides to the next job than the calendar.

Crop	Planting	Lifting	Days
Spring	Four to eight weeks before last frost	Early to mid summer	90 to 100
Late summer	Late summer to early autumn	Late autumn to early winter	About 90

The spring crop, step by step

The sequence and the intervals stay the same wherever you garden, even though the dates move. Read the timings below against your own last frost date.

Stage	Main jobs	How to judge it
Three to four weeks before planting	Buy seed potatoes, start chitting	Ready when sprouts are dark and up to half an inch
Planting	Cut and dry the tubers, plant	Soil settled above 45F (7C)
Three to five weeks after	Emergence, thin shoots, first earthing and feed	Thin at four to six inches tall
Six to nine weeks after	Second earthing, flowering, watch for blight	Finish earthing before the buds open
Twelve to fourteen weeks after	Lift once the foliage yellows	Dig after two or three dry days
After lifting	Dry, sort, store	Block all light, do not wash

The late summer crop

A late summer crop has less time and has to finish bulking before frost. In cold gardens the soil freezes before the crop is ready, so it is not worth attempting. It suits mild and average climates.

Stage	Main jobs	How to judge it
Late summer	Buy seed for the autumn crop	Choose small tubers you can plant whole
Planting	Plant, emergence	Wait until soil drops below 77F (25C)
Three to four weeks after	Thin shoots, earth up, feed	Do not thin as hard as in spring
Six to ten weeks after	Bulking, watch for frost	Row cover over the foliage keeps bulking going
Twelve weeks after	Lift	Lift once frost has killed the foliage

Combining the two

If you grow both in the same garden, use separate ground. Following a spring crop that had blight or scab with an autumn crop in the same bed means putting fresh seed into soil that still holds the organism, and the damage carries straight over.

The autumn crop yields less, but it gives you freshly dug potatoes in winter. Potatoes lifted in early summer start sprouting once they have been through the warm months, so an autumn crop also reduces how much you have to store.

Approach	What you gain	What is hard
Spring only	Reliable yield and quantity	Storing them through the warm months
Late summer only	Fresh potatoes in winter	Seed rot and racing the frost
Both	Two crops in a year	Disease carries over unless you separate the ground

Even in a year when you skip the autumn crop, move the spring bed. Grown in the same place every year, scab builds up reliably.

Recovering when things slip

Most years do not go exactly to plan. What matters is not the delay but which job absorbs it. If planting slipped by a fortnight, bring the thinning and the earthing up forward to compress the schedule.

Work from days since emergence rather than the calendar. Thin at four to six inches, finish the second earthing before the buds open, and a moderate delay disappears by harvest.

If it rains for days at planting time Skip planting while the soil is claggy. A few days late is recoverable. Seed set into mud and rotted is not.
If frost is forecast after emergence Draw soil over the shoots or lay row cover. Scorched leaves do not recover, so act before it hits.
When flowers open There is no need to remove them. Treat them as the deadline for earthing up and check the depth of soil over the row.
If a wet spell arrives at harvest Once about seventy per cent of the foliage has died back, do not wait for the rest. Lift. Waiting means the tubers start rotting in the ground.

What slipped	What happens	How to recover
Planting two weeks late	Harvest runs into wet weather	Thin early and bring earthing up forward
Never thinned, plants now a foot tall	Nothing but small potatoes	Pull the thin stems even now
Earthing up missed before flowering	Tubers exposed and greening	Mulch to block light and top up with soil
Long wet spell at harvest	Tubers rotting in the ground	Lift without waiting and dry them indoors

What to record for next year

Five things are worth writing down: the planting date, the emergence date, the date you thinned, the lifting date and the weight you got. With those you can tell next year whether you planted too early or earthed up too late.

Note the diseases you saw and where the plants were, too. Scab and blight recur in the same ground, and that record is the only real basis for deciding where to move the crop.

What to record	When	What it tells you
Planting date and variety	The day you plant	Whether you plant too early or too late
Emergence date	When half the row is through	Checks soil temperature and planting depth
Thinning and earthing dates	On the day	Whether you made the bulking window
Lifting date and weight	The day you dig	Compares varieties and spacings

Always record the variety. Emergence and maturity differ by more than a week between varieties in the same plot, so the record only means anything variety by variety.

Written byYasuGrowing vegetables and fruit in Chiba, Japan, and building Gadenin. Corrections are welcome. 15 years of growing.