Dendrobium orchid

About Dendrobium orchid

Dendrobiums are a huge genus of about 1,600 tree-dwelling orchids from India and China to Australia, with jointed, cane-like stems and sprays of 7-15 flowers in almost every color (NC State). The common kinds split into hard-cane types, such as the phalaenopsis-type D. bigibbum hybrids with long-lasting flowers, and soft-cane types, such as D. nobile hybrids, which need a dry, cool rest to bloom. They want about twice the light of a moth orchid, so they are a step up in difficulty indoors (Clemson, Wisconsin Horticulture).

Hardy outdoors only in zones 9-12 (NC State); it is grown indoors everywhere and can summer outdoors in bright, light shade once nights stay above about 52 F, Clemson's minimum night temperature.

When to plant

Timing is counted from your average last spring frost (and first fall frost). Sow & Tell works out the actual dates for your ZIP code.

Usually bought as a blooming nursery plant in bark mix; older plants can be divided at repotting (NC State, UF/IFAS).

Growing it indoors

• Light: It needs about twice the light of a moth orchid: a west window or a south window softened by a sheer curtain, with no hot midday sun; too little light means no flowers (Clemson, NC State).
• Water: While it is growing, water about once a week (twice in small or clay pots) and let the mix dry slightly in between, but never fully dry unless it is resting (Clemson, NC State). Too much water while it rests, or too little while it grows, can kill it, and overwatering is the most common killer of orchids (NC State, Clemson).
• Humidity: It wants 40-60 percent humidity or more with good air movement; a humidifier or pebble tray helps in winter (Clemson, NC State).
• Temperature: Clemson gives 52 F as the minimum night temperature, with days 10-15 degrees warmer; keep it away from cold windows in extreme cold.
• Feeding: Feed an orchid fertilizer weekly at a dilute rate during the growing season, or monthly at the label rate; plants in bark need a higher-nitrogen feed such as 30-10-10, and flush the pot with plain water once a month (NC State, Clemson).
• Repotting: Repot when the bark breaks down, about every two years, into the smallest pot that fits its small root system (UF/IFAS, NC State).

Soil

A bark-based orchid mix in the smallest pot that fits; clay pots drain best and keep the tall canes from tipping (NC State, Clemson).

Pot in a bark-based orchid mix in the smallest pot that fits, ideally clay with good drainage holes (NC State, Clemson).

Feeding

• Spring and summer, during the growing season: orchid fertilizer (higher nitrogen such as 30-10-10 for plants in bark). Weekly at a dilute rate or monthly at the label rate, flushing the pot with plain water once a month to clear salts (Clemson, NC State).
• After flowering, through the rest period: none, or much less. Cut back water and fertilizer until new growth begins (Clemson).

Overwatering, especially while it rests, is the most common way to kill it (NC State, Clemson).

Harvest

Many bloom in fall and winter, in sprays whose individual flowers last about 3-4 weeks on hard-cane types and less on soft-cane types (Clemson, NC State). Soft-cane kinds bloom after water is held back in late fall and early winter; after flowering, cut back water and fertilizer until new growth starts (NC State, Clemson).

Varieties (6)

NC State Extension names 6 species and hybrid groups; most dendrobiums sold are hybrids within these groups.

Pests to watch for

Mealybugs, Twospotted spider mite, Scale insects, Thrips

Diseases and problems

Root and crown rot, Leaf spots, Bacterial soft rot, Mosaic viruses

In the kitchen

Safety: Not listed as poisonous in the sources we opened (NC State gives no toxicity, and the ASPCA has no dendrobium entry).

Pets: Not listed by the ASPCA (no Dendrobium entry on its plant lists).