Some orchids, such as Neottia and Corallorhiza, lack chlorophyll, so are unable to photosynthesise. Instead, these species obtain energy and nutrients by parasitising soil fungi through the formation of orchid mycorrhizas. The fungi involved include those that form ectomycorrhizas with trees and other woody plants, parasites such as Armillaria, and saprotrophs. These orchids are known as myco-heterotrophs, but were formerly (incorrectly) described as saprophytes as it was believed they gained their nutrition by breaking down organic matter. While only a few species are achlorophyllous holoparasites, all orchids are myco-heterotrophic during germination and seedling growth, and even photosynthetic adult plants may continue to obtain carbon from their mycorrhizal fungi.
Catasetum orchids, along with the other members of the Catasetum alliance, have big, thick pseudobulbs with an attractive fan of thin leaves along their length. The flowers can be very showy, but are unisexual, so that male and female flowers look different. Lighting affects which kind appears. They need a dry rest after flowering when the leaves drop.
Orchid roots are surrounded by a tissue-paper thin membrane called velamen. This multi-purpose membrane soaks up large amounts of water quickly, adheres to rough surfaces, and promotes the exchange of minerals and salts. Like an expensive water meter, orchid velamen is an excellent indicator of your plant's water needs. Dry velamen is white or silvery, and freshly watered velamen is green or mottled (depending on the species).
Orchid flowers are all bilaterally symmetrical with three petals and three sepals. Their seeds develop in capsules and are extremely tiny, sometimes mistaken for dust or spores. Because the seeds are so small, they don’t contain enough nutrition to grow a new plant themselves, so they develop a symbiotic relationship with fungus, which provides the nutrients for them to grow.
The quality of water used, whether for spraying or watering, is of great importance. Since tap water has often been chemically treated, generally with chlorine, it should be used with caution. The best water for orchids is undoubtedly rainwater. Rainwater, as it passes through the air, dissolves and absorbs many substances such as dust, pollen and other organic matter. This enriched rainwater contributes to the nourishment of the plant.
Orchids of all types have also often been sought by collectors of both species and hybrids. Many hundreds of societies and clubs worldwide have been established. These can be small, local clubs, or larger, national organisations such as the American Orchid Society. Both serve to encourage cultivation and collection of orchids, but some go further by concentrating on conservation or research.
The Cypripedioideae subfamily is known for its lady slipper orchids, which are named after their slipper-shaped pouches that trap insects and help the flowers get pollinated. There are 5 genera in this subfamily: Cypripedium, Mexipedium, Paphiopedilum, Phragmipedium, and Selenipedium. Cypripedioideae orchids have two lateral, fertile anthers, which is unusual in most other orchids.
This is not a type of orchid you’ll want to place on your windowsill, because the stems grow up to four feet high. Phaius orchids have large, strappy leaves, and they usually produce petals that are yellow, purple, or white. Also known as the Nun’s Cap orchid, it is a winter bloomer and makes a great addition to anyone’s garden, regardless of what else is planted there.