Asked October 10, 2015, 8:09 PM EDT

i have 6 walnut trees and some years i get at least one large onion sack of nuts per tree but this year i got one for all six trees. am i supposed to fertilize with something? or is there something else going on?

Clackamas County Oregon

1 Response

English walnuts trees in Oregon are damaged by spring frosts some years. My mom's trees in Yamhill county have many nuts this year but frosts are often very localized, so that could be what happened to your trees. Is your crop generally consistent or does it seem to vary? Consider keeping a log of temperatures during the spring bloom times, perhaps a connection with will be clear. Attach a photo of ypur trees as perhaps other cultivation issues are evident. A prior answer in Ask an Expert about walnuts mentions that pollination can be low if the temperatures are very warm at that time, and this spring was early and hot, generally. I will post the answer to a client from about 4 years ago. It may prove helpful to you: "Even though black walnut trees can set nuts on their own, English walnuts require a different cultivar of English walnut within 100 to 200 feet which will supply pollen. (Other names for English walnuts are Carpathian walnut, Persian walnut and soft-shell walnut.) So, it might be that the pollenizer (the tree with the pollen) was on a neighbor’s property but has died or has been removed. Another possible reason for limited nut set is that the catkins (male flowers) didn’t shed their pollen when the female flowers were receptive. But from what I’ve found through my research, this is more likely to happen during unusually warm years, an uncommon event during recent years in our region. Another potential complication is that excess shade from dense branching or other reasons will reduce flower production. English walnuts require full sun. These publications from Oregon State University may provide additional clues: - “Growing Fruits and Nuts in the Home Garden” http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/13718/EC%20819.pdf?sequence=1 - “Growing Walnuts in Oregon” http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/20433/em8907.pdf "