This is a basic introduction to orchids. Learn all about orchids, their botany, how they grow in the wild, and other basic information about them:
The orchid family (Orchidaceae) is among the most diverse families of flowering plants, with about 25,000 species known to science so far (which makes identifying orchids difficult.) They come from every continent except Antarctica, though a substantial majority of orchid species are tropical. They range widely in size; Grammatophyllumspeciosumcan weigh in at more than a ton, while there are many miniature orchids that, in many cases, are only a few millimeters high!. Of course, they all have different flowers, too! For example, Paphiopedilumsanderianum flowers have three-foot-long (90cm) red petals, while Masdevallias have petals so small as to be nearly invisible! Visit my types of orchids page to learn more about the various orchid types, and see pictures of them. Orchid flowers come in all colors except blue and black.
Most orchids are epiphytes, meaning they grow on trees, with their roots clinging to the tree's bark rather than being in the ground. Other orchids are lithophytes, meaning they grow on rocks. Some are terrestrial orchids, or ground orchids. Temperate orchids are generally terrestrial, while tropical orchids tend to be epiphytic.
Epiphytic orchids' roots have an outer whitish layer called velamen, which absorbs moisture from the air and helps them cling to tree bark.
Orchids have two main growth habits, monopodial and sympodial:
Monopodial orchids have a single main stem, which grows vertically with a series of leaves growing on alternate sides. The growth tip at the end of the stem is continuously extending, and flower stems emerge from the main stem between the leaves. Examples include Vanda, Phalaenopsis, and Vanilla. (The Vanilla orchids are unusual in that they grow as a vine.)
Sympodial orchids have a rhizome (or horizontal stem) from which a series of vertical growths emerge, typically one per year. Each new growth matures, blooms, and then doesn't do much; usually old growths last several years. Rhizomes sometimes branch, so that the plant then has multiple leads producing new growths. Sympodial orchids often have thickened stems called pseudobulbs at the base of each new growth. Most orchids are sympodial, which is a good thing for orchid propagation: sympodial orchids are much easier to divide.
Most people are interested in orchids for their flowers! (Except for cooks, who mostly care about the Vanilla orchid's seed pods.) Orchids often have very interesting, showy blooms, and there are also many fragrant orchids.
Orchids' reproductive strategies vary widely. Most have a single pollinator, or a small selection of pollinators. Some are truly specialized: each species of Stanhopea, for example, is pollinated by a single species of male euglossine bee, which needs to gather the flower's fragrance to entice females. Angraecumsesquipedale has a spur on its flower a foot and a half long (45cm), with nectar at the bottom for its pollinating moth, which has a comparably long proboscis.Plants in the genus Orchis are even more unusual: the flowers mimic female bees, and are pollinated by male bees that try to mate with the flowers.
All orchid flowers share the same fundamental structure: three sepals (with the dorsal sepal along the flower's midline and the lateral sepals to the sides, except in lady slipper orchids, where the lateral sepals are fused into a synsepal, and a few other minor exceptions) and three petals, including two lateral petals to the sides an a lip, or labellum, positioned at the bottom of the flower and typically large and showy. The sepals and petals are together called tepals.
The pistil and stamen of an orchid flower are fused into a single structure called the column, which is positioned at the center of the flower. In most types, pollen occurs in hard lumps called pollinia.
The ovary of an orchid flower is always located behind the flower. If the plant is pollinated, this is where the seeds will grow.
Some orchid flowers, such as certain Angraecums, are positioned upside down. Most orchids, with "upright" flowers, have a 180° twist in the ovary. The "upside down" ones have either lost this or twist 360 degrees.
You may want to learn about caring for orchids too. Or if you mostly care about botany, peruse the sections below to learn all about orchids:
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