Onions, leeks and garlic
These members of the onion family (alliums) have been prized for many centuries and are an indispensable flavouring ingredient in many recipes. It is hard to decide which is the king of vegetables, leeks, or asparagus, which is a close relative.
All members of the onion family are prone to a nasty disease called white root rot. This malady is encouraged by growing onions in the same ground, year after year, or by bringing the infection in on affected plants, or even your boots. You can avoid it by growing onions in a minimum of a three-year rotation and practising strict hygiene. Grow your own seedlings if at all possible, as the disease is not carried on seeds. If you get it, it could be a decade or more until your soil recovers.
Onions come in a variety of colours and maturation times. There are white, brown and red, perennials that are propagated by division, and some that do not make bulbs, called spring onions, or scallions. The white bulbing types are sometimes grown as spring onions as well.
The main crop types of onion that keep well are very day length sensitive. If they are sown too soon before the shortest day, they will want to bolt, or run to seed. May to July are the main sowing months. Sown too late, they will mature in the wetter autumn months and be hard to dry for storage. There are strains that have been developed for sowing in late winter/spring, so use these if you are a little late. Pukekohe is the main brown onion in this group and is an excellent keeper, possibly the best. White Spanish also keeps well and is the best frying onion in my opinion.
The early, non-keeping varieties can be sown from early autumn into winter. They include the extremely mild red onions, such as Calred Early, a very large onion. Most of this group are white, Early Barletta, Late Flat White and Savages Flat White are good examples. Pearl Pickler is related to leeks and is sown in the winter. Onions are usually sown in rows about 30 cm apart with 5cm or more between plants. They can be sown in seed beds for transplanting or sown direct. The thinnings from direct sowing can be eaten as spring onions or transplanted.
Most of the spring onions are sown all year round and have little if any bulb. They are sown in rows 30 cm apart with about 1 cm between plants. Some varieties will reproduce by division, even though they are also propagated by seed. The French shallot makes no seed and reproduces by division in spring and early summer. Ishikuro is a Japanese variety that grows very large, almost like a small leek.
There are several sorts of perennial bulbing onions propagated by division. The Egyptian onion, which is native to North America, reproduces by two methods. The planted bulb divides and there are little bulblets formed on the tips of the leaves. It is also known as the tree onion. The potato onion is similar, but does not have the terminal bulblets on the leaves. It is often grown for pickling. The golden shallot is generally used for flavouring rather than for eating.
Onions need rich soil, not oversupplied with nitrogen. Too much of the latter creates thick necks that allow rots in, reducing the storage life. The early onions are often harvested before full maturity, while they are still green. Onions for storage are left until their stalks begin to fall over. The stalks on all the crop are then bent over and watering is stopped. After a week or two, they are pulled and allowed to dry on the surface of the ground, or put on racks in humid conditions. After they are fully cured in the sun, they can be put in a cool, airy place until needed. Pantyhose make excellent storage bags. Fill the legs and put them either side of a beam or line.
When transplanting onions, it is important not to plant them too deep. They will get neck rot. Mulching too deeply also causes problems with fungal disease. Plant your onions away from the garlic. The water requirement for onions is much lower than garlic and one crop or the other will suffer if their separate needs cannot be catered for. Leeks also require copious quantities of water, though this is usually in autumn/winter when there is plenty of rainfall.
Since their foliage is so meagre, onions compete poorly with weeds. Onions are quite resistant to heat and commercial organic growers are turning to flame weeders to combat emerging weed seedlings. The home gardener must be prepared for a considerable amount of hand weeding.
Leeks are generally blanched in Australia. The seedlings are transplanted into a trench when about the thickness of a pencil. The sides of the trench are then gradually filled in as the plants grow. An alternative is to make holes with a dibbler, which is a pointed stick. The holes should be about 15 cm deep. The seedlings are then dropped into the holes and the ground well irrigated to wash a little soil into the holes. The leeks then grow to fill the holes.
Garlic bulbs selected for propagation are the biggest, best and healthiest from the previous crop. The bulb is broken into its constituent cloves and the biggest are used for "seed." The size of the clove has an influence on the size of the resultant bulb, so the smaller cloves are rejected. The individual cloves are then planted at a depth of 2.5 to 5 cms, unmulched. When mulched, the cloves can be planted on the surface.
The most favourable planting time is autumn, almost immediately after lifting the crop. The longer the crop is in the ground, the larger the crop. The latest I have attempted to plant garlic is October, the earliest, February. The garlic was mature in February and January respectively, only 6-8 weeks' difference, despite the 8 month difference in planting times. This is because garlic is day length sensitive. Planting too close to the longest day can lead to small bulbs without separate cloves.