By: Peter Cundall | March 25, 2012
Parsnips and turnips are among the easiest of root crops to grow. With planning, these valuable vegetables can be harvested in temperate gardens through much of the year, thriving and maturing even through the coldest winters. They are also a remarkably cheap source of nourishment, with just a couple of packets of seeds producing enough to feed most families and plenty left over to give away.
Most root vegetables are nothing more than bulky fuel reserves. They allow plants to survive months of winter or dry-season dormancy in order to form seeds and reproduce. These roots become filled with complex carbohydrates, minerals and other nutrients. For thousands of years humans have harvested these storage organs as a vital source of food for survival.
For a couple of thousand years, enormous and rather coarse turnips – which perhaps gave this flavoursome food a bad name – were a significant part of the food eaten by humans and farm animals. Turnips were eventually replaced by potatoes as a staple and for many years their popularity waned, although nutritious ‘turnip tops’ were often eaten as spring greens.
Today, there are numerous varieties of turnips of all sizes, shapes and colours, and they are very much back in fashion. They are delicious eaten raw, baked, steamed, stir-fried with the leaves, or cooked in stews and casseroles. The Chinese value them so much they cut them into large, extra-thin slices and hang them up to dry.
Not only are turnips easily grown, but some varieties, such as the outstanding Japanese ‘Hakurei’ and ‘Tokyo Cross’, are ready to be eaten whole when the size of a ping-pong ball. In short, they are ready to begin harvesting within a few weeks of the seed germinating and can be allowed to continue to grow larger.
Turnips are undoubtedly the quickest maturing of all fast crops – apart from radishes – and grow to perfection in almost any soil and climate, including the coldest and even northern Australia.
In the subtropics, turnips do better and are more productive than parsnips, producing heavy crops – 100-150kg per 10 square metres. Sow in March for maturity in June, although plants can be left in the ground until November.
In cool temperate climates plant between August and March, while in warm temperate areas plant in late summer/early autumn and spring.
Turnips are brassicas, so should never be grown in soil in which any of the cabbage tribe have recently been harvested. They are an excellent follow-on crop after sweetcorn, yam, peas, beans and pumpkins.
Sprinkle a good fistful of blood and bone fertiliser over each square metre of surface. Add a 20mm layer of matured cow or sheep manure and use a garden fork to turn the lot deeply into the soil. Rake level, water deeply then leave to settle overnight. (Avoid high-nitrogen fertilisers such as chook manure unless turnips are mainly grown for the tops.)
Turnip seeds are small, round and hard. To sow, make a 10cm-wide, shallow drill with a hoe and sprinkle the seeds very sparsely along the entire width. Cover with a thin layer of potting soil and water.
The seeds germinate rapidly and the bright green seedlings are up and moving in less than a week. Competition caused by overcrowding encourages leaf production at the expense of root size. So be prepared to thin the seedlings weekly either by hand or by using a light hoe. Keep the bed well watered and growth will be extremely fast, especially if pushed along with heavily diluted fish emulsion (1 part emulsion to 100 parts water) every week.
Harvest and storage
When small, the entire plants can be eaten raw. The Japanese white turnips are remarkably tender, sweet and delicious. Successive sowings can be made every month right through the year in cool and temperate districts to provide a continuous supply of tasty globes. In temperate climates, other varieties such as ‘Purple Top White Globe’ can be left in the ground during winter and are best eaten when the size of a tennis ball. However, once they start producing a flowering stem, they become fibrous and hollow-centred.
These vegetables may look like white carrots but, although related, they have a totally different flavour and are much closer to parsley or celery. Some people describe the sweet, aromatic taste of cooked parsnips as similar to celery-flavoured butterscotch. Unlike carrots they lack beta-carotene, but are a good source of B vitamins, folic acid and fibre. Long before cane sugar arrived in Europe, parsnips were made into popular sweet dishes, drinks and syrups. This tradition was resurrected in the UK as a result of sugar rationing during the First and Second World Wars. Generally though, they are used like carrots in soups and stews, steamed and baked.
Parsnips can only be successfully grown by directly sowing the seed where the plants are to be raised. Even small seedlings resent disturbance and attempts at transplanting causes the plants to bolt uselessly into flower to form tough, tasteless roots.
Above all, parsnip seed must be completely fresh as it loses viability – the ability to germinate – faster than any other vegetable. When buying seeds, carefully check expiry dates on packets. Should seed racks be exposed to heat or direct sunlight at any time, make your parsnip purchases elsewhere.
The most common cause of failure after sowing parsnip seed is erratic, poor or non-existent germination. This is almost always due to old or badly stored seed. Place sealed packets of newly purchased seeds in a refrigerator if they are not to be opened immediately. The most viable of all parsnip seeds are those we harvest ourselves.
Sowing times depend on location and climate: in cool districts from October until early autumn; in warm, temperate districts from August until mid-March. In the subtropics, parsnips can be challenging because the cool season is brief. Get your seed in no later than April to avoid plants bolting in spring.
Parsnips grow best in deep, well-drained conditions, preferring a sweet, loamy, deeply dug, cool soil and full sun. The roots will not properly form in hot, stony ground, heavy clay or acidic conditions. The plants have a low need for fertilisers and resent over-rich, heavily fertilised soil which is the main cause of deformed, badly forked roots of little value.
Ideal beds are those that have been manured or fertilised to grow greedy vegetables such as brassicas or sweetcorn the previous season. Don’t bother adding fertilisers or organic matter, but apply lime where needed. The soil should be broken up and raked to a fine tilth, especially the surface. It helps if the bed is then given a soaking down to the sub-soil the day before and left to settle.
‘Hidebeni Red’ turnip. PHOTO: GREEN HARVEST
The oddly shaped, lightweight, flattish seeds are difficult to handle when sowing. To avoid overcrowding the seedlings, mix the contents of a typical packet into about half a cup of fine, very dry sand, which will space them apart more evenly. (If necessary buy a small bag of horticultural sand, spread it over a sheet of black plastic in the sun to dry off, then shake it through a kitchen sieve, discarding the large particles).
Put the sand into a screw-top jar with a finger-sized hole in the lid and mix thoroughly. This can then be poured through the hole, directly into a drill (impression in the soil) no more than 10mm deep. A good straight drill can be made by pressing a garden stake or rake handle into
the soft surface.
Then give the seed-bed a deep soaking using a fine sprinkler-head so as not to wash out the seeds. This will gently wash them in, making backfilling unnecessary. However, during extra-hot conditions pulverised coco-peat may be sprinkled along the drill line to help retain moisture around the swollen seeds.
Germination and harvest
The most hazardous stage with parsnips is during the 10 to 15-day period between seed sowing and germination. It is vitally important that the soil does not dry out during this crucial period. If it does, even for a few hours, the seeds will die. This means watering several times a day if necessary, especially during hot, dry and breezy weather. The most important times to water are in the evening and again early in the morning. This ensures the seeds remain fully engorged with moisture during germination.
When the seedlings emerge, thin as soon as possible, spacing those left in the ground about 5cm apart. About six weeks later, every second plant can be harvested as tasty, extra-tender, finger-sized roots for immediate eating either raw or steamed. Those left in the ground should be no closer than 10cm apart.
The most delicious parsnips are those which are left in the ground to be heavily frosted in winter. The extreme cold converts much of the starch into sugars to make them even more delicious. In cool temperate regions, the roots are best stored in the ground during winter to be pulled as required.