As the weather begins to cool, fall is a great time to enjoy Stanhopea blooms and watch new growths emerge. This is also a good time to repot or rebasket plants because it is still warm and many Stanhopea will continue growth through fall. By the end of December, most warm growing Stanhopea will complete their growth cycle, and wait for spring/summer to continue growth in preparation for summer or fall bloom.
· Continue watering all Stanhopea regularly and keeping them moist. I usually water these orchids three to four times a week under normal temperature conditions. If temperatures rise above 90°F (28°C) and humidity is low I mist and lightly water every day. Guarding against low humidity is particularly critical growing Stanhopea outdoors in southern California due to the Santa Ana winds we often receive. These winds are warm to hot and are devoid of humidity. By the end of fall you can often begin to reduce watering slightly to just two times a week, or less if rainfall is plentiful.
· Continue fertilizing all species regularly. I often reduce the manufacturer’s recommendations to one third or one half and fertilize every week, or what is known as weakly-weekly. Stanhopea can be rather heavy feeders when they are in active growth.
· Fall is an excellent time to repot smaller Stanhopea or larger baskets. I usually wait until mid to late October to rebasket because this allows the growths to increase in size and makes it less likely that you will injure them. This is a prime time for growth for several species and rebasketing is advantageous.
· Weed baskets to prevent ferns and other plants from taking up space in baskets.
· In mid fall (November) I remove or roll up most of the saran shade cloth and store it until spring. This allows the Stanhopea to receive more sunlight, albeit diffused light during the fall and winter months. This will assist those species that grow all year and often complete their growth in the winter.
· If you know temperatures are going to increase and humidity levels drop, you may want to consider moving a Stanhopea that is coming into bloom to a shadier more humid area, or as I often do onto my covered patio. That way I can enjoy the flower show right from my window. This often prevents early desiccation of flowers and they tend to last the average three to five days instead of just two.
· Throughout fall make sure to check for growing inflorescences and ensure that their growth is unimpeded by other plants or the basket. If need be place a plastic label underneath the inflorescence to help direct the growth out of the basket. Some inflorescences may emerge from the baskets as late as November or December in some species.
· Use of a methaldihide product or an organic substitute such as Sluggo is advised on a weekly basis at this time to prevent slugs from disfiguring new growth and impacting new inflorescence and bud growth. I often use a product called “That’s It” that is a granular form and therefore leaves less residue in the growing media. I am currently testing Sluggo as a more organic method of slug control.
· Check for spider mites through fall as our weather is still warm and dry. Small yellow spots on the foliage signal that these pests are active on your Stanhopea. Spray infected areas with rosemary oil spray or an insecticidal soap to kill the pests as soon as possible to prevent them from damaging the plant further and spreading to other orchids.
· You should also be diligent in keeping watch for fungus infections at this time on leaves. Several fungus attack leaves when humidity is high and temperatures are warm. Black or brown spots of leaves and yellowing of leaves in odd patterns are usually the cause of fungus or bacterial infection. Treat with a fungicide or bactericide. I often use Physan 20 to deal with the problems and prevent further damage to the plants.
· The warmer temperatures and reduced breezes combine to cause fungal infections such as black spot on some Stanhopea species and hybrids. The key to reducing this problem is to make sure your Stanhopea are grown in a breeze way that gets constant air flow, or to place a fan in the growing area that produces a very slight breeze at all times. This will prevent the fungus from settling on the leaves and disfiguring them. This problem does not impact the health of the plant to a large degree but it does look unsightly.