Parsnips will grow equally well in heavy clay or light loam but the soil does need to be deep and well manured from a previous crop or manured in autumn of the previous season, otherwise, the roots will fork instead of growing straight and clean.
The parsnip is usually the first vegetable crop to be sown each year, in the south, they can be sown at the end of February, whilst it is normally the end of March in the north. If they are sown later in April, then they tend not to grow as large but they are more likely to germinate better because the ground will have warmed up.
Drills should be 1in. (25mm) deep and about 15 in. (381mm) between rows. Because parsnip seed germinates badly, it is less important that the seed is sown thinly. The fact that they germinate slowly does have its advantages because other quick growing crops such as radish may be sown with parsnips for when space is required for the host crop, the catch-crop (the radish) will be ready to harvest.
Keep the ground free from weeds but take great care not to damage the root, as they will succumb to canker. Make sure that they have plenty of water to prevent the roots from splitting and so that they are able to develop and grow well.
Parsnips are slow-growing occupying the ground for several months before they are ready to lift; they may be dug up any time after the foliage begins to die away.
They taste better when they have been touched by frost as this will sweeten them adding to their flavour, and therefore they may be left in the ground until late in the winter.
If the ground is needed for other crops before the frosts have arrived, the parsnips may be dug up and left on the ground in a heap, where they can await the frosts. In excessively hard frosts the roots should be taken into a dry shed and covered with a sack, alternatively, they can be stored in boxes of peat or Vermiculite.