Question
I have a river birch that has three distinct trunks about 5 inches in diameter each.  About two years ago I cut one of the trunks to about 3 feet off the ground.  The cut trunk just fell over and and I notice considerable rot.  In fact the rot extends about a foot into the ground and is about 3-4 inches in diameter.  Will I lose the rest of the tree?  If the rest of it falls at an inopportune time it will do some damage to a patio.  Should I cut the rest of it down?

Thank you

Answer
Pruning a trunk or branch not flush with the trunk or solid wood or leaving a long branch stub will allow decay fungi to enter the trunk. The wound can not heal over a stub. In this case the decay fungi has grown into the stump of the cut fork and if it enters the other forks this low on the trunk it can cause the trunks to become weakened and the roots can not hold the tree up. I think you may see some leaning or cracking of the other trunk near the ground before they break. IF you like the tree I would fertilize it with 10-10-10 fertilizer at the rate of 1 lb of fertilizer per inch of trunk diameter scattered around the tree and watered in good. Apply just before a good rain strom and you will not need to water. Fertilize this Fall and again in the Spring. This will increase the root health and help the tree have a better foundation and strength. If you see problem then you can always cut the trees.