It may be propagated by seeds, or by divisions in spring. Ordinarily, however, the species is increased by hard-wood cuttings of two-bud lengths from the best old shoots, and made in spring. Leave the top bud just above the ground. =Hyacinthus= (Hyacinth). _Liliaceæ._ Seeds are employed for the production of new varieties. These are sown the same season they mature, in light, sandy soil, and are covered not more than a half-inch deep. In four or five years, or sometimes even longer, the bulbs will be large enough to flower. Varieties are perpetuated by means of the bulbels which form freely upon some varieties. These are treated in much the same manner as mature bulbs, or they may be handled in pans or flats. They make flower bulbs in two or three years. To increase the numbers of these bulbels, the bulbs are variously cut by the Dutch growers. These practices are described and illustrated on pages 27 and 28, Figs. 12-14. Hyacinths can be propagated by leaf cuttings. Strong leaves should be taken in early spring and cut into two or three portions, each portion being inserted about an inch in good sandy loam, and given a temperature of about 75°. In eight or ten weeks a bulblet will form at the base of the cutting (see page 52). The lower leaves give better results than the upper ones. These bulblets are then treated in the same manner as bulbels. =Hydrangea=, Hortensia. _Saxifrageæ._ The hardy species are usually propagated by green cuttings in summer, under glass (see Fig. 57). The tender species are increased by cuttings taken at any time from vigorous young wood, usually in late winter. Layers are occasionally employed, and suckers can be separated from some species. Sometimes the hardy species are forced for purposes of propagation by cuttage. _H. quercifolia_ is propagated by little suckers or "root pips." _H. paniculata, grandiflora_ can easily be propagated from the young wood, taken in June and planted under glass. =Hymenocallis.= _Amaryllideæ._ Treated the same as Pancratium, which see. =Hypericum=, including Androsæmum. _Hypericineæ._ Easily increased by seeds, cuttings, or by strong pieces of the roots of creeping-rooted species. Hard-wooded cuttings taken in fall, are commonly used. =Hypoxis.= _Amaryllideæ._ Propagation is effected by seeds and offsets. =Hyssop= (_Hyssopus officinalis_). _Labiatæ._ Seeds. Division. =Iberis= (Candytuft). _Cruciferæ._ The annuals and biennials are increased by seeds sown in light sandy soil, in spring or autumn. The sub-shrubby sorts are also increased by seeds sown in spring, but more often by divisions or by cuttings. =Idesia.= _Bixineæ._