Completely topping a plum tree is a risky business. Cut too much, and you’ll kill your tree. That said, you do need to trim the top of your tree to encourage bushy growth, maintain your tree’s vase shape, and limit size. 

A plum tree's central leader (or trunk) should never extend more than 3 feet above the highest branch. When you first plant your tree, cut the central leader so it’s 2 to 3 feet tall. As it grows, cut it back 12 to 20 inches until it reaches its desired height. Never prune more than one-third of the new growth.

White vinegar does not kill ivy on trees because its acetic acid concentration is not high enough to overpower it. Vinegar is an effective herbicide for weeds and other plants, but not for the strength of most ivies, including poison ivy and English ivy. You should use an herbicide to kill ivy, such as one with glyphosate, imazapyr, or triclopyr.

The amount of time it takes for a tree trunk to rot depends on several factors, including the tree’s size, species, and environmental conditions. It can take anywhere from a few years to several decades for a tree’s trunk to rot. A tree stump, on the other hand, can take up to 10 years to disappear after it’s decayed naturally.

The average lifespan of an oak tree is 100 to 300 years, so long as it isn’t impacted by diseases like sudden oak death. Some species will last shorter or longer, depending on where you live.