Planting potatoes: wait for workable soil, then earth up

Plant potatoes when the soil is workable, drained after rain and warming, rather than because a calendar says it is time. The French gardening society SNHF uses about 10°C soil temperature as a guide and gives very different planting windows for southern France, the Paris region and mountain areas. Prepare tubers sold for planting, set them into soil that can be worked without smearing, then plan to draw soil around the stems as they grow. Local conditions matter more than a single national date.

Is the soil ready for planting?

Look at the bed after rain. If soil sticks to tools, compacts into a lump or feels saturated, wait for it to drain. Planting into cold, wet ground will not make it warm sooner, and working saturated soil can damage its structure. The SNHF potato guide gives around 10°C as a soil-temperature reference for planting into drained soil. That is not the air temperature and it is not a promise about how quickly a crop will grow.

Potatoes also need a sunny site. The RHS growing guide recommends a sunny position and organic matter, and warns that emerging shoots are vulnerable to late frosts. Its advice is written for UK conditions; use the frost principle, not a date from another country, when deciding whether to protect shoots in your own garden.

Which planting window should you use?

The SNHF examples show how much timing can vary: late February in the south of France, April in the Paris region and the first half of May in mountain areas. These are regional examples, not guaranteed dates for every plot in those places. Altitude, aspect, soil type and the weather in a particular year all affect when the bed is workable and warm enough.

Start with a local seasonal guide, then inspect the soil and check the forecast as planting approaches. If the ground is still cold or wet, waiting is a sound growing decision. The vegetable sowing and planting calendar can help organise jobs, but it cannot tell whether your own soil is ready or whether frost is forecast for your garden.

Seed potato or true seed?

A potato plant is normally started from a tuber sold as a seed potato, not from a botanical potato seed. The word “seed” here describes planting material: it does not mean a small edible potato or a seed from the plant’s fruit. Buy tubers intended for planting and keep them clearly labelled. Starting from true seed is a different propagation route and is not the usual way to establish a home-grown potato crop.

Chitting means allowing seed potatoes to produce short, sturdy shoots before planting. Keep them in a bright, cool, frost-free place and handle them gently so the shoots are not knocked off. Chitting can make the condition of the tubers easier to see; it does not make cold soil suitable for planting. If shoots are ready before the bed is, keep the tubers sheltered and check them rather than forcing an early planting.

How should you set out and cover the tubers?

Wait until soil can be opened without being kneaded into a wet mass. Place the tubers with shoots facing upwards. For a practical in-ground layout, the RHS recommends a 15 cm-deep trench; space UK “earlies” 30 cm apart in rows 60 cm apart, and “maincrops” 37 cm apart in rows 75 cm apart. These are RHS UK measurements for its two crop groups, not universal dimensions for every variety and soil. Check the guidance supplied with your seed potatoes as well, and adapt the layout to the space available. Leave room to earth up the stems and harvest without exposing other tubers to light.

Once shoots emerge, watch for frost and for the stems to grow. Earthing up means drawing soil around the base of the plants as they develop; the SNHF includes it in its growing guidance. Keep developing tubers covered. Tubers exposed to light can turn green. Work when the soil is neither saturated nor baked hard, so the job does not compact the bed.

What if the season does not match the calendar?

Delay planting while the ground is too cold or wet. If frost threatens after emergence, use a suitable cover for the shoots and adjust it as conditions change. No covering guarantees protection in every cold spell. Heavy clay needs particular care: wait until it is workable, as explained in the guide to working clay soil in a vegetable garden.

In a garden notebook, record the planting date, soil conditions, variety and jobs completed. Those notes help you compare your own seasons and decide when to earth up or protect shoots, while direct observation of the plot remains essential.