Orchids

By Peggy Rice, UC Master Gardener

	Orchids are: · Mostly epiphytes that grow on branches, roots in air · Not parasites, but are fully photosynthetic · Recognize by flowers - 3 sepals and 3 petals (lip), fused reproductive organs · Over 27,000 recognized species, grow everywhere except polar and desert regions (they can be grown there, but don’t grow naturally)
Care of Orchids: varies by species, here are the basics: Water: do not overwater; roots need to dry out ·  Use room temperature water; no ice cubes ·  Alternate water and fertilizer; allow water to drain from the pot ·  Too much water: leaves are sickly green or yellow ·  Too little water: leaves or pseudobulbs shrivel or wrinkle

Temperature: most orchids need cooler nights; needs vary by species

• Warm daytime temperatures are tolerated - 70 to 85^°F
• Cooler nights - 60 to 65^oF is best
• Too cold: mottled yellow leaves
• Too hot: brown or dry leaves

Light: orchids need more light than you might think

• Position near an east or north facing window
• Too much light: leaves develop burned patches or turn brown; add a thin curtain to diffuse light
• Too little light: leaves are dark green, floppy, and will not flower

Humidity: group orchids together, or with other plants to increase humidity

Some orchids require very high humidity (Vandas, from Thailand), others require less

• Too much humidity: results in fungal growth
• Too little humidity: plants grow poorly and will look dry
• Use a tray of gravel under pots to increase humidity,
• Avoid hot, dry, or windy conditions

Fertilizer: 30-10-10 is recommended for indoor orchids; alternate with water

• Use fish emulsion for outdoor orchids
• Cymbidiums need 10-30-10 before and during flowering

Purchasing an orchid:

• Select a plant with green, undamaged leaves, with both buds and flowers
• Examine the leaves and stems for insects, scale, mites before purchasing
• Isolate the new orchid from other plants for 6 months to monitor any developing insects or mites

Popular indoor and outdoor orchids

Phalaenopsis (Fayl-eh-NOP-siss) - the moth orchid

• Tolerates low light, but needs more light to rebloom (1250-1500 foot candles for 12 daily
• Prefers warm nights (65°F) when resting after bloom
• Needs 55-60°F at night for 4-6 weeks to rebloom.
• Do not get water in the crown of the plant or it will rot
• Cannot divide but it may make keikis - new plants on the flower stem
• Most are grown by tissue culture.

Cattleyas (KAT-lee-ah) - very showy flowers

• May need short days to flower, need medium light (more than Phals)
• Crosses with other species

Oncidium, Brassia, Miltonia

• Needs low to medium light
• Miltonias are sensitive to high temperatures
• All need more water than Catts or Phals

Cymbidiums (Sym-BID-ee-um) - grown mostly outside

• Can grow anywhere in SLO County, but protect from frost
• If danger of frost, cover, or move indoors for the night
• Can tolerate some heat, but keep shaded and cool in northern SLO County
• If very hot, mist the leaves instead of watering

Repotting Orchids:

• Most orchids like a crowded pot; a pot that’s too large can result in conditions too wet
• Only repot every 2-3 years; don’t repot just before, during, or just after flowering
• Repot when roots or pseudobulbs are creeping out of the pot, or the bark has broken down
• Select a pot that will drain; plastic and glazed ceramic are suitable,
• Use orchid bark - there are 3 grades: small is for seedlings, medium is best for most orchids
• Large bark can be mixed with medium for cymbidiums or other large orchids
• Some people use just bark, others mix in potting soil, moss, or perlite
• Wet the bark and other amendments before adding to the pot
• Place the oldest part of the plant in the back of the pot
• Tap the pot to settle the medium and add more bark or soil if needed
• Label plants with name, date and color of bloom

Dividing orchids: similar to repotting, except you get more plants

• Sterilize your tools - use 1 part bleach to 9 parts water
• Use scissors or pruning shears to divide
• Aim to get 2 to 3 strong plants from each mother plant
• Sterilize all tools again after working each orchid

Orchid Ailments: Isolate new plants for 6 months to help prevent insects or diseases from spreading plant to plant

• First provide the needed water, temperature, light, humidity, fertilizer to ensure plant health and vigor
• Mites - very small, hard to see; feeding results in brown or silvery patches on leaves; creates webbing for protection and transportation
• Scale - small, brown, dry shells-like structures on stems and the upper and undersides of leaves. Remove by hand using a cotton swab and water, or insecticidal soap if needed . Scale produces sticky honey dew
• Aphids are pale green and mealybugs have a white cottony appearance. Both also produce honeydew and can be removed with water or insecticidal soap
• Fungus – Sooty mold can develop on honey dew covered leaves. Other fungi can cause leaves to brown and watery at tips. Cut infected leaves well below symptomatic areas

Resources and References

Five City Orchid Society:  https://www.fcos.org/  

American Orchid Society:  https://www.aos.org/