Orchid Culture

Culture For Commonly Grown OrchidsBecause of our temperate climate, many orchids can be grown outdoors in our area. This section provides an overview of the orchids most commonly grown here with basic culture information.

VAOS Member Culture Tips – This section provides basic culture tips compiled from members and local growers that are specific to our south Florida growing area.  Remember that each grower’s conditions and needs will vary.

What orchids grow best in South Florida?

Cattleyas, dendrobiums, oncidiums, vandas and bulbos grow well outdoors in our area. Phalaenopsis and paphiopedilums grow well but require more shade and should be hand- watered and not exposed to rainfall. Phragmipediums grow well and prefer to have their “feet wet” (set in saucer of water).  Most cymbidiums, miltonias and odontglossums are cool growing plants and will not bloom well here unless purchased from a local grower and bred to be “warmth tolerant”. Any species plant requires special attention – your success is based on your ability to match its’ natural habitat. Consult wwww.species.com or Bakers Culture Sheets for species habitat information.

How Often Should I Water my Orchids?

Water your orchids once or twice a week or more frequently when it is very hot. Water thoroughly, wait 15 minutes and then water thoroughly again. Allow cattleyas, dendrobiums and oncidiums to dry out before the next watering. Use the pot “heft test” to determine if the pot is light and the plant needs watering. Bulbos, phals, paphs and phrags require more frequent watering – keep them evenly moist but not wet. Vandas and other mounted plants grown with no media will require daily watering during the warm months. Seedlings will require more frequent watering. Rain water or reverse osmosis (RO) filtered water is best as it is pure, but, our Venice area water is excellent. Do not use a water softener – the salt will kill the plants.

How much light and/or shade do my orchids need?

Cattleyas, dendrobiums, oncidiums and phragmipediums flourish in bright light with 15% to 30% shade – about what a screened patio, lanai or pool cage provides or a shade tree. East or south exposure is best. Slowly acclimate your new orchids to higher light conditions to avoid sunburn.  Phals, paphs and bulbos require bright, indirect light – they often do well under a patio overhang providing them protection from the sun and rain. Vandas require high light. The most frequent reason for lack of blooming is too little light. There are mico-climates in every growing area and often moving a plant to another area will improve blooming. Watch for and adjust for seasonal changes in sunlight exposure in your growing area.

How important is air circulation?

Good air circulation around your orchids is critical especially during the warmer months to reduce the risk of fungus and pests. The higher the heat, the more water and air circulation is needed. Ceiling fans work well supplemented with smaller fans to maintain a slight breeze around your plants 24/7.  Avoid crowding plants to allow air to circulate around them.

What type of fertilizer should I use?

Any good orchid fertilizer will do, some people even use tomato or african violet fertilizer.  Use a 20-20-20 balanced fertilizer and supplement occasionally with calcium and magnesium. Or use a Michigan State University (MSU) – type fertilizer that contains micro-nutrients including calcium and magnesium.  The rule of thumb is to fertilize “weekly-weakly”, using 1/4 to 1/2 tsp. fertilizer to a gallon of water. When the plants’ pseudo bulbs have matured and the plant begins dormancy in the cooler months, fertilize less frequently.  Many local growers recommend supplementing with a timed-release fertilizer (Nutricote sold as Dynamite at Home Depot).

What type of media works best?

Orchids grown outdoors in South Florida require an open mix that drains rapidly after our heavy rains.  Most growers use a bark mix (bark, charcoal, sponge rock) or a cocoanut husk chunk (CHC) mix (CHC, charcoal, sponge rock). Some growers use a partial or 100% inorganic mix composed of one or more of the following: lava rock, charcoal, aliflor (clay pellets), dyna-rok, sponge rock or other media for their mature plants. Use smaller size media for seedlings or fine root plants and larger size media for mature plants. Some growers prefer sphagnum moss in clay pots for Phalaenopsis, but sphagnum moss holds water, is tricky, and should not be used in plants exposed to rainfall.

The best quality media can be found at local orchid nurseries or purchased through online orchid suppliers.

If you use cocoanut husk chunks (CHC), be sure to rinse it thoroughly before use. Soak and rinse in clear water three times and then add calcium nitrate to the final rinse to remove all salt residue.

What type of pots should I use?

Using clay or plastic pots is a matter of personal preference. Clay pots dry out faster and help to keep plants cooler in hot weather. They also add weight to stabilize the plant in heavy winds. Plastic pots are less expensive and hold moisture longer. Many growers pot seedlings and moisture loving plants in plastic and mature plants in clay.  Some outdoor growers will set plastic pots into clay pots for added stability.  Azalea (short) clay pots with slotted holes work well. Aircone plastic pots are popular.  Whichever pot you choose, be sure that it has sufficient drainage holes. Wood or plastic baskets are also popular and are used for vandas, agraecums and those genera that like to wander.

What works best for pest and fungus control?

Many pest and fungus problems can be avoided by keeping your growing area clean and increasing air circulation during hot weather. Monitor your plants carefully and if you find a problem isolate the plant and treat it.  Remove dry sheaths where scale often hides. Spray clean your work areas and plant shelves with Physan or a 10% bleach solution.

Common pests in our area are scale, thrips, aphids, mealy bugs and slugs.  If you have a small collection or if the problem is not widespread, try a non-chemical treatment first – Neem Oil, All Seasons Oil, 50/50 alcohol and water solution or just plain dish washing soap in water.  Several treatments will be necessary. Saturate the plant, spraying under the leaves.  Do not spray oils on a hot day.  See www.firstrays.com for some popular home remedies.

If a pest problem is widespread or cannot be eliminated by non-chemical treatments, the next step is a pesticide.  Merit 75 or Orthene WP 97 is recommended for scale, thrips, mealy bugs and aphids. Follow label directions carefully and wear protective clothing. Rotate pesticides.  Routine preventative spraying with pesticides is not recommended.

Treat slugs with slug and snail bait pellets (sprinkle small amount on top of media) available from Home Depot or Lowes. Mites require a miticide such as Kelthane or Pentac. Ants can be eliminated with Orange Guard,  Sevin or Orthene.

Neem oil and All Seasons Oil will control pests and also fungus. For widespread fungus problems treat with Banrot 40 WP or Zyban. Preventative spraying with Banrot or Zyban in spring and early summer will help to prevent fungus problems during the rainy season.

Several websites recommended in Section 5.0 Resources will help to identify pests and diseases and suggest treatments.

What is the best way to sterilize my pots and cutting tools?

Pots and tools must be sterilized to prevent the spread of disease.  Three common approaches to sterilizing tools are 1) propane torch, 2) 10% bleach solution and 3) use disposable razor blades.  A propane torch is probably the best method.  Alcohol and Physan are not effective.  Soak used pots in a 10% bleach solution for one day, rinse and dry before reuse.