Seeds should be sown as soon as ripe--in summer--in pots or pans, and placed in a slight bottom heat or in the open air. In either case, place the seedlings in 3-inch pots, and winter in a cold-frame. Dividing the roots, after flowering is over, by separating the crown, so as to preserve one or more buds and as many roots as possible to each piece. Cuttings of young shoots three inches long, taken off close to the old root at nearly the same time, should be placed singly in small pots of light, sandy soil and kept close, and shaded in a cold-frame until rooted. If cuttings are made during winter, a gentle bottom heat must be given. Also grafted (see page 88). See also Althæa. =Honesty.= See Lunaria. =Honey-Locust.= See Gleditschia. =Honeysuckle.= See Lonicera. =Hop.= See Humulus. =Hop Hornbeam.= See Ostrya. =Horehound= (_Marrubium vulgare_). _Labiatæ._ Seeds, in early spring. Division. =Horkelia.= See Potentilla. =Hornbeam.= See Carpinus. =Horse Chestnut.= See Æsculus. =Horse Mint.= See Monarda. =Horse-Radish= (_Nasturtium Armoracia_). _Cruciferæ._ Root-cuttings ("sets"). These are made from the small side roots when the horse-radish is dug. They may be anywhere from one-fourth to one inch in diameter, and three to six inches long, one end being cut slanting, to mark it. These are planted obliquely, two to four inches deep, in spring. They may be buried during winter. (Fig. 48). The old crowns may be planted, but they make poorer roots. =Hottonia.= _Primulaceæ._ Propagation is effected by seeds and divisions in spring. =House-Leek.= See Sempervivum. =Houstonia.= _Rubiaceæ._ Seeds. May also be increased by carefully made divisions in autumn or spring. =Hovea=, Poiretia. _Leguminosæ._ Propagation is best effected by seeds, sown in well-drained pots of sandy peat soil in spring, and placed in a gentle bottom heat. Cuttings are difficult to strike. =Hovenia.= _Rhamneæ._ Increased by seeds. Root-cuttings are also used. Ripened cuttings should be placed in sand, under a hand-glass. =Hoya= (Honey Plant, Wax Flower). _Asclepiadeæ._ For layering, good-sized shoots should have a few of their leaves removed, and should then be put in pots of soil until rooted. The plants may afterwards be grown on, and repotted according to their strength. Cuttings may be taken in spring or later in the year, from shoots of the preceding summer's growth, and placed in a compost of peat and sand, and plunged in bottom heat in a frame. A slight shade and careful watering will be necessary. _H. bella_ does best when grafted on a stronger growing sort. =Huckleberry.= See Vaccinium. =Humea=, Agathomeris, Calomeria. _Compositæ._ Sow seeds in light, finely sifted soil, and place in a frame in early summer. =Humulus= (Hop). _Urticaceæ._