Dahlia

Dahlia is a genus of bushy, tuberous, perennial plants native to Mexico, Central America, and Colombia. There at least 36 species of Dahlia. Dahlia hybrids are commonly grown as garden plants. The Aztecs gathered and cultivated the dahlia for food, ceremony, as well as decorative purposes [1], and the long woody stem of one variety was used for small pipes.

In 1872 a box of Dahlia roots were sent from Mexico to the Netherlands. Only one plant survived the trip, but produced spectacular red flowers with pointed petals. Nurserymen in Europe bred from this plant, which was named Dahlia juarezii with parents of Dahlias discovered earlier and these are the progenitors of all modern Dahlia hybrids. Ever since, plant breeders have been breeding Dahlias to produce thousands of cultivars, usually chosen for their stunning and brightly coloured flowers. Dahlia plants range in height from as low as 12" (30cm) to as tall as 6-8 feet (180-240cm). The flowers can be as small as 2" (5 cm) in diameter or up to a foot (30 cm) "dinner plate". The great variety results from Dahlias being octoploids (they have eight sets of homologous chromosomes, whereas most plants have only two).

Dahlias are used as food plants by the larvae of some Lepidoptera species including Angle Shades, Common Swift, Ghost Moth and Large Yellow Underwing.

The dahlia is named after Swedish 18th-century botanist Anders Dahl. In Germany they were known as georgines until recently. They were named by the botanist Carl Ludwig Willdenow after the naturalist Johann Gottlieb Georgi of St. Petersburg, Russia.

A tall, slender stalk leads to an exquisite flower composed of three inner petals, three outer petals, and a cupped petal distinct from the rest. Labellum, inflorescence, sepal—the names of the anatomical parts sound as fabulous as they look. The whole exotic composition is almost alien in appearance, extravagant in the extreme, yet possessed of a delicate intricacy. Orchidaceae is arguably the most stunning and elegant family of flowering plant known to man. For millions of years, the orchid family has thrived and expanded, defying evolution, Mother Nature, and the exploitation of its greatest opponent—Man.

One hundred and twenty million years ago, when dinosaurs roamed the earth, a magnificent flowering plant came into being—the orchid. Evolution led to the demise of many plants and animals, but the orchid flourished, thriving on every continent save Antarctica. Orchids have adapted to live in all kinds of environments—mountains, bogs, grasslands and rainforests. At least 35,000 orchid species now populate the planet—and there is always the possibility that unknown species still await discovery.

Orchids attract pollinators for reproduction by several ingenious methods: scent, mimicry and stealth. Orchids with sweet scents usually attract bees; those with a rancid smell lure flies. The orchid can also draw pollinators through visual mimicry, imitating insects including bees and butterflies with the patterns on its petals. A third technique is stealth. The slipper orchid lures a prospective pollinator to the edge of its slippery pouch, and the insect falls in. When it finds the single exit, it brushes against the pollinia. Some orchids are pollinated by crawling insects, and thus have long petals that brush the ground. And insects alone do not pollinate orchids—small mammals, hummingbirds, bats and the wind also contribute to the survival of the species.

For centuries, the orchid has been a symbol of love, luxury and beauty. To the early Greeks, the orchid represented virility, and the Chinese called it "the plant of the king's fragrance." During the Middle Ages, the orchid was considered an aphrodisiac and was used in love potions. Serious orchid collecting began in the 18th century, but because of their rarity at the time, only a few botanists and wealthy amateurs could enjoy them. In 1818, William Cattley became the first person to bloom an orchid (the Cattleya, top photo), an event that changed the flower world forever. Forests were stripped of millions of orchids, putting many on endangered species lists. A single orchid sold for thousands of dollars. This practice has since been banned, and species are now bred and cultivated specifically for sales.

What will the future bring for Orchidaceae? Its greatest challenges are now those imposed by Man. Will our environmental blockades prove overwhelming? Or will the orchid's resilience, tested over millennia, outlast even our own? In spite of the obstacles to its survival, the orchid will retain its elegance and prehistoric mystery in the minds of all admirers.

latin name: Aechmea fasciata
common name: Silver vase
family: Bromeliaceae (b)
group: Bromeliads
minimal winter temperature: 18°-20°C
ideal temperature: 26°-28°C
soil: bromeliad soil A
Height: 60 cm
rarity: yes

Aechmea fasciata is an epiphytic Bromeliad from Brazil. Aechmeas are among the most beautiful of all Bromeliads for indoor decoration. Large, colorful blooms rise high above the vase-shaped rosette of leaves.

Blooming time: Most Bromeliads will flower naturally when they reach maturity; they can also be made to flower by supplying the substances which begin bud formation: for example, enclose the entire plant ( with its cup empty of water to prevent excessive humidity buildup) in a plastic bag together with a ripe apple. The apple gives off ethylene gas which stimulates flowering in Bromeliads. Leave plant and apple in the plastic bag for 7-10 days; f lower will appear in 1-2 months.

Culture: Add peatmoss to an equal volume of general house plant mix for a humusy and well drained combination. Soil may dry out between waterings. Keep water in central cup formed by leafy rosette. Fertilize every 1-2 months, applied to the soil. Or fill the cup with half-strength dilution of fertilizer every month.

Propagation: After flowering, Bromeliads produce side shoots (offsets), which may be removed while young and rooted for additional plants.