Lettuce Growing Methods

Press, Volume CV, Issue 30958, 14 January 1966, Page 6

Lettuce Growing Methods

Lettuce is our most important salad crop which, although invariably eaten fresh, can be cooked like cabbage. There is, however, but one way of obtaining a crisp, mild and even flavoured end product and that is by growing it without a check. Receiving a check is one of the most usual causes for bitterness of flavour in lettuces.

Although they will grow relatively successfully in most types of soil, best results are to be achieved in lighter, fertile loam soils which have good drainage yet are moisture retentive —so vital to lettuce culture. Being a plant grown for its leaves, a high organic matter content in the soil, or applied additionally in the form of nitrogenous fertiliser, is desirable. Only sufficient lime should be added to bring an acid soil to near neutral as neutral or excessively alkaline conditions can have adverse effects on growth. Lettuce prefers cooler weather for best results but there are many varieties and strains available today which have been raised especially to withstand warmer conditions. One of the reasons for poor results, especially during the summer months, is frequently traceable to incorrect selection of variety for the particular season. A few suitable varieties for various times of the year are given below but perusal of a good seed catalogue will usually reveal many additional ones. For winter or early spring such lettuces as Imperial 615, Webbs Wonderful and Imperial D are most suitable. For the warmer periods of the year Iceberg (New Yorker), Great Lakes, Imperial 847 can be grown. All Year Round will yield satisfactorily almost throughout the year. Seed Sowing

Sowing the seed itself is quite an important aspect in the raising and bringing lettuces to maturity. If sown too deeply it will fail to germinate and there is often a similar noticeable lack of response with seed sown during very hot weather. Depth of seed placement in the soil will be somewhat dependant on soil type, greater cover being desirable for the lighter ones; half an inch is the maximum one should place it. If the soil is dry when sowing, water immediately afterwards and keep it damp but definitely not saturated until the seedlings appear.

As soon as the plants are sturdy enough, transplant them as left too long in the seed beds they become overcrowded, drawn and take very much longer to recover when finally moved. Transplanting in the late afternoon or evening will give them a chance to settle before the oncoming day. Avoid damaging the roots and, in the event of a very strong sun on the days after transplanting, shading will assist to reduce excessive loss of water from the plant by transpiration through the leaves.

Tn summer it is a sound policy to sow one or two very thinly-seeded rows which can subsequently be thinned still further to achieve correct spacing. As aeration plays an important role in keeping down disease, allow 15 inches between rows and 10 to 12 inches between plants, de-

pending on variety grown. Subsequently, weed suppression by means of regular light hoeing and watering will be necessary. Watering Methods Water should not be given spasmodically for the reason already given nor should it be given in excess. Surface applications are preferable to overhead watering, again primarily to minimise the onset of disease and also because it can cause a certain lack of firmness at maturity. Side dressings of organic fertilisers are frequently required to boost growth, especially in early spring. Nitrate of soda is most commonly used as it is the most quickly available to the plant. Sulphate of ammonia is a suitable alternative. When applying be most careful to avoid spilling on the leaves, especially on the heart, as severe burning of foliage will result. Botrytis rot or grey mould is a fungus disease which can cause collapse of seedlings, and yellowing and subsequent disintegration of older plants when it is often accompanied by bacterial soft rot. A fangicide, such as captan, is a justifiable control measure where onset is noticeable among the seedlings. ' Another fairly common fungus disease of lettuce, and one which is carried over on infected plants and in the soil, is solerotinia rot. Plants can wilt and collapse quite rapidly under wet and humid conditions revealing white fluffy growth dotted with irregularsized black lumps. It is a persistent disease and only attention to hygiene and spacing can assist in its control. As it will attack many other vegetables as well, sterilisa- i tion of the ground may be advisable where attacks have ] been very bad. Birds can be a major destructive influence towards satisfactory lettuce growing, particularly during the early stage. Netting, cotton, suspended objects which will rustle with the slightest breeze, or the use of a proprietary webbing which is now on the market, are suggested deterrents. Lettuce varieties are both numerous and varied, not. only in their seasonal suita-' bilities but also in colour, | form and texture.

There are crisp-headed varieties which form a rather firm, crisp-leafed lettuce. New York (Iceberg) is one and the many strains have been developed from it, such as the Imperials and Great Lakes. The butter-headed include the very early but small Tom Thumb All-Year Round and the excellent but comparatively new introduction to New Zealand, Butter Crunch. This type of lettuce is soft textured, very finely flavoured and rather softer headed. Then there are the Cos, or romaine, lettuces which are distinguishable by their upright habit, spatulate leaves and elongated heads. They are generally much

crisper than the other r types and frequently sweeter. Cos White Paris and Cos Red are examples of this type. Salad Bowl and Bronze i Beauty are outstanding repre- 1 sentatives of the less fre- ; quently grown loose-leaf van- ; eties which are characterised

Iby a rather spreading, loose 'habit of growth which does I not form a heart. By making successional sowings every two to three weeks it is possible to grow and try all of those mentioned and thus provide lettuce for most of the year.