September Orchid Care Calendar

Compiled by Dixie McCulloch, a longtime KOS member who joined in 1988.

Temperature Range (˚F)DaysNights
Cool house59-6554-55
Intermediate house70-7359-69
Warm houseup to 7970 or more

Climatic changes are more predominate this month. Temperatures can drop sharply, so be sure to check your heaters. It is this time of year that you may need them unexpectedly, so be ready.

Autumn is the time for the emergence of buds on many orchids, from the cattleyas, vandas, cycnoches, catasetum, and miltonias. Begin grooming each soon-to-bloom plant in order to realize the best possible display.

Select an ideal spot for the plant. This will likely be atop an inverted pot for those types with arching or pendulous inflorescences. Position the plant so that it receives ideal light for most of the day. Support the inflorescence as it emerges. Sometimes it is necessary to open the sheath to prevent the accumulation of excess moisture around the developing buds, even before they emerge. Plus, it is a time to remove dried cataplylls from cattleya pseudobulbs as the newest growths are securely staked.

Towards the end of the month we have the fall equinox. This is when the sun crosses the equator on its move south. The day length equals the nighttime length. Now the days will gradually get shorter. It is this that triggers the fall blooming cycle in orchids.

If you grow under lights, set them at 14–16 hours of light, as the days outside are getting shorter. Then in a few months reset them again to 10–12 hours of light for the wintertime.

Nitrogen and calcium, the two primary components of cell development, are not needed much now. Phosphorous and potassium, beneficial for good root growth and flower development, should be increased.

As temperatures start to cool, the time is right to repot plants that are sensitive to heat, such as miltoniopsis and masdevallias. This will give these plants a chance to establish themselves before summer rolls around again.

The temperate section can go without heat until night temperatures drop to 50 degrees. Special attention should be given to see that plants do not get burned in the process, because we can still have some bright, sunny and extremely warm days in the late fall.

Watering and spraying should be done judiciously as days get cooler and shorter. Plants should be allowed to dry off completely before nightfall, water early in the day. Now that cooler temperatures are approaching it is a good time to start using a fungicide or bactericide to combat rots that may start. This should be continued throughout the winter months on a regular basis.

You may want to consider moving the plants in that you placed out in the spring. If temperatures drop too sharply you may have to move them in quickly. Cymbidiums can stay out longer than the other types of orchids because of their need for a 20 to 30 degree temperature change. The only thing you have to look out for is frost.

Check over each plant carefully, wash the pots, remove weeds from the potting material, and give the plants a good spraying with an insecticide such as malathion before they are brought in.

Cattleya and Laelia: Now is the time that the new growths made during the summer should be ripened, for it is the well-ripened growths that produce the best flowers.

Once the plants are back indoors, they will need plenty of fresh air until they adjust to the new growing conditions.

Water all cattleyas whenever the potting material becomes almost dry. Pseudobulbs and leaves should be misted on bright, sunny days to keep them plump and healthy.

The importance of light this month cannot be overstressed. The strongest growth is always attained with the greatest amount of light the plants can safely tolerate. Too much strong light too suddenly will cause the leaves on the pseudobulbs that are farthest back on the plant to become shriveled and even to fall off. All potting should be finished. Late potting never is good for cattleyas.

Paphiopedilum: If you have Paph. insigne, keep it cool at night (around 55 degrees) to set buds. At this time, to set buds on most species and hybrids of the temperate zone, you should keep them at a cooler temperature for several weeks.

Dendrobium: Annual growths should be matured in plants of both types. Den. phalaenopsis, and its related hybrids, are already showing buds and therefore need additional light to make the plants bloom. Keep the plants well watered. Den. nobile, and related species, will begin their resting period at the end of this month. You can start to withhold water and nitrogen fertilizer, also keep them cool. They also need to have as much light as you can give them.

To avoid confusion, water all dendrobiums as they begin to show their terminal leaves. When the pseudobulbs have matured, the amount of water can then be reduced even further for a while.

Phalaenopsis: Keep warm and begin to watch watering more carefully, and reduce feeding proportionately with reduced watering needs. An extra dose of phosphorus and potassium is beneficial. Use a blossom booster or high-acid-type fertilizer.  Shading should not be removed from these until winter storms set in. Finish repotting this month.

Masdevallia: Keep cool, well watered, and give lots of fresh air.

Odontoglossum: Complete repotting this month. They should be fertilized with 30-10-10 or 18-18-18 and kept well watered.

Catasetum and Cycnoches: For both genera, autumn is typically the end of their growing season. Plants may produce flowers from pseudobulbs with leaves, or in some instances, from bulbs that have already lost their leaves. Support the basal racemes of catasetums as they emerge; and consider putting the plants on inverted pots to provide room for them to hang freely.

Vanda, Ascocenda, etc: Continue to give as much light as they will tolerate. They should be kept warm and well watered. Any last minute potting is appropriate.

Oncidium alliance: Growth should be fairly well completed. Spikes may be starting to show. Keep them moist but not soggy.

Miniatures without pseudobulbs must be kept moist. This means they do not have a resting period since they have no bulbs for the preservation of water.

Miltonia: The Brazilian ones can be repotted after blooming if not done in the spring. The Colombian ones may be starting to bloom again. Racemes can be very heavy, even when carrying only a single bloom, so do provide support.

Information for these culture calendars are taken from The AOS Bulletin, Orchid Digest, a book Orchids and How to Grow Them by Gloria Jean Sessler and some of my own experiences.