Repotting should be done by now, but keep an eye on those oddball
species that like to grow roots as they flower. Many bifoliate cattleyas
need to be repotted just as they come into flower. Some like C bicolor
with 3 foot pseudobulbs are particularly frustrating since buds emerge
about the same time as new roots. It is not unusual to see this same
characteristic in their offspring.
Insects are cold-blooded, which means they grow faster when greenhouse
temperatures are warm. This is true for both scale insects and mobile
pests such as roaches. Roaches, mealybugs, and other mobile animals that
live in pots can reduce all your carefully protected root tips to little
white nubs. Unfortunately, this mostly happens at night so there is
always some uncertainty as to the identity of the offending culprit. If
you are a night owl, a quiet visit with your flashlight to your growing
area at night may get you a quick view of the culprit. If you are having
this problem, mix up a 5 gallon bucket of liquid Sevin, 1 teaspoon per
gallon and dip the entire orchid pot for a minute or two and see what
comes out. Roaches will make themselves known, but many smaller animals
such as snails & slugs will just die in the pot. Either way, problem
solved. For hobbyists who place their orchids outdoors in summer and
bring them inside in winter, remember this treatment to avoid importing
pests.
There are a few orchids in my collection that should love the heat of
summer, but Angraecum hybrids and species often develop rots in their
new leaves as they emerge. Keep a bottle of household hydrogen peroxide
in the growing area. After you water, put a few drops in the crown of
angraecums or any other monopodal orchid (phals, vandas, etc) that grow
on a vertical stem and the rot problem will disappear.
Summer is a time of both heat and humidity. If you are growing outdoors
don’t forget last month’s watering advice. Always keep in mind that cool
weather will require a reduction in watering frequency. There is always
the possibility here in the Southeast of a tropical system lasting for
days. Tropical systems import fungal and bacterial spores. The heat and
humidity that accompany these storms encourage their growth. These
disease-causing organisms are always around and there is nothing that
can be done.
If you grow outside and your orchids are naturally watered by the rain,
it may be necessary to provide some shelter if several days of tropical
rain is expected. In my greenhouse, I also spray down all surfaces under
benches, on walls, etc with a strong anti-biotic. Copper Sulfate
(Kocide) works well as can a solution of Clorox. However, these products
can damage orchids if they get on leaves. If orchids are wet there is
less danger or a less toxic product can also be used.
Kocide, used in a more dilute form is safe to use on some orchids, but
only if the water you mix it with is on the basic side of the pH scale,
i.e. above 7. Even then, there can be damage on tender new phal leaves
as well as to other sensitive orchids. There are other products such as
Phyton 27, approved for direct application to orchids. It is easier to
prevent infections than cure them.
Once the tropical system has passed it is wise to treat your orchids
with some type of anti-fungal or anti-bacterial agent. Some hobbyists
that have small collections use the same hydrogen peroxide noted above,
place it in a spray bottle and spray their plants. Remember to keep air
moving around your orchids. Once the rain stops and humidity drops it is
also a good idea to let your orchids dry thoroughly.
