Gypsophila.—­Of value for table bouquets, etc.  They will grow in any soil, but prefer a chalky one.  The herbaceous kinds are increased by cuttings; the annuals are sown in the open either in autumn or spring.  They bloom during July and August.  Height, 1 ft. to 3 ft.

H

Habrothamnus.—­These beautiful evergreen shrubs require greenhouse culture, and to be grown in sandy loam and leaf-mould.  The majority of them flower in spring.  Height, 4 ft. to 6 ft.

Halesia Tetraptera (Snowdrop Tree).—­This elegant shrub will grow in any soil, and may be propagated by cuttings of the roots or by layers.  The pendent white flowers are produced close to the branches in June.  Height, 8 ft.

Hamamelis (Witch Hazel).—­An ornamental shrub which will grow in ordinary soil, but thrives best in a sandy one.  It is increased by layers.  May is its season for flowering.  Height, 12 ft. to 15 ft.  H. Arborea is a curious small tree, producing brownish-yellow flowers in mid-winter.

Harpalium Rigidum.—­A hardy perennial, producing very fine yellow flowers in the autumn.  It will grow in any good garden soil, and may be propagated by seed sown in early autumn, or by division of the roots.  Height, 3 ft.

Hawkweed.—­See “Crepis” and “Hieracium.”

Heartsease.—­See “Pansies.”

Heaths, Greenhouse.—­For their successful growth Heaths require a well-drained soil, composed of three parts finely pulverised peat and one part silver sand, free ventilation, and a careful supply of water, so that the soil is always damp.  If they suffer a check they are hard to bring round, especially the hard-wooded kinds.  Some of the soft-wooded Heaths, such as the H. Hyemalis, are easier of management.  After they have flowered they may be cut hard back, re-potted, and supplied with liquid manure.  The stout shoots thus obtained will bloom the following season. (See also “Ericas.”)

Hedera.—­See “Ivy.”

Hedychium Gardnerianum.—­A hothouse herbaceous plant, delighting in a rich, light soil, plenty of room in the pots for the roots, and a good amount of sunshine.  In the spring a top-dressing of rich manure and soot should be given.  From the time the leaves begin to expand, and all through its growing stage, it needs plenty water, and an occasional application of liquid manure.  The foliage should not be cut off when it dies, but allowed to remain on all the winter.  While the plant is dormant keep it rather dry and quite free from frost.  It may be increased by dividing the roots, but it blooms best when undisturbed.  July is its flowering month.  Height, 6 ft.

Hedysarum.—­Hardy perennials, requiring a light, rich soil, or loam and peat.  They may be raised from seed, or increased by dividing the roots in spring.  H. Multijugum bears rich purple flowers.  Height, 6 in. to 3 ft.