FAQs: Onions and root vegetables

It seems easier to raise onions by planting sets than by sowing seeds. Are there any disadvantages?

Sets are specially produced miniature onion bulbs. They can be planted early in spring (when the ground is still unsuitable for sowing), are easy to handle, and the food reserves in the set give the onions a head start over ones raised from seed. They are also less susceptible to attack from onion fly. The principal drawback is that they are more likely to bolt (run to seed) than seed-grown onions. To minimise this risk, select the smallest sets or use heat-treated ones (which cannot be planted until late March). Sets are more expensive than seed, and at present are available only in a few common onion varieties.

What exactly are Japanese onions and what are their advantages?

The Japanese onions are very hardy, autumn-sown onions, maturing in the onion ‘gap’ in June and July, before the spring-sown crop is ready. Sowing time is critical: sow in the first week of August in the north of England, in the second and third weeks of August in the midlands, south, and south-east, and in the last week of August in the south-west and Wales. Sow the seeds 25 mm (1 in) apart in rows 225 mm (9 in) apart, thinning to 50 mm (2 in) apart in spring. One of the earliest varieties is ‘Express Yellow’; heavier varieties include ‘Imai’ and ‘Kaizuka’. Japanese onions are unsuitable for storing.

My onions never keep well. Can you give me any advice?

Obviously, first make sure you are growing storing varieties, such as ‘Sturon’, ‘Hygro’, or the ‘Rijusburger’ types. Good harvesting is the key to successful storage. When the onion leaves die back naturally (do not bend them over; this damages them), ease them out of the soil, place them in wooden trays, and dry them in the sun for several days. Dry them as fast and as thoroughly as possible, bringing them indoors to finish if the weather turns wet. Handle them with great care: storage rots start from tiny cuts and bruises. Store them somewhere dry but frost-free with plenty of air, plaited in ropes, suspended in nets or nylon stockings, or laid in single layers in seed trays.

I am told spacing is very important in growing beetroot. Is this so?

Yes. The precise spacing depends on when you are sowing, but never crowd your beetroot. Very early beetroot, sown under cloches in late February or early March (using a bolt-resistant Detroit variety), needs to grow very fast. Sow in rows 175 mm (7 in) apart, thinning to 100 mm (4 in) between each plant. The main summer crop, sown in May and June, can be in rows 300 mm (12 in) apart, thinning to 25 mm (1 in) between plants. For late-autumn and storage beet, sown in late June and early July, the rows should be 200 mm (8 in) apart, thinning to 90 mm (3V6 in) apart in the rows. For pickling beet, aim to harvest no more than 215/m2 (20 per square foot); this involves rows 75 mm (3 in) apart, with plants thinned to 56 mm (2 ¼ in) apart in the rows.

Every year carrot fly ruins my carrots. What can be done?

There is no guaranteed chemical remedy for the amateur gardener, but various preventive measures can be taken. Very early sowings (February and March) and late sowings (June) avoid the worst attacks. The Amsterdam and Nantes types of carrot, which are less ‘leafy’, are less susceptible than maincrop varieties. Sow away from tall plants and hedges, which may shelter adult flies. The flies are said to fly low, so try growing carrots in raised boxes or tubs, or with 200 mm (8 in) high boards around the beds; or put cloches over them in the early, more vulnerable stages. Sow very thinly, and when the time comes for thinning out, do this in the evening, when the flies are not about, and remove all thinnings . Lift all carrots by mid-October to prevent the late batch of grubs developing, and burn any damaged roots and rubbish.

I want to try some unusual root crops. Can you suggest a few?

How about Hamburg parsley, which gives you both a root and green parsley leaf in winter; Jerusalem artichoke, a marvellous winter standby and an excellent grower on rough ground; the long thin ‘twins’ salsify and scorzonera, which do best on light soil; and celeriac, with its subtle celery flavour? Another possibility (though not strictly a root crop) is kohl-rabi, a very-fast-growing brassica, which can be sown directly in the ground from February (in mild districts) until August or early September. These underrated crops are all very nutritious, and are delicious on their own, in stews or soups, grated raw in salads, or cooked and eaten cold, which brings out their flavour superbly.

What are the differences between early, second early, and maincrop potatoes?

The main difference is in the length of time they take to mature. Earlies will mature in about 100 to 110 days; second earlies in about 110 to 120 days; and maincrop potatoes in 125 to 140 days. The earlies tend to be the lowest yielding, but there is no reason why you should not sow earlies late, or maincrop potatoes early—you will just have to wait longer for the crop!

What is the best way of storing root vegetables?

Very hardy roots such as parsnips, Hamburg parsley, and celeriac can be left in the soil and covered with straw or bracken, so that they will be easier to lift in hard frost. Beetroot, swedes, carrots, and turnips can be stored in sheds in boxes in layers of sand, peat, or sieved ashes, or outdoors in clamps. Start a clamp with a 200 mm (8 in) layer of straw, pile the roots on top, cover them with another 200 mm layer, then leave them to sweat for two days before covering them with 150 mm (6 in) of soil. Store potatoes somewhere dark and frost-free, in double-thickness paper or hessian sacks. Never store diseased or damaged roots.

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