Hi. I live in Bend in the Ponderosas. A year ago I planted 4 aspens and a maple. Today I planted a crabapple and 2 more aspens. I haven't fertilized them yet, just compost mulch. I have fertilizer tree spikes. Is it recommended to fertilize my trees this fall? The year old ones? The newly planted ones? Thanks, Steve Dyer
Deschutes County Oregon
I don't know if the ponderosas is a neighborhood, or if you live among many ponderosa trees, but please know that aspen (and crabapple for that matter) need ample sun to thrive, so fertilizing won't do any good if they don't have the right growing environment. Some maple tolerate shade depending on the variety.
OK, now on to your other question about fertilizing your trees.
You can fertilize your young trees with a slow release fertilizer in the fall, but you will want to wait until the trees are beginning to show signs of shutting down, you don't want to encourage a flush of growth that could result in tree damage with a frost. Also make sure to fertilize away from the trunk of the tree and out past the dripline to encourage root growth.
I recommend "Fertilizing Shade and Ornamental Trees" by Oregon State University Extension Service for more tips and good photos on how, when, and with what to fertilize. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/16953/fs103.pdf
Best of luck!