How to Grow Lettuce
How to Grow Lettuce
Lettuce – Lactuca sativa
The cultivation of lettuce as a salad plant is said to date back to ancient Greek and Roman times. These plants have a wide distribution in central and southern Europe, as well as in Asia.
Lettuce is largely used in salads, and is valued because of its protective food content. It is the outer leaves which are of the most value and not the inner or blanched leaves, which so often are the most highly regarded.
Lettuce is divided into two main sections,and cos, the former being the most widely grown. There are many types of these, the so-called butter varieties, with their soft lightish green leaves being most in demand.
There are varieties suitable for winter and summer production, some being quite large, others, such as Tom Thumb, making small specimens. Many varieties can be grown under heated or cold glass, in greenhouses or frames. By proper management it is possible to have fresh lettuce available throughout the year.
Although an easy crop to grow, it is important to provide sufficient moisture, particularly for summer varieties. Avoid dryfor this can cause plants to bolt. Ideally, a cool well-drained medium loam is best, with a fairly high water-table. Plenty of if forked into the soil during the early preparation will be helpful.
Fresh manure should be avoided although really decayed matter,, in fact anything which will add bulk, will be of great help in getting the soil into a condition for the promotion of fibrous roots. A dressing of fresh manure, 3oz to the square metre, well worked in will ensure that feeding material is available. If there is lack of lime, a dusting previous to sowing will be of benefit.
It is best to sow summer lettuce where they are to mature. The earliest sowings can be made towards the end of March, although there is no point in doing so in very cold districts or when the soil is wet. It is better to sow a little seed at frequent intervals rather than large quantities at any one time.
Make the drills about 25 mm deep with at least 30cm between them, and cover the seed with fine soil. Thin sowing should be practised, so that there is little necessity of thinning the rows.
It is a good plan to use some of the plants before they grow too large. This prevents overcrowding, which because of root competition can sometimes lead to bolting. Weeds must be kept down.
Winter lettuce can be sown in light well-drained soil. If the plants can follow a crop which was well manured this should encourage steady growth. Here again, if some good organic fertiliser is worked into the surface soil, at the rate of 3oz to the square metre, it will be helpful.
Seed of winter lettuce should be sown in late summer making the rows 30cm apart and thinning the plants out early so that there is about 13cm between them. Thin the rows later, every alternate plant being removed, and although these plants will not have formed a real heart, they can be used in the kitchen. Winter lettuce can also be sown in pots or boxes; in fact, this may be necessary in cold and northern areas. Seedlings raised in this way will be ready forin October according to soil situation and district. It is of course, possible to leave the lettuce in seed beds to over-winter, the plants being put out in March. They will then be ready for use later in the spring.
When heat is available lettuce can become a really profitable crop. There are certain varieties which have been bred for production under glass in winter. With all of these, plenty of light is essential and this is one reason why it is necessary to keep the glass clean. An important part of the growing process of lettuce is the raising of the. If a properly made compost is used there should be no trouble from botrytis infection.
Sow the seed in the standard size trays and if carefully done, 150 seeds will be sufficient for each tray. The seedlings can be planted into their final cropping places as soon as they are well developed and the first pair of true leaves are showing.
Final spacing varies according to variety, some sorts growing larger than others. Even the largest varieties should not need more than 23cm each way, and many are placed in rows 18 to 20cm apart, with 18cm between plants.
Once the greenhouse or frames are filled it is a good plan to water them well straight away and to maintain a temperature of just over 15°C. After about ten days the temperature can be lowered to 10°C or so. Little more water will be necessary until they are established after which time it will need to be given much more freely.
When planting out seedlings, whether in the open ground or in greenhouses make sure the tap root goes straight down an dis not turned up in the hole.
Lettuce sometimes bolt or run to seed prematurely. This condition is often caused by dry growing conditions and by the check of transplanting especially if the roots are broken.
Lettuces are ready for gathering as soon as the heart is nicely solid. Once growth begins to push up from the centre, it is a sign that the plants are beginning to run to seed and they should therefore be moved as soon as possible. If it is not possible to use them immediately they can be pulled up completely with roots and placed in a cool, shaded position in vessels of very shallow water.
The majority of the best modern varieties of cos lettuces are self-folding and need no help by tying. Even so, during spells of dry weather they may not heart up well, and it is a good plan to give a light tying with raffia, soft string, or to use a rubber band although the latter sometimes cut into the leaves rather badly.
There are some varieties of lettuces, chiefly of American origin, which do not heart, and in these cases individual leaves can be pulled of and used as required. Notable among these is Salad Bowl which is shaped like a large flat rosette, about a foot across, with curled and fimbriated leaves. As a result of international comparison trials the number of lettuce varieties in general cultivation has recently been reduced but there are still many sorts offered in nursery catalogues. They are usually grouped under separate headings which give an indication of their type.
Crisphead or Butterhead: Avoncrisp, Buttercrunch, Great Lakes, Iceburg, Kwiek, Tom Thumb, Webb’s Wonderful.
Loosehead sorts: Grand Rapids, Salad Bowl.
Cos Lettuce: Little Gem, Paris White. Hardy Winter Lettuce: Arctic King, Imperial and Valdor.
Forcing varieties: Kordaat, Kloek, May Queen and Premier, all of these being excellent for sowing under glass in the autumn.
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