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.