When to Plant Potatoes: Expert Tips for a Bigger Harvest

Seed-packet numbers, well-meaning advice from a neighbour and lunar calendars can quickly make potato growing seem confusing. Instead, an experienced grower relies on clearly measurable signs: soil temperature, local weather conditions and the condition of the seed potatoes. Keep an eye on these factors and you can get considerably more from every square metre of garden – even on a balcony.

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

The real starting signal comes from the ground rather than a date in the diary. Potatoes only begin to grow properly once the soil is warm enough and severe frosts are no longer expected.

A soil temperature of around 7 to 10 degrees at a depth of ten centimetres is ideal – this gives the tubers a reliable start to the season.

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

• Mild areas and coastal locations: 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 simple physical check can also help: if you can sit on bare ground for a few minutes without feeling cold, conditions are broadly right. If the soil feels icy, patience pays off. Planting a week later is often preferable to forcing tubers into cold, heavy ground.

Getting an earlier start with black film

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

One point remains essential: even with film in place, late frosts must not reach the young shoots. If overnight frost is forecast again, temporarily cover the rows with horticultural fleece or an old blanket.

Good soil and strong tubers: the foundation of large harvests

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

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

Preparing soil for potato growing

Planning in autumn means less pressure in spring. These tried-and-tested measures are useful:

• Work in compost: Spread three to four centimetres of mature compost over the plot and rake it in lightly. This improves both structure and nutrient availability.
• Add sand: Mix some sand into very loamy soil. It helps water penetrate more easily instead of pooling.
• Follow crop rotation: Do not grow potatoes in the same plot more frequently than once every four years. This lowers the likelihood 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 enough. Remove large stones and old roots so the tubers can develop without obstruction.

Why supermarket potatoes can cause problems

It may seem convenient: buy a bag of eating potatoes from the supermarket, notice that a few are sprouting, then put them straight into the bed. Specialists advise against it. 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 checked for disease and usually produce substantially higher yields.

As a broad guide, 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 crop should choose early or second-early varieties and prepare them specifically for planting.

Chitting: a rapid start for early potatoes

Chitting speeds up early growth considerably, particularly in cooler regions or when an early harvest is wanted. It takes little effort but has a noticeable effect.

Garden professionals do the following:

• Take the seed potatoes out of their net four to six weeks before the planned planting date.
• Place the tubers in shallow boxes or empty egg cartons, with the eyes facing upwards.
• Keep them somewhere bright and cool, such as an unheated hallway or by 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 once planted out. If spotted in time, simply move the boxes to a better location.

Planting day: how to set potato tubers correctly

On planting day, the soil should have dried out but not be dusty dry. Potatoes do not tolerate waterlogging, nor do they cope well with severely hardened ground. Choose a sunny, airy site where rainwater drains away properly.

Spacing and planting depth in a bed

These guide measurements 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 a garden bed, make a furrow with a spade or hoe. Set the tubers in the soil with the shoots pointing upwards, then cover them loosely. Tubers planted too deeply emerge more slowly, while those planted too shallowly can turn green.

Growing potatoes in pots or balcony planters

Potatoes can also be grown surprisingly successfully on a balcony or terrace. The key considerations are:

• Use large containers holding at least 30 litres.
• Put a drainage layer of expanded clay or gravel at the base.
• Use loose vegetable compost, or a mixture of garden soil, compost and a little sand.
• Plant only a few tubers in each container so they have enough room.

This approach is especially popular in cities, as containers can be moved temporarily closer to the house wall or indoors during cold weather.

Earthing up: the simple way to produce more potatoes

When the young plants reach around 20 centimetres tall, it is time for a step professionals never miss: earthing up. Pull soil from either side towards the plant to form a small ridge.

Earthing up keeps tubers in darkness, prevents them from turning green and encourages the plant to produce more underground shoots, resulting in more potatoes.

Repeat the process a second time after two to three weeks. In containers, it is enough to add more soil 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 season

Potatoes are considered hardy, but they react noticeably to poor care. Two issues stand out in particular: water and disease.

During extended dry spells, plants need a steady water supply, especially while flowering and shortly afterwards, when the tubers are growing rapidly. Water less often but thoroughly, so moisture reaches 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 ground repeatedly also increases the risk of soil pests such as wireworms, as well as diseases that build up over time.

Useful additions: choosing varieties and harvest timing

For one household, a combination of early and later varieties is worthwhile. Early varieties provide tender, thin-skinned tubers for immediate eating in June or July. Late varieties produce storing potatoes for autumn and winter. Packets are usually labelled accordingly.

The harvest date depends largely on what you want from the crop. For new potatoes, carefully dig at the edge of a plant once its foliage is well developed. For potatoes intended for storage, wait until the foliage has mostly died back. The skins will then harden more effectively and the tubers will keep for longer.

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

Once you understand these signs and techniques, there is no need to guess in spring. A look at the bed, the weather forecast and the seed potatoes is enough to identify the ideal moment to begin – and turn a few unassuming tubers into a remarkably abundant harvest.