When to Plant Potatoes: Expert Tips for a Large Harvest

Seed-packet figures, well-meaning advice from neighbours and lunar calendars can quickly become confusing. Growing professionals instead rely on clearly measurable indicators: soil temperature, local weather conditions and the state of the seed potatoes. Keeping an eye on these factors can help you get considerably more from every square metre of garden – even on a balcony.

The ideal time to plant potatoes: follow the soil, not the calendar

The real signal to begin comes from the ground rather than the calendar. Potatoes only grow properly once the soil is warm enough and severe frost is no longer expected.

“A soil temperature of around 7 to 10 degrees at a depth of 10 centimetres is ideal – at this point, the tubers can start the season reliably.”

Professionals use a soil thermometer, available from garden centres for under £20. Once it reads above 10 degrees, planting can begin. Depending on the region, the usual windows are:

• Mild regions and coastal areas: generally from late March
• Central Germany and many towns and cities: roughly from mid-April
• Colder locations and higher upland areas: often not until early May

A straightforward body test can offer extra guidance: if you can sit on the bare ground for several minutes without getting cold, conditions are usually about right. If the soil feels icy cold, it pays to wait. Planting a week later is often preferable to forcing tubers into cold, heavy ground.

Get an earlier start with black sheeting

For anyone who cannot wait, there is a professional-growing technique: dark mulch material. Black sheeting or specialist plastic mulch raises soil temperatures by two to three degrees. This can bring the planting date forward by one to two weeks, which is especially useful in cooler areas.

Important: even with sheeting in place, late frost must not reach the young shoots. If overnight frost is forecast again, cover the rows temporarily with horticultural fleece or an old blanket.

Good soil, strong tubers: the foundation for large potato harvests

Potatoes thrive in loose, deep soil. In compacted, wet ground, tubers are more likely to rot, remain small or become misshapen.

“If a handful of soil forms a sticky, firm ball, it contains too much clay and loam – the ground needs air and structure.”

How to prepare soil for potatoes

Planning in autumn means less pressure in spring. These tried-and-tested measures can help:

• Work in compost: Spread three to four centimetres of mature compost over the area and lightly rake it in. This improves both soil structure and nutrient availability.
• Add sand: Mix some sand into heavily loamy soil. Water can then penetrate more effectively instead of collecting in the ground.
• Follow crop rotation: Do not grow potatoes in the same plot more than once every four years. This reduces the risk of diseases such as potato blight and nematodes.

Where soil is already loose and rich in humus, thorough digging or loosening with a garden fork is often sufficient. Remove large stones and root debris so the tubers can develop without obstruction.

Why supermarket potatoes can cause problems

At first, it may sound convenient: buy a bag of eating potatoes from the supermarket, notice that a few are already sprouting, then put them straight into the bed. Specialists advise against this. These tubers are often treated to prevent sprouting or may carry pathogens that can become established in the garden.

“Certified seed potatoes from a specialist supplier are the better choice – they are tested for disease and usually produce considerably higher yields.”

As a broad rule of thumb, 1.5 kilograms of seed potatoes can yield 10 to 20 kilograms of potatoes, depending on the variety, site and care. Anyone wanting an early harvest should choose early or second-early varieties and prepare them specifically.

Chitting: a turbo start for early potatoes

Chitting gives potatoes a noticeably faster start, particularly in cooler areas or where an early harvest is wanted. It takes little effort but has a clear effect.

Garden professionals do it like this:

• Take seed potatoes out of their net bags four to six weeks before the intended planting date.
• Place the tubers in shallow boxes or empty egg cartons, with the eyes facing upwards.
• Keep them somewhere cool and bright, such as an unheated hallway or beside a cellar window.
• Look for short, sturdy sprouts: shoots measuring one to two centimetres are ideal.

Long, pale shoots indicate insufficient light. These tubers establish less well in the bed. If spotted early enough, the boxes can simply be moved to a better location.

Planting day: how to set potato tubers correctly

On planting day, the soil should have dried out but must not be dust-dry. Potatoes cope poorly with waterlogged conditions, just as they do with severely compacted soil. A sunny, airy spot where water drains well after rain is ideal.

Spacing and planting depth in the bed

These guide values apply to most varieties:

Feature	Recommendation
Planting depth	8–10 cm
Spacing within the row	30–35 cm
Distance between rows	60–70 cm

In the garden, make a furrow with a spade or hoe. Set the tubers into the soil with the sprouts pointing upwards, then cover them loosely. Tubers planted too deeply emerge more slowly, while those planted too shallowly may turn green.

Growing potatoes in pots or balcony planters

Potatoes can also be grown surprisingly successfully on a balcony or terrace. Key points include:

• Use large containers holding at least 30 litres.
• Add a drainage layer of expanded clay pellets or gravel at the bottom.
• Use loose vegetable compost or a mix of garden soil, compost and a little sand.
• Plant only a few tubers in each container so they have adequate space.

This approach is particularly popular in towns and cities, as containers can be moved temporarily closer to the house wall or indoors when temperatures fall.

Earthing up: the simple trick for more potato tubers

Once young plants reach around 20 centimetres in height, there is one step professionals never omit: earthing up. This involves drawing soil from the sides towards the plant to create a small ridge.

“Earthing up keeps the tubers in the dark, prevents them from turning green and encourages the plant to produce more underground shoots – and therefore more potatoes.”

Repeat the process a second time after two to three weeks. In containers, simply top up the compost until only part of the foliage remains visible. Consistent earthing up also reduces the risk of light reaching the tubers – green potatoes are inedible.

Water, nutrients and risks: what matters during the growing season

Potatoes are considered hardy, but they respond noticeably to care mistakes. Two areas stand out: water and disease.

During prolonged dry spells, plants need a consistent water supply, especially when flowering and shortly afterwards, as this is when the tubers grow strongly. Water less frequently but thoroughly, allowing moisture to reach deep down to the roots.

Standing water encourages rot and fungal diseases. Loose soil and sensible spacing help foliage dry quickly after rain. Reusing the same areas repeatedly also increases the risk of soil pests such as wireworms and diseases building up.

Practical additions: choosing varieties and harvest time

For one household, combining early and later varieties is worthwhile. Early types provide tender, thin-skinned tubers in June or July for immediate eating. Late varieties produce storing potatoes for autumn and winter. The packs are generally labelled accordingly.

Harvest timing depends largely on your aim: if you enjoy new potatoes, carefully dig around the edge of a plant as soon as the foliage is well developed. For potatoes intended for storage, wait until the foliage has largely died back. The skins then cure more effectively, allowing the tubers to be stored for longer.

Store potatoes in a dark, cool and dry place. Light causes green patches and the formation of solanine, which should not be eaten. A wooden crate in a cool cellar is often enough to make a home-grown harvest last for weeks.

Once you understand these signals and techniques, there is no need to guess each spring. Checking the bed, weather forecast and seed potatoes is enough to identify the ideal time to begin – and turn a few unremarkable tubers into a remarkably plentiful harvest.