The Palette Of Flowering Plants

The Attraction Of Flowers

The stamens — the male organs consisting of filaments topped with pollen-carrying anthers — are also often decorative features. In winter-flowering shrubs such as hamamelis, winter sweet (Chimonanthus praecox) and sarcococcas the flowers are little more than bundles of scented stamens, less susceptible than soft petals to frost and rain damage. Australian trees -and shrubs including acacias and callistemons also have flowers in which stamens are most prominent.

Stamens are modified into petals in some plants, resulting in 'double' flowers. These are less likely to produce fertile seed; in the wild they would not reproduce, and in the garden they generally have to be propagated from vegetative cuttings. (For the gardener this is a mixed blessing. A double-flowered Rugosa rose is less likely than a single one to produce the autumn bonus of attractive hips; on the other hand double flowers usually last many more days than single ones, since they are not hurrying to form seed.)

In other flowers it is the female organs that have evolved into a particularly decorative form. In the bearded iris, for example, the true petals are the three 'falls' and the three 'standards Each of the three innermost 'petals', however, is actually a female style modified into A flattened petal-like form, with the frill);'crest'- arching outwards to, protect its fertile stigmatic surface.

Bracts are a form of modified leaf at the base of a flower stalk or on the stem of a cluster of flowers. When the bracts are bright and decorative they are generally grouped around clusters of very small flowers that have no petals. The pocket handkerchief tree (forms of davidia), all euphorbias (including the exotic-looking poinsettia) and many dogwoods as well as the tropical bougainvilleas have sterile bracts instead of petals. The small flowers are fertile, but the sterile bracts provide an insect- or bird-attracting display. With lace-cap hydrangeas what are loosely identified as decorative flowers are in fact large flattened corymbs of fertile flowers surrounded by a ring of more conspicuous infertile ray florets. In the familiar mop-headed hortensia hydrangeas all the florets are sterile.

The 'flower' of members of the arum family is really a showy bract or spathe, with an interesting role in the pollination mechanism.- The actual flowers Are enfolded in, the swollen base of the spathe, clustered around the central spadix, the lower female ones maturing earlier than the male ones higher up. The spathe's inner surface is lined with minute downward: slanting hairs: these trap flies that have crawled or fallen in, lured by the nectar, for long enough to fertilize the receptive females with pollen brought from a previously visited flower. Gradually the hair wither and allow the flies to crawl upwards and escape — on their way passing the now-mature male towers, and so becoming dusted with the pollen, which they may transport to a new flower.

In some species coloring and patterning such as spots or lines, as in horse chestnut, mimulus and eye- bright, are designed to provide insects with a route to the nectar. Not all these signals are perceived by the human eye. Bees, wasps, beetles and birds have slightly different vision. Bees, for instance, perceive short wavelengths of light in the ultraviolet range invisible to humans (stamens are often 'lit up' in this way) but cannot distinguish longer-wavelength reds. Birds possess excellent color awareness, though they lack a sense of smell. Despite their poor sight, beetles can locate large white plants and strong scents.

Having achieved their role in attracting a pollinator, petals normally .start to wither, but some, such as those on double flowers, being sterile are not transformed by fertilization. Those flowers with fragile petals are very transient: rock roses and cistus, day- lilies and giant water lilies last only for a day, while morning glory flowers shrivel by afternoon. Many flowers that open at specific times perform only for their pollinators: marvel of Peru is called the four o'clock plant for this reason. Most of these plants produce a succession of short-lived flowers, and this quality assures them a place in the garden.

Some of the longer-lasting flowers change appearance dramatically during the flowering period. Buds about to open are often very different in color from open petals; fading blossoms are tinged with a new range of tones. Some flowers actually change color once effectively pollinated, usually becoming less rich and vivid as the need to attract pasns; leaves also, especially those of crisp grey or silver plants, fade after the flowers have been fertilized.