Question
My Magnolia "Yellow Bird" which has been growing well for 14 years has suddenly developed brown leaves and evidence of dieback. We have had regular Vancouver spring weather- rainy. Only cultural difference this year is a light top dressing of a local compost, sand and mushroom manure mix. Any ideas what is happening? Thanks

Answer
Magnolia trees like more acid soil. Magnolias like acid soil (5.0), so there might be a pH problem. Soil test kits can be found at most garden centers. Sometimes yellow or very dark green leaves can be a sign of a pH imbalance. And the local compost and the mushroom manure will usually be more alkaline and change the pH of the soil. This will depend on the make up of the compost and the age of the compost. I would say that maybe your problem. alkaline and change the pH of the soil. This will depend on the make up of the compost and the age of the compost. I would say that maybe your problem. pend on the make up of the compost and the age of the compost. I would say that maybe your problem. Here is a web link on how to lower the pH of a soil. Removing the compost if you can will also help.

http://www.ipm.iastate.edu/ipm/hortnews/1994/4-6-1994/ph.html