I sowed some parsnips today. I used the space from my 'magic broccoli' which had finally past its peak several weeks ago. We had some overnight rain again so the soil was easy to work, and I weeded and dug over the patch. There is a knack to sowing parsnips. I have inherited a very useful 6ft long, solid iron bar with a point on the end, which is perfect for making holes in the soil. Make a hole about 8 or 12" deep and fill it up with loose sandy compost. It is important that parsnip seed is fresh each year as it deteriorates quickly and you might have germination problems using old seed.
The prepared holes can be between 6" and 12" apart, depending on how big you want your parsnips. I usually sow 3 or 4 seeds in each hole to be sure that I can choose the best one to live. Some people over plant radishes between rows so that you can see where the row is until the parsnips germinate. Last year my germination was brilliant and I had the invidious task of choosing who will live and who will die. I prefer to use small nail scissors to despatch the unlucky seedlings as pulling up may disturb the roots. I have sowed a variety called "Hollow Crown" I find it to do very well in the London clay soil, it never goes hard or woody.