Stanhopea Summer Culture Checklist

 

The spring season of 2013 was warm and mild.  It has been warmer than the spring of 2012, so this helped the Stanhopea recover from our cold winter.  Due to the warmer and dry spring I have had less problems with fungal and bacteria growth on leaves compared to the rather cool and moist spring from last year.  Even with the warm spring, inflorescence production seems to be approximately two weeks late from last year.  I attribute this late inflorescence growth to our colder than normal winter.  Perhaps this warmer spring/summer weather will allow the orchids to speed up inflorescence growth.

·       Continue watering all Stanhopea regularly and keeping them moist.  I usually water my orchids three to four times a week under normal temperatures.  If temperatures rise above 90°F (28°C) and humidity is low I mist and lightly water every day.

·        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.

·         Weed baskets to prevent ferns and other plants from taking up space in baskets.

·        If you grow your Stanhopea  in a sunny area or a greenhouse that receives strong sunlight you may want to place saran shade cloth over the growing area in early spring and summer before the sunlight becomes too strong for them.  You may also want to consider moving the Stanhopea to another shadier growing area for the summer.

·        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 shady 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.

·        In late spring/summer 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.

·       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.

·        Keep a careful eye out for spider mites as the spring continues and our weather begins to warm and dry out.  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.   The leaf fungal problems do not impact the health of the plant to a large degree but do look unsightly.

Stanhopea Pests

Stanhopea are relatively pest free orchids when compared with other genera.  The common pests are snails/slugs and spider mites.  For me the snails/slugs are a constant battle, and are the more serious pests.  These mollusks can damage new growth, inflorescences, and flowers.  They usually do not have any more of an impact on a plant other than cosmetic damage, though long term damage can occur if they continually eat new growth and prevent the plant from growing well.

Bush snails (orchid snails)
from Orchidboard.com

I use metaldehyde based snail and slug bait (e.g. That’s It) to control these pests that is a granular form, and doesn’t leave a meal residue in the pots and baskets. I also have been recently trying “Sluggo Plus” suggested by a blog visitor.  This product breaks down into iron and phosphorus which plants benefit from, and it is less environmentally damaging. "Sluggo" seems to be a good product to use and does not adversely impact children, pets, and wildlife in the amounts used as directed.

Spider mite spots on leaves of Stanhopea.
From Orchidboard.com

Spider mites on underside of plant
leaves. From Got Pests? website
at Maine.gov

 

Spider mites can be a problem for Stanhopea and are generally noticed when light yellow spots appear on the leaves in large numbers.  I have had very few problems with spider mites in my collection perhaps because I grow most of the Stanhopea outdoors where spider mites have to deal with predators.  That being said, environments that are low in humidity and dry often allow plants to harbor spider mites. The best control I have found for these is to apply a rosemary oil based mite control (e.g., SNS-217) to the leaves and pseudobulbs every few weeks.  This treatment removes the spider mites and then you can ensure that they don’t return by increasing humidity in the environment and checking your plants often to spray again when necessary.  These rosemary oil based sprays are organic and pose less of a threat to pets and wildlife.