There is often not a large choice of parsnip varieties to be found in shops. Some parsnips are longer than others, and there are small differences in whiteness. Long parsnips will perform well on loose sandy soils. If your soil is heavy, shorter parsnips may be a better choice. Whatever type of parsnips are grown, they are deliciously sweet when cooked, whether roasted in the oven covered in oil, or adding their unique flavour to soups.
Parsnips can be affected by carrot fly and canker. Unfortunately, both problems build up where parsnips are grown often, and is common on allotments. The best solution if crops are affected is to find a fresh location to grow them. There are also hybrid F1 varieties that have been bred to show resistance to these problems.
The sweetness of parsnips improves with the onset of cold weather, as a sharp ground frost will increase their sugar content. Parsnips are hardy vegetables and will keep for many months through winter in the soil where they grew, and dug up when required. If this is the intention, remember to clearly mark the location of the parsnips as the above grown vegetation will die away.
On my plot, which has loose sandy soil, I find it best to sow parsnip seeds direct into the soil in early spring, just when the weather starts to improve. At this time of year, the soil will be moist for many weeks, giving sufficient encouragement to parsnip seeds to germinate. Attempting to germinate parsnip seed in warmer dryer conditions is notoriously unreliable. The seedlings should be thinned to approximately 3 inches or 8 centimetres apart to allow them to reach full size.