mesquite tree is oozing black sap

Question

My mesquite tree is oozing black sap in several places where it was pruned. It’s staining my new patio stone. It’s been doing this for the past 3 years–it’s not slime flux, as it has no odor. How can I divert this sap to drip on the soil next to tree instead of patio? I have put containers to catch some of the sap but it is a mess and people will trip on them. This particular mesquite tree is very old–probably 60 years or so. There is no odor to his sap and it’s more watery than sticky. The patio was installed this past summer so it previously dripped on the soil where it was absorbed and was not a problem.

Answer 1

The flow of black sap is a common occurrence for old native mesquite trees. It can happen at any time of the year, but more often in the spring, which is also a time when a lot of trees start flowing sap after a period of dormancy. Since the sap has no smell you are probably correct in that it is not slime flux. A strong smell would indicate the presence of bacteria. Drainage tubes used to be a remedy for this issue but are no longer recommended.

Does the flow still happen on hot dry summer days? I have read that the flow of the sap may be related to the amount of irrigation that the tree is receiving.

Do your trees look healthy? Is there wilt or dieback on the branches, is the bark dying? If any of these conditions were happening I would suggest things like bacterial canker or borers which are discussed in the link below:
https://www.gardeningknowhow.com/ornamental/trees/tgen/what-is-tree-sap.htm

However, I do think what is happening to your tree is a normal occurrence and there really isn’t anything you can do to stop that sap from flowing.

For more information on the care of mesquite trees, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/mesquite/growing-mesquite-trees.htm