Fertilizing Japanese Maple trees

11 years ago

We have japanese maple trees in containers on our balcony. Two of the JM, their leaves have fallen almost all off. We think the leaves have fallen prematurely though maybe someone can advise? Also, we haven't used any fertilizer on our JMs, which we got at earlier this year (2012). When should they be fertilized? I was planning to get Espoma Tone Tree Food and see if that will help.

Also, one of the JM has white powdery mildew on its leaves. Any recommendations as to what I can use to get rid of it? If the leaves are falling, will the white powdery mildew affect the JM when it grows new leaves in spring?

Comment (1)

gardengal48 (PNW Z8/9)
11 years ago
Nothing premature about a JM losing leaves by late November.....rather, I'd be very surprised if they hadn't!

Any plant grown in a container will need routine fertilization. There are insufficient nutrient levels in potting soil to begin with and every time you water, you leach out what may be there. Unless it is a water soluble formulation, organics (like most Espoma products) do not work very efficiently for container plantings. I use a slow release like Osmocote when potting up and then again seasonally each spring for all my potted trees. I also supplement during the growing season with a water soluble product - all work about the same - around once a month or so or when I fertilize my seasonal and edible container planting.

Powdery mildew is a seasonal ailment, usually appearing in late summer or fall when conditions are dry but evening humidity high. Making sure the containers receive adequate water at that time of year is important - that can greatly reduce the incidence of PM. Also, adequate air circulation (don't crowd the plants on your balcony). Gather up and dispose of any fallen leaves and don't worry about overwintering spores. Not enough of a concern to be an issue :-)