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Lettuce (Lactuca sativa The Lettuce)

(Lactuca sativa). The Lettuce is a hardy annual, which has been extensively cultivated in this country since, and most likely long previous to, 1562. Botanists agree in looking upon the garden Lettuce as a cultivated race which has originated from L. scariola. The old Greeks and Romans cultivated the Lettuce as a salad plant (Theophrastus mentions three varieties), and in the Orient it was, perhaps, grown at a still more remote period. There are two distinct types, termed respectively Cabbage and Cos varieties. The latter may have been introduced from the Greek Archipelago or the Levant, as it derives its name from an island there, originally known as Cos. Cabbage Lettuces are distinguished by their broad, rounded leaves, forming a low, spreading head nearly close on the ground. Cos varieties grow upright, and the leaves are more of an oblong shape. Lettuces, especially good Cos varieties, are very popular, and amongst the most useful of salading plants. To insure crisp, thoroughly-blanched hearts, it is necessary, with some sorts, to close the outer leaves together, and tie them. There are others which overlap, and do not require this attention to secure the desired end. Acres of land are devoted to the first spring crop in the neighbourhood of large towns, the demand for a supply of Lettuces being very great at this season. There are few gardens in which some are not grown according to requirements, and, practically, none in which a few would not be acceptable. Cultivation. Lettuces are in request nearly all the year round, in places where they are procurable. The spring and early summer supply is, perhaps, generally the most important. The most successful method adopted with plants for this crop is to sow in frames about the middle of September, and again in October. The frames should be prepared some time in advance, by having a bed of fermenting material, from 1ft. to 2ft. thick, placed beneath them, and the inside filled up to within 1ft. of the glass. About 6in. of light soil should be laid over the surface, after the manure has been evenly trodden down. Fermenting material admits of free passage for water, and, consequently, keeps the plants well drained; its heating properties are not required. Seeds may be sown broadcast, and the sashes kept on until germination takes place, when air should be freely admitted in fine weather. When the plants are large enough to handle, the weakest should be thinned, so as to leave the others about 2in. apart. But little water will be required during the winter, the object being to induce a hardy and sturdy growth, and prevent damping. This latter is chiefly to be guarded against in winter time, as it frequently causes much injury. Frost should merely be excluded by coverings of dry litter, or similar material, and this should be removed by day on all favourable occasions. Growth may be encouraged as the days lengthen, and the plants be gradually inured, and placed outside in February, where they are intended to grow. The state of the weather, and the severity of the season, must be taken into consideration, as these may vary each year, and cause special arrangements to be made.

Lettuces like a rich, rather light, soil, which should be manured deeply down, where the roots are situated. A distance of about 1ft. apart each way allows sufficient space for the plants to develop. If dibbers are used, the holes should be well filled in, either at the time of planting, or afterwards with a hoe. Growers of early Lettuces on a large scale are particular in filling dibber-holes from the south or sunny side, as, although apparently a trifling matter, the plants are found to succeed much better than when the reverse plan is adopted. Frequent hoeings in fine weather greatly encourage growth, and also prove beneficial in keeping down weeds and destroying slugs, which always prove very destructive to young Lettuces.

In mild and favourable localities, the foregoing method of winter cultivation and protection is not generally followed; hardy varieties being selected and grown on south borders outside. When intended for outside culture, they should be sown a month or more earlier than when frames are to be used for winter protection, in order that the plants may be large, and better able to withstand frost and wet. A sheltered border, sloping to the south, should be selected, and none but hardy varieties grown, such as the Hammersmith Hardy Green Cabbage, and Brown or Bath Cos. In many gardens, these varieties are sown about the middle of August, and the plants transferred, during the autumn, to any warm or sheltered positions; the foot of a south wall being usually one amongst others selected. Cabbage varieties may be placed from 6in. to 9in. apart, and a reserve stock should be kept in the seed-bed for filling up any blanks that occur. If some of the plants from this sowing are placed 6in. apart, on an old hotbed, under glass, and kept protected during winter, they will prove useful in spring, before those grown outside are ready. Seed sowing of Lettuces in spring should be commenced in a warm frame about the end of January, or early in February, and be repeated at the end of the latter month for a succession. Small plants thus raised must be pricked out under hand glasses, or on a spent hotbed, until they are sufficiently strong for placing in the open ground. From the middle of March until August it is advisable to make successional sowings, according to requirements, in open borders, at intervals of two or three weeks; then, if one lot should run to seed quickly, because of hot weather, another will soon be coming on. Timely thinning in the seed-bed is very important, as the plants, if once allowed to draw, never do so well afterwards. Few positions are unsuited for Lettuces in summer, provided they are attended to, by careful planting and watering at first, and there is sufficient light to prevent the leaves drawing up instead of forming close hearts. In small plantations, it is preferable to transplant with a trowel in summer time, to prevent a severe check being caused by injury to the roots. Advantage should always be taken of cloudy weather, if possible, for the operation. Any of the autumn crops may be lifted before the appearance of frost, and re-planted, rather closely, in any spare frame or house, free from drip, and where frost is merely excluded. By adopting this method of preservation, the season of supply may be considerably prolonged. Seed-saving. Where it is desirable to save seed, the finest specimens should be selected for the purpose, such as form good hearts, and do not previously show a disposition to seed early. Different varieties must be kept isolated, or separated in some way, when in flower, to keep the product true to the original character. The parts which flower, and, consequently, ripen the seeds first, produce the best; and they should be secured in preference to waiting for the ripening of the whole lot. If the branchlets are collected, and laid on a cloth in the sun, when the seeds are in a forward state, the latter soon ripen, and may be rubbed out. Seeds may keep good for three or four years, but they are always considered best the second year, and should be tested before being depended on afterwards.

Sorts. The names of these are extremely numerous; but large numbers of supposed sorts, when grown under similar conditions, have been found synonymous, or insufficiently distinct to merit their separate names. The following is a list of good varieties in each class; those marked with an asterisk are specially recommended.

Cabbage Lettuces. *ALL THE YEAR ROUND, very hardy, compact, and of good quality. BROWN DUTCH, much like the White Dutch, except that the leaves are more brown where exposed; it forms a good-sized head, which blanches white, and is of excellent quality. *EARLY PARIS MARKET, a valuable early sort, much grown in France. *HAMMERSMITH HARDY GREEN, leaves thick, dark green, wrinkled; one of the hardiest and most extensively grown sorts of this class. LARGE WHITE, heads large, somewhat flattened, withstands hot weather well; a good sort for summer use. MALTA, heads flat, compact, blanches well; leaves pale green, somewhat soft. *NEAPOLITAN, heads large, firm, and crisp, habit dwarf; a good variety, of excellent quality, considered the best for summer. STANSTEAD PARK, compact, good for autumn sowing, with light protection in winter; very similar to White Dutch *TENNIS BALL, small sort, forming close hearts, which are white and crisp. TOM THUMB, very compact and of excellent quality; good for all seasons. *WHITE DUTCH, a hardy sort, which hearts readily; larger than Hammersmith Hardy Green.

Cos Lettuces. ALEXANDRA WHITE, of immense size, crisp, fine flavoured. *BROCKET HALL BROWN, hardy, and of excellent flavour; stands a long time before running to seed. *BROWN OR BATH BLACK-SEEDED, large, hearts well when tied up; a very hardy variety, the best of all for standing the winter. EARLY GREEN, tolerably hardy variety, smaller but a little earlier than Paris Green. *MOOR PARK, large and crisp, hardy, and not liable to run to seed. NUNEHAM PARK, solid and crisp, grows to a large size. *PARIS GREEN, resembles Paris White, except that it is hardier; the leaves are dark green before being blanched; an excellent variety, requiring no tying. *PARIS WHITE, large, heart very white, crisp, and excellent; blanches well without tying; generally esteemed as the best summer Cos variety in cultivation. SUGARLOAF, good hardy variety for autumn sowing; requires no tying.

Injurious Insects. In common with most salad herbs and potherbs, Lettuce suffers from the ravages of many kinds of larvae; and it is also the chosen food of a few insects. The roots are eaten by the larvae of Click Beetles (Wireworms) and of Cockchafers (May Bugs). The leaves are devoured by the caterpillars of not a few of the larger Moths, including the Tiger Moth (Arctia Caja) and its allies, and the genera Agrotis, Noctua, Mamestra, Plusia, and other thick-bodied night moths. For the methods of destroying such larvae, see Insects, Surface Caterpillars, and Tiger Moth. The Lettuce Fly (Anthomyia Lactucae), in the maggot stage, feeds on the fruits, eating out the seeds, and thereby destroying the harvest when plants are grown for seed. The maggots are footless, tapering near the head, truncate and toothed at the tail, dirty yellowish-white, and a little over 1/4in. long when full grown. In the Lettuce head, or on the ground, they turn to pupae, oval in form, and red-brown in colour. The flies emerge from the pupae in early summer. They are about the size of a house-fly, and are rich brownish-black, with brown wings. Infected seed should not be used for sowing; and, as soon as the plants are seen to be diseased, the whole crop should be carefully looked over, and the larvae removed, or, if not worth this trouble, the plants should be burned, to destroy the maggots. Aphides, or Green Flies, of several species, feed on Lettuces, two or three kinds of Siphonophora feeding on the leaves and young shoots, and species of the genus Pemphigus dwelling on the roots. The latter are far more hurtful than the former, as they kill the roots, and thus destroy the plants. Pemphigus belongs to a group of Aphides that want the two tubes so conspicuous in the others on the hinder segments of the back of the abdomen, and that have the cubital vein third from the body in the front wing not forked. The species hurtful to Lettuce are P. fuscifrons and P. lactucarius. Both live in cavities hollowed out of the soil beside the roots, and lined with fine cottony filaments secreted from the bodies of the insects. The second species is usually the more common and destructive of the two, and forms the secretion more plentifully than the other. Prevention is difficult; nor is an attack usually suspected till the drooping of the plants indicates injury to the roots. The Aphides are generally found on scraping away some earth from the surface of the roots. Soaking the ground around the plants with soapsuds, lime-water, or tobacco-water, has been suggested as a remedy; but the gain would scarcely repay the cost. Infested plants should be speedily and carefully removed, so as to destroy the Aphides on the roots; and the ground should have quicklime or gas-lime dug into it to destroy any of the pests that may remain in the soil. Attacks may, perhaps, be prevented by surface-dressings of soot, lime, or other substances disagreeable to insects. Both species live also upon the roots of various grasses and other plants; hence it is difficult to eradicate them.

Fungi. Of these, the most hurtful is the Lettuce Mildew (Peronospora ganglioniformis). Affected leaves show a yellowish discoloration on the upper surface, and on the lower surface there is a coat of fine white velvety threads, too small to be seen with the unaided eye. Under the microscope, the hairs are seen to be bifurcated from five to seven times, and each ultimate branch ends in a flattened dilatation, which bears four minute stalks on the corners, and one in the middle, each surmounted by an oval or nearly globular minute one-celled spore. In cold weather, in autumn, resting-spores are also produced in the tissues of the host plant. Their special use is to withstand the cold season, and to propagate the fungus when the weather becomes fit again to stimulate growth in spring. The velvety threads above described are pushed through the stomata, or little mouths of the plant. After a time, the patches of the leaf that bear the fungus begin to decay, and soon pass into a pulpy, rotten condition. The outer leaves are the first part affected, in spring, while the flowers and seeds also frequently suffer much in the autumn. The more crowded the Lettuce plants are, the more liable are they to injury from this fungus. If the plants are grown in a close, damp atmosphere, such as that in a frame for forcing them, in spring, or if weakened in any way, the Mildew does far greater mischief than where there is free access of air. Exposure of the plants to cold air has been found to materially check an outbreak of Mildew; but the only method that that can be relied upon is to remove the diseased plants as quickly as possible from among the healthy ones, taking care not to leave infected stumps of old plants in the ground. It is necessary also to keep the ground clear of Groundsel, Thistles, and other weeds belonging to the order Compositae, since they also are food-plants of this Mildew.