March 22
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Plant Genus of the family Rosaceae

Genus Description Cultivation
Amelanchier Amelanchier consists of 30 or so species of deciduous shrubs and small trees with attractive white spring blossom; all but 2 are native to North America (including Mexico). One species occurs in China, another in Europe and Turkey. All have smallish oval or elliptical leaves on slender stalks, often downy beneath and with finely toothed margins. The flowers, each with 5 narrow petals, are borne in small sprays terminating spur shoots as in the related Malus (apples) and Pyrus (pears); the small hawthorn-like fruit with sepals persisting at the apex also betray their membership of the pome-fruit subfamily of the rose family. The fruits mostly ripen to blue-black and are edible, although often not palatable until overripe. They are regarded as important food for wildlife, especially birds. Some serviceberries make attractive ornamentals, displaying their clouds of white bloom just before or with the new leaves, though the display is brief. The silvery down on new growths of some species is another appealing feature, as is the autumn foliage color. CULTIVATION: Amelanchier are mostly woodland plants that prefer moist sheltered sites and are most effective planted against a backdrop of darker foliage. Some species tolerate boggy ground and do well at the edge of a pond or stream. They are prone to the same pests and diseases as apples, pears and hawthorns, including the dreaded fireblight. Propagation is normally from seed, germination being aided by cold-stratification, or by layering of low branches or suckers. Cultivars are often grafted.
Aronia This genus of deciduous shrubs from woodlands of eastern USA contains 2 species and a naturally occurring hybrid. A member of the large rose family, it is closely allied to Pyrus (pear) and Sorbus (rowan). The shrubs are of compact size bearing white or pale pink spring blossoms that are followed by small berry-like fruits of red, purple or black which give rise to the common name of chokeberry. The foliage colors attractively in autumn in shades of red and crimson. CULTIVATION: These shrubs are well suited to informal plantings and woodland edges. They require a deep moist well-drained soil and will grow in semi-shade or sun. Sunnier sites will encourage better fruiting and autumn coloring. The shiny black cherry and pear slug can cause unsightly damage to the foliage but can be controlled with a carbaryl or pyrethrin preparation. Propagate from half-hardened cuttings, layering, removal of suckers or seed sown in autumn.
Chaenomeles This genus, belonging to the Rosaceae family, has 3 species of spiny deciduous shrubs and is native to the high-altitude woodlands of Japan and China. Some species grow into small trees up to 20 ft (6 m) in height. Their early red, pink or white flowers appear before the leaves on last year?s wood and are highly valued. The leaves are alternate, serrate, oval and deep green. The flowers, usually with 5 petals, unless double, are cup-shaped and appear from late winter to late spring, singly or in small clusters. The roughly apple-shaped, rounded, green fruit turns yellow when ripe and like the true quince, Cydonia species, is aromatic and used in jams and jellies. CULTIVATION: They will grow in most soils except very alkaline soil. In too rich a soil they will produce more foliage and less flowers. Generally, a well-drained moderately fertile soil, in sun or part shade will give best results. Grown against a south wall in colder climates they will carry more flowers. Chaenomeles can also be used for hedging and is a good ornamental shrub. A few flowers may sometimes appear in late summer. Half-hardened cuttings can be taken in summer or later in autumn. Seed can be sown in autumn in containers with protection from winter frosts or in a seed bed in the open ground.
Cotoneaster This genus in the Rosaceae family consists of about 200 species of evergreen, semi-evergreen or deciduous shrubs and trees from the northern temperate areas. The leaves range from rounded to lance-shaped, and all are simple, smooth-edged and arranged alternately on branches. The small flowers are white, sometimes flushed pink or red, with 5 petals, and are borne singly or in cymes. They are followed by red-black or red fruits with rather dry flesh and 2 to 5 nutlets. Grown for its profuse flowers and fruit, it can also be used as a hedging plant and as an attractive specimen. CULTIVATION: Cotoneasters grow well in moderately fertile well-drained soil. Dwarf evergreens and deciduous plants fruit better in full sun, while taller evergreens grow well in part-shade. In exposed situations they may need protection from cold drying winds. Propagate by taking half-hardened cuttings of evergreen species in late summer and deciduous species in early summer. Seed needs to be sown as soon as it ripens in a position sheltered from winter frosts, although not all species come true from seed.
Crataegus This genus within the Rosaceae family contains around 200 species. Most are spiny large shrubs or small trees. The leaves are alternate, simple or lobed, some toothed and deep green in color. The white to pink flowers have 5 sepals and/or petals depending on the species, and are carried in corymbs or are solitary. They are followed by nutlets, the fleshy covering of which is edible. The colors of the fruit can be black, yellow or bluish green but the majority are red. Crataegus laevigata and C. monogyna have been used as hedging plants for centuries. CULTIVATION: Grow in sun or partial shade in any soil. Cultivars may be budded in summer or grafted in winter. Sow seeds as soon as ripe in a position protected from winter frosts. Germination may take up to 18 months. Some hawthorns are prone to fireblight.
Cydonia The quince, a member of the pome fruit group of the Rosaceae or rose family and therefore closely related to apples and pears, has been cultivated for thousands of years in its area of origin, northern Iran, Armenia and Turkey. From there it was spread, firstly throughout the Mediterranean area and then northwards through Europe. It was a symbol of love and fertility to the ancient Greeks and Romans and some believe that it was the ?forbidden fruit? in the Garden of Eden. The quince is a deciduous tree, up to 25 ft (8 m) in height with a rounded, umbrella-like crown. The flowers are self-fertile so even a single tree is capable of producing fruit. CULTIVATION: Quinces will grow in a variety of soils and seem to survive neglect more than most fruit trees. They will weather quite hard frosts but, conversely, will also fruit in subtropical conditions. They like a sunny position, but with protection from wind. Surplus shoots should be removed in winter, but meticulous pruning, as carried out with apples and pears, is not necessary. Cydonia can be propagated by cutting, but cultivated forms are normally grafted onto cutting-grown quince rootstocks.
Exochorda This genus of 4 or 5 species of deciduous shrubs in the family Rosaceae is native to northeast and central Asia. All are attractive, spring-flowering shrubs, many with arching branches which become festooned with pure white, waxy flowers borne in terminal or axillary racemes; leaves are simple and alternate. CULTIVATION: Members of this genus are easy to cultivate. They prefer a moderately fertile soil, a cool, moist climate with adequate summer rainfall and a sheltered position in full sun. They may become chlorotic on chalk soils. Pruning consists of the removal of about one-third of the length of the basal shoots in late winter, to make room for new growth; spent flower clusters should be removed immediately after flowering. Seeds germinate readily when sown in spring in a warm, humid atmosphere. Soft-tip or half-hardened cuttings taken in summer or autumn can be rooted under cover, or hardwood cuttings from winter pruning can be used.
Kerria This genus with a single species in the Rosaceae family is native to China and Japan, where it has long been cultivated?the double-flowered form can be seen in almost every Chinese garden today. It was named after William Kerr, a plant collector from Kew Gardens, who introduced the plant into England in 1804. It is a low, suckering deciduous shrub with bright yellow flowers and graceful cane-like stems with rather sparse but attractive foliage, and makes an interesting addition to a shrub border. CULTIVATION: Kerria japonica will grow in any moderately fertile soil with free drainage, preferring a sunny or lightly shaded position and a cool moist climate. Several of the older flowering shoots should be removed at the base after flowering each year to make room for new shoots; no further pruning is necessary. It is easily propagated; soft-tip or half-hardened cuttings taken in spring or summer strike readily, or stems can be layered and lifted a year later.
Malus The apples and crabapples comprise a large genus of around 30 species of ornamental and fruiting small to medium-sized deciduous trees. They belong to the rose family and are widely cultivated throughout the temperate regions of the world. Nearly all have soft green leaves (?apple green?). The fruits are pomes, in which the core structure of several seeds is enclosed within a swollen fleshy covering. Not all crabapples are edible, some being too bitter, but most can be used to make a pleasant-tasting jelly. The origin of the cultivated eating apple is to be found in the crabapples, but just when the transformation of the species found growing wild in the forests of the Caucasus and adjoining parts of Georgia occurred is not certain. Apples were grown by the Egyptians as early as 1300 bc and by the time of the Romans were well known. They went to America with the Pilgrim Fathers and to Australia with the First Fleet. The cultivated apple is one of the most widely grown of all edible fruits and the many species and cultivars of crabapple are equally valued as ornamental trees. They will grow in all cool-temperate regions and are now grown also in highland regions in the tropics as well as in the harsh conditions of Siberia and northern China. CULTIVATION: Apples and crabapples flower in spring; most cultivated varieties of apple require a cross-pollinator in order to produce fruit. Fruit is set in clusters of 3 to 5 and some thinning may be necessary for a maximum crop. While cultivated apples require careful pruning in winter, as well as spraying against a variety of pests and diseases, the crabapples, being largely ornamental, need less attention although some are also susceptible to leaf diseases. Propagation is by grafting onto a range of apple rootstocks, some of which have the effect of producing a dwarfed plant.
Photinia This genus in the rose family, Rosaceae, consists of around 60 species of evergreen and deciduous shrubs and trees, the majority coming from the Himalayas to Japan and Sumatra. Photinia is derived from the Greek photeinos, meaning ?shining?, describing the simple, smooth, non-hairy leaves. The leaves are often strikingly colored when young, especially in spring. Flowers are small, mostly white, with 5 petals and produced in dense, flattish, corymbose panicles along or at the ends of shoots. The fruit is a small, usually red, pome. The evergreen species are cultivated for their striking foliage color and are popular hedging plants, while the deciduous species are more reliable in flowering and in autumn their deciduous foliage can be attractively colored. CULTIVATION: Most are fairly adaptable with good drainage being a key requirement. For best results, plant in a well-drained fertile soil in a sunny position. Prune to promote dense growth, particularly when used as hedging plants. Pruning of Photinia serratifolia is not essential except to shape. Propagate from seed or cuttings.
Physocarpus Found in North America and temperate northeastern Asia, the 10 deciduous shrubs in this genus are notable for their showy flowerheads; their foliage, which is attractive in spring and sometimes also in autumn; and for their flaking bark, the many layers of which gives the genus its common name. Most species have conspicuously veined lobed foliage reminiscent of that of raspberry or blackberry. The flowers, which are white or pale pink, are individually small, though massed in flat corymbs they make an appealing display against the fresh spring foliage. Interesting inflated fruits with 3 to 5 lobes ripen in late summer. CULTIVATION: They are best grown in full sun with fertile well-drained soil that remains moist through summer. They are not fussy plants but dislike lime; if exposed to drought the foliage becomes desiccated and brown. The plants naturally form thickets of stems and pruning is a simple matter of thinning these and cutting back the remaining growth after flowering. Propagate from seed or half-hardened cuttings.
Potentilla This is a large genus of some 500 species in the rose family. While most are herbaceous perennials, the shrubby species are exceptionally useful as small ornamentals, being very hardy, thriving in most soils, in sun and in partial shade. The flowers are like small single roses, and are produced over a long period, from spring throughout summer and in some species well into autumn. CULTIVATION: These plants prefer a fertile well-drained soil. Cultivars with orange, red or pink flowers tend to fade in very strong sunshine and should be given a position where they receive some shade in the hottest part of the day. Propagation is usually from seed in autumn or cuttings in summer.
Prunus Including both ornamental and fruiting species, many of great commercial significance, this widely grown genus is naturally widespread throughout the northern temperate regions and also has a toehold in South America. Best known for the edible stone fruits (cherries, plums, apricots, peaches and nectarines) and their ornamental flowering cousins, the genus includes a wide range of shrubs and trees, mostly deciduous, ranging from 3?ft (1?m) to over 80?ft (24?m) tall. Most bloom from late winter to early summer, producing 5-petalled flowers either singly or in clusters, in colors from white through to dark pink, followed by fleshy single-seeded fruit. The leaves are usually simple pointed ellipses, often with serrated edges, and sometimes develop brilliant autumn colors. This large and variable genus is divided into several subgenera, based mainly on their flowering and fruiting characteristics. CULTIVATION: Although hardiness varies with the species, most need some winter chilling to flower and fruit properly. Wind protection is important to gain the most benefit from the flowers, either ornamentally or for setting fruit. Some species prefer long cool summers, but most need summer heat to ripen their fruit. Most species are not overly fussy about soil type, though few are drought tolerant and most prefer cool, moist, well-drained soil that is both fertile and humus rich. Correct pruning techniques are important for the fruiting varieties, less so for the ornamentals. If silverleaf disease is present do not prune in winter, instead cutting back in summer or immediately after harvest. Propagate the species from seed, the fruiting forms by grafting and the ornamentals by grafts or in some cases by cuttings. Special forms such as weeping standards require 2 or more grafts.
Pyracantha This small genus in the pome subfamily of the rose family consists of 9 species of mostly spiny shrubs, the majority from eastern Asia, one from southeast Europe. The name is derived from the Greek pyr, meaning ?fire?, and akanthos, meaning ?thorn??hence the common name firethorn. They have simple leaves that are often toothed on the margins, and whitish flowers in corymbs are produced at the ends of branches. The flowers are followed by attractive masses of fruit which persist into winter. These fruits are usually small red, orange or yellow berries, edible but without taste. The seeds may cause stomach complaints. Most species occur in scrub and woodland areas and perform best in cool, moist climates where they are useful landscape subjects for the shrubbery or used as an espalier or for hedging. There are many cultivars and hybrids within the genus. Pyracantha species can naturalize in favorable areas. CULTIVATION: Most are fairly adaptable shrubs tolerating exposed sites in full sun. They perform best in a fertile well-drained soil. Pruning is not essential but may be helpful to control size; hedges can be pruned early to mid-summer. Watch for fireblight, scab and wilt problems. Propagate from seed or cuttings.
Pyrus Widely distributed through Europe and Asia, this genus of about 20 species is related to the apple (Malus) and is part of the rose family. It consists of small to medium-sized deciduous trees, some thorny, with simple leaves sometimes coloring to yellow and red in autumn. Flowers are mostly white followed by fruits, edible in some species, that vary in size and shape. The ornamental species are deep-rooted, tolerant of drought and reasonably tolerant of atmospheric pollution. Fruiting forms require a cross-pollinator to set fruit. CULTIVATION: Pears will grow in most moderately fertile soils and are at their best in cool-temperate climates. Pruning of the ornamental species is seldom necessary apart from forming a well-shaped tree in the early stages. They can be propagated from seed sown very fresh, but clonal forms are propagated by grafting.
Rhodotypos The sole species in this genus is a deciduous shrub native to China and Japan. A member of the rose family, it is cultivated mainly for its spring flowers and, to a lesser extent, for the black berries that ripen over summer and last well into winter. The serrated foliage is a fresh green throughout the warmer months and sometimes develops slight red or yellow colors in autumn. CULTIVATION: Rhodotypos is frost hardy and easily cultivated in most temperate areas in sun or partial shade. It prefers a well-drained humus-rich soil and ample summer moisture, which will also result in a better fruit crop. Prune in winter after the last berries have fallen. Propagate from stratified seed, layers, or hardwood cuttings in winter, or half-hardened cuttings in summer.
Rosa The genus Rosa is one of the most widely grown and best loved of all plant genera around the world. It belongs to the large rose family, which includes a wide range of favorite fruiting plants such as apples, plums and strawberries as well as ornamentals. Since ancient times roses have been valued for their beauty and fragrance as well as for their medicinal, culinary and cosmetic properties. There are between 100?150 species of rose, which range in habit from erect and arching shrubs to scramblers and climbers. The majority of species are deciduous and most have prickles or bristles. They are found in temperate and subtropical zones of the Northern Hemisphere; none are native to the Southern Hemisphere. The pinnate leaves are usually comprised of 5 to 9, but sometimes more, serrated-edged leaflets. Flowers range from single, usually 5-petalled, blooms to those with many closely packed petals. They are borne singly or in clusters. Many are intensely fragrant. The majority of species and old garden roses flower only once but most of the modern cultivars are repeat blooming. Rose fruits (hips or heps) are very rich in vitamin C. They are usually orangey red, but can be dark, and can be very decorative. They may be small and in clusters or single large fruits. Roses have been bred for many centuries and are divided into a number of recognized groups. The old garden roses were originally bred from a handful of species and include groups such as Gallica and Alba. In the late eighteenth century the repeat-flowering China rose (Rosa chinensis) arrived in Europe and subsequent cross-breeding extended the number of Old Rose groups further. The Tea roses, also repeat-flowering, followed in the nineteenth century, and fifty years later a Frenchman bred the first Large-flowered rose, heralding the start of modern rose breeding. Large-flowered, Polyantha, Cluster-flowered and Shrub roses proroses proliferated in the twentieth century. While most of the species and Old Roses are in shades of pink, red and purple or white, modern rose-breeding programs have seen the color range increase to include shades of yellow and orange. CULTIVATION: Roses can be grown in separate beds or mixed borders, in formal and informal settings, as ground covers, climbing up arches and pergolas, scrambling up trees, as hedging and in containers. Such is the popularity of roses that numerous books are devoted to their cultivation. Generally, roses require a site that is sunny for most of the day, as shade inhibits flowering. They should not be overcrowded and there should be good air movement around the plants, factors that help reduce the risk of disease. Roses will grow in most well-drained medium-loamy soils in which compost or organic manure has been incorporated. When planting, the point at which the plant is grafted should be about 1 in (25 mm) below the soil. Granular or liquid rose fertilizer can be applied once or twice a year from spring. Plants should be watered well in dry periods and a mulch will help to conserve moisture in summer. Roses that flower more than once should be deadheaded to encourage further blooms. Roses should be pruned to maintain strong healthy growth, a good shape, and to let light into the plant. A number of pruning regimes are promoted for different rose groups, but recent research has shown that a simple ?tidying up? of dead wood and pruning for size may be just as effective. Most pruning is done when the plants are dormant in winter. Fungal diseases such as rust, black spot and mildew can be a problem, particularly in humid areas. A number of insect pests can also be troublesome, the most common being aphids. Others include spider mites, thrips, leafhoppers, froghoppers and scale. Fungicidal and insecticidal sprays, both chemical and organic, are available to combat these problems. Roses planted in a position previously occupied by another rose can suffer rose sickness?to prevent this a generous amount of the old soil should be removed and replaced with a fresh supply. Most roses are very hardy and indeed benefit from a period of winter cold, but some of the old Tea roses are a little tender and are better suited to warm-temperate climates. In warm areas roses often grow much larger than their cool-climate counterparts and can be more prone to problems caused by mild winters not killing off pests and diseases. Propagation in commercial quantities is usually from budding, but the gardener can take hardwood cuttings in autumn or softwood cuttings in summer. While hybrid plants will not come true from seed, the species can be propagated in this way; there may be some variation from the parent plant, and chance hybrids may occur.
Rubus There are more than 250 species of climbing, low-growing or upright shrubs, often with prickles on stems and leaves, within this genus from the Rosaceae family. Found throughout the world, from mountains to lowland thickets and coastal regions, many species are cultivated for their ornamental value but even more are cultivated as a valuable food source. Most species have biennial stems or canes, which means they produce fruit only on second-year wood; the leaves on the first and second year?s growth often have a different shape. CULTIVATION: Because this genus has such a large distribution, it has a variety of habitats and the only place its members will not grow naturally is in dry, arid, desert-like conditions. Most species thrive in fertile, humus-rich, moist, free-draining soil and some will grow in moist to boggy heathland. Many species will grow in full sun to moderate shade, and some, such as Rubus spectabilis, will even grow in deeper shade under deciduous trees. A large number will grow in acid to neutral soil but quite a few will grow in alkaline soil; R. caesius and R. ulmifolius tolerate chalky soil. They can be propagated in several ways. Divide suckering species in spring. Take half-hardened cuttings from evergreen species and root them in a seed tray heated from below. Take softwood or hardwood cuttings from deciduous species, or layer. Grow from stratified seed in spring, but as some species hybridize freely, they may not come true from seed.
Sorbaria This genus, native to Asia, is a member of the rose family and is commonly called false spiraea as the flowers are similar. There are 4 species of deciduous, usually suckering shrubs with pinnate leaves; they bear large terminal panicles of small white flowers in summer followed by masses of small brownish seed capsules which often persist into winter. CULTIVATION: These attractive plants are grown for both their foliage and flowers. They prefer a fertile moisture-retentive soil in sun or part-shade and should be planted in a position with protection from strong winds which may damage the foliage. Cut back in early spring and remove any old weak branches at ground level. Propagation is by removal of suckers or from cuttings taken in summer.
Sorbus There are some 100-odd species of deciduous shrubs and trees in this genus from the northern temperate zones. They belong to the rose family and in flower and fruit are often reminiscent of their relatives, Crateagus (hawthorn), Pyracantha (firethorn) and Cotoneaster. The foliage is usually pinnate with serrated-edged leaflets, but may be simple and oval to diamond-shaped. Clusters of white or cream, sometimes pink-tinted, spring flowers, somewhat unpleasantly scented, are followed by heads of berry-like pomes that ripen through summer and autumn. The foliage of some species colors well in autumn, developing russet to red tones. The timber of some species is used to make small items. CULTIVATION: Most Sorbus species are very hardy and generally prefer a cool climate, suffering in high summer temperatures. They grow best in moderately fertile, deep, humus-enriched soil with ample summer moisture, but adapt well to most conditions. Plant in sun or partial shade, prune to shape in autumn or winter and propagate from stratified seed or by grafting. Where present, fireblight can cause significant damage. Also, pear slugs sometimes skeletonize the foliage.
Spiraea A genus of about 70 species of mainly deciduous, sometimes semi-evergreen, flowering shrubs in the rose family, it is valued for its flowering and foliage qualities. Leaves are simple and alternate, variously toothed and lobed. The genus is found in many northern temperate areas, mainly in eastern and southeastern Asia and in North America. CULTIVATION: They thrive in most soils, though some grow poorly on chalk, and prefer a sunny position and cool moist conditions. For pruning purposes, they fall into 2 groups: those that flower on the current year?s growth, which can be hard pruned in spring, and those that flower on the previous year?s growth, which should have old flowering shoots removed just after flowering. Propagation is from soft-tip or half-hardened cuttings in summer.

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