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Vol. 11(4), pp. 10-14The McAllen International Orchid Society JournalApril 2010

Dendrobium kingianum Bidw. ex Lindl. in Edwards' Bot. Reg. 30: Misc. 11 1844. H. M. R. Rupp in Orchids N.S.W. 116. 1943.

R J Ferry

(common name: pink rock orchid)

Distribution

Eastern Australia; Southeastern Queensland; from the Hunter River in northern New South Wales to near the tropic of Capricorn.

Description

Pseudobulbs clustered, 1-33cm. high, substance rather stout in dwarf members, slender in others, thickened toward the base, coloration green to purple, somewhat furrowed. Leaves 2-7, rather thin, oblong lanceolate to lanceolate, usually acute, 2-13 cm. long, 1-1.5 cm wide. Inflorescence racemose, bearing 2 to more than a dozen flowers, borne distally from the pseudobulb or between the leaves. Flowers are variable in coloration from purple to mauve, pink, cream, or white, often fragrant, 2.5 to 3 cm diameter, pedicels (including the ovary) to 2.7 cm. long, bracts acute. The sepals are broadly lanceolate, the lateral ones acute. The petals are nearly as long as the sepals, but are much more narrowed. The spur is conical and slightly incurved. The labellum is shorter than the sepals with its lateral lobes prominent, almost oblong and more or less obtuse with the mid-lobe longer and very broad, sub-reniform. The callus displays three raised lines which extend to the base of the mid-lobe. The column is short and stout with a broad foot.

Habit

Dendrobium kingianum usually grows as an extended mat in rock crevices on the faces of cliffs. It is particularly abundant near waterfalls. It is not uncommon to note young plants form from the apex of the pseudobulb which, when mature, fall to the ground (or on another substrate) and become established. In nature, it is occasionally found with the scented orchid Thelmitra aristata, with both flowering at the same time.

Horticultural Notes

Fig. 1. Pl#200575-2. D. kingianum 'Planting Fields' CBM/AOS. Digitalized 35mm Kodachrome transparency, ex Slide #8 dtd20Feb76. Clone ex Planting Fields Arboretum, Long Island, New York; Courtesy Dorothy Harrison, curator.

This species is widespread in cultivation. Many subspecies and varieties of color forms have been named, and flower awards have added clonal names as well. A white-flowering form was designated as Dendrobium specio-kingianum by Lawrence in 1892, and the clonal name "The Dove" was tagged to another white flowered form received from the Huntington Gardens (California, USA) collection in 2005. This worker cultured a division of the clone D. kingianum 'Planting Fields' CBM/AOS in his Long Island, New York greenhouse as long ago as the mid-1970's (Fig. 1). Dendrobium kingianum ssp. kingianum is a much darker purple form, and cross-pollination among locally isolated populations in nature has resulted in various other color forms as well. Color forms have been wild-collected, propagated, and selectively bred by orchidists so that the present day sees the several color forms from the purple D. kingianum ssp. kingianum to the pure white (ssp. alba) form. Naturally, as the hybridists have worked, they have attached clonal names to designate one form from another.

Culture

For over thirty five years, this orchidist has seen D. kingianum grown as an epiphyte; usually in fir bark or some other bark substrate mixed with Sphagnum moss; at times in Osmunda fern fiber; even on bark slabs of sassafras wood. The reason is simple: most hobbyists are "schooled" by other hobbyists to grow tropical orchids as epiphytes, and hobbyists seldom take the trouble to study how each species grows in nature! This was graphically illustrated by some "professional" scientists a few years ago as a quote from a previous MIOS Journal of 2004 illustrates:

"Interestingly, D. kingianum was one of the orchid plants taken into space by the Russians a few years ago. Czerevczenko and Kosakovskaya (1990) selected three epiphytic orchids, Epidendrum radicans, Doritis pulcherrima, and Dendrobium kingianum, to determine the suitability of epiphytic orchids for cultivation under prolonged space flight. They noted plants of D. kingianum lost their leaves during the flight, a phenomenon they said, "does not even occur in this species during its rest period." Also, on return to earth, despite being greenhoused, the D. kingianium died, and they were at a loss to understand why they had experienced such problems with this species.

Reading the article, your editor was thunderstruck! It wasn't even necessary go back to W. H. Nicholls' Orchids of Australia (and a few other sources) to verify the cause! One has only to look at the wiry roots of D. kingianum to get a clue that this is not really an epiphyte, but a terrestrial! Sure enough, the Nicholls tome confirmed that--for all the space technology and studies--the cosmonaut-researchers were trying to space-grow a terrestrial as an epiphyte! Although commonly cultured in bark or some other pot mix preferred by epiphytes, success relies greatly on good quality of water, very good drainage at the roots, and--certainly--not allowing the potting substrate to become stale, or soggy, or dried out. As with many terrestrials, Dend. kingianum wants some moisture, but very good drainage at the roots; not the classic wet-then-dry treatment accorded most epiphytic orchids!" (pp. 4-5)

The above having been said, D. kingianum may well be found in nature serendipitously growing on trees overhanging waterfalls or near them, or in close proximity to a river, or stream, but it's preferred habit is as a "rock orchid;" a lithophyte! Baker and Baker (1996) report "plants are found in pockets of leaf-mold on rocks in open forests or on cliff faces between sea level and 3950 ft. (0-1200 m). They are usually found on rocks, but occasionally may also grow on trees." Now the questions are: what type of rock substrate does it prefer? On what species of trees is it found? This worker's educated guess is that its rock substrate may be a limestone substrate; somewhat porous, yet conducive to good drainage in a humid-to-wet environment. It makes one fantasize about constructing a limestone/granite rock pile within a greenhoused fountain and pool that has access to a stored supply of rain water.

Fig. 2. Pl#160605-15. D. kingianum 'The Dove.' (Plant division ex Betty Dunton, S. Pasadena, California) Digital photo Tues-30Mar04.

More realistically, this worker repotted Pl#160605-15. D. kingianum 'The Dove on 23 May, 2008 (Fig. 2) into a 30.48 cm (12-inches) diameter plastic "bulb pan" pot with a depth of ca 18 cm (7 inches). The bottom 6 cm of the pot was layered with Douglas Fir bark above which was a 6 cm layer of a mixture of two parts New Zealand Sphagnum moss & one part Fir bark. The top layer was completely of Sphagnum. The plant had nearly doubled in size, with pseudobulbs showing lengths of 31-32 cm, with 6-7 healthy leaves at their apices.

On 25 March, 2009, although about 3 cm of free space remained all around the plant mass, the plant was depotted, inspected, and then lodged in an even larger lattice basket. No pests were observed on the plant or in the potting mix when the plant mass was depotted. Root growth was profuse in the Sphagnum and only slightly less so in the Sphagnum-bark mix. However, although the lower layer of pure bark had not broken down and was in very good condition, there was virtually no root growth into the pure bark substrate, although this depth of "shallow rooting" may be typical of this species.

With minimal disturbance of the roots except to spread them outward in all directions a bit, the plant was lodged in the wood-lattice basket. The very bottom of the basket was layered with a centimeter of crushed limestone, over which was sprinkled a layer of Sphagnum. Another cm of crushed limestone was followed with a sprinkling of Sphagnum, over which the plant mass's roots were spread outward as the plant was centered in the basket. Some of the old potting substrate remained with the plant. A 2:1 mix of Sphagnum-bark, overlaid with a sprinkling of crushed limestone was added around the remaining space between the plant mass and the basket's framework, and the entire mass covered over with a top-dressing of Sphagnum. Drainage should be excellent, and the Sphagnum should ensure the substrate will not become overly dry should attention to the watering and fertilizing schedules be remiss to a minor degree.

Fig. 3. D. kingianum 'The Dove,' plant basketed and hanging by chains in the greenhouse. Digital photo DSC_3519.jpg Pl# 160605-15. Sat-27Mar10.

The outlook should be quite bright for this plant's prosperity, but there is one distinct downside to having chosen to "rebasket" the plant mass in this manner: weight! The "12-inch bulb pan" was not a featherweight, but with the copious use of crushed limestone and the weight of the wood-constructed lattice basket, the result approaches being a "hernia maker" to lift! The basket has been hung (using chains) from one of the 1-inch galvanized pipe support structures, and will remain there except to infrequently rotate it 180o should it show the unlikely tendency of leaning toward the light one way or another (Fig. 3).

The above recap of the depotting and re-basketing of this species is not expected to be a "Master's Word" on how to best culture Dendrobium kingianum, and we may have to wait for another year or even longer to see how well this method turns out. However, one of the intriguing aspects of being an orchidist is trying something, and seeing what happens. In fact, when it comes to orchid culture, there probably are about as many "correct" ways as there are orchidists! We'll see how this effort works out for this grower, and report on the results.

Fig. 4. D. kingianum, keikis repotted & benched. Digital photo DSC_3519.jpg Pl# 160605-15. Sat-27Mar10.

In addition to having basketed the large "specimen" plant, a few keikis had been languishing in small pots, and they each were repotted in a mix of New Zealand Sphagnum and the crushed limestone rock (Fig. 4).

References

Baker, M. L. and Charles O. Baker. 1996. Orchid Species Culture. Dendrobium. Portland, Oregon: Timber Press. 852pp.

Czerevczenko, T. M., and Irene V. Kosakovskaya, pp. 251-263, in Arditti, J. ed. 1990. Orchid Biology: Reviews and Perspectives, V. Portland, Oregon: Timber Press, Inc. 451pp.

Ferry, R. J. 1975 (handwritten greenhouse records). Pl#200475-1. Dendrobium kingianum. also Pl#160605-15.

_______. 2004. Currently In Flower, Locally. MIOS Journ. 5(4): 3-5.

Nicholls, W. H. 1950-58. Orchids of Australia. Parts 1, 2, 3, & 4. Melbourne: Georgian House pty. Ltd. (this is set # 92 of 1030 printed, of which 1000 were made available for sale).

_______. 1969. Orchids of Australia. D. L. Jones & T. B. Muir, eds. The complete edition. Copy #22 of 150 printed. Sydney: Thomas Nelson Ltd.

Upton, W. T. 1989. Dendrobium Orchids of Australia. Portland, Oregon: Timber Press, Inc. 237pp.

Veitch, J., and Sons. 1887-94. A Manual of ORCHIDACEOUS PLANTS. vol II. London: H. M. Pollett & Co. 80pp., Tribe Cypripedieae 108pp., Tribe Sarcantheae 142pp. Oncidium 137pp., Tribe Vandeae, Sub-Tribe Eulophieae 194pp. Glossary 10 pp. Misc. 6pp. Note: this is an original volume from which the reprint of Vol. II was taken.

Copyright © 2010 R J Ferry