Dendrobiums and Allied

Mel Steven

Mel is familiar to many of us who have been to any show where EMOS is exhibiting as he is their show team co-ordinator. He has been growing orchids for 30 years, and has tended to specialise in Dendrobiums.

This group are found mainly in tropical SE Asia from India to PNG & Australia. They are considered a confusing group, which the taxonomists are in the process of sorting out – whether successfully or not remains to be seen! There are around 1250 species of which 450 are found in PNG within 32 sections. Borneo is next with 170, but many more are yet to be discovered due to the difficult terrain. Within Dendrobium itself there are 42 sections. Previously there were 48 recognised, and some of these have been elevated to genus status eg. Dockrillia, Epigeneium, although they will almost certainly be labelled as Dendrobiums. The largest section is Grastidium, with 192 species, although these are rarely seen in cultivation. There are 18 groups with 6 or less species in them, and many of these are endemic. The commonest sections are Nobile (eg. nobile) and Callista (eg. thrysiflorum) which are both freely available and can be grown without too much difficulty in the home or greenhouse. Section. Dendrobium (eg. anosmum) and Latouria (eg. spectabile) can also be grown easily.

Mel’s greenhouse is a 20 x 10’ home design and is sunk into the ground. It is brick based with quad walled polycarbonate on top for heat retention. Fans at each end circulate the air, however small areas of varying microclimates exist whish can be used for selected plants that need something a bit different. Many plants are hung up on wires for improved light and heat, and also to ‘get more plants in there’. The Greenhouse has benches just around the outside which allows a centre ‘wall’ mesh to be installed which is where all the mounted plants hang out. The polycarb roof has inbuilt aluminium braiding, so no extra shading is required even in summer. Light reaches up to 4500 ft. Candles. He collects rainwater at 42ppm, ensuring that the water temperature is no lower than 10C/50F when used by storing 1000L in the greenhouse. Fertiliser is the RainMix balanced low nutrient. Over winter this is applied at 270ppm, and 560ppm in summer when in active growth – with a PH between 5.8 & 6.5. Heat is supplied by 2 x 3KW heaters running to a minimum of 58F, and a maximum of 85F. Vents are used only in the hottest of weather – when a humidifier also helps to lower the temperature.

The Dendrobium family is extremely variable in its growing habitats – some need a rest and others don’t. Some see monsoons, and others grow in much drier conditions. As a result each plant (esp. Species) is researched, and listed on a traffic light system for watering – which runs to many pages of A4. This is essential as many need a dry rest (no humidity?) alongside light and temperature variations to help induce flowering rather than to produce kiekies. An ultra-violet zapper light helps to control flying insects, alongside the usual controls of Provado and liquid Sluggit. Repot often is useful to check all is well, and uses good quality bark (the new stuff from Peter White) alongside coco chips and perlite. Those that are hung up tend to be put into clear pots. One of his good tips is to buy plants at the time they start to grow – usually May/June time to help reduce the shock.

Mel then showed us pictures of a wide range of species flowers. With there being so many different species it isn’t possible to cover them all, or even a sample of many of the sections. Here’s just a few of those covered;- spectabilis (Section Latouria) is well named for it is a spectacular flower of many colours from white to brown.

antennatum (Spatula) is one of the antelope types with 2 petals as twisted ears. This one is white with a hint of purple veining on the lip.

biggibum (Phalaenanthe) The section helps to describe the shape of the flowers that have a similarity to Phalaenopsis. White to pink and ‘blue’.

aphyllum (Dendrobium) is quite common with long pendant canes and flowers on naked canes. Flowers are white to pale pink.

bracteosum (Pedilonum) is fairly common, and tends to have shorter canes with tight clusters of many flowers. All colours from white to deep pink, with an orange lip – apart from the album form which is pure white.

chrysotoxum (Callista) is one of a large group with tall uptight canes that produces bunches of flowers on a pendant spike from the top of the cane or just under. This one is a bright yellow. chrysocrepis (Dendrobium) is quite unusual as the lip has evolved into a pouch/slipper. It is called the golden slipper Dendrobium due to the shape and colour.

cucumerinum (Dockrillia) is an Australian oddity with strange leaves that are lumpy like a small cucumber. The flowers are upside down.

denudans (Stachyobium) is a smallish plant with a pendant spike of long petaled pale green flowers.

fimbriatum v. oculatum (Dendrobium) is part of a species complex. The flowers all have frilly lips on flattish golden flowers with a dark mask. The standard form is a clear colour. The leafless canes will re-flower over a period of many years.

fleckeri (Dendrocoryne) is a small flowered species from Queensland with almost triangular apricot flowers.

glomeratum (Pedilonum) is a striking species of bright pink clustered flowers. jenkinsii (Callista) is like a smaller version of lindleyi with orange flowers. The bulbs are very short, and can form a spectacular tight mass of short flowers.

mohlianum (Calyptrochilus) is a small species with very fleshy orange flowers.

munificum (Inobulbum) is a plant with large fleshy leaves, and long racemes of small starry flowers of brownish green.

polysema (Latouria) is similar in shape to spectabile, but is more white, purple and green – quite spectacular as well.

trantuanii (Breviflores) is pale pink and has a small fleshy and furry brown lip. It was only discovered in 2003 in Vietnam.

unicum (Dendrobium) is noted for its bright orange flowers and has been widely used for this colour in breeding.

bellatulum (Formosae) is a spectacular flower of white petals and a striking orange lip.

dearii (Formosae) is a large white flower – nearly 3” wide.

lowii (Formosae) has interesting flowers with a lip that has columns of hairs. sanderae (Formosae) is another species complex of white flowers. The main varieties are major with a split lip, and luzonicum with a large flat lip. Var. minor is a more compact form of major.

That was just a taste of what the genus and allied has to offer, and a hearty round of applause was given. Thank you Mel.