Leaves splitting

[TracyLee9]

Just a quick question...was wondering why leaves split down their centre from the ends. I read that this sometimes happen with big, older, heavier leaves...and I've seen this happen with a couple of mine...but now I see one of my new leaves is splitting. It's just about to drop it's last flower (after 4 months in bloom) and is otherwise healthy, I think. Is leaf splitting anything to worry about? Can it be prevented?

[tryingtoflower]

I too had this happen on a new growth on a cattleya. I hope someone can solve this problem for us.

[Cym Ladye]

Leaves on Cyms will bend and split due to lack of light, too much nitrogen or not enough other nutrients to maintain a strong core. Needless to say, anything falling on them may also cause breakage or splitting, but I do not think that is what is pertinent here.

CL

[jeremyinsf]

One of the causes is low humidity and/or rapid changes in humidity.

[TracyLee9]

Perhaps it is time to repot...it's been in there for 2 years now and I can't actually see inside...will put it in a clear pot next time.

[Cym Ladye]

Originally Posted by jeremyinsf

One of the causes is low humidity and/or rapid changes in humidity.

Why do you feel this would contribute to leaf splitting?

[Ray]

Originally Posted by Cym Ladye

Why do you feel this would contribute to leaf splitting?

One hypothesis is that the leaf cells at the surface "harden off" and become less flexible in low humidity, so cannot "give" as the interior swells.

It happens in tomatoes that receive too much late-season rain, but I don't know the validity of that with orchid leaves.

[NYCorchidman]

Unless the humidity is super low as in the desert, and the plants that are not from desert are exposed to such low humidity, I don't think it is responsible for cracking on the leaves.

I haven't seen any on my plants of any kind even during the winter when the indoor air gets quite dry.

Plants are covered with cuticle layer which does not easily split because of low humidity found in common household.

With this said, I have bought many cattleyas from greenhouse growers where the humidity is kept fairly high at all times and these plants had some terrible cracks and splitting on the leaves.

I believe it is usually mostly due to mechanical damage, plus what CL mentioned contribute to splitting of leaves.

[Oskar]

Originally Posted by NYCorchidman

Unless the humidity is super low as in the desert, and the plants that are not from desert are exposed to such low humidity, I don't think it is responsible for cracking on the leaves.

I haven't seen any on my plants of any kind even during the winter when the indoor air gets quite dry.

Plants are covered with cuticle layer which does not easily split because of low humidity found in common household.

With this said, I have bought many cattleyas from greenhouse growers where the humidity is kept fairly high at all times and these plants had some terrible cracks and splitting on the leaves.

I believe it is usually mostly due to mechanical damage, plus what CL mentioned contribute to splitting of leaves.

This is just speculations:
Maybe if the plant experience a dry period and then gets thoroughly watered it's cells swell to a point where the cuticle layer have adapted to the earlier "size" of the leaves and then cracks?

English isn't my first language so i hope i could give a decent explanation of what i meant.

[NYCorchidman]

That is definitely a possibility and called micro fissure, especially on the orchid roots. One reason not to let orchids (especially the terrestrials) bone dry too long, as micro fissure gives easy access for pathogens to enter the broken tissues.

However, I don't think it would cause such massive scale split as the one that the original poster described.

I have had a phal that got ignored and the leaves got all wrinkly a bit, then after I soaked it well and there were no split of any kind developed.
The same goes with my oncidiums and dendrobiums and cattleyas on their pseudobulbs.

I believe the cuticle layer is somewhat flexible in that once the plant tissues shrinks a little bit due to dehydration, it has no problem shrinking a little and then plump back up when the internal pressure returns.

Tissues that developed under low water condition may mature "hard" and smaller than ideal, but then once mature, they will not increase in size even when there is enough water supplied later on.

Even within the same leaf that is still growing for example like an onsidium leaf, the part that grew while being underwatered may crinkle up a bit, then when the watering is done properly, the crinkled up part won't get fixed but stay that way while the new part of that same leaf will grow out normally.