Part 16

H. LIBONATES.--This species bears dark green Rosemary-like leaves, and yellow flowers that are produced very abundantly. South Europe.

H. PILOSUM.--South of France, 1831. This bears white flowers that are of good substance, and about an inch across.

H. POLIFOLIUM (syn H. pulverulentum).--Europe (Britain), and North Africa. This is a neat-growing shrub, of very dwarf growth, with hairy leaves and yellow flowers; and H. polifolium roseum, has pretty rosy-red flowers.

H. UMBELLATUM.--South Europe, 1731. A neat, small-growing species, with white flowers and glossy-green leaves covered with a rusty-white tomentum beneath.

H. VULGARE.--Common Rock Rose. Europe (Britain), North Africa, and West Asia. A widely distributed native plant, of dwarf growth, with linear-oblong, hairy leaves, and usually yellow flowers. H. vulgare nummularium differs in having the leaves green and sub-orbicular, with yellow flowers. H. vulgare barbaturn is of erect habit, with silky, hairy, oval leaves. H. vulgare mutabile bears pale rose flowers, marked with yellow at the base. H. vulgare grandiflorum is remarkable for the large, bright yellow flowers, and is one of the most beautiful and worthy varieties. H. vulgare ovalifolium (syn H. serpyllifolium) bears yellow flowers and ovate leaves, with the margins revolute. H. vulgare hyssopifolium bears reddish flowers, but the colouring varies considerably, and saffron is not uncommon.

The Rockroses are very valuable plants, in that they will succeed on poor, gravelly banks where few other plants could eke out an existence. They cannot withstand stiff soil, nor that at all inclined to be damp, their favourite resorts being exposed, rocky ground, and dry, gravelly banks. Being readily increased from cuttings, which take root well under a hand glass or in a cool house, it is advisable, at least with the more tender forms, to have at hand a stock, so that blanks in the shrubbery may be filled up.

HIBISCUS.

HIBISCUS SYRIACUS (syn Althaea frutex).--Syrian Mallow. Syria, 1596. An old occupant of our gardens, and one that cannot be too freely cultivated. When favourably situated, it often reaches 6 feet in height, with three-lobed, neatly-toothed leaves, and with large, showy blossoms that are borne towards the end of summer. The typical species has purplish flowers, with a crimson spot at the base of each petal, but others, varying in colour from snow-white to purple and blue, are common in cultivation. H. syriacus coelestis bears bright blue flowers, while H. syriacus variegatus has beautifully variegated foliage. Of the double-flowered forms, there are several beautiful and worthy plants, the following list containing some of the best varieties of this popular shrub:--

H. syriacus albo-pleno. " amaranthus. " amplissima. " ardens. " caerulea plena. " carnea plena. " De la Veuve. " elegantissimum. " fastuosa. " Lady Stanley. " Leopoldii. " lilacina plena. " paeoniaeflora. " puniceus plenus. " rosea plena. " rubra plena. " spectabilis plena. " violacea.

HIPPOPHAE.

HIPPOPHAE RHAMNOIDES.--Sea Buckthorn, or Sallow Thorn. Though generally considered as a sea-side shrub, the Sea Buckthorn is by no means exclusively so, thriving well, and attaining to large dimensions, in many inland situations. The flowers are not at all conspicuous, but this is amply compensated for by the beautiful silvery-like leaves and wealth of fruit borne by the shrub. In not a few instances, for fully a foot in length, the branches are smothered with crowded clusters of bright orange berries, and which render the shrub during November and December both distinct and effective. It does best in sandy soil, and is readily increased from suckers, which are usually plentifully produced by old plants. For sea-side planting it is one of our most valuable shrubs, succeeding, as it does, well down even to high water mark, and where the foliage is lashed with the salt spray.

HOLBOELLIA.

HOLBOELLIA LATIFOLIA (syn Stauntonia latifolia).--Himalayas, 1840. An evergreen climbing shrub that is more often found under glass than out of doors. In the South of England, however, it is quite hardy against a sunny wall. It grows 12 feet high, with shining green leathery leaves, and fragrant purplish-green flowers. H. latifolia angustifolia has decidedly narrower leaves than the species, but is in no other way different.

HYDRANGEA.

HYDRANGEA ARBORESCENS.--North America, 1736. This is a plant of large growth, but the flowers are greenish-white, and by no means conspicuous.

H. HORTENSIS (syn Hortensia opuloides).--China, 1790. This is an old-fashioned garden shrub that is only hardy in the south and west of these islands and in the vicinity of the sea. In some of the forms nearly all the flowers are sterile, the calyx-lobes being greatly expanded, and in others the outer flowers only are sterile. According to the nature of the soil the flowers vary much in colour, some being pure white, others pink, and others of varying shades of blue. There are some very beautiful and distinct varieties, such as H. hortensis japonica; H. hortensis Otaksa, with large panicles of sterile blue flowers; H. hortensis rosea-alba, with large rosy flowers; H. hortensis Thomas Hogg, a very free-flowering and welcome form; H. hortensis mandschurica, and H. hortensis stellata flore-pleno, with partially double flowers, are worthy of attention.

H. PANICULATA.--Japan, 1874. This is one of the most distinct species, in which the flower-heads are elongated, not flat, as in most other species, and from which the finest form in cultivation has been obtained. This is H. paniculata grandiflora, in which the flowers are sterile and pure white, forming large panicles often a foot in length. It is a magnificent variety, and, being perfectly hardy, should be extensively planted for ornament. The flowers are produced in late summer, but remain in good form for fully two months, dying off a rich reddish hue.

H. QUERCIFOLIA.--Oak-leaved Hydrangea. Florida, 1803. This species has neatly lobed leaves, and terminal panicles of pinky-white, but partially barren, flowers.

H. SCANDENS.--Climbing Hydrangea. Japan, 1879. This is not very hardy, but with the protection of a sunny wall it grows freely.

The Hydrangeas require a rich, loamy soil, and, unless in maritime districts, a warm and sheltered situation. They are readily propagated by means of cuttings.

HYMENANTHERA.

HYMENANTHERA CRASSIFOLIA.--A curious New Zealand shrub with rigid ashy-coloured branches, and small leathery leaves. The flowers are violet-like in colour, but by no means conspicuous. The small white berries which succeed the flowers are, in autumn, particularly attractive, and very ornamental. It is perfectly hardy and of free growth in light peaty earth.

HYPERICUM.

HYPERICUM ANDROSAEMUM.--Tutsan, or Sweet Amber. Europe (Britain). A pretty native species, growing about 2 feet high, with ovate leaves having glandular dots and terminal clustered cymes of yellow flowers.

H. AUREUM.--South Carolina and Georgia, 1882. This soon forms a neat and handsome plant. The flowers are unusually large, and remarkable for the tufts of golden-yellow stamens with which they are furnished.

H. CALYCINUM.--Aaron's Beard, or Rose of Sharon. South-east Europe. This is a well-known native species of shrubby growth, bearing large yellow flowers from 3 inches to 4 inches in diameter. It is a prostrate plant, with coriaceous glossy leaves with small pellucid dots, and of great value for planting in the shade.

H. ELATUM is a spreading species from North America (1762), growing to fully 4 feet in height, and bearing terminal corymbs of large, bright yellow flowers in July and August. Leaves rather large, oblong-ovate, and revolute. On account of its spreading rapidly from the root, this species requires to be planted where it will have plenty of room.

H. HIRCINUM.--Goat-scented St. John's Wort. Mediterranean region, 1640. A small-growing and slender species, with oblong-lanceolate leaves 2 inches long, and producing small yellow flowers in terminal heads. There is a smaller growing form known as H. hircinum minus. The plant emits a peculiar goat-like odour.