CONVOLVULUS

This genus comprises around 200 species of twining climbers, soft-stemmed shrubs, and herbaceous perennials from many temperate regions. The leaves are mostly narrow and textured, and shrubby species should be trimmed regularly to encourage density of growth. The flared funnel-shaped flowers appear in succession over a long period from summer to autumn. Blooms appear in a wide range of colors, from white and pink to crimson. The genus name come from the Latin convolvo (to intertwine), which describes the twisting nature of the plants.


CULTIVATION


Most are hardy plants adaptable to a range of soils and situations, and all prefer full sun. They are easily propagated from cuttings.


Top Tip


Most Convolvulus plants are easy to gow in full sun with dry to moist well-drained soil. Take care to manage plants properly as some can become invasive, such as C. alathaeoides.

CONVALLARIA

Better known as lily-of-the-valley, this plant has been cultivated since at least 1000 B.C., which is not surprising considering its unique and intense fragrance and the ease with which it grows. The sole species in the genus is a low-spreading perennial found over much of the northern temperate zone. Its vigorous rhizomes can colonize a large area, and in spring it produces bright green lance-shaped leaves and short-stemmed flower-heads with their well-known white bell-shaped blooms. A pale pink-flowered by red berries. When seventeenth-century herbalists prescribed lily-of-the-valley to strengthen the heartbeat they were correct, because it contains glycoside compounds that have been used in modern-day heart medications.


CULTIVATION


Plant in dappled shade with deep, moist, well-drained soil. A cool winter is required for proper dormancy. The rhizomes, known as pips, are somewhat invasive in loose soil. Propagate by division.


Top Tip


Lily-of-the-valley can be grown indoors in a container, than planted ouside after flowering. A top-dressing of leaf mold is recommended in autumn.

CONSOLIDA

A Eurasian buttercup family (Ranunculaceae) genus of around 40 species, consolidas are the annual cousins of the delphinimus, with which they were once grouped. Commonly known as larkspurs, most grow to 18-36 in (45-90 cm) tall with fine feathery foliage; about half their height is taken up with upright sometimes branching heads of 5-petalled flowers. Pretty in the garden, they also make excellent cut flowers. Their name comes from the Latin consolida, meaning to make whole, referring to the medicinal use of the plant to heal wounds. The juice of the leaves has also been used in herbal preparations, but parts of the plant, especially the seeds, are poisonous.

CULTIVATION

Plant in fertile well-drained soil in full sun. The plants thrive under most conditions and will often self-sow, through the flowers of wild seedlings rarely amount to much. They may need staking. Raise from seed.

Top Tip


The taller Consolida cultivars produce flowers that are suitable for drying, as well as cutting. They may need to be staked when they become top-heavy. 

COLUMNEA

Named by Linnaeus in honor of Italian botanist Fabius Columna (1567-1640), this mainly epiphytic genus from the African violet family (Gesneriaceae) consists of around 160 shrubby species native to the New World tropics. They have slightly arching pendulous stems that form a crown of foliage. The leaves are small, oval to lance-shaped, in opposite pairs, and usually downy, as are the stems and outer whorls of the tubular flowers. Orange and red are the common flower colors, but while, yellow, pink, and maroon also occur.


CULTIVATION


Intolerant of frost, Columnea plants do best as house or greenhouse plants outside of the subtropics. They are nearly always grown in hanging baskets so that their trailing flower stemps may be best appreciated. They prefer steady temperatures, not necessarily hot, but not widely varying; they need dappled light and shelter from cold drafts. Allow to dry in winter. Propagate from half-hardened tip cuttings.


Top Tip


Most Columnea species prefer high humidity. For best results grow them in an open compost mix containing sphagnum moss, peat, or charcoal, and mist regularly.

COLCHICUM

This genus of around 45 species of corms is found from eastern Europe to northern Africa and eastwards to China. Although not related to the true crocuses, the common name of autumn crocus is an apt description of the habit and appearance of many of the species. The plants are dormant and leafless in summer. Their flowers have 6 petals, usually in 2 whorls, and start to appear from early autumn before the foliage develops. Double-flowered forms are available. This genus is famous as the source of the cancer treatment drug colchicine, a mutagen that affects cell division; it is sometimes used by plant breeders to produce new cultivars.


CULTIVATION


Hardy and adaptable plants that are great favorites with enthusiasts of rockery gardens, Colchicum species thrive in zones that have 4 distrinct seasons. Some species require a hot dry summer to flower well, but most plants are happy in any fertile well-drained soil in either full or half sun. They also do well in containers.


Top Tip


Take care when handling Colchicum plants. Although the flowers are pretty, all parts of the plant are poisonous and can irriate the skin and eyes.

CLIVIA

Named not for Robert Clive of India (general and colonial administrator) but instead for his granddaughter, Lady Charlotte Clive, Duchess of Northumberland, this amaryllis family (Amaryllidaceae) genus is made up of just 4 species of perennials from southern Africa. They are commonly known as Kaffir lilies. Clump-forming with stocky rhizomes, they have long, bright green, strappy leaves and at various times, depending on the species, produce strong flower stemps topped with heads of large funnel-shaped flowers in yellow, orange, and red shades.


CULTIVATION


Tolerating only light frost but otherwsie easily grown, Clivia plants are superb as greenhouse container specimens. Outdoors they are best grown in dappled shade. Water well during the warmer months and allow to dry off for winter. They are usually propagated by division.


Top Tip


Dark red berry-like fruits often follow the colorful flowers of Clivia species. These showy fruits can made an unusual yet highly attractive addition to fresh flower arrangements.

CLEMATIS

Known by many as Virgin's bower or traveller's joy, the 200 species in this genus belong to the buttercup family (Ranunculaceae) and ecompass a wide range of plants. Mainly climbing or scrambling, through sometimes shrubby or perennial, deciduous or evergreen; flowering at any time and in any color; occurring in both northern and southern temperate zones and at higher altitudes in the tropics-there seems to be a clematis for any season and place. Their leaves may be simple or pinnate, and their flowers are nearly always showy, with 4 to 8 petallike sepals. Numerous fluffy seed heads follow. The name Virgin's bower comes from a German legend that Mary and Jesus sheltered under clematis during their flight into Egypt.


CULTIVATION


The general rule is that the foliage should be in the sun while the roots are kept cool and moist. Incorporate plenty of humus-rich compost before planting, and water well. Clematis wilt disease is a problem in many areas. Propagate from cuttings or by layering. Species may be raised from seed but sex will be undetermined before flowering.


Top Tip


Clematis vines can become tangled; they need yearly pruning to achieve maximum flowering. Pruning techniques vary, depending on the plant group.

CLARKIA

Afuchsia family (Onagraceae) gunus of 33 species of annuals, commonly known as godetia, Clarkia species are found mainly in western North America. They develop quickly from spring to be in flower by the summer solstice. The leaves are small, linear to lance-shaped, and sometimes toothed, but the foliage is of little consequence as it soon disappears under an abundance of large, brightly colored, dark-blotched, 4-petalled flowers, usually in pink, red, and mauve shades. Borne on leafy slender stems, they make spendid cut flowers. The genus was named by the Scottish botanist David Douglas after the North American explorer Captain William Clark (1770-1838).

CULTIVATION

An easily cultivated temperate-climate genus, it requires only a bright sunny position with moderately fertile well-drained soil. Deadhead frequently to encourage continued flowering. Propagate from seed, which can be sown in autumn in areas with mild winters.

Top Tip

When growing clarkias, make sure that the soil is slightly acid. If the soil is too fertile, clarkias do not flower well. They also dislike heat and humidity.

CITRUS

Grown in most of the warmer countries of the world, this genus comprises around 20 species of evergreen shrubs and small trees that are greatly valued for their edible fruits and aromatic volatile oils. Highly ornamental, the citrus family crops longer than any other fruit tree, and the dark glossy fliage holds its attractive appearance throughout the year. The fragrant, white, star-shaped flowers appear singly or in clusters at different times of the year, depending on the variety. The tough skin of the fruit, dotted with many tiny cavities that are filled with oil, encloses a white "pith" of varying thickness. Within this, the characteristic juice-filled segments are contained.


CULTIVATION


In frost-free conditions most Citrus plants thrive in fertile well-drained soil in a sunny position protected from the wind. During the growing season they need plenty of water and regular applications of nitrogenous fertilizer to promote growth and fruit size. In general, Citrus plants need little pruning, except to remove shoots below the graft union and, when mature, to remove damaged or dead branches and reduce overcrowding within the tree. Propagation is by budding or grafting the desired Citrus species onto a suitable rootstock.


Top Tip


Citrus species make excellent decorative and fruiting trees for large posts. They should receive plenty of sunlight and be protected from frosts and wind.

CISTUS

This genus is made up of around 20 species of resinous evergreen shrubs from the Mediterranean region and nearby Atlantic islands. Commonly known as rock roses, they have simple, gray-green to bright green, elliptical leaves, sometimes shallowly toothed. The foliage and young stems are often sticky to the touch and covered with fine downy hairs. Reminiscent of single roses, the flowers have 5 crepe-like petals and a central boss of goden stamens. They come in white or pink shades, sometimes with contrasting central blotches. The aromatic resin, known a gum labdanum, has a history dating back to Ancient Greek and Roman times and is still used as a fragrant binding agent by perfumers.


CULTIVATION


Although they are frost-tolerant, these temperate-climate plants are not suitable for harsh winter conditions. Situate in full sun with light, gritty, free-draining soil. While they are drought and heat resistant, rock roses flower better if well watered and fed. Propagate from cuttings or seed.


Top Tip


Tip prune young plants to encourage thicke growth. Established plants will remain tidy if they are given a light trim and old stems are removed.

CHRYSANTHEMUM

Numerous species in this once-large genus have been moved to other genera, leaving just 5 European and North African annual species plus a number of hybirds known as florists's chrysanthemums, which are sorted into groups based on flower form. Perennials originally from China, where they have been cultivated for over 2,500 years, chrysanthemums were used medicinally and for flavoring as well as for ornamental purposes. The Japanese adopted chrysanthemums and frequently use them in their art as a symbol of longevity and happiness. The annual species are small plants that closely resemble their daisy family (Asteraceae) relatives and are mainly used for summer bedding or in borders.


CULTIVATION


The annuals thrive in a sunny position with light well-drained soil. Florists's chrysanthemums prefer a heavier richer soil and will tolerate some shade. They also need pinching back when yound and disbudding to ensure the best show of flowers. Annuals are raised from seed; the florists's forms are propagated by division when dormant or from half-hardened summer cuttings.


Top Tip


Chrysanthemums make great pot specimens. Use a good organic poting mixture and do naot over-water. fertilize in summer.

CHAENOMELES

This genus belonging to the Rosaceae family, and commonly known as flowering quince, has 3 species of sping, deciduous shrubs that are native to the high-altitude woodlands of Japan and China. Some species grow into small trees up to 20 ft (6 m) tall. Their early pink, red, or white flowers appear before the leaves on last year's wood and are highly valued. The leaves are alternate, serrated, 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 is used in jellies and preserves.


CULTIVATION


Chaenomeles species will grow in most soils, except for very alkaline types. 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. In colder climates, they will carry more flowers if grown against a south wall. They can also be used for hedging and as ornamental shrubs. Half-hardened cuttings can be taken in summer or autumn. Seed can be sown in autumn in containers with protection from winter frosts or in a seedbed in the open ground.


Top Tip


Easy-to-grow, this adaptable genus is ideal for cutting. From early spring cut stems can be brought indoors to add long-lasting vibrant color to the home.

CERCIS

This small genus of 6 or 7 deciduous trees and shrubs is found in the temperate zone from North America to Southeast Asia and is grown for the showy spring flowers. The leaves are alternate and mostly brodly egg-shaped. The flowers are pea-shaped, with 5 petals in a squat calyx, usually borne on  bare stems before or with the early leaves. The fruit is a flat legume with a shallow wing along the edge. In North America, this genus is commonly known as the redbud, but in some parts of the world it is known as the Judas tree. Tradition holds that it was a Cercis tree from which Judas hanged himself after betraying Christ.


CULTIVATION


Cercis species prefer a moderately fertile soil that drains well, and exposure to sun for most of the day. All species are frost hardy. Some early shaping is needed to select a main leader, but little regular pruning is needed after that. They do not respond well to transplanting. Propagation is usually from freshly harvested seeds, which need pre-soaking in hot water to soften the hard coat. Half-hardened cuttings may be taken in summer or early autumn.


Top Tip


As Cercis species do not transplant well, consideration should be given to their suitability and long-term needs when choosing a site to plant.

CENTAUREA

Widespread in the temperate zones, this daisy family (Asteraceae) genus, commonly known as cornflower or knapweed, encompasses around 450 species of annuals, perennials, and subshrubs. They are a variable lot, though most are readily identifiable by their thistle-like flower-heads, which emerge from an egg-shaped whorl of bracts. The flowerheads often have distinctly different inner and outer florets, with those on the outer having narrow petals. Flower colors include white, yellow, pink, mauve, and blue. Plant size varies greatly, but common features are feather-like foliage, often silver-gray, and an upright habit. Centaurea was named after Chiron the Centaur, the Greek mythological figure farmed for his healing powers, because some species have been used to treat wounds.


CULTIVATION


Plant in light well-drained soil in full sun. Good ventilation will lessen any mildew problems. Annuals such as the common cornflower (Centaurea cyanus) are raised from seed; perennials may be propagated by division or from softwood cuttings of non-flowering stems.


Top Tip


Cornflowers will bloom reliably over a long season. Deadheading will often encourage a further show of flowers and increased flower production.

CELOSIA

Found in the tropics of Asia, Africa, and the Americas, this genus of around 50 species of annuals and perennials is a member of the amaranth family (Amaranthaceae). The annual Celosia argentea is the only widely cultivated species, and it has been developed into many vriably flowered and colored seedling strains. They are upright plants, some growing up to 6 ft (1.8 m) tall, though most are far smaller. Most have simple lance-shaped leaves and tiny vivid yellow, orange, or red flowers massed in upright plumes or combs. Commonly known as cockscomb or woolflower, the genus name Celosia comes from the Greek word keleos (burning), which is an apt description of the flamelike color and shape of the flowerhead.


CULTIVATION


Although as annuals they can be grown far outside their natural tropical range, Celosia plants do need ample warmth to perform well. Plant in fertile well-drained soil in full sun and water well. Raise from seed.


Top Tip


Cut Celosia blooms and hang in a dry and well-ventilated location. The dried flowers are ideal for indoor arrangements, with their excellent color retention properties.

CEANOTHUS

Native to North America, and commonly known a the Californian lilac, this genus of around 50 species of evergreen and deciduous shrubs and small trees belongs to the buckthorn (Rhamnaceae) family. Plants are characterized by deep green fliage and vivid blue flowers. Size and shape of the leaves vary, but they are usually small, with noticeable veining, and shallow-toothed edges. The individual flowers are tiny but are borne in rounded heads or conical branching clusters. As well as shades of blue they may be white, cream, or occasionally pink. In common with Monarda, the leaves of some species were used as a tea substitute during the American Revolution.


CULTIVATION


Hardiness varies, with the common western U.S.A. natives being more tender than the few eastern species in cultivation. Plant in full sun with moist well-drained soil. They are drought tolerant but need regular watering when in flower. Propagate from cuttings, by layering, or raise from seed.


Top Tip


Ceanothus plants are undemanding and are tolerant of coastal conditions. Low-growing varities are suited to rock-garden planting or for use as a ground cover.

CATTLEYA

This genus, from tropical America, is one of the most popular group of orchids in cultivation. These rock and tree dwellers have showy, colorful, long-lasting, and sometimes fragrant flowers produced on stout plants with club-shaped to cylindrical bulb-like stems, known as pseudobulbs. They are topped with 1 (unifoliate) or 2 (bifoliate), dull green, leathery leaves. Most species require warmth in winter, though many of the Brazilian, biofliate, autumn-flowering types will stand cooler winter temperatures for short periods of time while dormant if kept dry. Healthy plants will develop an extensive system of thick white roots, which are long-lived and freely branch. Thousands of hybirds have been developed within the genus, with many of the larger flowering types grown commercially for cut flower production and often used in corsages.


CULTIVATION


Cattleyas must have unimpeded drainage and prefer a coarse bark-based medium. The plants can be grown in porous pots or hanging baskets with suitable coarse fibrous compost. After several years, if may be necessary to report them when dormant.


Top Tip


Cattleyas make wonderful house plants, but need reasonably high humidity and protection from intense sunlight-indirect or dappled light is preferred.

CATHARANTHUS

Although related to the common periwinkle (Vinca), the 8 annuals and perennials of this genus are far less hardy and will not tolerate frost. All species are native to Madagascar, and they are busy plants with simple elliptical leaves on semi-succulent stems. Flat 5-petalled flowers, mainly in pink and mauve shades, appear at the stem tip and leaf axils. Though considered a weed in the tropics and subtropics, the widely cultivated species Catharanthus roseus is a perennial often grown as a greenhouse plant or as a summer bedder in temperate gardens. Although highly toxic in its natural form, this species is the source of the drugs known as vinca alkaloids that are used to treat Hodgkin's disease and lymphocytic leukemia.


CULTIVATION


These plants are very easily grown in part-shade, and can withstand strong sunlight. They are drought tolerant, but flower more heavily with summer moisture. Water moderately in the growing season. Gently pinch back to encourage bushiness. In cool climates with winter frost, bring indoors or discard and replace in spring. Propagate from seed or half-hardened summer cuttings.


Top Tip


Tip prune Cathranthus species to maintain their fullness, but don't get too enthusiastic-over-pruning can discourage flowering. A bit of liquid fertilizer once a month is also recommended.

CANNA

Found throughout the tropics and subtropics of the Americas, and widely naturalized elsewhere, there are just 9 spices in this genus. Cannas are vigorous perenial plants with strong, upright, reed-like  stalks that sprout from rhizomes and bear long lance-shaped leaves. Heads of lily-like flowers generally an shades of yellow, tengerine, and red, either as solied colors or in patterns appear throughout the growing season. They make excellent pot plants and are effective in mass plantsings. The common name indian shot comes from the story that the hard, round, black seed were sometimes substituted for buckshot; the seeds are certainly hard enough, but they are so light that thier range would have been very limited.

CULTIVATION

Although often tropical in origin, most spices can withstand light frosts when dormant if thier roots are well insulated with mulch. Plants in full sun in moist, humus-rich, well-drained soil, and feed well. propagation of selected forms is by division in early spring. Seeds will often self-sow but rarely result in superior plants.

Top Tip

cannas are not restricted to the tropics they will happily grow in cold climates in a container or green house.Divide the clumps for easy propagation.

CAMPSIS

This genus is a member of the bignonia family (Bignoniaceae), and consists of 2 species of deciduous vines, one found in China and Japan, the other native to the U.S.A. Commonly known as trumpet creeper or vine, Campsis specie are vigorous growers that can cling to most surfaces by using pads of aerial roots, and they can be trained onto walls in the same way as ivy. The large leaves are featherlike, with elliptical leaflets that have toothed edges. In summer and autumn, clusters of large, trumpet-shaped 5-lobed flowers appear, usually in orange-red shades, less often yellow or cimson. Flowers are nectar-rich and very attractive to hummingbirds and honeyeaters. The name Campsis comes from the Greek kampa (bent), refering to the curved stamens.


CULTIVATION


Although these vines are hardy, late frosts can cause severe damage, so prune established plants in spring after frosts. Plant in full sun with moist, humus-rich, well-drained soil. Suckers often emerge some distance from the main plant and have the potential to be invasive. Propagate by cuttings or layering, from rooted suckers or seed.


Top Tip


Campsis species grow well against a warm sunny wall. They can be trained to grow on a pillar, fence, or tree, and may need extra support.