Growing
Tips for April 2001
by
Courtney T. Hackney
EMAIL
at Hackneau@bellsouth.net
Spring is the ideal time to repot most Orchids. Unfortunately,
many new hobbyists are either too anxious to repot or neglect to repot
when it is needed. As noted in last month’s column, the condition
of the media is important if a plant is to get adequate moisture and oxygen
to its roots. For the novice, repotting is a major challenge. First
there is the problem of what to use, where to get it and then finally
exactly how is it done. All three of these subjects will be covered this
month.
How do you know if the plant needs repotting?
For Cattleyas the plant should either be growing out of the pot or have
media that has become degraded. Orchids in clay pots usually grow out
of the pot before the media breaks down. In plastic, however, the extra
moisture retained by plastic pots usually accelerates the breakdown of
bark and necessitates repotting every two years or so. Phalaenopsis in
ProMix or other soilless mixture must be repotted at least once a year
or even more frequently if you have over watered and damaged the roots.
Paphs, unlike most Orchids, like to be repotted every six months, while
Vandas in baskets or Orchids mounted on cork or wood never need repotting.
Many novices buy mounted Orchids only to see them whither and die. If
you cannot maintain adequate humidity for mounted Orchids you should try
setting the Orchid, mount and all, into a clay pot large enough to hold
them. Try this before taking the Orchid off their mounts and potting
them. The clay pot will maintain some humidity around the plant even
inside or under lights.
There are many different medias used in
Orchid culture. Commercial Orchid nurseries are largely guided by cost
and availability. The hobbyist, however, can use the one best suited
for their growing conditions. But what is the best? If you are just
beginning to grow Orchids this is a difficult question to answer. The
best approach is to ask a couple of more experienced growers that grow
under conditions similar to your own, what they use. They may not all
give you the same answer, but it will limit your choices. Also look at
your plants and if some are doing very well in a specific media try that
type first. Remember that the pot should be included in your deliberations
as this is part of the media. Some Orchids will adhere to the pots more
than the media. Fortunately, many types of Orchid media are available
in local garden stores. More experienced growers can also provide guidance
as to where to find media.
In my greenhouse there are Phalaenopsis
potted in ProMix, Fir Bark, and New Zealand Sphagnum, Cattleyas potted
in a Fir Bark, Charcoal, Treefern Mix and in Osmunda fiber, Oncidiums
in Lava Rock, mounted on cork, and in bark, and Vandas in baskets and
in pots with Osmunda. What is best? They are all best for the individual
plant and for their location in the greenhouse. Knowing what each plant
requires is what makes repotting so difficult and separates the novice
from the expert. The best advice is to look at what your plant is currently
potted in and use that mix if the plant is growing well. Eventually,
you may find another; better media, but that will take experience and
knowledge of what different types of Orchids require.
Always remember that most Orchids grow attached
to trees in nature and the job of the Orchid grower is to make the plant
believe that it is attached to the outside of the tree by supplying air
to the roots alternating with enough moisture to allow the plant to grow.
Once you pick a media and decide your Orchid needs repotting you are
ready to repot. Water the plant thoroughly before repotting. This softens
roots and makes removal from the old pot easier. It also gives the Orchid
a supply of water that will have to last until you water it again. Most
“how to books” recommend that you wet the media before using
it. DO NOTFOLLOW THIS RECOMMENDATION.
Begin by placing extra drainage in the bottom of the new pot. Some growers
use Styrofoam peanuts, lava rock, or broken crockery. Then place the
plant in the pot. If the plant is a Cattleya, Dendrobium, or Oncidium
place the oldest bulbs against the side of the pot and new growths toward
the center. This will allow maximum time for plant growth before you
need to repot again. Carefully fill the pot with the new media and press
down hard with your fingers. Do not bury the rhizome. It should be above
the media. Pound, yes pound, the media down with a semi-pointed piece
of broomstick and keep adding media until the roots are tight in the media.
There should be a half to an inch between the top of the media and the
top of the pot. You must convince the roots that they are attached to
a tree or they will not grow without being damaged each time the rhizome
moves when you water.
Phals, Vandas, and Paphs should go in the
center of the pot. Gently shake the media around the roots being careful
not to bury the base of the leaves in the media. Do not pack this media
with a stick or press down hard with your fingers. Gentle tapping usually
packs media tight enough for these Orchids. Vandas may need to be tied
in place as they are usually potted in very course media or placed in
baskets and pots with no media at all.
The admonition to use dry media is to prevent
bacterial infection through damaged roots. Dry media allows the root
to seal all of the damaged areas. The only exception is sphagnum moss.
Sphagnum moss should be moistened, but not dripping. Bacteria infections
are rare in this media because of the extreme acidity of the moss.
Repotting is not only important for the
health of the Orchid, but for the education of the hobbyist as well.
As you examine the degraded media and the old plant roots, you will begin
to gain an understanding of what your watering regimen has done to the
plant and the media and appreciate differences between media. Orchids
are fairly tough plants and usually survive repotting even by amateurs.
After a few years you will be able to use your experience to aid the next
group of amateurs.