When to sow parsnips

Parsnips are sown straight into the bed from March to May. They are slow to germinate and struggle in cold, wet soil, so an early sowing gains you little: April is usually the best month in Germany, Austria, Switzerland and most of the UK. February sowings only make sense in very mild gardens.

Parsnips need a long season, about five to seven months from sowing to a full-sized root, so don't sow much later than May.

Buy fresh seed every year. Parsnip seed loses its ability to germinate quickly, often within one or two years, and old seed is the most common reason for gappy rows.

Choose a sunny spot with deep, loose soil that doesn't waterlog. Clear stones and loosen compacted layers, or the long roots fork. Don't dig in manure or compost just before sowing either: parsnips do best in ground that was well fed for the previous crop.

Draw drills about 0.4–0.8 in deep and 12 in apart. Because germination is patchy, sow in stations: three seeds together every 4–6 in along the row. Cover lightly and keep the soil moist until the seedlings are up, which can take two to four weeks.

When the seedlings have a couple of true leaves, pull out all but the strongest at each station. Leave 6 in between plants for big roots, or 4 in for smaller ones.

A 120 × 80 cm raised bed takes three rows 12 in apart. At 6 in in the row that is 8 plants per row, 24 in all; at 4 in, about 36.

Parsnips grow slowly at first, so the gaps between rows can hold a quick catch crop such as radishes or lettuce, harvested before the parsnip leaves close over.

Weed carefully by hand near the plants; a hoe easily nicks the shoulders of the roots, and damaged roots are more prone to canker.

Water in long dry spells, and then thoroughly. As with carrots, a sudden soaking after the soil has dried right out makes the roots split.

By late summer parsnips form large, leafy plants. Handle the foliage with care on sunny days (see below).

Parsnips are ready from about October, when the leaves start to die back. Most gardeners wait for the first frosts: cold turns some of the starch in the root into sugar, and the flavour gets noticeably sweeter.

They are fully hardy, so the easiest store is the bed itself. Leave them in the ground and dig them as you need them until March, loosening the soil with a fork first; the roots are long and snap easily. A layer of straw or fleece keeps the ground workable in hard frost.

Lift the rest before they start growing again in spring. If you want a store indoors, keep them like carrots: cold, just above freezing, and humid, in boxes of damp sand.

Parsnip canker shows as rough orange-brown or black patches, usually around the shoulder of the root. Several fungi cause it, and it gets in more easily through wounds, such as carrot fly damage or a slip of the hoe, and in cold, wet soil. Grow canker-resistant varieties such as 'Albion' or 'Picador', and avoid damaging the roots.

Carrot fly attacks parsnips as well as carrots. The same protection works: fine insect mesh over the bed and as little disturbance of the foliage as possible.

Parsnip sap contains furanocoumarins. If it gets on your skin and the skin is then exposed to sunlight, it can cause burns and blisters. Wear long sleeves and gloves when handling the leaves on sunny days, especially when clearing old plants or seed heads, and wash off any sap.

Parsnips belong to the carrot family (Apiaceae), with carrots, parsley, celery and celeriac, dill and fennel. Don't sow them where any of these grew recently: leave at least four years.

Mixed-planting tables pair parsnips with onions, leeks or lettuce. We found no solid evidence for specific benefits; the practical reason to mix is the catch crop mentioned above, which uses space while the parsnips are small.

The rule with a real reason: keep parsnips away from other carrot-family crops, because they share carrot fly and soil-borne diseases.