The genus Dendrobium is prolific and diverse, comprising some one hundred species, which vary greatly in size and shape. A single species has been found to adjust itself to entirely different places. Members of the genus grow on trees, in the ground, and on bare rocks, through great extremes of temperature and elevation. Some have been found as high as 1500 to 2000 feet in Burma at 1200F. The Dendrobium plant is unusual in appearance, being sym-podial, epiphytic, and bulbless, but possessed of heavy cane-like stems, which also produce the papery-green leaves. Especially in the deciduous types these canes store sufficient moisture and food to tide the plant over periods of extreme drought.
The genus is divided into deciduous and evergreen, which again divides into warm- and cool-growing plants. All evergreen Dendrobes (the name affectionately given the genus by orchidists) are handsome plants with their leafy, graceful foliage.
They have cane-like stems, taking the place of pseudobulbs, and bear the flowers in erect panicles (clusters, as of grapes), singly at the nodes, or in drooping racemes (stems with flowers attached at intervals). Evergreen Dendrobiums may be accommodated in the warm house.
Deciduous Dendrobiums are peculiar-looking plants, becoming dry and shriveled bamboo-like canes each year after the leaves drop off. Amazingly, and lovelier by contrast, the flowers bud and bloom from the nodes (joints) of these dry canes.
Deciduous Dendrobes bloom on the old wood, and evergreen Dendrobes on the new growth. They may be accommodated in the warm house and removed to a cooler spot while resting.
Dendrobium, of sympodial growth, will put forth little plant-lets, complete with bulb and roots, at the slightest provocation. These plantlets develop from the cane-like flower stems. If the beginner keeps his Dendrobiums, especially the deciduous type, too warm and moist during the dormant season they will waste their strength in plantlets and fail to bloom.
Many commercial growers pick the entire cane on flowering and, after cutting off the blooms, lay the canes on damp, warm sand or gravel to allow plantlets to develop from the dormant eyes. Dendrobiums are easily divided or grown from seed.
Dendrobium in many species lacks pseudobulbs, but even the long cane-like flower stems, along which the leaves grow in pairs, are capable of storing food and moisture.
Evergreen dendrobium orchid care will require a moderate amount of water at the roots at all times, but the deciduous Dendrobiums must be allowed to dry out thoroughly during dormancy, at which time they resemble dry bamboo canes.
They need cooler conditions during dormancy. When the new growth is made and the joints of the cane begin to swell, indicating initiation of flower growth, they must be given large amounts of water and moved to a warmer spot.
It will be helpful to the grower and dendrobium orchid care to have some method of marking plants after watering so that she will not water them again too soon. Segregating plants of one kind is not very satisfactory, since orchids are individuals and one will dry out sooner than another.
Marbles or colored stakes in the pot may answer the purpose. But no mechanical system is infallible and any system must be supplemented by close observation. Signs of need for watering are easily distinguishable.
The experienced grower 'hefts' or weighs the pot in his hand: if light, watering is indicated. The dry pot leaves no ring on the bench. The appearance of the potting material is an indication, but not always an accurate one.
The amateur will soon learn to recognize signs of well-being or need in his plants. Jewel-tipped roots and fat, rosy growths are indications of health. Root growth is usually, though not always, apparent, and pots indicating healthy roots can be watered more frequently than those where root growth is doubtful. The latter should be treated to plentiful overhead spray.
This brings us to consideration of the importance of the overhead spray and dendrobium orchid care. Orchids appreciate diffused water as they do diffused light. A fine spray makes a hot, dry day bearable for all the plants.
A daily spray is routine except for dark, cold days in winter; at the height of summer two or more sprays a day will be gratefully re-ceived.
Daily light spraying over the potting material is prescribed for tiny seedlings, backbulbs without roots, sick plants, and newly potted plants. Healthy roots attest the value of this treatment.
Some growers pot with damp material and allow the newly potted plants to go without pot watering until roots show. Light spray over the top of the potting material supplies enough moisture to prevent shriveling.
Damping is the simplest of the watering operations. Its virtue is enhanced because it is hard to do damage with this method. It consists of watering down the walls, floors, paths, and benches between the pots. In most climates this should be almost a daily procedure, omitted only when the house is too cold or the outside air too damp.
But there is one caution that should be heeded. It is popularly believed that orchids grow in steamy jungles. This is a misapprehension. What takes place in the jungle is rapid evaporation. Steam is injurious to orchids, and when the house is being damped down, care should be taken not to play the water on hot pipes.
Finally, it is imperative that the plants have water with an acidity reading of approximately 4.5 to 5 pH.1 Where the local water supply is very alkaline, some method of putting it on the acid side must be arranged. It is advisable to have the water supply analyzed and a remedy for deficiency suggested by a local chemist.
Some growers collect rain for watering, but if this is done they should be sure that the roof has not been sprayed with any injurious paint or stain. Other growers dip watering cans into vats containing water whose pH has been altered by the addition of acid. Hydrochloric acid is most frequently used, but resultant acidity should be checked by some sort of acid meter. It is wisest to consult a chemist about exact methods.
Dendrobiums need to be repotted immediately after flowering since they start new growth almost at once. Osmunda agrees with them, although the addition of sphagnum is often helpful. The deciduous canes may be cut from D. nobile and D. superhum and laid on the gravel under the benches.
They will break at the eyes and form new plantlets. Dendrobiums may be accommodated in a variety of containers, but, since they thrive in confinement, the receptacle should be as small as possible. Rafts or baskets are suitable for the drooping types.
Drooping canes should be allowed to follow their inclination unless room is scarce, in which case they may be tied up. Other types will do well in pots with Osmunda as medium. See Dendrobium care