Repotting Cattleyas

Repotting Cattleyas can be tricky.  A Cattleya orchid grows by sending out new "eyes" or meristematic growth from a pseudo-bulb.  The plant grows laterally.  In nature, Cattleyas grow on trees.  And like most tropic orchids, they are epiphytes.

You'll need a couple of things when you go to repot your Cattleya orchid.  Here's a list of useful things:

70% Isopropyl Alcohol or weak 10% Clorox bleach disinfectant solution in a plastic container
Sterile razor blades
Sterile hand sheers or Exacto knife
Polystyrene peanuts (plastic foam chips) that aren't biodegradable
New plastic orchid pot 2" bigger than previous pot (6" to 8" should be the largest size you'll need)
Bag of Orchid firbark
Old newspaper to cover your workspace

1)  Place newspaper to cover your workspace.
2)  Look at the Cattleya.  Make sure its a candidate for repotting.  Has it outgrown its pot?  Are new roots visible coming out of the pot?
3)  Take the plant out of the pot.  You can tell if the plant needs to be divided if there are at least 7-8 pseudo-bulbs on the plant.  If not, don't divide the plant.  If there are enough pseudo-bulbs, divide the plant so each new division has at least 3-4 pseudo-bulbs with leaves.  Use sterile razor blades or exacto knife to divide the plant. 
4)  When you take the Cattleya out of the its old pot, look at the roots.  Remove any old fir bark media from the roots by gently picking away the rotting media.  Once that is done, make sure the root bulb (or root mass) isn't rotting.  Trim away dead roots with sterile hand sheers or razor blades.
5)  Once you have your orchid ready, line the base of the new pot with polystyrene chips.
6)  Place the Cattleya in contact with one side of the pot.  Making sure not to damage the lead growth (or eye). 
7)  Place fresh fir bark into the pot with your fingers.  Make sure not to cover the "eyes".  Leave a 1" gap at the top of the pot for watering.
8)  Water the pot so water drains away from the orchid.  The Cattleya's roots shouldn't be standing in water.  Root rot is the quickest way to kill an orchid.

Some advice.  Make sure you sterilize your razor blades and hand sheers before you start working.  This prevents infection and the spread of orchid viruses which can ruin the Cattleya flower.  I water about once a week.  I use an orchid fertilizer for fir bark.  I fertilize at 1/4 strength every 4th watering.  I use a calendar to tell me when to water.  I find this works best for plants that are grown under artificial lights and indoors. 

If you're interested in learning more, go to the American Orchid Society website:  AOS.org or contact the Orchid Society of Greater St. Louis.