Orchid Variety Guide and Southern Blight Control Methods

Orchids are one of China's top ten famous flowers, one of the Four Gentlemen among flowers, and the city flower of Baoding, Longyan, Yilan, Guiyang, and Baoshan. So, what varieties of orchids are there? How do you control southern blight? Here we introduce them to you.

I. What varieties of orchids are there?

There are many orchid varieties, such as Cymbidium aloifolium (striped-petal orchid), Cymbidium bicolor (hard-leaved orchid), Cymbidium dayanum (drooping-flower orchid), Cymbidium cyperifolium (sedge-leaved orchid), Cymbidium defoliatum (winter phoenix orchid), Cymbidium faberi (deciduous orchid), Cymbidium eburneum (Duzhanchun), Cymbidium cyperifolium (sedge orchid), Cymbidium ensifolium (Jianlan), Cymbidium erythraeum (long-leaved orchid), Cymbidium faberi (Huilan), Cymbidium floribundum (many-flowered orchid), Cymbidium goeringii (Chunlan), Cymbidium hookerianum (tiger-head orchid), Cymbidium insigne (beautiful orchid), Cymbidium iridioides (yellow cicada orchid), Cymbidium kanran (cold orchid), Cymbidium lancifolium (rabbit-ear orchid), Cymbidium lowianum (jade orchid), Cymbidium macrorhizon (large-root orchid), Cymbidium mastersii (large-snow orchid), Cymbidium nanulum (pearl dwarf), Cymbidium sinense (ink orchid), Cymbidium suavissimum (fruit-scented orchid), Cymbidium tracyanum (spotted-tongue orchid), and others. They differ in color and form; a few of them are introduced here.

1. Cymbidium aloifolium (striped-petal orchid): an epiphyte, found in Guangdong, Guangxi, Guizhou, and southeastern to southern Yunnan in China, growing on trees in open forests or thickets or on rock walls beside streams and valleys, at an altitude of 100-1100 m, flowering April-May, occasionally in October; leaves thickly leathery, 4-5 in number, raceme with 20-35 flowers, sepals narrowly oblong to narrowly elliptic, petals narrowly elliptic, lip nearly ovate, sepals and petals pale yellow to cream-yellow, lip white or cream-yellow densely marked with chestnut-brown longitudinal stripes, slightly fragrant.

2. Cymbidium cyperifolium (sedge-leaved orchid): a terrestrial or semi-epiphytic plant, found in Guangdong, Hainan, southern Guangxi, southwestern Guizhou, and southeastern Yunnan (Mengzi, Yanshan, Malipo, Pingbian) in China, growing under forest in well-drained, stony ground or in rock crevices, at an altitude of 900-1600 m, flowering October to February of the following year; leaves strap-shaped, 4-12 in number, raceme with 3-7 flowers, sepals linear to broadly linear, petals narrowly ovate, lip ovate, sepals and petals yellow-green or apple-green, lip paler or sometimes tinged white or pale yellow, with a lemon fragrance.

3. Cymbidium erythraeum (long-leaved orchid): an epiphyte, found in southwestern Sichuan, northwestern to southeastern Yunnan, and Tibet (Bomi, Zayu, Medog) in China, growing on trees in forests or at forest margins or on rocks, at an altitude of 1400-2800 m, flowering October to January of the following year; leaves strap-shaped, 5-11 in number, raceme with 3-7 or more flowers, sepals narrowly oblong-oblanceolate, petals falcate, lip nearly elliptic-ovate, sepals and petals green with reddish-brown veins and irregular spots, lip pale yellow to white with reddish-brown veins and spots, fragrant.

4. Cymbidium hookerianum (tiger-head orchid): an epiphyte, found in southwestern Guangxi, southwestern Sichuan, southwestern Guizhou, Yunnan, and southeastern Tibet (Zayu) in China, growing on trees in forests or on rocks beside streams and valleys, at an altitude of 1100-2700 m, flowering January-April; leaves strap-shaped, 4-6 in number, raceme with 7-14 flowers, sepals nearly oblong, petals narrowly oblong-oblanceolate, lip nearly elliptic, sepals and petals apple-green or yellow-green with dark red spots, lip white to cream-yellow with chestnut-colored spots and markings, fragrant.

II. How do you control southern blight in orchids?

1. When does the disease occur?

Orchid southern blight, also known as white silk disease or sclerotium disease, is caused by a fungus of the Deuteromycotina. Infection begins in April to May, with the peak incidence from June to August; the pathogen overwinters as sclerotia in soil, in fertilizer, or on undecomposed residues, germinates the following year, spreads through the soil, and invades from the base of the orchid leaves to cause damage. It can be transmitted by flowing water, irrigation water, rain splash, and fertilization; the disease is most severe in acidic soil, and hot, humid weather easily triggers it.

2. What are the symptoms?

The disease starts from the stem near the ground of the orchid plant, initially appearing as yellow to light brown water-soaked lesions, then turning brown to dark brown and rotting, and spreading over the soil surface around the roots and the stem base, destroying the stem and infecting young leaves and roots; the affected parts become water-soaked, soft-rotted, and blackened until the leaves wither. When the pathogen spreads to the pseudobulbs, the entire leaf cluster of the plant dies.

3. What control methods are there?

(1) Before the disease occurs: this disease easily occurs in acidic conditions (pH below 5.3), so mix plant ash at 1/10 by volume into the substrate to bring the pH to around 6.5. After new shoots emerge above the soil surface, spray with 0.05% chloramphenicol once a week for 2 to 3 consecutive sprays to prevent bacterial infection; you can also water and spray with 1500 times diluted aspirin solution to enhance the orchid's immunity and block pathogen invasion and spread.

(2) When the disease occurs: remove the substrate contaminated with mycelium, disinfect the remaining substrate with 600 times diluted 50% carbendazim wettable powder, sprinkle in fresh plant ash, cut off diseased roots, and spray with 1500 times diluted 70% thiophanate-methyl for disinfection. Cut off diseased leaves, soak the whole plant in 10% copper sulfate solution for disinfection, or drench the diseased plant with a 2000 times aqueous solution of medical-grade chloramphenicol injection, once a day for 3 consecutive applications.

The above is an introduction to orchid varieties and control methods for southern blight, and we hope it is useful to you.