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Search Results for: Trees in cities | Search the catalog for: Trees in cities

Plant Answer Line Question

Keywords: fastigiate trees and shrubs, Cornus kousa, Trees in cities

Can you recommend some narrow or fastigiate trees for the space between our house and the house next door? The space is about 14 feet wide. Will Cornus kousa 'National' work?


From what the experts say, Cornus kousa grows 20-30 feet high and wide in cultivation. They can grow to twice that size in the wild.

I found this and other information that might help you in the sources below:
1. Trees and Shrubs for Pacific Northwest Gardens, by J. Grant, 1990, p. 71
2. Trees & Shrubs Hardy in the British Isles, by W.J. Bean, 1976, p. 703
3. Manual of Woody Landscape Plants, by M. Dirr, 1998, p. 260
4. North American Landscape Trees, by A. Lee Jacobson, 1996, pp. xiii, 144

The Seattle City Arborist's Office recommends the following narrow trees:
1. Magnolia grandiflora 'Little Gem' - 15 ft. high, 10 ft. wide. White flowers, evergreen.
2. Malus 'Adirondack' - 18 ft. high, 10 ft. wide. White flowers, red fruit, excellent scab resistance.
3. Malus 'Red Barron' - 18 ft. high, 8 ft. wide. Red flowers, red fruit, yellow fall color.
4. Malus 'Golden Raindrops' - 18 ft. high, 13 ft. wide. White flowers, yellow fall color, abundant yellow fruit.
5. Prunus serrulata 'Amanogawa' - 20 ft. tall, 6 ft. wide. Pale pink double flowers, bronze fall color.

Here are additional sources:

Date 2018-04-05
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Plant Answer Line Question

Keywords: Picea, Trees in cities, Trees--Care and maintenance

We just moved into a new house that has a beautiful 20-foot-tall Colorado blue spruce planted too close to the house. Can it be topped and shaped so it could be left in that spot? If we wanted to remove it and plant it somewhere else could we do that? Or will it just die anyway? What to do?


I would not recommend topping the tree. Since this tree can reach mature heights of 30 to 60 feet or more, it may not be the right tree for the site. Here is a page about Colorado blue spruce (Picea pungens) from University of Illinois Extension's Selecting Trees For Your Home.

Here is information from a local organization, Plant Amnesty, on why topping trees is not a good solution to your landscaping problem.

This organization has an "Adopt-a-Plant" service, if you think you would like to give the tree away. There are also referral services available from Plant Amnesty if you need the tree removed or moved to another location. You could also contact a certified arborist through the International Society for Arboriculture.

I would suggest looking at resources like Great Plant Picks, which lists trees and shrubs which will do well in our area, and includes information on their growth habits and ultimate size at maturity.

Date 2017-04-22
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Plant Answer Line Question

Keywords: Arborist, Trees in cities, Roots--Wounds and injuries, Plant diseases, Fungi and mushrooms, Arbutus menziesii

We recently bought a house on San Juan Island with lots of beautiful madronas (Arbutus menziesii) on the property. Two of them show no signs of life... others have the occasional dead branch here and there. We have been advised that this is likely caused by a fungus and that it can spread rapidly. We have been shown blackened excavated areas on the trunks of the dead trees.. and similar though less extensive areas on some of the others. What can be done to save our beautiful madronas?


It is possible your trees are suffering from canker fungus (Nattrassia mangiferae), or some other type of fungal disease. Here is a link to a file called "The Decline of the Pacific Madrone" edited by A. B. Adams (from a symposium held here at the Center for Urban Horticulture in 1995).

You may want to call a certified arborist to look at the trees, determine the extent of the disease, and help you decide whether the trees can be salvaged. (Search the Pacific Northwest Chapter of the International Society of Arboriculture for a local arborist.)

Below is a response to a question similar to yours from the University of British Columbia Botanical Garden and Centre for Plant Research:

"What you describe are the classic symptoms of 'Arbutus decline,' which is postulated in the literature as being caused by mostly naturally-occurring, weakly pathogenic fungi, made more virulent by the predisposition of Arbutus to disease, caused by urban stresses, especially root disturbance." (see also: "Arbutus Tree Decline" from Nanaimo. B.C.'s Parks, Recreation and Culture department)

Nevertheless, I am convinced that much of the die-back we are seeing on established Arbutus trees stems not from disease, but primarily from the complications of damage, competition, shading and especially, drought stress (we have had a run of very droughty summers). Typically, the most affected natural stands of Arbutus are very dense, with poor air-circulation, internal shading and intense competition for resources (characteristic of rapid growth after clearing). And because this region is becoming increasingly urbanized, with more vehicular and marine traffic (marine traffic evidently accounts for a huge proportion of the pollution in the Fraser Basin air-shed), I would not discount atmospheric pollution as a contributor to the decline (one more stress).

I think the reason your shaded trees are not as affected is that their roots are probably deeper and less exposed, and there is reduced evaporative demand on the leaves. However, as the shade increases, these plants, or at least their shaded branches, will succumb.

What to do? I do not think there is anything you can do to save the existing trees, except, perhaps, to minimize human influence around them. You should avoid both disrupting roots and damaging above-ground portions of the trees (with pruning, for example), as any wound is an open invitation to disease-causing micro-organisms. Interestingly, a friend of mine who kayaks has seen black bears foraging for fruit in the tops of Arbutus trees on Keats Island (he should have told them they are not helping the situation any).

Irrigation of established plants is nearly always counter-productive because it encourages surface rooting (which is typically short-lived and considerably less resilient than deep rooting), and summer irrigation is worse, as Arbutus are well adapted to our conditions (at least, where we find them growing naturally) and normally somewhat dormant in summer. You can plant more Arbutus, as a previous correspondent in this thread has, to replace what you are losing, but there is no guarantee that these plants will survive the next drought or indeed, your well-intentioned meddling. (I suspect his plant was lost for the same reason most young Arbutus are lost--by root damage from saturated or compacted soil conditions). The natural succession on your island is probably (as elsewhere in similar places along the coast) tending toward open Douglas fir forest with a few scattered Arbutus in the more inhospitable places. In other words, you can plant what you will, but the larger the Douglas firs, the fewer Arbutus will be able to survive around them. Neither species is particularly shade tolerant and resources are pretty limited on rocky ground, where both prefer to grow locally. Expect change.

Date 2017-05-12
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Plant Answer Line Question

Keywords: Trees in cities, Tree planting, Magnolia

How do I go about planting a new Magnolia tree this fall?


The City of Seattle's Department of Transportation has perhaps the best set of instructions and tips for planting trees in the Pacific Northwest. It includes a diagram of how to plant a tree. This same site also has guidelines for care of young trees. If your tree is a "street tree" (planted in a parking strip), then be sure it is appropriate. The left-hand menu here gives lists of trees that are and are not appropriate, under Street Trees.

The current consensus is that you do not need to amend the hole with new or superior soil from another source when you fill in the hole, as this just creates an environment the roots do not want to leave. In order for a tree to become established, the roots need to grow outward, into the native soil. Washington State University Extension professor Linda Chalker-Scott discusses this subject as well as whether or not to disturb the root ball, how to handle balled and burlapped trees(remove the wire basket!), and whether staking is necessary.

The University of British Columbia Botanical Garden Forums includes the following comments about planting some varieties of magnolias:

"I would only use a well seasoned compost for a Magnolia as a top dress at planting time. We advised people to dig the hole three times the width of the root ball and place the dug out soil back in the hole with no other soil additives. Providing a root shock preventer such as liquid Vitamin B1 at a rate of one fluid ounce per gallon of water is optional. A good choice to use when planting these Magnolias on a warm day in a warm climate but generally not needed in the Pacific Northwest. What we have to guard against is planting this and others of this series too low in the ground. We like to plant these in a raised mound for a yard planting. Never plant these trees with the graft union at soil level, try to plant them about six inches to a foot above the soil level and allow for settling in later. A Spring planting is regarded as being best for these Magnolias but in the warmer climates can be planted almost year round as our soils here seldom ever are frozen."

I would add to this that planting too deeply is a common mistake, but another mistake is to plant "too high" (as is suggested above, when the writer mentions planting in a "raised mound"). Some people think that such a mound can be buried in mulch; it is much better to plant at the proper depth and use mulch from about 6 inches away from the trunk to the outer edge of the root ball, creating a 'dam' as described by Seattle Department of Transportation.Then you can turn the hose on low and let the water fill the 'moat' created by the dam. During the winter, be careful that your mulch is not too deep, as it can actually keep water from getting into the soil (3-4 inches of mulch is plenty). Mulch in the spring through fall is much more important for keeping water from evaporating from the soil surface, as well as for slowing down the weeds. Be careful not to pile mulch against the trunk of the tree, as this can cause rot.

One more thing, as mentioned below on University of British Columbia Botanical Gardens Forum, do not fill the planting hole with water, as this may contribute to root rot.

Date 2018-03-07
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May 23 2018 14:32:42