Parsnip is considered a winter vegetable because its flavor is not fully developed until the roots have been exposed to near-freezing temperatures for 2 to 4 weeks in the fall and early winter. The starch in the parsnip root changes into sugar, resulting in a strong, sweet, unique taste.
Cobham Improved Marrow (high sugar; half-long shape; better for heavy soils)
When to Plant
Plant seed in early April or May in a deep, fertile soil that is well prepared. Because parsnip seed is very short-lived, you must obtain a fresh supply each spring.
Spacing & Depth
Plant seeds 1/2 to 3/4 inch deep. Because germination of even the freshest parsnip seed is often mediocre, seed thickly, at least two or three seeds per inch to ensure a good stand. Space rows 18 to 24 inches apart or plants 8 to 10 inches apart in a bed. Parsnip seed is slow to germinate and some gardeners drop a radish seed every foot in the furrow to mark the row and help break the soil crust. Once parsnip seedlings are up and growing, pull the radishes and thin parsnip seedlings to 2 to 4 inches apart.
Keep young parsnip plants free of weeds by shallow hoeing or cultivation. Watch for swallowtail-butterfly caterpillars, which feed on most members of the carrot family. Handpicking the caterpillars from the leaves normally gives adequate control. Water thoroughly once a week in periods of extended dry weather to keep growth from slowing in summer.
Dig the roots (usually 1 1/2 to 2 inches in diameter and 8 to 12 inches long) with a shovel, tilling spade or spading fork. Yields frequently exceed one pound per foot of row (single roots may weigh more than one pound each).
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.
Questions & Answers
Q. Do parsnip seeds germinate poorly?
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.
Q. Can parsnips be left in the soil over winter?
A. 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. The roots lose flavor and become fibrous if you do not harvest them before new tops and seed stalks begin to grow.
Q. Are parsnips poisonous?
A. Parsnips (Pastenica sativa) are not poisonous at any time during the first growing season nor after the roots have been left in the soil over winter.