Petiole is the stalk that attaches the leaf blade to the cane, stem or bulb. In many orchid species, the base of the petiole is broad and wholly or partially surrounds the stem. This type of petiole is often referred to as clasping.
This characteristic is found in both epiphytic as well as terrestrial orchids.
In many plants, margins of leaves, petals and sepals are wavy in characteristics. This type of wavy margin is termed undulate.
In the family of Orchidaceae also, undulating leaves, petals and sepals are not an uncommon characteristic, but certainly not with the lip. Only a few orchid species have their lip margin undulate. Genus Phaius is an example with a few species possessing undulate lip margin.
In a few orchid genera, plants produce plantlets asexually. They arise from the nodes and base of the canes and flowering stems. These little new plants are called keikis. This happens because of the accumulation of growth hormones at those points. The word Keiki is Hawaiian, meaning “little one”.
Genera like Dendorbium and Phalaenopsis are famous for producing Keikis.
Many orchid flowers are with ridges on its lip, known as lamella. It can be a single one or upto 5 in numbers. Lamellae can be of the same length, shorter or longer, wavy etc. However, most of them are entire in structure, meaning without any hairy outgrowths. However, there are certain orchid flowers that have multiple lamellae that are hairy (fimbriate).
It is believed that this highly developed mechanism has something to do with pollination of the flowers.
In extremely rare cases, orchid plants produce flowers with all 3 petals of same size, shape and colour, instead of turning one into the otherwise modified form – the lip. These types of flowers are termed peloric.
Pelorism, the term for the formation of flowers that varies from its normal structure, was first described by Charles Darwin.
Spur is an extension of the lip, arising from its base, hence almost in all the cases it is of the same colour of the lip or of a lighter/darker version. However, there are a few species that produce spur with unusually bright colour that is entirely different from that of the colouration of the lip and also of other flower parts.
This is a highly evolutionary method adopted by orchid plants to attract pollinators.
An interesting and mostly unnoticed characteristic in orchid plants is the shape of its leaf apex (tip). It varies in shape and size – acuminate to subacuminate, bilobulate, cuspidate, mucronate, obtuse to rounded, tridenticulate, unequally bilobed etc.
The reason behind leaf apices attaining different shapes is a bit unknown and complicated, but the general theory is that the shape and size of leaf apices help leaves drain rainwater efficiently. Rapid removal of water droplets from its leaf surfaces is very important for plants to avoid damage.
Whatever the reason, the shape and size of leaf apices help a lot in identifying several species, while they are not in bloom.
Rarely in a few orchid species, due to their individual genetic disorders, plants produce white flowers, the Alba form, instead of their original colour. These are mainly due to the absence of pigments which define the flower colouration.
Generally, white colour dominates the whole flower parts, but there are instances that the white colour dominates only a certain area of the flower.