Earthy and homely, parsnips really do provide the quintessential taste of winter. Worth growing just for the smell you get when you pluck a parsnip from the soil on a cold winter’s day. Unlike carrots, they are relatively easy to grow (once you have persuaded them to germinate), needing very little attention. They will also stay in the ground quite happily (through even the worst winter weather) until you’re ready to eat them.
Dig bed deeply in winter but do not manure (causes forking in roots). Break down clods, rake well and add an organic fertiliser a week before sowing. Most parsnip seed packets will tell you to sow them in February - don't do it. Far better to leave it until late April or early May. The seeds won’t germinate in cold, wet soil and later-sown parsnips are less likely to get canker. Germination takes up to three weeks. Make a drill 1cm deep – if soil is dry, dampen. Sow three seeds every 6 inches in rows 12 inches apart and cover in with soil. When seedlings appear, pull out the two weakest ones. This spacing will produce medium sized roots. If you want larger roots go to 8 inch spacing.
How much to sow?
According to GIY Patron Klaus Laitenberger, the parsnip "season" runs from October to March - you start eating them fresh from the ground in October and you will be able to store them until March (after that any remaining roots will most likely start to rot). So if you want to eat 3 parsnips a week for the 24 weeks between October and March you will need to grow 72 parsnips. In a standard bed (1.2m wide) you will get three rows of parsnips - if you space the parsnips at 6 inches in each row you will get 20 parsnips per meter, so you will need a bed 3.5m long to get 72 parsnips.
Very little maintenance needed. Weed carefully until well established. Watering shouldn’t be necessary except in dry spells.
Parsnips are ready to rock when the foliage starts to die away in autumn but flavour improves after first frosts. Leave in soil until ready to eat but lift by February. Lift carefully with a fork. If you have water-logged soil in winter you should lift the crop and store in a box of sand in a frost-free shed.
Canker (a fungus that produces brown/black growths on roots) is the main issue. Avoid sowing too early and use canker resistant varieties. Rotate parsnips as part of your root rotation. Earth up parsnips in summer - this will prevent spores reaching the roots. Occasionally carrot root fly can be a problem.