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Orchidaceae
Spiranthes delitescens is a slender, erect terrestrial orchid of about 50 cm in height when in bloom. The plants have five to ten slender, grass-like leaves which grow basally on the stem. Roots are fleshy and swollen, about 5 mm in diameter. The twisted spike inflorescence may contain up to 40 white flowers. Flowering occurs in July, when temperatures range from 60F at night to 100F during the day. The plants are visible during July and August, and essentially impossible to find during any other time of the year. The fruits mature three weeks after flowers appear, usually during the end of August. The average longevity is 3 to 4 years, and during severe drought condition, plants return to the heterotrophic condition.
The habitat preferred by Spiranthes is a marshy wetland or cienega, intermingled with tall grasses and sedges, at elevations of 5000 ft. Of the four known occurrences within Arizona, three are privately owned and grazed. The fourth site is owned by the Nature Conservancy. Short term declines in numbers of individuals have been noted by The Nature Conservancy at two sites. It is listed endangered under the Endangered Species Act.
Threats to Spiranthes include grazing, competition with Equisetum (horsetail), sedges, and Johnson grass, and possibly fire suppression. There is anecdotal evidence that species may actually require disturbance in order to become established.
Since the seeds of orchids are without endosperm, or stored nutrients, the seeds are short-lived. Germination of such seeds is challenging, and must be conducted under sterile conditions on an agar media, to eliminate potential contamination and competition with fungal growth. Seeds have been collected by Desert Botanical Garden in the past and sent to a tissue culture specialist in Cincinnati, Ohio. From thousands of seeds, only seven plants were generated. Eventually all but one plant died, and the remaining plant was severely stunted. It flowered, then died. Little is known about requisite mycorhizal (root fungal) associations of Spiranthes. Although the plant was being grown in soil taken from its native habitat, apparently no fungal mutualism had taken place.
Investigation into seed storage requirements, germination requirements, and horticultural information is critical. Additional collection of seed is also necessary.
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