Unpredictable Pleurothallids

Steve Manning is a well known UK grower of the miniature ‘New World Orchids’. This covers an area from the Caribbean in the east, through Central America and down to Columbia and Ecuador in the south. Generally most are found in the mountains of the northern part of South America, with very few down towards sea level. Most are therefore cool growing, but some do tolerate warmer conditions. The climate tends to make the Pacific coast cooler, with the Atlantic coast and Caribbean being warmer. Over the years Steve has built up a huge collection of plants and is now considered an expert in the subject and has recently written a huge book on the topic. The collection became a National Collection some years ago, and due to its size is now held at Chester Zoo.

Pleurothallids have been known since at least 1731 when they first appeared as line drawings. They are characterised by not having any psuedobulbs, but have a short rhizome that produces single leaves that can each produce the flower(s). It is a huge and varied range of species totalling around 3,500, and is consequently impossible to cover in such a small amount of time. It is also hard to know just where to begin, and where to end, and the middle could be just as difficult! The talk was punctuated by a number of old fashioned line drawings of humans in situations. The first was on ‘discovering a bad smell’ as 2 of the smelliest species were shown. These are Masd. fragrans and Masd. caesia stinks like rotting flesh. Interestingly for the genus neither of these is hirsute. Masd. glandulosa however is pleasantly scented and hairy. Many however are hairy and have no scent or are scented and not hairy. Both the Stelis and Dracula genuses are very hairy.

Stelis cypripedioides is interesting as it has more of a pouch than a lip, as does Stelis pilosa. Both use the pouch in the same saw as a slipper to trap the tiny pollinating insect with inward facing hairs, other than at the rear where they point upwards to aid escape through the pollinia and stamen. Stelis rodrigoi has a hinged lip that attracts the pollinator, and then tilts them towards the reproductive organs, where it either collects or deposits pollen prior to escape. It has to be the right pollinator otherwise the ‘trap’ doesn’t work and the insect is free to leave. Restrepia pandurata (meaning Violin) has tiny thin petals with globules at the end that emit pheromones to attract pollinators. Masdevallia wurdackii has a delicate hinged lip to attract and ‘trap’ insects.

The Zootrophions are an odd genus with hooded flowers. Frequently the flowers never look as if they open, but tend to have slits down the sides that allow the pollinators to crawl in. This can even include slugs that have been found in the flowers. Often the slits are interpetal gaps (eg. hirtzii) with the tips being fused. Masd. lucernula and notosibirica have long tubular flower that possibly uses a hummingbird to pollinate.

Many Masdevallias produce single flowers; however there can be great variations such as ovaavis that has a cluster of almost hooded flowers. brachyantha tends to have 2 flowers as does tovarensis. biflora (obviously) has 2 flowers. Sometimes species can be described as having 2 flowers on all spikes in one flowering, only for it to produce single flowers the following year. It is thought that it is a chemical imbalance that causes this.

Speklinia (formerly Pths.) grobyi will produce long flower spikes with well spaced flowers whereas Platystele examen-culicum can resemble a swarm of mosquitos despite most of the Platysteles tending to produce umbels. Stelis yungasensis (syn. purpurata) is just about the smallest plant in the group – you need to be careful not to mislay it.

Lepanthes are an interesting genus as they tend to have variegated foliage – calodictyon is a good example. caloura is more bizarre as it has plain leaves with one side green and the other brown, then they swap colours. Dryadella paranensis (syn. lilliputiana) has small flowers on a small but fleshy leaved plant.

The Masdevallias and Dryadellas produce their flowers from the base of the leaf, but Pleurothallis species produce theirs from the leaf joint – such as titan. This section, formerly Acronia have smallish but simple single flowers. dilemma is worth its name as the leaf is elongated and forked at the end resembling horns. Acianthera johnsonii is unique in that it produced flowers from both the base and the leaf axils. Acianthera pectinata has a short axil raceme with flowers that alternate along its length. Acianthera sicaria produces its flowers more towards the centre of the leaf. Stelis cocornaensis produces lots of small dark brown flowers at the rear of the leaf! Pleurothallis nuda has a very variable lip, with over 7 variations, and it may or not produce nectar. It may be that there are a variety of pollinators for this species – perhaps it is one for the ‘Splitters’ to look at (Steve is happy as a ‘Lumper’). Myoxanthus punctatus is a larger brown flower with petals resembling antenna that produce pheromones to attract pollinators. Octomeria densiflora (syn. crassifolia) produces a mass of tiny flowers that each has 8 pollinia, only 2 of which are viable.

The spike of Stelis kefersteiniana is very delicate, and need the support of the leaf to prevent it snapping off. This leads nicely to Stelis immersa which has a similar problem, but has developed a solution by immersing it in a groove up the leaf. This is where it develops prior to flowering, and it can be teased out by a small knife to prove the point (best to wait until after it has finished flowering. Pleurothallis scoparum has gone one stage further whereby the flowers are almost at the end of the leaf. Pleurothallis silverstonei produces the first of its flowers as soon as the leaf splits apart, and then will produce many more over a period of years. Most Pleurothallis species will produce multiple flowerings on each leaves. Don’t be drawn into thinking that a leaf is looking pale and chop it off as it may well flower again.

Wow, what variety within a wide range of species and genuses, and it is wise to know what you are buying and how it will produce flowers etc. (avoiding the unpredictability). This was just an overview and can’t possibly cover many of the ‘common’ species. There aren’t very many hybrids within this group, apart from in the Masdevallias which have undergone a widespread development. Several questions were asked followed by a hearty round of applause. Many thanks Steve.