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Plant Genus of the family Ericaceae

Genus Description Cultivation
Andromeda Two fully hardy, low-growing evergreen species make up this genus found growing in the acid peat bogs of the Northern Hemisphere. The somewhat leathery, smooth-edged, small oblong leaves form a deep green background to the white or pink, tiny bell-like flowers held in terminal clusters during spring. CULTIVATION: The 2 species within this genus require an acid soil where constant moisture is assured and are best grown in peat beds, shady woodlands or rock gardens. They can be propagated by suckers, layering or from softwood cuttings.
Arbutus This small genus contains about 8 to 10 species of small evergreen trees belonging to the erica family, which are commonly known as strawberry trees due to their strawberry-like fruit. They occur in the Mediterranean region, western Asia and southwestern USA, with a few species in Central America and Mexico. All have attractive bell-shaped flowers and red or yellow fruit of little economic value, and in some cases have red or cinnamon-colored stringy, peeling bark. Height varies from about 10?20 ft (3?6 m). CULTIVATION: Arbutus like a well-drained soil, preferably free of lime, and an open sunny position protected from coastal winds. Most species are tolerant of sustained cold winters. Little pruning is required. Propagation is by half-hardened cuttings taken in autumn or winter; scions can also be top-grafted on seedling understocks. Seeds can be sown in spring.
Arctostaphylos There are about 50 species in this genus of mostly evergreen small shrubs and trees in the family Ericaceae. The genus is found only in North America, except for 2 species that extend through the alpine-arctic regions of the Northern Hemisphere. They have reddish brown ornamental bark, smooth or peeling in flakes. The leaves are alternate and smooth or toothed. Flowers are in terminal racemes or panicles of tiny bells or are urn-shaped, and may be white or pink. Fruit of some species has been used for juicing and also to make flour. Leaves of A. uva-ursi leaves are used for tanning and in Russia as a tea; in the UK it has been used as a urinary antiseptic since the thirteenth century. CULTIVATION: All species require lime-free soil. They should be watered freely and fed during the growing season, if grown in pots. During the dormant season feeding should stop and watering should be reduced. Seed benefits from immersion in boiling water for 15?20 seconds before sowing and should be sown in autumn (as soon as it is ripe) with protection against frosts. Prostrate species should be layered in autumn. Plants will sometimes root naturally at nodes. Plant half-hardened cuttings in summer. This genus is generally disease-free except for leaf spot.
Calluna There is only 1 species in this genus that belongs to the Ericaceae family. Native to north and western Europe from Siberia to Turkey and Morocco and the Azores, it has naturalized in parts of North America. The height and spread of this small shrub is 2 ft (60 cm) on average, but this can vary greatly in some of the 500 or more cultivars. The leaves grow in overlapping pairs, arranged oppositely, along the stems, and look more like scales. The leaves are dark green, usually turning reddish or tinged with purple in winter. Calluna differs from Erica in that the corolla is hidden by the calyx. It produces pink to purplish pink flowers from summer to late autumn. CULTIVATION: This plant prefers acid soil in an open, well-drained position in full sun. Stems can be layered in spring and detached once rooted, or cuttings of half-hardened wood can be taken in mid-summer.
Cassiope This genus of 12 species of small evergreen shrubs is closely related to the heaths and heathers. They are found mainly in northern Europe and northern Asia with outliers in the Himalayas and western North America. They are very much cool-temperate to cold climate plants, with a few species ranging into the Arctic. They seldom exceed 8?in (20?cm) high and have tiny leaves arranged in 4 distinct rows on wiry whipcord stems. The flowers, which appear mainly in spring, are small, usually bell-shaped and carried singly, though often in large numbers, on fine stems. CULTIVATION: Cassiopes prefer moist well-drained soil that is humus-rich and slightly acidic. They are not drought tolerant and need ample summer moisture. Very frost hardy, they prefer a climate with distinct seasons with a cool moist summer. They are best shaded from hot summer sun. Trim lightly if necessary and propagate from self-layered stems or by taking cuttings.
Erica This genus in the family Ericaceae includes about 750 species of evergreen shrubs ranging in form from small subshrubs to trees. The majority come from the Cape region in South Africa, but the genus ranges widely, from Africa, Madagascar and the Atlantic Islands to the Middle East and Europe. Its habitat includes wet and dry heathland and moorland. Most of the plants are frost tender except for the European species, which are mostly frost hardy. The small needle-like leaves are linear with rolled margins; they are whorled and rarely opposite. Flowers are bell-shaped or tubular and the predominant colors are pink and white, but all colors occur, except blue. Briar pipes are made from the woody nodules at the base of the tree heath, Erica arborea, and some species yield a yellow dye. The majority are cultivated for ornamental use in gardens. CULTIVATION: All prefer full sun or partial shade. Germination of some of the Cape heaths is helped by smoke treatment. A small group, the winter-growing heathers, are lime tolerant and will grow in neutral and alkaline soil while the summer-flowering ones like acid soil, but both can be grown in neutral soil. Container-grown plants need feeding once a month during the growing season. They also need plenty of water, but this should be reduced during the dormant season. Propagate by taking half-hardened cuttings in mid to late summer, or by layering in spring.
Gaultheria This genus, named after Canadian botanist Jean-Francois Gaultier, contains some 170 species of evergreen shrubs. It has a wide natural distribution that ranges from the Americas to Japan and Australasia. In the main they are tough bushes with leathery foliage and a preference for temperate to cool climates. Many are small plants, often found in mountainous areas, where their bright, relatively large fruits stand out among the short alpine vegetation. They are members of the erica family, a fact often apparent in their flowers, which tend to be bell-shaped and pendulous. The fruit that follows may be small and fairly dry or a fleshy berry, depending on the species. Many species are aromatic, often highly so, especially the fruit. CULTIVATION: Frost hardiness varies with the species, the toughest being among the large broadleafed evergreens. They prefer moist, well-drained, humus-rich, slightly acidic soil with ample summer moisture. The exposure preference also varies with the species, though few do well in full shade. Propagate from seed, half-hardened cuttings or layers, which often form naturally where the stems remain in contact with the ground.
Gaylussacia Endemic to the Americas, this genus is made up of some 40 species of deciduous or evergreen shrubs. It belongs in the erica family and is closely related to Vaccinium, sharing the common name huckleberry with some members of that genus. The leaves, which are fairly small, may be toothed or smooth-edged and are sometimes coated with a sticky resin. In spring, racemes of small white, pink or red bell- or urn-shaped flowers develop in the leaf axils. These are followed by berry-like fruit that, while edible, are often very seedy. Some species, especially Gaylussacia baccata and G. frondosa, are hosts of the blueberry maggot fly and should not be grown near commercial blueberry crops in regions where this pest occurs. CULTIVATION: Along with most of the erica family, huckleberries prefer moist, well-drained humus-rich soil that is on the acidic side, with a position in sun or partial shade. In the wild, many species grow in boggy peaty ground and, although this is difficult to replicate in gardens, it indicates one of the main requirements?the soil must remain moist. Propagate from seed, which germinates best if stratified, from summer cuttings or from layers, which often form naturally.
Kalmia This genus of 7 species of mainly evergreen shrubs in the family Ericaceae was named after Dr Pehr Kalm, a botanist and explorer of the east coast of North America in the 1770s. Most are native to northeastern USA, a single species occurring in Cuba. They are grown for their attractive foliage and their showy flowers, which range in color from pale pink to deep red. The leaves are simple and alternate and the flowers are generally carried in terminal corymbs, well clear of the foliage; the fruits are small capsules that contain quantities of very small seeds. CULTIVATION: Kalmias require conditions similar to those of rhododendrons, to which they are closely related. They are at home in slightly acid, peaty soil but resent clay and lime in any form. Adequate water is needed in hot summer weather. Dappled shade under tall deciduous trees in a cool moist climate is ideal. Little pruning is necessary apart from the removal of spent flower clusters. The simplest method of propagation is from seed, which should be collected as soon as ripe and sown the following spring. Firm tip-cuttings taken in late summer through to winter may be struck, though not easily; alternatively, simple layers can be set down in autumn and severed a year later.
Ledum The 3 or 4 evergreen species of this genus, closely related to Rhododendron, grow in damp woodlands and wet swampy areas in higher latitudes in the Northern Hemisphere. They are all bushy shrubs, flowering in spring with masses of small white flowers. CULTIVATION: These plants grow best in neutral to acid soil that is slightly wet, rich in humus and has good drainage, preferring shade or part-shade. Annual mulching with leafmold or other organic material is recommended. Propagate from seed sown in autumn or spring, by layering branches in autumn, or from half-hardened cuttings in late summer.
Leiophyllum There is just a single species of dwarf evergreen shrub in this genus that is part of the same family as Rhododendrons. Native to eastern USA, it has small box-like leaves and is grown for its tiny, starry, spring flowers. CULTIVATION: This shrub dislikes lime and should be grown in humus-rich soil in a sheltered site with morning sun or light shade. It is suitable for growing in the rock garden. Propagation is from seed or half-hardened cuttings.
Lyonia The 35 species of evergreen shrubs and small trees in this genus come from 2 different regions: the low warm-climate woodlands of the Himalayas and East Asia, and an area that includes the USA, Mexico and the West Indies. All plants have attractive, simple, alternate, shiny, leathery leaves but their primary attraction for the gardener is their dense axillary heads (more rarely, short racemes) of pendent white to pink flowers. Some species have the advantage of flowering towards the end of summer when most gardens are in need of a splash of color. Flowers of different species take different shapes but are usually cylindrical or urn-shaped. CULTIVATION: Generally frost hardy and relatively free of pests and diseases, all species prefer at least partial shade, and some deep shade. The essential requirements for all species are a neutral to acid soil and plenty of moisture. They will not tolerate a drought. Pruning is generally not necessary but may be performed in late spring to keep plants shapely. Propagate via seed in autumn, half-hardened cuttings in summer or layering in spring.
Menziesia This genus of 7 species of deciduous shrubs belongs in the erica family and in general appearance is reminiscent of the more commonly grown Enkianthus. Native to temperate East Asia and North America, they bear drooping heads of small bell-shaped flowers in pink and cream shades, usually in late spring or early summer. Small seed capsules follow. The foliage is often noticeably hairy and quite attractive, though it usually shows only slight autumn color. CULTIVATION: Requiring the typical cool-climate erica family conditions?well-drained, humus-rich, slightly acidic soil and a position in sun or partial shade?menziesias are ideal for combining with rhododendrons, camellias and other acid-soil plants. They also do well in large, partly shaded rockeries. Pruning, other than light trimming to shape, is seldom necessary. Propagate from seed or late spring cuttings.
Oxydendrum The single species of deciduous shrub or small tree in this genus, native to North America, belongs to the same family as Rhododendron. It has a slender trunk, which is sometimes multi-stemmed, with rusty red fissured bark. In autumn, small white flowers appear and the leaves color vividly before falling. CULTIVATION: This plant is suitable for growing as a specimen or in open woodland. Grown in full sun, flowering is better and the autumn colors more intense. As do other members of the Rhododendron family, this species needs an acid soil that is moist but well-drained. Plants are slow growing and take time to become established. Propagate from seed in autumn or spring, or softwood cuttings in summer.
Phyllodoce This is a genus of 5 species of small, evergreen, heath-like shrubs native to the Arctic and to the alpine regions of the Northern Hemisphere, western North America and Japan. They have crowded, alternate, linear leaves with finely toothed margins and terminal racemes or umbels of nodding, open, bell-shaped flowers in spring and early summer. They make ideal rock-garden plants for regions with cool summers. CULTIVATION: Fully frost hardy, this genus grows best in moist, acid, peaty soil in partial shade. In warm areas do not allow plants to dry out in summer, and mulch to ensure cool root conditions. Lightly trim after flowering to maintain a compact habit. Propagate from seed or by layering in spring, or from cuttings in late summer.
Pieris Widely cultivated and extensively hybridized, the best known of the 7 species in this genus are common garden plants, being among the most popular evergreen shrubs for temperate gardens. These familiar species are evergreen shrubs from subtropical and temperate regions of the Himalayas and eastern Asia, but the genus also includes a vine and some shrubby species from eastern USA and the West Indies. Typically the leaves are simple pointed ellipses, often with serrated edges, and the flowers are bell-shaped, downward-facing and carried in panicles. They usually open in spring and are sometimes scented. CULTIVATION: In common with most members of the erica family, Pieris species prefer cool, moist, well-drained soil with ample humus. A position in full sun yields more flowers, light shade results in lusher foliage. Heavy pruning is seldom required as they are naturally tidy; light trimming and pinching back will keep them that way. Propagate from half-hardened cuttings or layers.
Rhododendron This very diverse genus of 800 or more species of mostly evergreen and some deciduous shrubs is widely distributed across the Northern Hemisphere, with the majority growing in temperate to cool regions. Particular concentrations occur in western China, the Himalayas and northeastern Myanmar, while the so-called ?tropical? Vireya rhododendrons grow mostly at higher altitudes throughout tropical southeastern Asia, as far south as the northern tip of Australia, with more than 200 species occurring on the island of New Guinea alone. Deciduous azalea species are scattered across cooler Northern Hemisphere climates, notably in Europe, China, Japan and North America. Rhododendrons vary in form from tiny, ground-hugging, prostrate and miniature plants adapted to exposed conditions to small trees, often understory species in the forests of mountainous areas. Many species grow at high altitudes of 3,000 ft (900 m) or more and some can grow as epiphytes in the branches of trees or on rock faces. As members of the erica family, they are closely related to heathers (Erica and Calluna species), Pieris and strawberry trees (Arbutus species) and have similar growing requirements, particularly the need for a moist, organic and acid soil. Some rhododendrons have solitary flowers but most bear terminal racemes, known as ?trusses?, of up to 24 or more spectacular blooms, in a wide palette of colors including whites, pinks, reds, yellows and mauves, excluding only shades of pure blue. Flowers may be a single color but are often multi-colored, with spots, stripes, edging or a single blotch of a different color or shade in the throat of the flower. With the exception of some Vireya species and hybrids, fragrant rhododendrons are always white or very pale pink. Blooms vary in size and shape but are generally campanulate (bell-shaped), with a broad tube ending in flared lobes, and usually single. Flowers with double petals do occur, particularly among the evergreen azaleas, which may also be ?hose-in-hose?, when the calyx is enlarged and the same color as the petals. Most rhododendrons flower from early spring (early season) to early summer (late season), although some bear spot flowers briefly in autumn, and Vireya rhododendrons can flower at various times during the year, often in winter. Deciduous azaleas flower in spring on bare branches just before or at the same time as new leaf growth starts to emerge. The fruit is a many-seeded capsule, normally woody but sometimes soft, and sometimes bearing wings or tail-like appendages to aid transportation. Rhododendron species and hybrids are cultivated as ornamental plants, valued for their masses of colorful flowers and year-round foliage in great diversity of form; some are also sought for their attractive textured bark and rich fragrance. The new leaf shoots of evergreen rhododendrons often form attractive perpendicular ?candle-sticks?, while mature leaves vary enormously in size, from less than 1?2 in (12 mm) long to as much as 3 ft (1 m) or more. The foliage of deciduous azaleas progresses through the growing season from bright green shoots in spring to bronze in summer, followed by rich reds to yellows in autumn before falling. The genus is divided into 2 botanically distinct groups known as lepidotes and elepidotes, and these groups are subdivided further into the various rhododendron types. Plants from one group may not breed with plants from the other, thus limiting the options for hybridizers. The leaves, and sometimes the flowers and other parts, of lepidote rhododendrons are covered with scales, which is thought to aid transpiration. This group includes many of the cool-climate evergreen plants, including the Vireya rhododendrons. The rest of the genus, the elepidote rhododendrons, with no scales on leaf or flower parts, includes the remaining cool-climate evergreen plants and the evergreen and deciduous azaleas, which are normally rather more compact plants with 5 stamens rather than the more usual ten. Azaleas were originally classified as a separate genus but are now regarded as botanically part of the rhododendron genus. Vireya rhododendrons can be grown in just about any climate as long as protection from frost is provided. Many are well suited to growing in hanging baskets and containers. The nectar of some species and some flower parts are poisonous and care should be taken when handling the flowers. CULTIVATION: Establishing an ideal growing environment before planting is the key to success with rhododendrons. Many of the problems likely to afflict them in the home garden can be minimized by maintaining soil quality and ensuring adequate ventilation. All prefer acidic soils between pH 4.5 and 6, high in organic matter and freely draining. A cool root run is essential and is best achieved by applying a deep mulch of organic material that also helps to reduce moisture loss and control weed growth, while minimizing disturbance of the delicate roots. Many rhododendrons, particularly those with larger leaves, prefer a shaded or semi-shaded aspect. They are ideally suited to planting under deciduous trees, allowing winter sun and summer shade. While most prefer some protection from wind, sun and frost, many others are tolerant of these conditions and some are well suited to exposed rock gardens. Rhododendron bugs can pose a problem in the Northern Hemisphere, and are most effectively controlled with a systemic insecticide for sucking insects, which is also the best defence against weevils, particularly vine weevils, thrips and mites. Disease problems are mostly fungal, such as petal blight and bud blight or blast and root rot, while rusts and mildews can pose a lesser problem in some areas. All can be controlled by the use of appropriate fungicides and minimized by improving growing conditions. Evergreen rhododendrons may be propagated by taking tip cuttings of new growth in spring, while deciduous azaleas are best grown from hardwood cuttings taken in winter. Plants may be grown from seed but germination and development is slow, and plants grown from the seed of hybrids are unlikely to be the same as their parents. Layering enables new plants to be created from low-hanging branches pinned to the ground and covered in a moist organic medium such as sphagnum moss. Plants which are difficult to propagate and establish by other means can be grafted onto the roots of stronger plants with more vigorous root systems. Regular pruning of rhododendrons is not necessary other than as required to control size, maintain shape and to remove damaged or diseased material, while some species and hybrids actually resent unnecessary pruning. Cultivated rhododendrons are normally more compact and attain only about half the height of similar plants growing in the wild. The growing habit of all species and hybrids varies widely according to the amount of shade the plant receives.
Vaccinium This genus of around 450 species of evergreen and deciduous shrubs, small trees and vines includes the blueberries, cranberries and huckleberries as well as the delightfully named farkleberry, whortleberry and bilberry. They occur over much of the Northern Hemisphere with a few species found in South Africa. Their main features are small but colorful and/or edible fruits, often very tasty, and sometimes vivid autumn foliage. Their flowers too can be attractive, usually small, urn-shaped and downward-facing, carried singly or in clusters. The leaves are usually simple, oval to lance-shaped, often pointed at the tip and sometimes serrated around their edges. CULTIVATION: As with most plants of the erica family, Vaccinium prefers cool, moist, humus-rich soil that is acidic and well drained with shelter from the hottest summer sun. Some species thrive in boggy ground in the wild, but in cultivation the type of conditions preferred by rhododendrons and camellias tend to give the best results. Many Vaccinium form dense thickets of stems and can be cut back hard to encourage compact growth. The shrubbier species should be pruned to shape: after flowering if the fruit is not required, otherwise at harvest. Propagate from seed, cuttings, layers and in some cases division.

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