How to Grow Parsnips
Another hardy biennial cultivated as an annual for the long, tapering, yellowish-white roots. Parsnips have been grown at least since Roman times and the wild form is fairly common in Britain. The sweet-tasting flesh of the roots contains significant quantities of sugar and starch which help to make it an important cooked vegetable in winter. This crop must have a long growing season if good sized roots are to be produced and, on many occasions,occupy the ground for a full twelve month period. The roots are ready during autumn and winter but tradition has it that the flavour is not fully developed until they have been frosted.
Soil and fertilizer requirements
Parsnips have similar needs to carrots. Deep, rich, open-textured soils which are stone-free produce the best crops of well shaped roots. You will need to sow early to get good sized roots and sunny situations give the best results. Parsnip roots, too, will be ‘fanged’ if there is fresh organic manure in the root zone. A base dressing of 75 to 100g per m2 (3 to 4oz per sq yd) of a well balanced fertilizer should be spread and worked in before sowing.
Seed sowing and crop management
Sow as early as possible to get the maximum length of growing season. Late February or early March is ideal or as soon afterwards as possible.
Germination can be erratic so it is best to be fairly liberal with the seed and thin thelater if necessary. The drills should be 2cm (1in) deep and 45cm (18in) apart. Thin the plants to 15 to 20cm (6 to 8in) apart in the rows. An alternative method is to sow 4 or 5 seeds at each station where a plant is finally required. After emergence the strongest seedling is retained and the remainder pulled out. Keep the down by regular hoeing.
The leaves will go yellow and begin to die down from early November onwards. The roots can then be lifted as required. Since parsnips will withstand quite severe weather it is best to leave them in the ground until you want them. Lifted and stored roots quickly soften and deteriorate. Regrowth prior to flowering will start again in March and parsnips must be used before then.
Pests and diseases
Carrot fly and aphids attack parsnips in the same way as carrots. Larvae of the celery fly tunnel in the leaves producing blister-like chambers. Severe infestations cause reduced growth and plants must be well cultivated to withstand and grow away from the attacks. Moisture fluctuations will lead to root splitting but the most important disease is parsnip canker. This fungus causes a black/brown rot to develop from the crown of the root. Secondary infection by other fungi and bacteria soon follows, rendering the roots totally useless. Canker-resistant cultivars are now available.
‘Avonresister’: small roots; grow at 10cm (4in) spacings; resistant to canker. ‘Improved Hollow Crown’: long, tapering roots. ‘Offenham’: intermediate sized roots; useful on shallow soils. ‘Leda’: new cultivar; tapering roots.