Why are my parsnips small, forked or rotting at the shoulder?

Parsnips look simple and then produce three different disappointments. Separating them matters because the fixes point in different directions: one is about time, one is about soil preparation, and one is about protecting the shoulder of the root from wet and damage.

Step by step

1. Check when you sowed.Parsnips need most of the growing season. A sowing made in mid-spring into warm soil, and left in the ground until after the first frosts, produces a full-sized root. A June sowing does not.
2. Thin to a proper spacing.About 15cm between plants in rows 30cm apart. Parsnips left crowded stay small no matter how long they are in the ground. Thin early, while the seedlings are tiny.
3. Deal with forking by preparing the soil, not by feeding it.A tap root forks when it meets a stone, a pocket of fresh manure or a compacted layer. Fork the bed deeply, remove stones, and never add fresh manure to a root bed. Manure goes on the potato bed, two or three years earlier in the rotation.
4. Identify canker if the shoulders are rotting.Rusty orange-brown, or black, sunken rot at the crown and upper shoulder, spreading down into the root. It gets in through cracks, carrot fly damage and exposed shoulders, and it is far worse in wet, heavy, acid soil.
5. Earth the shoulders up.Drawing soil up over the exposed crowns in late summer keeps them dark and dry and reduces canker markedly. It is the simplest control available.
6. Choose canker-resistant varieties.Resistance varies a lot and is stated in catalogues. On heavy wet ground it is the single most effective change.
7. Keep watering even.Roots that dry out and then get a soaking split at the shoulder, and splits are exactly where canker enters. Mulching the row keeps it steady.
8. Mesh against carrot fly.Carrot fly attacks parsnips too, and the tunnels it makes are entry points for canker. The same 60–75cm barrier or fine mesh covers both crops.
9. Leave them in the ground into winter.Frost genuinely improves the flavour by converting starch to sugar, and parsnips stand happily in the ground until early spring. Lift them before they start regrowing.

Tips

• A deep bed of stone-free soil, or a raised bed, transforms parsnip results on stony or heavy ground.
• If your soil is impossible, make a planting hole with a crowbar, fill it with sieved compost and station-sow into that — an old exhibition-growers' trick that works in an ordinary garden.
• Parsnip foliage can cause a painful blistering skin reaction in sunlight on some people. Cover your arms when clearing the tops on a hot day.
• Mark the row. Parsnips take so long to appear and are lifted so late that it is easy to dig them over by accident.
• Cankered parsnips are usually still usable — cut the rotten shoulder off generously and use the sound root below.

Common mistakes

• Adding manure or a rich compost to the root bed before sowing — It causes forking and hairy, coarse roots. Root crops follow the manured crop in a rotation rather than being manured themselves.
• Sowing late to avoid germination problems — It solves nothing and costs you the length of season parsnips need. Sow into warm soil in spring and manage moisture instead.
• Leaving the crowns exposed all autumn — Exposed shoulders crack, green and canker. Drawing soil over them takes minutes.
• Lifting the whole crop in autumn to store — Parsnips store far better in the ground than in a shed, and improve with frost. Lift them as you want them.

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