I enjoy reading your column in SO. Here's my question: how do you pot your cattleyas?
Thank you very much for your positive feedback. Let me see if I can help you with your cattleyas.
First: try to re-pot only after your cattleya has bloomed, and before it starts to send new growth. The cattleya always sends out new growth right after a bloom.
Trim the old roots and remove dead ones, also remove soggy medium.
Pot size should be just as you would guage a child's clothes — enough room for a year's growth — no more, no less.
The medium can be one of the following or a mixture of both, which is usually called orchid mix. Whichever one you choose, soak in water for two hours, as dry mixture sucks the moisture from the plant, and you don't want that.
Charcoal, tree fern bark, each with a few pebbles.
Put a little into the pot, and hold the plant with your left hand, hold the orchid roots on top of the mix while pouring the mix with your right hand, ease the plant if it is being covered too much, as you don't want the crown (heart) of the plant to be covered; in other words pour the mix around the plant , not on top of it.
Whenever you repot your cattleya, do not water for two to three days.
The morning sun is very important to the cattleya orchid, but not direct sunlight, which will burn the leaves. Give them about the same light you would a dendrobium 50/50, increase humidity by using plastic to cover roof.
Water cattleyas only when the medium is dry; however, cattleyas need more water just before and during the blooming period.
What is the best fertiliser to use on my orchids? What kind of fungicide and insecticide must I use to keep insects and fungus off my orchids, and also how regularly must I use it?
Your questions cannot be answered directly.
As I have often said, just as you cannot get all the nutrients for your body from one type of food, the same goes for fertilisers. One has to know what is required for and of the plant. You may require the plant to bloom, hence you would want to give it bloom booster, or the plant might need a little nitrogen if it is on the yellow side; maybe you might want to give it some vitamins as in Superthrive.
What I am trying to say is, do not give your plants just one fertiliser. Try to feed it with different solubles, as one won't be good enough, and it won't have all the nutrients. I fertilise three times per week, maybe you can give a different one each time.
I usually suggest a fungicide that prevents root rot. I am most afraid of root rot especially in the rainy season. A good one is Phyton 27, but this is not the only one you will need, as your orchids will get sick from other fungi from time to time. When this happens, you will need to get a fungicide for that specific fungus from the farm store (take along a leaf in a zip lock bag). I use fungicide once per week, but during the rainy season I use it twice per week.
I'm suggesting that you use an insecticide that is good for the control of thrips and mites, such as Newmectin. It works like a charm and can be bought at your farm store. When other insects attack your orchids, head for your farm store. Remember, there is no general insecticide or fungicide that will treat all pests. You use insecticide only once every two weeks to prevent, and once per week to get rid of insects.
Betty Ashley is an avid orchid enthusiast who has spent decades successfully cultivating orchids for herself, as well as for orchid lovers across the island, earning herself the title 'Orchid Doc'. Send your orchid questions and/or concerns to: firstname.lastname@example.org.