Growing and Caring for Orchids
By Peggy Rice, UC Master Gardener
Orchids Are:
- Mostly epiphytes that grow on branches, with roots in the air
- Not parasites; fully photosynthetic
- Recognized by flowers with 3 sepals and 3 petals (one modified as a lip), and fused reproductive organs
- Over 27,000 recognized species worldwide
- Native everywhere except polar and desert regions (though they can be grown there)
Care of Orchids
Care varies by species. These are general guidelines:
Water: Do not overwater. Roots need to dry between waterings.
- Use room-temperature water; avoid ice cubes
- Alternate water and fertilizer; allow full drainage
- Too much water: leaves turn sickly green or yellow
- Too little water: leaves or pseudobulbs shrivel or wrinkle
Temperature
Most orchids require cooler nights. Needs vary by species.
- Daytime: 70–85°F
- Nighttime: 60–65°F
- Too cold: mottled yellow leaves
- Too hot: brown or dry leaves
Light
Orchids need more light than many people expect.
- Place near an east- or north-facing window
- Too much light: burned or brown patches (use sheer curtain to diffuse)
- Too little light: dark green, floppy leaves and no flowering
Humidity
Group orchids together or near other plants to increase humidity.
- Some (e.g., Vandas) require very high humidity; others need less
- Too much humidity: fungal growth
- Too little humidity: poor growth and dry appearance
- Use a gravel tray beneath pots
- Avoid hot, dry, or windy locations
Fertilizer
- 30-10-10 recommended for most indoor orchids; alternate with water
- Fish emulsion for outdoor orchids
- Cymbidiums benefit from 10-30-10 before and during flowering
Purchasing an Orchid
- Select plants with green, undamaged leaves and both buds and flowers
- Inspect for insects, scale, or mites before purchasing
- Isolate new orchids for 6 months to monitor pests
Popular Orchids
Phalaenopsis (Moth Orchid)
- Tolerates low light but needs 1,250–1,500 foot-candles daily to rebloom
- Prefers 65°F nights when resting
- Needs 55–60°F nights for 4–6 weeks to trigger rebloom
- Avoid water in crown to prevent rot
- Produces keikis (baby plants) on flower stems
- Most are tissue-cultured
Cattleyas
- Very showy flowers
- Need medium light (more than Phalaenopsis)
- Often hybridized with other species
Oncidium, Brassia, Miltonia
- Low to medium light
- Miltonias sensitive to high temperatures
- Require more water than Cattleyas or Phalaenopsis
Cymbidiums
- Often grown outdoors
- Can grow throughout San Luis Obispo County; protect from frost
- Provide shade in hot northern areas
- Mist leaves (not soil) during extreme heat
Repotting Orchids
- Most prefer slightly crowded pots
- Repot every 2–3 years
- Avoid repotting just before, during, or immediately after flowering
- Use pots with good drainage (plastic or glazed ceramic)
- Use orchid bark (small, medium, or large grade depending on plant size)
- Pre-wet bark before potting
- Place oldest growth at back of pot
- Label with name, bloom color, and date
Dividing Orchids
- Sterilize tools (1 part bleach to 9 parts water)
- Divide with clean scissors or pruning shears
- Aim for 2–3 strong divisions
- Re-sterilize tools between plants
Orchid Ailments
Isolate new plants for 6 months.
- Mites: cause brown or silvery patches and webbing
- Scale: small brown shell-like structures; remove manually or use insecticidal soap
- Aphids and mealybugs: produce honeydew; rinse or treat as needed
- Fungal issues: sooty mold from honeydew; remove infected tissue