Do spent leaves still photosynthesize ?

[Mike Corazzi]

This is a Robur oak.

I am calling the leaves "spent" as opposed to "dead."
I read conflicting advice as what to do with them. Some say leave them on and wait for new ones to push them off.
Also some say to remove them.
Are they still "working" and providing good things for the tree or not?



And if ...remove... cut or pull them off?
Sure are a bunch of them.

 

[dbonsaiw]

The green we typically see in the leaves is from chlorophyl which performs the photosynthesis. No green = no chlorophyl = no photosynthesis. (Note: leaves changing color still have chlorophyl, but has carotenoid or xanthophyll pigments that provide the different colors.

Not sure if removing the leaves makes a difference in budding etc., but I typically just cut the petioles. I remember reading somewhere that marcescent trees keep their leaves to keep the deer away and protect the buds, but not sure if that is true.

 

[Mike Westervelt]

Agreed, if brown and withered not providing the tree with anything, I also have heard the leaves remain in place to protect new buds, definitely wouldn't pull the leaves, could damage buds, if they bother you, best to cut as dbonsaiw said.

 

[tigerscott79]

oaks that drop leaves in spring versus fall/winter keep them to protect the forming buds that swell in spring . imho what ik of oaks , they are keeping the buds safe and its natural protection, given bonsai are ever more succeptiable to natures effects of cold and wet and drying out via winds (depending where you live) id suggest to leave them be . it only protects the bonsai further and like above stated can damage the forming buds causing more harm then good. unless your keeping it in a damp cellar for the over wintering process the leaves wont mold or rot thus removing them is bad not a good thing, only other reason to remove them would be if the plant is infected with pests. often people try to tidy up nature and end up doing alot more harm then good . personally leaving it only helps the plant. but correct spent leaves serve no purpose further to photosynthesize as they no longer are alive or have active chlorophyll working however again they are used now to protect the forming buds . so in end its your call but i honestly would leave it . extremely rarely does leaving them on trees til spring cause any bad issues and removing them is more likely to adversely affect the tree itself.

 

[Mike Corazzi]

I clipped early this year and all it did was make leaves smaller. I also have heard of the protecting buds.

Bigger leaves


clipped



smaller leaves after clip



I'll TRY to let them drop this year. Maybe.

 

[Shibui]

Leaves without green are not producing food for the tree.
They can be clipped off but that's a lot of work. Unless you really want to see the structure leave them to fall naturally.
I've also seen the theory that the leaves are held through winter as protection for the buds. Not sure if that's proven or just someone's bright idea. With bonsai you're likely to provide some cold protection for the tree anyway so leafy cold protection may not be needed.

 

[rockm]

This is a Robur oak.

I am calling the leaves "spent" as opposed to "dead."
I read conflicting advice as what to do with them. Some say leave them on and wait for new ones to push them off.
Also some say to remove them.
Are they still "working" and providing good things for the tree or not?

View attachment 524506

And if ...remove... cut or pull them off?
Sure are a bunch of them.

Trees that hold onto their dead leaves in winter are called "marescent." Beech trees are the obvious marescent species. The persistent leaves can happen on many trees--my Korean hornbeam and some kinds of trident maples sometimes retain their leaves after the leaves die in the fall off, for instance

The reason for this is not really understood. Some say it helps protect new leaf buds on the branch from colder weather, for instance. If the leaves are brown and crunchy, they're not functioning. They're dead. You can remove them if you want. Sometimes they come off easily, other times not.

 

[Paradox]

This is a Robur oak.

I am calling the leaves "spent" as opposed to "dead."
I read conflicting advice as what to do with them. Some say leave them on and wait for new ones to push them off.
Also some say to remove them.
Are they still "working" and providing good things for the tree or not?



And if ...remove... cut or pull them off?
Sure are a bunch of them.

If they are not green, they are no longer photosynthesizing.
I typically remove all the dead leaves from my trees before I put them to bed for the winter.
If they are particularly stubborn and dont want to come off easily (ie Beech), Ill cut the petiole which will fall off when its ready.
I do this to help keep the cold frame a bit cleaner over the winter.

 

[Glaucus]

It is not true that if they are not green, they are no longer photosynthesizing. Yes, chlorophyll is green, so green means a lot of chlorphyll. But a non-green colour doesn't mean there's zero chlorophyll. It could mean there are other pigments that dominate. So indeed less green than normal will mean less chlorophyll than normal, and less photosynthesis than normal. But it doesn't mean zero.

That said, leaves that are dessicated are dead, like on Carpinus. So there no photosynthesis happens there. But a red maple leaf, it may still have photosynthesis happening.