Low soil fertility is a common problem. However, in well maintained garden soils adequately supplied with organic matter and fertilizer, this ordinarily should not be a problem. If plants begin to look light green or stunted during the season due to low fertility, the problem usually can be overcome by side-dressing with a complete fertilizer in late June. Avoid fertilizing with fresh clumps of organic matter where parsnips will be grown. This can cause misshapen or forked roots.
Parsnips are relatively free of both insects and diseases.
A. Parsnip seeds germinate very slowly even under the best conditions. The seeds also lose their ability to germinate after the first year, so discard unused seeds. Sowing a few radish seeds with parsnip seeds provides early plants to mark the parsnip row so you can cultivate before the slow-germinating parsnip plants appear. If you leave parsnips in the soil over winter, throw a few inches of soil over the crowns after the first fall frosts. Stored starches are changed to sugar in early spring as the old plants prepare for new growth, thus roots harvested in early spring are especially tender and sweet.