December To Do List

General

• Short days and cold nights in December will slow down the metabolism of most of your orchids and initiate spikes on Fall/Winter blooming orchids.  Watch them very carefully and cut back on water and fertilizer as cooler days and nights prevail.
• As watering needs of most plants decrease during the winter, be sure to leach your plants thoroughly. Extend your last watering to remove any accumulated salt built-up in the substrate and root system. Excess mineral built-up prevent plants from absorbing the fertilizer and nutrients they need and may lead to deficiencies during dryer conditions. The St. Augustine Orchid Society hosts a very good collection of articles on water quality.
• Protect outdoor orchids from winter rains.  Keeping them on the dryer side will allow them to tolerate the cold winter nights we can experience in Southern California.
• Bring in cold-sensitive, warm growing orchids (phals, paphs, tolumnias, most vandas and some warm growing cattleyas such as violacea, dowiana and their hybrids) to protect them from night temperatures below 50o. An excellent article on ‘Cold Tolerance of Orchids’ by Sue Bottom of the St. Augustine Orchid Society can be found in their October Newsletter (pgs. 9-11)
• Cold tolerant orchids, including Odontoglossums, Miltonias, Pleurothallids, Masdevallias, and Draculas, will welcome the cooler weather and respond by initiating growth so continue to water and fertilize them during this period but also protect from freezing temps.
• Fall/winter blooming Cattleyas and Cymbidiums are now in bud or bloom. Provide adequate water and fertilizer, but do so in the mornings so plants dry out before nightfall. Stake cymbidium spikes to guide inflorescences for support of buds and blooms.
• Maintain good hygiene practices to minimize transmission of pests and viruses. Watch for fungus and bacterial rot in cold and wet weather.
• More details on specific genera can be found on the AOS website

Indoors and Greenhouse

• Carefully monitor greenhouse temperatures and check that circulating fans, automatic vents, humidifiers and heaters are in good working order. 
• Continue to provide good air circulation for indoor plants to discourage diseases and pests such as mealy bugs and scale. Be sure to check all edges of the pot and neighboring pots. Pests, especially mealy bugs also can be found on the bottom of pots. Treat early to avoid spreading to other plants. More info on pests and diseases can be found at the AOS website.
• Cut back on watering and frequency of fertilizing in winter. Avoid over fertilizing to minimize root damage and growth of soft growths. Keep to one half to one fourth the recommended amount on the package.

Outdoors

• Continue to monitor and control snails, slugs and pests as cooler and wet weather will bring them out. They can do considerable damage to plants in short order.
• Try not to use water that is much cooler than the plants as their tissues can be shocked. Watering early in the day will facilitate that and allow plants to dry before nightfall in order to minimize bacterial and fungal diseases.
• Most Cymbidiums are now in spike or bloom so switch from high nitrogen fertilizer to one with higher phosphorus and potassium (Hi Bloom such as 10-30-20) to initiate and stimulate spike production.  Stake spikes early to train them to grow upright while spikes are flexible. Find out more at the AOS culture pages for Cymbidiums.
• Members of the Catasetinae family (catasetums, clowesia, cycnoches, and mormodes) are entering their dormant period as evidenced by the yellowing and dropping of leaves. Note that some actually initiate spikes at the outset or during their dormant period.  Cut back and eventually eliminate water and fertilizer until Spring as recommended by Fred Clarke on his website.
• Most Phalaenopsis are very sensitive to cold and should be inside your home or in a greenhouse by now and starting to spike.  Be sure to stake spikes early to train them to grow upright for optimal display of blooms.  
• For Phalaenopsis lovers, Orchid Digest Magazine devoted their most recent issue (Oct., Nov., Dec., 2013, Vol. 77-4) to this popular class, including topics on culture and temperature sensitivity and recent advances in Phalaenopsis breeding.  The issue has some great articles and fantastic pictures and, for individuals who don’t subscribe, it can be ordered from the Orchid Digest website.