sanderianum leaf growth speed....

[jrod]

The discussion of base vs. tip growth of leaves is pretty interesting. Another way I've been able to observe leaf growth regions is on "dirty" leaves. Often dust and grit will collect in the older leaf axils during slow growth periods. When faster growth resumes, you'll see a line of dust/dirt moving out from the crown of the plant. This is especially noticeable on monopodial plants, and plants which grow like a string of connected monopodials, like the paphs. Just my $.02

[IdahoOrchid]

Another way I've been able to observe leaf growth regions is on "dirty" leaves.

I treated the leaves of my charlesworthii compot with a natural product that is antifungal and bacterial. It left a red stain on the treated leaves and I have noticed that growing out as the plants mature. A nice thing to see on such tiny and delecate plants.