The Orchid family is a Monocot family of 28000 species and 763 genera. It is thought to have arisen around the time of the dinosaur extinction and then rapidly diverged into 5 subfamilies. There are 56 species native to Britain of which 9 are fairly common. Flowering times for these orchids are found in the tables below. The Orchid family is named after the genus Orchis which means in Greek ‘testicle’ after the shape of the twin tubers in some orchis species. The majority of orchids are perennial epiphytes growing on trees or shrubs in the tropics. Others are terrestrial and can be found in temperate grasslands. There are more than 100,000 hybrids and cultivars. The flower of the orchid is complex.
Basic Flower Parts – 6 tepals (3 sepal-like, 3 petal-like), 1 Stamen (with 2 pollinia), 3 united Carpels with 2 fertile stigmas. Inferior ovary. Some have nectaries. Fruit a capsule. containing many tiny seeds. Terrestrial species grow from tubers or rhizomes.
This is a single flower of the Green-winged Orchid. These tiny flowers are typical of the Orchid family in which flowers have 6 tepals in two whorls. The 3 outer tepals form a green-veined purple hood. There are 2 inner tepals (which can’t be seen in this photo) that enclose the reproductive parts and one, called the labellum, which is enlarged and is prolonged backwards into a spur. The labellum forms the landing pad for pollinating insects. The reproductive parts consist of the pollinia, rostellum and stigmas arranged in a vertical structure called the column.
In orchids pollen grains are fused together into a long club-shaped structure called a pollinium (plural pollinia) and transported whole by the pollinator. In the orchid shown here, there is one vertical stamen with 2 pollinia, one on each side. There are 3 stigma but only 2 are fertile, the upper stigma has become the rostellum, which separates the male and female parts. The 2 lower fertile sigmas are joined together and are behind the rostellum at the throat of the spur.
As the bee tries to reach into the spur, the rostrum ruptures and the pollinia stick to its head. As it flies away the pollinia rotate through 90 degrees to be directed forward. When it tries to access the spur of the next orchid the pollinia are in the correct position to be transferred to the sticky stigmas below the rostellum at the spur entrance.
Some orchids reward pollinators with nectar but some, including the Green-winged Orchid, employ food deception – they look like they offer nectar but do not provide any. How this could evolve puzzled Darwin and there is still no fully-accepted explanation of how it arises. One possible theory is that it increases the chance of outcrossing as the thwarted bee takes the pollinia to a distant similar orchid some way off and tries again to get a nectar reward.
|Early Purple Orchid||Apr-Jun|
|Common Spotted Orchid||May-Aug|
|Early Marsh Orchhid||May-Jun|
|Common Twayblade Orchid||May-July|
Flowering times for early flowering orchids. For photos click HERE