The same idea can be applied to the vegetable garden. Some gardeners plant beans to climb up corn plants, for example. And making successive plantings as crops mature keeps the soil in use the entire growing season. It's listed as Sorrel de Beleville. The Latin name for this perennial is Rumex acetosa.
People use the fresh young leaves in soups and salads.
Gather photos of the tree showing its overall habit and location, and a sample of the twig or leaf showing the problem. Many garden centers and nurseries can make recommendations. Another option is to consult your county extension office. To find it, check the phone book under county name or MSU Extension in the government listings section. You also may contact the Michigan State University Plant and Pest Diagnostic Clinic.