Parsnips are slow to come up, so sow them in April

Sow parsnips outdoors from late March to mid-May. Sowings from mid-April onwards often do better than early ones, because the seed comes up faster and more evenly in soil that has started to warm.

Parsnips are sown where they’re going to grow, never in pots or trays, and they take a long time: around 110 to 140 days from sowing to the first roots.

Why later can be better

Parsnip seed is famously slow. It can take three weeks to germinate, and in cold, wet March soil it may sit there and rot instead. An April sowing catches up with a March one within a few weeks and usually gives a fuller row.

The dates here are for a typical lowland garden in England or Wales, with a last frost around 20 April. In Scotland, the north of England and frost pockets, aim for late April or May. In the south-west, near the coast and in cities, late March sowings stand a better chance. If you want to start early anyway, warm the soil for a week or two first with a cloche or a sheet of polythene.

Always use fresh seed. Parsnip seed doesn’t keep, and last year’s half-used packet will give you a patchy row, or nothing.

How to sow

1. Pick a sunny spot with deep, light soil and no fresh manure. Manure and stones both make the roots fork.
2. Rake the soil to a fine tilth and make a drill 1 cm deep.
3. Sow two or three seeds every 15 cm, with rows 30 cm apart.
4. Cover lightly, water gently, and keep the surface moist until seedlings appear.
5. When they’re a few centimetres tall, thin each group to the strongest seedling. Snip the extras with scissors rather than pulling, so you don’t disturb the one you keep.

Because parsnips take so long to show, it helps to sow a few radish seeds thinly along the same drill. The radishes come up in a week, mark the row so you don’t weed it by mistake, and are ready to pull before the parsnips need the space.

On stony or heavy clay soil, try a stubby variety, or make holes with a crowbar, fill them with sieved compost, and sow a few seeds on top of each.

Looking after them

Keep the rows weeded while the seedlings are small. Once the leaves are up and spreading, parsnips need little attention apart from water in long dry spells. Watering steadily matters more than watering a lot: dry soil followed by a soaking can split the roots.

Parsnips are good neighbours for onions, garlic and radishes. Keep them away from carrots, as both are hit by carrot fly and planting them together makes an easy target.

When to dig them

Parsnips are ready from mid-September and you can keep digging until early March. Most growers wait until after the first frosts, usually around the end of October in a typical garden, as the cold makes them noticeably sweeter. The roots are hardy to about -15 °C, so leave them in the ground and lift them as you need them.

Loosen the soil alongside with a fork before you pull. Parsnip roots are long and snap easily. If the ground is likely to freeze hard, lift a few in advance and keep them in a cool shed, or mark the row and cover it with straw so you can still dig.

Lift any that are left by early March, before they start growing again.

Common problems

Canker. Brown or orange rough patches on the shoulders of the root. It’s worse on very rich or acid soil and where roots are damaged. Grow a canker-resistant variety, sow a little later and closer, which gives smaller roots that are less prone to it, and keep up with crop rotation.

Forked roots. Caused by stones, compacted soil or fresh manure. Still edible, just awkward to peel.

Carrot fly. Rusty tunnels in the root. Insect mesh over the row from sowing keeps the fly off.

Gaps in the row. Old seed or a dry surface. Resow fresh seed into the gaps by mid-May.

VegLog works out these sowing dates from your own town’s frost dates and reminds you when the window opens.