December 12
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Plant Genus of the family Apocynaceae

Genus Description Cultivation
Allamanda This genus of around 12 evergreen shrubs includes both upright and semi-climbing species. They are native to tropical America and are the very essence of a tropical shrub: lush, colorful and flamboyant. The large, glossy, deep green leaves are the perfect foil to the flowers, usually a deep golden yellow . The flowers appear mainly in summer and autumn and are trumpet-shaped with a widely flared throat of 5 large, overlapping petals. CULTIVATION: Protection from frost is paramount and a moist subtropical to tropical climate is best, though it is possible to grow allamandas in very sheltered areas in cooler zones. For a prolific flower display give them rich well-drained soil and plenty of summer moisture. They also do well in conservatories but watch out for mealy bugs, scale insects and mites. Propagation is usually by half-hardened cuttings.
Allocasuarina Until 1980 the casuarina family (Casuarinaceae) was regarded as consisting of the single genus Casuarina. An Australian botanist who specialized in this group of plants argued for the recognition of 3 additional genera, into which were transferred all but 17 of the 90 known species in the family. Largest of these new genera is Allocasuarina, with 59 species entirely confined to Australia. They are all trees or shrubs and share with Casuarina a pine-like appearance and unique structures. The fine twigs appear leafless, but in fact they have whorls of narrow leaves fused flat against their surfaces, with only the tips remaining free and appearing as rings of minute teeth at regular intervals along the twig. The number of teeth per ring is a characteristic feature of each species. Flowers are mostly of different sexes on different plants and are highly reduced in structure. Male flowers consist of little more than a single tiny stamen, but are strung in whorls along the branch tips in large numbers, coloring the male plants golden brown to rusty red at flowering time. Female flowers similarly consist of little more than a pair of delicate red styles, but are grouped in small dense heads arising from the thicker twigs. The cone-like ?fruits? are in fact short spikes of tightly packed woody bracts; these eventually split apart to release the ?seeds?, actually the true fruits, which are small blackish nuts tipped by a membranous wing. Allocasuarina species can be put to good use as screens and windbreaks, though not quite such vigorous growers as true Casuarina species. As ornamentals they are not to everyone?s taste, but the dull purplish color that the foliage often takes on in winter adds to their appeal. The trunk and branches make excellent firewood and some species have been grown for this purpose. CULTIVATION: Most species are adapted to poor sandy or stony soils, low in essential plant nutrients. Planted in better soil the shrub species tend to ?bolt? and may fall over under their own weight; however the taller tree species mostly adapt well to more fertile soils, particularly A. luehmanniana and A. verticillata which occur naturally on clays. They make fast growth in the garden and require little maintenance, although the fall of masses of dead branchlets on paths and lawns can sometimes be a problem. Propagation is always from seed, which quickly falls out of gathered cones and germinates readily.
Alloxylon Belonging to the protea family, Alloxylon comprises 4 species of evergreen rainforest trees native to tropical and subtropical eastern Australia and New Guinea. Among Australian Proteaceae, Alloxylon is most closely related to the the waratah genus Telopea, and its species are similarly prized as ornamentals, with conspicuous red or pinkish flowers in large terminal clusters that attract nectar-feeding birds. The leaves are irregularly lobed or pinnate, though tending to become unlobed and simple on flowering branches. Individual flowers are like those of Grevillea on a larger scale. The flowerheads differ from those of Telopea in not having a ring of conspicuous red bracts. The fruit is a large follicle that splits to release winged seeds. CULTIVATION: They are somewhat demanding, requiring a subtropical climate with year-round rainfall, or tropical hill conditions with a not too severe dry season. Soil must be well drained and moderately fertile, and the trees sheltered from strong winds. Young plants are prone to sudden wilting and death for no apparent reason, but once above a height of 10?15 ft (3?4.5 m) they usually remain healthy. Propagation is from seed, sown as soon as collected.
Aloysia Mostly from South America in subtropical and temperate climates, this genus of tender shrubs and perennials belongs in the Verbenaceae family. All the species contain volatile oils in their foliage, with fragrances resembling citrus, lavender, camphor and mint, utilized in perfumery and traditional medicine, commonly for respiratory conditions. One species is a substitute for oregano. Another Brazilian species was used as a tea substitute and its fruit are also eaten. The species with widest appeal is undoubtedly the lemon-scented verbena. Small flowers in clusters at the ends of branches (on current season?s wood) can be abundant. CULTIVATION: These plants prefer well-drained loam and summer rainfall or irrigation. They will tolerate only light frosts so require a warm and sheltered position. Straggly growth should be regularly trimmed to encourage new wood and maintain foliage density. Propagate by cuttings which strike readily in summer.
Alstonia There are about 40 species in this genus of evergreen trees and shrubs, related to frangipani (Plumeria) and the humble periwinkles (Vinca). Most are native to tropical Asia and Australasia, but smaller numbers occur in tropical America and Africa. Some are tall rainforest trees, others range into much drier monsoonal scrubs. All their parts bleed a milky, caustic sap when cut, and the bark and roots are intensely bitter and probably poisonous?a variety of local medicinal and pesticidal uses have been recorded. The simple, smooth-edged leaves are in whorls of up to 7 and the branches of saplings are likewise whorled, in a manner reminiscent of pines (Pinus); but later upward growth is by one or more lateral branches from the previous growth flush, curving at the base to become erect, and this pattern is repeated. Flowers are in clusters terminating branchlets, mostly fairly small with 5 white petals arranged in the same propellor-like manner as periwinkle flowers. Fruit are slender and bean-like, splitting when ripe to release silky-plumed seeds into the wind. CULTIVATION: All species are frost tender and some will only thrive in the tropics and nearby subtropics. In fertile soil and a sheltered position the trees make fast growth, preferring full sun. Propagation is normally from seed, although cuttings can be struck.
Alyogyne Once included within the genus Hibiscus, these 4 distinctive evergreen Australian shrubs, despite their delicate silky blooms, are native to the drier regions of the western half of the continent. The leaves are variable; in some species they can be entire while in other species they are palmately lobed. They are fast growing and, as though to make up for their short-lived single blooms, usually in pinks or mauves, they flower profusely over a long period. CULTIVATION: These are hardy plants for non-humid areas. Most are able to survive frost. They do best planted in full sun and can survive in all soil types but appreciate good drainage. Pruning is sometimes necessary to control shape. Propagation is from easily struck cuttings or by seed.
Alyxia This is a genus of some 70 species of mainly coastal evergreen shrubs, notable for their 5-petalled white flowers which are often scented, and the colorful but poisonous fruits that follow. The leaves are usually small and often have a glossy waxy coating that is typical of salt-tolerant seaside plants. The genus is perhaps centered on Australia, though representatives are found through much of the warm-temperate and tropical Asian-Pacific region. The Hawaiian species, Alyxia olivaeformis, is used for producing leis and has a strong fragrance reminiscent of frangipani (Plumeria), to which it is related. CULTIVATION: Hardiness and adaptability varies greatly with the origin of the species. Those from the tropics generally prefer warm, moist conditions and fairly rich soil, while A. buxifolia is a very tough shrub that can tolerate most conditions, with the exception of extreme cold. Most species can be propagated by seed or half-hardened cuttings.

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