Gardening Answers Knowledgebase
Search Results for ' Pseudotsuga menziesii'
PAL Questions: 2 - Garden Tools: 1
I have some large second growth Douglas firs in my yard that were topped about 20 years ago. The last several years, almost all of them have developed pitch oozing down their sides from up high. What might be wrong with my trees, and what do you think I should do now?
Disease and pest diagnosis is impossible without actually examining the affected plant. However, based on the symptom of oozing pitch you described, these Pseudotsuga menziesii (Douglas fir) could be suffering from one (or more) of the following pests:
For a proper diagnosis you could hire an arborist. The Pacific Northwest Chapter of the International Society for Arboriculture has a directory of certified arborists.
You could also take many photos and a plant sample to a Master Gardener clinic. This is a free service run by volunteers trained by WSU faculty. Clinic locations and times can be found at this link.
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We have some Douglas Fir trees along a ravine. There is some construction nearby, and one of the trees is looking like it has been affected. It's losing lower branches and has much less new growth than its neighbors that are farther away from the construction. Is there anything we can do to save it?
It certainly could be compaction, though it is not possible to diagnose from a distance. However, symptoms of soil compaction damage include drooping branches, wilted or scorched foliage, and conifers dropping inner needles. This came from the Minnesota DNR's web site, which also discusses treatment. Here is an excerpt:
"Compaction can be partially alleviated by drilling a series of two inch diameter holes to a depth of 12 to 18 inches. Begin three feet from the trunk and continue drilling holes at two foot intervals in concentric rings around the tree and continue to at least the dripline. Each hole may be refilled with sand, peat moss or mulch. Don't recap the hole with a sod plug. There are other alternatives, such as soil injections of air or pressurized water, available from some professional tree care services."
A WSU extension formerly available online ("Construction Damage to Trees") explains that careful watering and fertilizing can help damaged trees, though it is best to help them before damage is noticed.
Another good resource is the University of Minnesota extension's "Protecting Trees from Construction Damage: A Homeowner's Guide." Much like the WSU resource, it discusses how to care for damaged trees and when to remove them, but in more detail.
Finally it would be a good idea to consult the Plant Amnesty referral service at 206-783-9813, or search for an arborist at the PNW International Society for Arboriculture site under "Hire an Arborist."
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Don't despair if verticillium wilt lives in your garden's soil because there are many resistant plants. A few verticillium-resistant trees include Apple and Crabapple, Mountain Ash, Ginkgo, Sweet Gum, Katsura, Douglas Fir, Arborvitae and White Oak. A long list of susceptible and resistant trees, shrubs, perennials and vegetables.
There is some evidence that broccoli (chopped up new shoots worked into the soil) can act as a soil fumigant, if added to the soil before planting. Studies were done by Krishna Subbarao at University of California, Davis, and showed reduced incidence of wilt in cauliflower crops where broccoli had been planted and its residue added to the soil.
Season: All Season
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June 24 2013 12:55:25