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Gardening Answers Knowledgebase

Plant Answer Line Question

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

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 2017-05-11
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Plant Answer Line Question

Keywords: Plant identification, Betula

Are there any tree identification guides online? In particular, I am interested in weeping birch.


For several excellent images of weeping birch (Betula pendula), go to Oregon State University's http://oregonstate.edu/dept/ldplants/>landscape identification site and click on Betula pendula. Look at all the images associated with this species of birch.

Also try Virginia Tech's tree identification page.

Here are some other online tree identification guides:
What Tree Is It
University of Wisconsin's Tree i.d.
Cal Poly's Urban Tree Key

Date 2018-06-22
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Plant Answer Line Question

Keywords: Aphids, Betula, Trees--Diseases and pests

I have just taken over management of the small landscaped yard for my condominium and we have two trees (weeping birches I've been told) in the front that appear to have been infested with aphids. The trees are about 15 feet tall and are located between the building and the sidewalk to the entrance. They have southern exposure. There's a few evergreen bushes around the trees, no grass.

I am not familiar with aphid controls, so have done some internet research, including your very useful site. We want to avoid using pesticides, so from what I've read, the best control is insecticidal soap. Before I try to spray this on the trees I have a few questions I was hoping you could answer. 1. Can you verify that this is aphid damage? 2. It seems to me that the amount of white material on the undersides of the leaves has decreased in the last month. Given that it is getting late in the growing season, is it still worth treating the trees? 3. Does insecticidal soap seem like a good treatment in this situation, and if so do you have any application tips to make sure the undersides of the leaves are treated?

4. Do you have any recommendations for preventative actions to decrease the impact of aphids on these trees in the future?


Birches are commonly afflicted with aphids, and the aphids suck sap and secrete honeydew, which can be a nuisance, and is usually why homeowners contact us. Unfortunately, if your birches are overhanging a sidewalk, it is probably getting sticky from the honeydew. Otherwise, you could probably ignore the problem (except in the most severe infestations).

You can try spraying the aphids off the leaves with a strong jet of water. You can also encourage natural predators. Avoid over-fertilizing, or exposing the trees to lawn fertilizer, for example, as this will lead to succulent new growth which attracts aphids. Make sure the trees are not under any stress, as aphids are more likely to feed on a weakened tree. You may be able to avoid using the insecticidal soap as a control. If you do use it, you are correct that you need to reach all leaf surfaces, which is labor-intensive. Some of these soaps can cause damage, so it is always a good idea to test any such spray on a small area before coating the whole plant. An article by Colorado State University Extension provides information on insecticidal soaps. Aphids go through many generations in a year, and their eggs can overwinter.

Toxic-Free Future (formerly known as Washington Toxics Coalition) has created a document on managing aphids in the landscape.

Here are additional links on aphid control: Aphids from University of California at Davis
Managing Aphid Problems without Pesticides from the Northwest Coalition for Alternatives to Pesticides

Date 2017-08-04
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Plant Answer Line Question

Keywords: Betula

A landscaper planted a River birch next to our house 9 years ago. The roots are everywhere. We heard that this is one of the worst trees to plant next to a house. We have a basement. What should we do?


River birch (Betula nigra) is rated as having moderate root damage potential by the Urban Forest Ecosystems Institute.

The following, from University of Saskatchewan's "Guide to Birch Trees," supports what you have heard about planting this tree near a structure, but takes the approach that it is not good for the tree, rather than a danger to the foundation. Excerpt:

"On a healthy birch, the roots will spread to a distance of at least twice the tree's height. This means that the roots of a mature tree may cover an area about one third the size of a football field. To permit proper root spread, trees should be planted as far as possible from any obstruction that may interfere with root development. Sidewalks, driveways, patios and building foundations will all limit root development. Where a tree is growing on heavy soils, aeration holes will help maintain root vitality."

Tree roots are not likely to infiltrate a solid foundation, but if there are cracks, it is certainly possible, and if tree roots expand sufficiently over time, they may begin to exert pressure on the foundation. However, birch roots are shallow, as indicated in this USDA Forest Service guide to growing birch trees.

It is not a good idea to plant any tree right next to a house, if only because the tree will undoubtedly require pruning to keep it out of the way of windows, doors, and so forth. If you like the tree and would like to move it to a better spot, you should consider contacting a certified arborist. Here are links to referral services.

Plant Amnesty

Pacific Northwest Chapter of the International Society of Arboriculture

Date 2018-06-22
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Plant Answer Line Question

Keywords: Betula, Trees--Diseases and pests

I am a professional landscaper in the Portland area. I am wondering if Betula jacquemontii have much of a problem with aphids or other pests. Everything I read says they do, but since this tree is one of the Great Plant Picks, I wonder if that's not the case.


There is certainly the potential for aphids with this type of birch. I don't think all the plants listed in Great Plant Picks are necessarily immune to problems, more that they can serve a particular purpose in the landscape. Betula utilis var. jacquemontii is also susceptible to bronze birch borer, according to Oregon State University.

University of British Columbia Botanical Garden Forums includes a discussion of the merits (or not) of this tree, including this comment from Seattle-area gardening expert Ron Brightman:
"Silver birch is customarily Betula pendula. It grows large and is an aphid magnet in my area. Betula utilis jacquemontii does not produce the same elegant weeping habit. But the clone commonly sold here displays stark white bark. Mine became infested with what looked to be the same leaf miner that can be quite abundant on native stands of B. papyrifera north of here. Finding the effects of the miners tiresome and this not being a rare tree here, I cut it down. Since native paper birch trees are abundant around Vancouver I would wonder if you might end up with the same problem."

Here's another link of interest, from Washington State University. It mentions that "this tree is susceptible to bronze birch borer, a wood boring beetle that will girdle the trunk. Aphids can be problem on the foliage. Excrement from aphid feeding can leave the ground sticky beneath this tree."

Jacquemontii birch is common as a street tree in Seattle, and as the neighbor of a row of three of these birches, I can say that so far they appear relatively pest-free (I've seen a hint or two of sticky aphid honeydew on the leaves ), but they make voluminous leaf and bark litter which blows into my garden. I keep thinking the bark is wastepaper (grocery receipts, etc.). It looks great on the trees, but is a minor nuisance when blown far and wide.

Date 2017-08-15
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May 31 2018 13:14:08