Although there does not seems to be a definite answer, this is probably due to organic aromatic compounds from lignin degradation (such as humic and fulvic acids). Other vegetal organic pigments such carotenoids and anthocyanins may also take part in that.
Roots are brown because they do not have chlorophyll which gives the green color to the plant.The plants are green because they contain chlorophyll its as simple as that.
because it is, well little trolls came and painted brown on every tree seed before they planted then they sped on segways
because dogs, cats and people keep taking craps on it
because the sky is blue. because with all the organisms, and dead plant materials mixed with everything else turns brown.
The leaves are dying
description of the leaves
A big dog pooped in the mud.
the tree stops making chlorophyll in the winter. (the chlorophyll is the stuff in the leaves that makes them green)
An olive tree has a light brown stems with kinda lightish darkish colour leaves. With olives of course.
Looks like you neglected the watering.
Does the tree need more watering?
You can't.
Possibly lack of moisture at the roots.
black spots on the leaves?
description of the leaves
Is Epsom salt good for Tibichina Tree with a lot of flowers but drooping leaves?
A wax myrtle tree my develop brown lesion on its leaves when infected with a leaf spot disease. The tree will regrow new leaves once the infection has cleared.
I have a four clump white birch tree which we planted seven years ago. The tree has been beautiful and about fifteen feet tall. THis year three of the clumps did not get leaves on and the clump that did get leaves on the leaves are brown and dying. What could have happened?
if it its leafs are turning brown then that probably means that it is sick or is not getting enough light.
Try some Epsom Salts this may be a Magnesium deficiency.
The tree goes dorman in winter.......
The leaves turn shades of red,yellow, orange & brown. Then the tree slowly sheds its leaves. The leaves fall of the tree and the tree is completely bare.