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Plant Answer Line Question

Keywords: Prunus padus, Styrax, Laburnum, Davidia, Ribes, Larix, Chamaecyparis, Picea, Tsuga, Cedrus, Fagus, Betula, Flowering trees, Pinus, Ericaceae (Heath family), Conifers

Are there any lists of shrubs/small trees that are best viewed from below, such as Styrax or Halesia?


While there are no lists of shrubs/small trees best viewed from below, there is a list of trees with weeping habits in The Pacific Northwest Gardener's Book of Lists (Ray and Jan McNeilan, 1997). Many genera of conifers - Cedrus (cedar), Chamaecyparis (cypress), Larix (larch), Picea (spruce), Pinus (pine), and Tsuga (hemlock) - have weeping forms, often indicated by a variety name 'Pendula' or 'Pendulum'. There are weeping birches (Betula), beeches (Fagus), and cherries (Prunus), too.

You are correct about Styrax and Halesia. Additionally, I ran across a few individual species that may be of interest to you as I researched this question:
--Davidia involucrata
--Laburnum anagyroides
--flowering currants, Ribes spp.
--flowering cherry trees, particularly Prunus padus
--various plants in the Ericaceae family have bell-shaped flowers that hang on the underside of the stem.

I would add that any tree which has a naturally graceful branching pattern and/or delicately shaped foliage (such as Japanese maples) would be pleasant to view from below, as well as from other angles.

Date 2018-08-23
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Plant Answer Line Question

Keywords: Trees--Diseases and pests--Washington, Pinus, Master gardeners

Recently we noticed that one of our evergreen trees has a lot of needles that are turning yellowish brown and dropping off. I would say about 25% of the needles are affected, some in the middle of the branches, some at the ends. The needles are about 3 - 1/2 inches long and are in bunches of five - I think it is a pine.

Is this normal for that type of tree? Or is it more likely the tree is stressed for some reason and we need to deal with it?


This will be a lengthy answer and I will assume you live in the Pacific Northwest---the following information will not apply to other areas.

In order to get an accurate diagnosis you will need to take a sample of your plant (including both healthy and affected parts if possible) to a Master Gardener clinic.

Meanwhile, to learn about diseases common to pines in the Pacific Northwest, go to the Pacific Northwest Plant Disease Management Handbook and search using the term pine.
There are several possibilities with good photos. Remedies are included with each disease.

Insect information is more difficult to get, so following are the most likely-sounding pests:

1. Pine (Pinus) - Black pineleaf scale (Nuculaspis californica)

Pest description and crop damage
Mature scales are almost circular, 1/16 inch in diameter, and yellowish brown to black. Young hatch in spring and summer. Scale feeding is restricted to the needles and results in their becoming splotched with yellow patches. Heavy infestations cause premature needle drop and may result in death of the tree. Affected trees often display a thin crown, yellow or reddish coloration, and a shortening of the needles. This insect attacks various species of pine, ponderosa most commonly, as well as Douglas-fir and hemlock.

Biology and life history
This scale overwinters as an immature. The crawlers start to disperse to fresh foliage in spring. There may be one to three generations per year.

Management-cultural control
Trees under stress tend to be particularly susceptible to attack, as are trees growing in dusty conditions. Avoid creating these types of conditions.

Management-chemical control (home)
Dormant season:
Apply with enough water to cover the entire tree thoroughly.
1. horticultural oil. Apply during delayed-dormant period.
Growing season:
insecticidal soap

2. Pine (Pinus) - Eriophyid mites (Trisetacus spp.)

Pest description and crop damage
Eriophyid mites are tiny, wormlike, whitish or tan mites which feed under bud scales or in the needle sheaths, often between the needle bases. Symptoms of eriophyid mite infestations include yellowing, distortion, and stunting of new needles, and development of numerous buds where a bud has been infested (rosetting). Severe infestations may kill needles and cause needle drop, leaving naked branch tips. Rosettes may develop into witches' broom growths. Two-needle pines, particularly lodgepole or shore pine, are affected.

Management-cultural control
Prune out heavily infested growths.

3. Pine (Pinus) - European pine shoot moth (Rhyacionia buoliana)

Pest description and crop damage
Adult moths are reddish-orange with silver markings on the wings. The mature larvae are about 5/8 inch long and reddish-brown with black heads. The larvae of the European pine shoot moth feed on tips of branches, boring first into needles or bud bases, then into the shoots. Infested tips are covered with pitch-covered webbing, often develop a characteristic "shepherd's crook" shape, and may die back. Infested needles are yellowed near the twig tips and eventually turn brown and die. All pines are susceptible, especially two- and three-needle species.

Biology and life history
The insect overwinters as larvae in the mined buds, covered with resin-coated webs. The adult moth lays eggs on new shoots near leaf bases in the late spring. The larvae hatch and bore into the needles, which turn brown by summer. By midsummer, they are mining in the buds and cease feeding by August. There is one generation per year.

Sampling and thresholds: Check for yellowed leaves at shoot tips in midsummer.

Management-cultural control
Prune and destroy infested tips in spring, before adults emerge. Be sure to prune far enough down the branch to remove the insects.

Management-chemical control (home)
1. azadirachtin (neem extract)

Date 2018-09-26
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Plant Answer Line Question

Keywords: Pittosporum, Wind-tolerant plants, Morella californica, Arbutus unedo, Osmanthus, Pyracantha, Chamaecyparis, Arctostaphylos, Pinus, Cotoneaster, Ceanothus

I am looking for evergreen hedges that will tolerate a windy site. Do you have any suggestions?


Sunset Western Garden Book (2007 edition) has a list of wind-resistant plants. From that list, there were a few plants which meet some of your site's needs (evergreen, fast-growing, about 7-10 feet tall). They are:

  • Arbutus unedo (Strawberry tree)
  • Arctostaphylos (Manzanita)
  • Ceanothus
  • Chamaecyparis
  • Cotoneaster
  • Escallonia
  • Morella californica
  • Pinus species (you would need a dwarf pine for your size limits)
  • Pittosporum (many of these grow taller than 10 feet over time, but P. tobira might work)
  • Pyracantha

I don't know if it is tolerant of winter winds, but Osmanthus delavayi makes a nice, dense evergreen hedge with flowers, and reaches about 8 feet. It grows fairly quickly also.

Two good resources for finding more information on the plants above are Oregon State University's Landscape Plants and Great Plant Picks.

Also, I found an article (no longer available) on wind tolerance from Colorado State University Extension which may be of interest. Here is an excerpt about the physical characteristics of wind tolerant plants:

"When considering which trees and shrubs do well in windy conditions, examine the shape and thickness of the leaves, stems and branches. Wind-resistant trees usually have flexible, wide spreading, strong branches and low centers of gravity. Wind tolerant shrubs often have small, thick or waxy leaves or very narrow leaves (or needles), to help control moisture loss. Plant species that have large, flat leaves "catch" wind. These plants have a tendency for branch breakage when strong gusts blow, or if laden with heavy, wet snow. Evergreen (conifer) trees are an excellent choice, having needles and being flexible in high winds."

Date 2018-07-19
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Plant Answer Line Question

Keywords: Pinus, Nuts

Which pine species are the best for edible nuts? Are any of the pine trees that grow here in the Pacific Northwest possible sources? The cost of store-bought pine nuts is prohibitive, and it would be nice to be able to forage locally.


According to The New Oxford Book of Food Plants by J.G. Vaughan and C. Geissler (Oxford University, 1997), different species around the world have seed kernels which are used for edible purposes. In Spain, Portugal, and Italy, the main source is stone pine, Pinus pinea. In the southwestern United States, Pinus edulis (piñon pine) is used. In the western United States, the best source is Pinus monophylla, single-leaf piñon. Other species used include P. cembroides, P. cembra, P. gerardiana, P. sibirica, and P. pumila. But it is Pinus koraiensis (Korean pine) which is by far the most common variety exported worldwide. This has led to problems, and a recent New York Times article expresses concern that the pine nut industry is having a negative effect on the ecosystems of Korea and the far eastern reaches of Russia. If you can find local sources of edible pine nuts, you will be saving the bears and boars and chipmunks from famine!

Of the edible varieties mentioned above, local author Arthur Lee Jacobson (Trees of Seattle, 2006) lists Pinus edulis, Pinus cembra, and Pinus cembroides as rare in Seattle; mature specimens of stone pine (Pinus pinea) are also uncommon, but there are examples in the Washington Park Arboretum, Laurelhurst Playfield, and the Hiram Chittenden Locks. Korean pine is very rare in Seattle, with examples in the Arboretum, Woodland Park, and the Locks. (Bear in mind that harvesting plant material—including seed kernels--from the Washington Park Arboretum is not allowed.)

You might try growing a tree of your own, selecting one of the species known to thrive here. The tree would have to be 10-15 years old in order to produce usable seed kernels. This permaculture website has information on growing pine trees for their edible kernels. You will need some patience and dexterity (it takes time for pine nuts to mature, and it takes skill to harvest them).

Date 2018-09-12
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