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Odontoglossum (Greek, tooth-tongue; in allusion to the crest on the labellum). Orchidaceae. Orchids which on account of their handsome flowers are great favorites of cultivators. O. crispum is one of the finest of all orchids.
Plants epiphytic, with short rhizomes and 2-lvd. pseudobulbs, often with sheathing Lvs. at the base: fls. in few- to many-fld. racemes or panicles arising from the base of the pseudobulb; sepals and petals spreading, free, or the lateral sepals rarely somewhat united at the base; base of the labellum ascending parallel to the column and sometimes adnate to the latter; lateral lobes small, often erect; middle lobe large, spreading, variously shaped; column clavate, narrowed at the base, longer than in Oncidium.—About 100 species, natives of the higher regions of the Andes from Mex. and Guatemala to Colombia, Bolivia and Peru.
This genus is closely related to Oncidium and Miltonia, some of the species of the latter being generally cultivated as odontoglossums. These two genera are easily distinguished from Odontoglossum by the labellum, which expands directly from the base of the column. There is perhaps no genus of orchids in which the species are more variable and more closely related than in Odontoglossum. Numerous varieties connect the species by intermediate links, and the occurrence of many natural hybrids makes the limitation of species in this genus almost impossible. However much this may add to the perplexiy of the botanist, it gives the genus an additional horticultural value and interest resulting in the production of numerous garden hybrids and in the selection of many varieties, one species, O. crispum, having over a hundred named kinds.
Cultivation of odontoglossums.
Odontoglossums follow the high western mountain ranges from southern Mexico to southern Peru, and usually grow at great altitudes. With few exceptions, they are found in extremely moist situations where the annual rainfall is excessive and the temperature more or less even and cool throughout the year.
The extreme heat of our summer interferes somewhat with the culture of odontoglossums in America, especially those of the O. crispum section, and it is necessary to use every precaution during that season to insure success.
A lean-to or half-span roof structure of northern exposure, protected by a brick or stone wall on the south side, and with ample means of ventilation, is best suited to Odontoglossum culture. Moreover, it should be provided with rolling shades elevated on framework 18 or 20 inches above the glass, to afford abundance of light, free access of air and requisite shade, with the additional assistance of keeping down the temperature in summer. The interior is best fitted with solid beds, if possible, but benches of stone flags or wood covered with ashes or gravel an inch or two deep will answer very well. These, with the floors, should be hosed down two or three tunes daily, to keep the house as cool and as moist as possible.
Ventilation is highly essential at all times, especially in dull or wet weather. When the atmosphere is overcharged with moisture, the quantity must be governed by outside conditions. Top ventilation is most satisfactory, because it allows the heated air to escape, gives less direct draft on the plants, and does not have the drying effect produced by side currents.
The temperature during winter should never rise above 65° F, even with mild sun heat, and may fall to 48° or 50° at night, or even lower, without injury; during summer it must be kept as low as the outside temperature will admit. Fire heat should be dispensed with as early as possible in spring.
Odontoglossums do well under pot culture, excepting a few, such as O. Londescoraughianum and O. brevifolium, with long creeping rhizomes; O. citrosmum, which has pendulous flower-scapes, and some of the smaller-growing species, such as the O. Rossii section, which are more easily cared for under basket culture.
Repotting should be attended to in October and November, never during the summer months. Chopped fibrous peat, live sphagnum and clean decayed leaves in equal quantity, well mixed together, afford a very satisfactory compost. About one-half of the pot space should be devoted to drainage of charcoal or broken potsherds. The plants should be firmly potted, leaving the surface slightly convex, thus elevating the base of the plant a little above the rim of the pot when finished.
The O. crispum section, which includes O. Coradinei, O. gloriosum, O. cirrhosum, 0. luteo-purpureum, O.nobile, and kindred species, requires an abundance of water at all seasons; in fact, the compost should never dry out, and judicious light overhead syringing once a day is beneficial in bright weather, but on very warm days it should be applied in the evening, at the same time allowing free ventilation to ensure good atmospheric action. Weak liquid cow-manure during the flowering period is also of assistance.
Species of the O. grande section do not require so much water at the roots as the O. crispum type; the compost should be allowed to dry out frequently. They are also benefited by a little sun during winter. O. citrosmum is an exception to the genus as regards temperature, and should be grown 10° warmer. It does very well in the cattleya department, enjoys a good supply of water at the roots at all seasons, and may be easily induced to flower freely by giving it a sunny location during winter.
Very few of the species can be satisfactorily propagated by division; the trade depends principally on fresh importation, and they come readily from seeds. (See the article on Orchids, beginning page 2380, for discussing of seed-growing methods of orchids in general.)
Among the worst enemies of odontoglossums are slugs and the small shell snails. They destroy the tender flower-scapes, often attacking them even in the leaf- sheath. A piece of cotton wrapped about the base of the pseudobulb will afford a means of protection, and many may be caught by distributing bits of apple, potato, or saucers containing dry bran freely among the plants. Look them over in the morning or evening with a lantern. Robert M. Grey.
Cool odontoglossums.
There has been a large measure of success attained in the culture of these Andean plants in several instances and near the seashore, or during a cool summer season. The plants do well under special conditions, such as a structure facing north, with ample shade by using roller-blinds a foot or more above the glass roof, and by using a spray of water on very hot days either under the benches or in the path, ejected with force to create a spray and cause rapid evaporation. Perforated pipes have been used, but these soon clog up and are ineffectual. It is best to turn off the spray at night as the outside air will be cooler. It is best in winter to bring the plants to a lighter house where they can get all the sun in the dull months, as most of the growth is made during the winter and needs to be well matured and strong to carry the plants through the flowering period of early summer months. In March, there are very bright days when a little shade is necessary, and early in April removal should be made to summer quarters in the coolhouse proper. One very hot summer has been known to undo the upbuilding of several preceding cool ones. Odontoglossums are freely raised from seeds by the hybridist in Europe, but have never been raised in the American collections. Their seeds germinate the readiest of any orchids, coming up like grass in a few weeks after sowing, but invariably go down again during the heat of "dog days" hi summer. The hybrids imported seem to have more vigor, especially those that have O. nobile as a parent. One of the most wonderful phases of the hybridists' work is seen in the great variety produced, the proving up of the origin of many supposed species of Reichenbach and others, the reproduction of fine types from seeds true to themselves in a measure, but usually with an admixture of the poorest present, showing the very complex origin of our most beautiful garden orchids as they were found first. The partial extinction of these odontoglossums by the march of cultivation of coffee and other valuable crops in the Andes has no longer any terror to the cultivator, equally good forms now being raised in gardens, and sometimes flowered in months rather than years. There is still the element of uncertainty as to what will appear, as with the native imported pieces. Even the once rare native natural hybrids are now produced, but from the finest types as parents, and sold now at modest prices. It is too much to expect that the cultivation of O. crispum and other coolhouse species will become general until there is certainty of control of temperatures in summer as in winter.
Good results have been gained by giving a weak solution of ammonium phosphate, two ounces potassium nitrate, three ounces to three gallons of water, using one ounce of this stock solution to each gallon used for the plants. This is known as the "Cookson formula," advocated by a cultivator who noticed that odontoglossums flourished in the vicinity of smoky cities, and it was traced to the deposit of soot on the glass roofs carried by rain-water into the cisterns to be used for the plants. Rain-water is seldom conserved here for watering orchids, but the addition of this slight quantity of fertilizer seems to be beneficial and to take the place of the rain-water.
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