How to Grow Parsnips in Australia

Parsnip (Pastinaca sativa) is a slow, cool-season root crop in the carrot family, Apiaceae, grown for its long cream taproot. It is sown once, left to grow for four to six months, and repays the wait with roots that frost turns sweet. Most failures start at sowing, with old seed or a seedbed that dries out before the seedlings show.

Three mistakes that matter

1. Sowing last year's seed. Parsnip seed stays viable for about one year, so an old packet can give a bare row. Buy fresh seed each season, keep the packet cool and dry, and sow it within the year.
2. Letting the seedbed dry out. The seed takes two to four weeks to come up, and a single dry spell in that time can kill a whole sowing. Cover the row and keep it moist until the seedlings show, as in Sowing Seeds.
3. Sowing into rich, stony or freshly manured soil. Stones, clods and fresh manure make the taproot fork, and too much nitrogen grows leaf at the expense of root. Dig deeply, remove stones, and sow where a well-fed crop grew before.

When to plant

Parsnip seed germinates in soil from about 6°C to 21°C, fastest in warm soil, and can take four weeks in cold soil. The plants grow best at 16°C to 20°C and can scorch above 30°C. Frost does not harm the roots. Sow a row each month through your zone's window for a longer harvest.

At the warm end of a window, shade the seedbed with shade cloth until the seedlings show. At the cool end of an autumn window, sow early, because seedlings need to establish before the cold sets in. In Sydney, that means by about Anzac Day.

Site, soil and setup

The root decides where parsnips grow: it reaches 25 to 40 cm long, and anything that blocks it makes it fork. Prepare the bed a month ahead so any lime has time to act.

Parsnips follow well after potatoes, cabbage or broccoli that were fed generously, because they like soil on the lean side.

Sowing Seeds

Sow parsnip seed direct where it is to grow, because the seedlings do not transplant.

Choosing a variety

Sowing direct

• Sow 5 to 10 mm deep in shallow drills 30 to 40 cm apart.
• Sow thickly, about 1 cm apart, because germination is often patchy.
• Cover with fine soil or sieved compost and firm it gently.
• Cover the row with hessian, shade cloth or a board, and keep the soil beneath it moist.
• Check daily and lift the cover as soon as seedlings show, usually in 14 to 28 days.

Water the drill with a fine spray so the seed stays in place. Resist resowing too soon: a slow row often comes up days after it looked lost.

Care by growth stage

Even moisture and weed control in the first two months decide the crop, because young parsnips grow slowly and compete poorly. Weeks count from sowing.

Hand weed until the seedlings grow strongly, then mulch between the rows to hold moisture and keep weeds down.

Thinning

Crowded parsnips grow thin, twisted roots, so thinning is the one job that shapes the harvest. Start when seedlings carry two or three true leaves, about three weeks after they come up.

• Thin in two passes to the spacing in Choosing a variety, leaving the strongest seedlings.
• Press the soil back around the plants that remain.
• Compost the thinnings, which are too small to eat.
• Wear gloves and long sleeves when handling the leaves on sunny days: the sap can blister skin in sunlight.

Companion planting

Parsnips hold their bed for months, so their neighbours need to suit a slow, tall crop.

Grows well with

• Radishes, sown along the parsnip row, which come up within a week to mark it and are pulled long before the parsnips need the room.
• Lettuce, a quick crop for the gaps between young parsnip rows, which celery mosaic virus does not infect.

Keep apart

• Carrots, celery and parsley, which are in the same family and share celery mosaic virus and soil diseases.
• Low crops on the shady side, because parsnip tops grow large; keep other rows at least 30 cm away.

Harvesting Roots

Parsnips are ready when the shoulders measure 3 to 7 cm across, and the flavour is best after a frost or two.

• Loosen the soil with a fork pushed in beside the row, then lift each root.
• Twist the leaves off about 2.5 cm above the crown.
• Wear gloves, as in Thinning.
• In cool weather, leave roots in the ground for up to two months and dig as needed.
• Lift the rest before spring, when a flower stem rises and the core turns woody.

Store the roots in the fridge, where they keep for several weeks near 0°C to 4°C. Keep them away from apples, bananas and tomatoes, which can make them bitter. In heavy clay, lift the crop before wet winter weather rots it.

Roast parsnips, mash them, or add them to soups.

Common problems

Forked or twisted roots. Stones, clods, fresh manure or rich soil, as in Three mistakes, or root-knot nematode, in Pests and diseases.

Split roots. A heavy soaking after a dry spell splits swelling roots lengthways and lets rot in; keep watering even, as in Care by growth stage.

Flowering early. A long cold spell can make plants bolt (flower and set seed early), and a bolted root turns hard. Sow within your zone's window and pull bolted plants.

Rot around the tops in late winter. Snails and slugs are the usual suspects on large roots, and water pooling at the crown adds to the rot. Keep drainage good and deter snails and slugs. Read more

Bare patches in the row. Old seed, a dried-out seedbed or cold soil, as in Three mistakes and When to plant. Read more

Pests and diseases

Parsnip trouble here comes mostly from mites, soil pests and leaf diseases. Carrot rust fly, listed in some gardening references, is not established in Australia.

Two-spotted mite (Tetranychus urticae). Mites under 0.5 mm long with a dark spot on each side suck the leaves, leaving them mottled and yellow. Numbers build fast in hot, dry weather. Check leaf undersides with a hand lens, and avoid needless sprays that kill the predators. Read more

Redlegged earth mite (Halotydeus destructor). Velvety black mites about 1 mm long with orange-red legs, active from autumn to late spring in southern Australia. They silver the leaves, and heavy numbers can kill emerging seedlings, so check new rows for the first five weeks.

Root-knot nematode (Meloidogyne species). Microscopic soil worms that raise lumps 1 to 10 mm across on the roots and stunt the plants. Rotate with crops they do not attack, pull host weeds, and dig in compost, which encourages their natural enemies. Read more

Parsnip canker (Itersonilia species). Orange-brown to black patches, often cracked, on the shoulders and crown, and small spots on the leaves. It is worse in acid soil, on damaged roots and on roots left long in the ground. Lift the crop soon after it matures and bin cankered roots and leaf litter.

Powdery mildew (Erysiphe heraclei). White powder on the leaves, worst in humid weather and where plants are watered in the evening. Spray 1 part full-cream milk to 10 parts water at the first sign. Read more

Prevention first

• Rotate as in Site, soil and setup, so canker and nematodes do not build up.
• Water at the base in the morning, so the leaves dry before night.
• Pull capeweed, wild fennel and other weeds that shelter mites and viruses.
• Skip unneeded sprays so predatory insects and mites keep pests down.

Tips

1. Save your own seed. Leave three or four of the best roots to flower in their second spring. Dry the ripe seed and store it in paper bags.
2. Chill roots from a frost-free garden. Roots held near 0°C to 2°C for about two weeks can turn starch to sugar, much as frost does. At home, the coldest part of the fridge comes closest.
3. Freeze a surplus. Peel, chop and freeze the roots for soups and mash; frozen parsnip turns soft, so it no longer roasts well.