Xtremehorticulture

Xtremehorticulture of the Desert

African Sumac Limb Disease

Leave a Comment / branch dying, dead wood, strong crotch, weak crotch, wind /

Q. My African sumac tree has a fungus in it. I am thinking of cutting off the whole main branch because of the disease but it’s a guide branch and I hate to do that. Or can I just cut off the branch that broke? Any info you have would be greatly appreciated! Bottom picture is limb of African Sumac reportedly dead. The top picture is the inside of the limb cut open to show the dead part inside. A. The disease won’t spread to healthy parts of the plant. The rot or disease spreads internally inside the tree because it’s what we call “saprophytic” and only attacks dead or very weak wood. There is nothing you can do to stop it. Tree Biology             The center of the tree is composed of dead wood. The only living part of the tree is a thin ring just under the bark. This living part is strong enough to stop the spread of this “saprophytic” disease. The only thing you can do to help your tree is to make sure that whatever you use to cut or prune the wood is as clean and sharp as possible. Narrow crotch angles are not good in landscape trees. They are shaped like the letter “V”. After time they start to split as their weight increases and rot can begin on the inside of the trunk. Narrow crotches start to split during the wind and its internal dead wood begins to rot. This rotting will not affect the living parts of the tree. Only the dead parts.             My guess is that this “rot” started at the top of a narrow crotch; where two limbs come together. Narrow crotch is making the letter V when you look at it. Week crotches can split in strong winds particularly if the inside of the tree has been starting to rot there. A strong crotch angle makes the letter “U” and less likely to start rotting in that spot and then split apart in strong winds.              Prune it enough to shape the tree the way you want it. Just cut off the branch that broke very close to the next larger branch and let it heal and completely close it off in three or four years. It takes longer to heal if it’s not cut close to the trunk so there is no longer a stub remaining. If the tree looks healthy to you otherwise then don’t worry about it. Cut off the limb close to the trunk with a clean blade.

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My Tree Trunk Is Dying from the Inside to the Outside

Leave a Comment / cambium layer, dead wood, heart wood, Tree trunk, tree trunk rotting /

Q. What’s wrong with my tree? The tree trunk is dying from the inside to the outside. A. The vast majority of trees are dead in the center of their trunk as they get older. This dead interior gets larger and larger as the tree gets older.The dead inside of the tree is covered by a thin layer that is living. This living thin layer is constantly getting bigger and bigger in diameter. To the inside of this thin layer, the dead wood is left behind. This occupies the vast majority of the center of the tree. Living part of the tree on the outside of the trunk growing over the dead inner portion of the tree             The only living part of the tree is a cylinder of living wood just below the bark. The living cylinder of wood can heal itself. The center part of the tree, which is dead, cannot. If this cylinder of living wood is damaged and the dead center of trunk is exposed, it can become infected. About 90% of the time this infection cannot spread to the living cylinder of the tree.This is because these infections only feed off of dead wood, not living tissue. The only living portion of this tree trunk is the green cylinder close to the bark             The dead interior of the tree rots. The living cylinder stays healthy. The dead center rots away leaving the center of the tree hollow. A tree like this can live for decades with the center of the tree gone or rotted. But the strength of the tree is compromised. It is more likely to be damaged during heavy winds that cause “shearing” damage. Hollow cylinders have good “compressive strength”, but poor “shear strength”, Here is the trunk of a Chinaberry tree. It has been damaged enough to expose the dead inside of the tree.             Normally, we don’t pay much attention if the center of the tree is rotting. We get concerned when the living cylinder becomes infected. From the pictures you sent, it looks like the dead interior is under attack. To me, this appears to be normal for a tree which has its center rotting out.

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Pruning Boxwood and Rosemary Hedge Can Result in Disaster

Leave a Comment / dead wood, pruning hedge /

Q. I have a neighbor concerned about his rosemary and boxwood hedges. He has been having trouble with the foliage browning and falling off. His landscapers recommend he cut them to the ground but he opted to cut them back by half instead and let them regrow. Can you tell me a little about these and your opinion about how to properly care for and what he should do to get them looking their best again? boxwood A. When rosemary and boxwood, or any plants for that matter, are continuously pruned with a hedge shears it causes them to get thick and bushy at the point where they are continuously sheared. This increases their density on the outer edges of the plants.             Shearing causes the interior of the hedge to become very dark. This darkness cannot support leaf or new stem growth. The older stems on the inside of the hedge drop their leaves.             All the new growth occurs only where it is sheared. Perhaps only an inch or two of the outer surface of hedged plants have leaves. The dark interior is leafless.             If we cut too far back into the hedge we expose the older wood that has no leaves. The wood is alive, but without leaves. Once this interior wood begins to receive sunlight again, new growth will usually occur on the older wood.             The rate of recovery of this older wood depends on the plant. Rosemary will come back faster than boxwood. rosemary             He will start to see growth coming from older wood exposed to sunlight as suckers. In technical terms we call this adventitious growth. Boxwood will do the same thing but it is much slower to react and fill in.             If he is patient he will see new growth slowly fill in the canopy.             If he had cut it back close to the soil surface, the same thing will occur on the Rosemary but it will be slow to grow back into a hedge. Boxwood will even be slower.             In cases like these most people do not want to look at a hedge trying to fill back in and would elect to replace these plants.             Once plants are cut with hedge shears for a couple of seasons they are very difficult to reestablish again as plants that are no longer a hedge. The interior of the hedge is just too woody.

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