Robin Gale-Baker, from Sustainable Macleod, discusses growing parsnips. This is one of a series of articles she has written about growing various veggies (see right hand sidebar). She has also written a number of articles about growing various herbs, growing various fruit trees and general growing techniques.
A version of this article was first published on the Sustainable Macleod website.
- Use fresh seed.
- Cultivate the soil to a fine tilth.
- Keep ground moist from seed sowing to emergence of seedlings.
- Thin seedlings at 5-6 weeks.
Parsnips like a sunny, open position that is well drained. Don’t worry about frost as frost actually sweetens the root, working wonders for flavour just before harvest. Roots will not freeze in the ground in our climate.
Soil preparation is important. Like all root vegetables, parsnip does best in soil prepared to a fine tilth. Remove any roots, clods or stones and cultivate soil until fine and powdery. This allows the roots to develop unimpeded and results in long, straight parsnips. Parsnips themselves aid the development of microbial activity in the soil. Soil pH should be between 6-7.
Seed must be fresh. Sowing it in the first 4-6 months is best and it will not last beyond one year.
Plant in furrows about 2cm deep. These are best made using the side of a hoe. The soil that mounds up on each side of the furrow should be raked across the furrows to backfill them. Rake across the furrows, backwards and forwards, removing any clods as you go.
Seed should be sown at intervals of about 6-7cm and later thinned out. The seed is of sufficient size that you can sow individual seeds for good spacing. Water well once the seed is sown and then water twice a week deeply until the seedlings emerge. Keep the soil well watered after that.
Parsnips, like all root vegetables, grow well in wicking beds where consistent water enables them to develop long, straight roots and helps to prevent forking.
The seeds are slow to germinate and may take 3-4 weeks to emerge from the soil. They need a temperature below 12degC to germinate so don’t sow in warmer weather. Once they are 5-6 weeks old, thin the seedlings to about 12cm intervals. Pulled seedlings do not re-establish well, if at all.
Weed by hand and not by hoe to protect the emerging crowns and to prevent easy penetration by damaging larvae (see pests below).
Parsnips do not need fertiliser and, indeed, fertiliser can make the tops grow at the expense of the roots. Manure can cause forking of the roots.
Parsnips are ready for harvest between 120-180 days. Succession planting is a good idea so that they are not all ready at once.
Pests and diseases
Carrot root fly
Carrot root fly produces black, eaten-out holes in the roots of carrots and parsnips, (also dill and parsley). The carrot root fly lays eggs on the leaf, and the larvae bury down into the soil and feed off the roots. An orange colour on the crown indicates carrot root fly larvae is working below ground. It can’t be cured but, in subsequent plantings, remove all old carrots or parsnips, plant in new ground and use a fine net to keep this small black fly out. Hand weed rather than hoe to prevent larger spaces developing around the root which enable larvae to descend more easily.
This affects the crown and appears as an orange or brown colour if caused by Mycocentrospora acerinai or purple or black colouration if caused by Itersonilia pastinacae, both soil borne fungi. Drought, water logging, crown damage, acid soil, or repeated planting in the same patch are the main causes. It is possible that improperly cleaned seed may also carry parsnip canker but this is a commercial problem and there is nothing that the home gardener can do about this.