why do cattleya grow "up"?
 

I just repotted a larger sized cattleya and the rhizome is growing sideways as well as up. The old pseudobulb is at least 1/2 below the newest growth. Can anyone shed some light on this?

it is the nature of plants to 'reach' for the light....thats all i can think of....

Bingo!

I have seen them in Nature and they tend to grow on tree branches that slant up. 9 times out of ten, they dont need to reach for the light. I think it is the nature in which they have adapted over 160million years to growing in nature.

yeah - I think it's because, it you picture an orchid growing on a tree limb, that it would likely need to grow upwards along the limb (that's my theory, and I'm sticking with it!) ;)

seems many of the epiphytic, sympodial orchids do this to some extent - some more noticeably than others

That is exactly what these ones did, they grew up the tree limb towards the leafy end, in a line. And typically, that line would slant upwards with the tree limb.

Seabead,

Try mounting it if it looks as if it will grow from the pot, ive seen cattleyas mounted on single wine corks, bricks, terracotta tiles, styrofoam, almost anything!

The stepping upwards is a result of the nature of having to want to conform to the contours of the tree limbs they grow on.

The way the leaf tip points and the direction where the rhizome grows is usually in the general direction of the light source. If the plant is used to growing towards the light source in one direction, and then you switched the direction of where the light source is coming from, the plant will eventually change the orientation by which the rhizomes grow and the leaves point through the subsequent new growths.

For the sake of argument, if the light source is coming from the right, the leaves will generally point to the right. If the direction from which the light source is coming from is changed to the left, the Cattleya will eventually try to get the rhizome to generally grow in the new direction of where the light source is and have the subsequent new growths point its leaves to the left. This is a simplistic way to illustrate this phenomena btw.