When the seedlings are about 2.5cm (1in) high thin out to leave one seedling per 15cm (6in) station.
Keep the soil weed free, hand weeding close to the roots to avoid damage. Keep the soil evenly moist to avoid splitting.
Carrot fly: Carrot fly is a small black-bodied fly whose larvae feed on the roots of carrots. The larvae tunnel into the developing carrots causing them to rot.
Remedy: Once you have an attack of carrot fly, there is nothing you can do to get rid of this pest. Prevention is the best cure, and you should sow thinly and avoid crushing the foliage as you thin out seedlings or hand weed. You can surround your carrots with 60cm (2ft) high barriers made of clear polythene which will exclude the low-flying female flies, or cover the plants with horticultural fleece, such as Enviromesh.
More info at rhs.org.uk
Parsnip canker: This orange, brown or purple-coloured rot usually starts at the top of the root. It is mostly caused by drought, over-rich soil or damage to the crown.
Remedy: Sow resistant cultivars such as ‘Avonresister’ and ‘Archer’, improve drainage and avoid damaging the roots. Avoid sowing seeds too early in the year. Protect from carrot fly.
The roots are ready to lift when the foliage starts to die down in autumn; use a fork to carefully lift them. They can be left in the soil and lifted as required, although lifting a few extra in November will ensure you still have parsnips to eat even if the soil is frozen. Lightly frosted roots tend to produce the best flavour.
Masterchef’s Greg Wallace transforms parsnips into nibbles to enjoy in front of the TV with his Crispy cheese parsnips
‘Albion’: Develops evenly tapered, wedge-shaped roots about 33cm/13in long which are about 6cm/5 1/4in wide at the top. The skins are smooth and white and slow to discolour. Ideal for organic gardeners, ‘Albion’ is resistant to parsnip canker, and other diseases.
‘Archer’ AGM: Very heavy yielding parsnip of very good flavour and resistance to canker.
‘Gladiator’ AGM: High yielding parsnip with good flavour and especially suited to heavy soils.
‘Palace’ AGM: Has good quality roots, and offers heavy yield and good canker resistance.
‘Tender and True’ AGM: This parsnip boasts long roots and gives moderate yield. Sizes are mixed and it's not resistant to canker.