DAHLIA (named after Dr. Dahl, a Swedish botanist, and pupil of Linnaeus). SYN. Georgina. ORD. Compositae. A popular genus of herbaceous plants, having a double involucre, no pappus, and a large scarious bracteole at the base of each floret. There are but a small number of species, and all are natives of Mexico and Central America. The Dahlia was first introduced into this country from Spain, in 1789, by the Marchioness of Bute. This importation, and another made by Lady Holland, in 1804, were, however, lost to cultivation. A third stock was afterwards brought from France, about the year 1815, and from this the numerous forms have been obtained. It is most probable that nearly all the types and varieties of the common garden Dahlia now in cultivation have originated from DAHLIA coccinea, DAHLIA Mercki, and DAHLIA variabilis. Being among the best of outside autumn-flowering plants, and, moreover, easily propagated and grown, Dahlias form indispensable subjects for flower-garden decoration, suitable for those of either large or small dimensions. There are four important classes into which Dahlias may be divided, in addition to a few minor ones, containing only a limited number of representatives. These are known as Show, Fancy, Bouquet or Pompone, and Single-flowered. DAHLIA Juarezii represents a small class, with semi-double flowers, distinct from any of the others. DAHLIA excelsa and DAHLIA imperialis reach a great height before flowering, and are best grown in pots for greenhouse decoration in autumn and winter. Show Dahlias are all double, and require to have large flowers of the most perfect form to be considered good. Selfs and pale-coloured flowers, edged or tipped with a darker colour, are included under Show varieties. Flowers of a similar size, but having florets dark-coloured at the base, and tipped or striped with a paler colour or white, are known as Fancy varieties. The Bouquet or Pompone, also those sometimes termed the Bedding section, have double flowers of a much smaller size; various colours are included, and all are invariably very pretty; the habit is dwarf and compact, constituting these the best for bedding purposes, and the flowers are most useful for cutting, when Double ones are required. The Single-flowered varieties have again become very popular, and are amongst the most beautiful and useful subjects for cut flowers. The form and size of flower-heads in all the sections have now attained a high degree of excellence. White, yellow, red, and purple, with a great variety between of these colours intermixed, are also represented in each of the large classes. PROPAGATION. Dahlias are propagated by seeds, cuttings, division of the roots, and sometimes by grafting. Seeds. These are produced by the Single varieties in large quantities, but not so freely by the Doubles. Obtaining seeds from the latter is mostly restricted to florists who make this plant a speciality, and who do it with a view to raising new varieties. The colours of the Single flowers are reproduced by this method tolerably true to character, and only those that are good should be selected from which to save seed. Sow thinly in pans, at the end of March, and place on a hotbed or in a propagating house. The seedlings will soon appear, and should then be placed singly in pots, and grown on for a time in the same temperature. Repot as becomes requisite, and gradually harden off in a cool frame, ready for putting outside at the end of May. If liberally treated, large plants and good flowers may be obtained the first season. Cuttings. This is the method of propagation usually adopted, and is easily accomplished in spring. The roots having been stored and kept dry in winter, should be introduced to bottom heat at the beginning of February, and these, but not the crowns, should be covered with soil. A slight syringing daily will be sufficient to induce the production of shoots, and each of these may be removed, if required, as soon as it has two joints. If placed singly in small pots of light leaf soil and sand, and plunged in a close frame, roots will soon be emitted, and the plants may be hardened, repotted, and transferred to cooler positions, as recommended for seedlings. Cuttings of Dahlias root best when taken in this way quite young; and, as a succession soon appears, any variety may be readily increased. The tops of the young shoots also strike freely in summer. Division of Roots. All Dahlias have several fleshy tuber-like roots that may be separated singly for propagating after they are started in spring, allowing one shoot to each. If these are inserted in large pots, vigorous plants may be obtained for placing outside later on; but the quantity will be limited to the number of tubers when divided, and will not generally be so many in the end as might have been procured from cuttings. Grafting is occasionally practised for preserving new varieties throughout the winter, when otherwise there would be a danger of losing them. The plan is to take a shoot with two joints, cut it below the bottom one, and remove a portion of the skin on one side. A fleshy root from a hardier sort should be prepared, by having a similar-sized hole or incision made for the reception of the graft. This should be tied in, and the matting covered over with clay, the whole being afterwards potted and placed under a hand glass until a union has taken place. To keep the scion alive in winter, it must be kept growing slowly, and cuttings from it may be obtained in spring. This system of propagation is not often resorted to. CULTIVATION. Being vigorous-growing plants, Dahlias require a rich, moderately heavy soil to give the best results; but their cultivation will often prove successful under conditions widely varied in this respect. When it is proposed to plant in masses, the ground should be trenched, and manure added if the soil is naturally poor. It is not advisable to apply strong manure in spring, as over-luxuriance in foliage would thereby be encouraged at the expense of the production of flowers. A light, open position, free from the shade of trees, is best; but surrounding shrubs or dwarf plants are often an advantage to Dahlias by protecting them from high winds. Mixed flower borders, backed up with shrubs, are good positions, and a fine effect may be produced in autumn, especially with the best of the Single varieties, by planting in masses, such as large circular beds. The Dwarf Pompone section is best adapted for use in smaller beds, and these, or others, may be kept still lower by pegging down when young. Planting out should not be attempted before the beginning of June, in most localities, as the least exposure to frost causes much injury. The heights of the different varieties must be ascertained, and their respective positions fixed accordingly. From 3ft. to 6ft. apart is none too much space for strong, tall-growing varieties. Seedlings, or late-struck cuttings, will not require quite so much. Water well after planting, and apply a temporary stake to each, for a time. Dahlias are much benefited by frequent applications of water during summer, and by liquid manure after the buds are formed. If exhibition blossoms are required, the shoots and flower buds must be thinned out in the younger stages of growth; but otherwise it will be unnecessary to do so. Permanent stakes of about 4ft. in height, must replace the others when the plants are established and growing. The most useful Dahlias to cultivate for cut flowers are the Single and Pompone sections; and the most distinct and highly-coloured sorts should be selected. Storing. Dahlias may remain in the ground until the tops are destroyed by frost, when they should be cut down to within 6in. of the ground, and afterwards lifted. Remove as much soil as possible with a pointed stick, attach the label of each to the stem, and store away in a dry, cool, frost-proof place. Looking over occasionally to remove any part of the roots that may be damping, is all that is required until starting again the following spring. Young plants, raised either from seeds or cuttings, will supply large roots in the autumn of the same season. INSECTS. Earwigs are most destructive to Dahlias, by eating out the young points of the shoots, and afterwards the florets, before they are developed. Small flowerpots, half-filled with dry moss, and inverted on the tops of the stakes, or hollowed bean stalks placed amongst the branches, are the best-known traps. They should be examined each morning, and any Earwigs found therein destroyed.