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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Insect pests--Identification, Pseudotsuga menziesii, Master gardeners

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:

Fir Beetle

Pitch Moth

Twig Weevil

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 website (Plant Clinic Schedule).

Date 2017-08-15
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Plant Answer Line Question

Keywords: Soil compaction, Trees--Care and maintenance, Pseudotsuga menziesii

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."

Date 2017-08-08
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Plant Answer Line Question

Keywords: Abies, Edible wild plants, Pseudotsuga menziesii, Ethnobotany

There seems to be a new fad of local foragers making tea from the needles of Douglas fir and Grand fir. I am guessing there are Native American origins to this practice. How safe is it, especially in an urban environment? Are there supposed to be benefits to drinking this kind of infusion?


There is a deep tradition of ethnobotanical uses of various parts of both Douglas fir (Pseudotsuga menziesii) and Grand fir (Abies grandis). Nancy Turner's book, Thompson Ethnobotany: Knowledge and Usage of Plants by the Thompson Indians of British Columbia (Royal British Columbia Museum, 1990) says that "a beverage tea was made by boiling Douglas-fir twigs with their needles. This tea was said to have tonic and diuretic properties."

Turner says there is a great deal of confusion surrounding both the English common names and Thompson Indian names for various fir species. This makes it difficult to know which species were intended for which uses. An infusion made from the boughs of a species that might be Grand fir (Abies grandis) "could be drunk for any illness." In Ethnobotany of Western Washington (University of Washington Press, 1973), author Erna Gunther notes both distinctions and confusions between Abies grandis and Pseudotsuga menziesii: according to the Green River informant she consulted, tribe members boiled Grand fir needles as a tea to treat colds, but a Swinomish informant believed Grand fir and Douglas fir to be the same species.

Douglas fir and Grand fir are not mentioned in Toxic Plants of North America (George Burrows and Ronald Tyrl, Wiley-Blackwell, 2013), but a plant's absence from a list of toxic plants does not mean that it is risk-free. Common sense says it would be best not to gather needles from urban trees that are not your own, since there is no way of knowing whether those trees might have been sprayed with pesticides, or exposed to air pollutants.

According to Stephen Facciola's Cornucopia II: A Source Book of Edible Plants (Kampong Publications, 1998), tea made from young foliage and twigs of Pseudotsuga menziesii is both refreshing and high in vitamin C. He says that the young branch tips of various species of Abies, including A. grandis, are used as a tea substitute.

I could not find reliable information about the recommended quantities of needles to water, ideal length of boiling time, or chemical properties of needles used for tea. Elise Krohn, author of Wild Rose and Western Red Cedar: The Gifts of the Northwest Plants (self-published in 2007) has information on her Wild Foods and Medicines blog about "making evergreen tree tip tea." My advice would be to proceed with caution and consult a medical professional in case a coniferous tisane might have potential interactions with other substances. (Even a popular beverage like Earl Grey tea can be problematic due to the Citrus-derived bergamottin which interacts with some medications).

Date 2018-04-11
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Garden Tip

Keywords: Biofumigation, Quercus alba, Malus sylvestris, Verticillium, Ginkgo biloba, Liquidambar, Katsura, Fraxinus, Pseudotsuga menziesii, Malus domestica

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.

Date: 2007-05-23
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May 23 2018 14:32:42