Center for Urban Horticulture
College of Forest Resources
University of Washington

Vol. 8, No. 3

Cooperative Extension
Washington State University

Summer 1990

LANDSCAPE

MAINTENANCE

SEMINARS

. . . for the landscape
professional

Cooperating: Center for Urban Horticul-
ture, University of Washington; Cooper-
ative Extension Service, Washington State
University; Edmonds Community College;
South Seattle Community College.

TREE PRESERVATION
ORDINANCES

Tuesday, July 24, 1990
8:30 a.m. to 4:30 p.m.; $35.00
Fee includes box lunch
Center for Urban Horticulture

I. Examining a Successful Ordinance.

Ed Macie, Urban Forestry Specialist, USDA
Forest Service, Atlanta, Georgia. An over-
view of the initiation, development, and en-
forcement of a successful urban tree preser-
vation ordinance.

II. Developing an Ordinance. City of
Tukwila, Washington. A review of the recent
problems, successes, concerns resulting
from developing a policy in the Northwest.

III. Legal Issues to Consider. Bob To-
bin, Attorney, Seattle City Attorney’s Of-
fice.

IV. Concurrent Groups. Presentations
on issues of policy development, enforce-
ment, tree preservation during con-
struction, greenbelt maintenance, or legal
specifics, including group discussion time.

V. Basic Tree Needs. Dr. Jim Clark, Asso-
ciate Professor, Center for Urban Horticul-
ture. To develop appropriate ordinances, an
understanding of tree needs is vital; this re-
view provides basic tree biology informa-
tion.

Success with Broad-Leafed
and Evergreen Trees and
Shrubs in the Landscape

Tuesday, August 14, 1990
9:00 a.m. to Noon; $13
Center for Urban Horticulture

This seminar qualifies for three hours
of WSDA pesticide license recertifica-
tion credit.

I. Selection and Care of Broad-Leafed
and Evergreen Trees and Shrubs. Dr

Ray Maleike, Extension Horticulturist,
WSU-Puyallup. A review of appropriate
plant selections for the Pacific Northwest
and their cultural requirements.

II. Managing Insect Pests of Broad-
Leafed and Evergreen Plants in the
Landscape. Dr. Art Antonelli, Extension
Entomologist, WSU-Puyallup. A presenta-
tion of management strategies for key insect
pest problems of common broad-leafed
and evergreen landscape trees and shrubs.

III. Recognition and Management of
Diseases in Broad-Leafed and Ever-
green Trees and Shrubs. Dr. Ralph By-
ther, Extension Pathologist, WSU-
Puyallup. A discussion of the limited disease
problems of these plants, including recogni-
tion and control or prevention.

Plant Selection Based on
Ecological Considerations

Tuesday, September 25, 1990
9:00 a.m. — Noon; $13.00
Center for Urban Horticulture.

I. Principles of Ecological Plant Se-
lection. Dr. Clem Hamilton, Assistant Pro-
fessor, Center for Urban Horticulture. A re-
view of the ecological factors to consider
when selecting site -appropriate plant mate-
rials.

Registration information
See page 3

II. Appropriate Selections for the Pa-
cific Northwest. Tim Hohn, Curator of
Plant Collections, Center for Urban Horti-
culture. An overview of landscape plants
which are suited to our particular regional
conditions.

III. Ecologically Based Design Con-
siderations. Dr. Iain Robertson, Assistant
Professor, Department of Landscape Archi-
tecture, University of Washington. Learn
how to evaluate the environmental stresses
of a site in order to select plant materials and
design planting arrangements that will work
to minimize maintenance needs.

PROHORT, Its
Eighth Year

It’s hard to believe that we are already mid-
way through our eighth season of ProHort
Seminars. The Seminars and Newsletters
began as cooperative planning efforts be-
tween horticultural educators at Washing-
ton State University, Edmonds and South
Seattle Community Colleges, and the Uni-
versity of Washington. ProHort is dedicated
to providing the latest information to per-
sons employed in the professional land-
scape field.

Dave Stockdale has revitalized an advisory
committee that has already met to discuss
ideas for future programs. Pat Elder, Seattle
Department of Parks and Recreation;
Susan Hanley, Evergreen Services; Ciscoe
Morris, Seattle University; Laurie Peterson
and Stacey Good, Bellevue Parks and Rec-
reation Department; Steve Magley, City
People’s Garden Store; Randy Droppert,
Everett Landscaping; and Steve Davis,
Parkwood Green, have volunteered plan-
ning time. Mike Brokaw, North Seattle
Community College; and Phil Coker, con-
sultant, have also provided feedback. If you
would like to volunteer some time (not a
lot!), please call Dave at 685-8033. Re-
gardless, we would like to have your ideas.

Homeoclimatic Plants for
Pacific Northwest
Landscapes , Part I.

By Clement W. Hamilton, Ph.D.

What plants are most appropriate for land-
scapes in the Pacific Northwest west of the
Cascade Mountains? The best way to an-
swer this question would be to consult the
results of rigorous, well-documented trials
that have tested each available plant taxon
in different urbanized and local climate con-
ditions. Unfortunately, such tests are largely
the figment of a wishful imagination, and we
must rely on practical experience and even
guesswork to help make optimal selections.

One way to improve that guesswork is to
approach the question from an ecological
perspective. Usually we seek plants that
perform dependably and that require very
little artifical improvement of growing con-
ditions once established. Therefore, we are
looking for plants that can survive our rela-
tively arid summers without threatening to
suck the last drops out of the reservoirs by
August.

Four regions of the world feature climates
that are similar to ours — rainy, cool winters,
and arid, relatively cool summers — at the
cool end of what is usually called a Mediter-
ranean climate. Those four regions are the
Mediterranean itself, southeastern Aus-
tralia, and much of Tasmania, southcentral
Chile, and the very tip of South Africa. In
the absence of empirical, quantitative data
on plant performance, we can turn to taxa
from these areas for plants that are “accus-
tomed” to the sort of stresses our climate
provides. In part one of this report we shall
review plants originating from the Mediter-
ranean Region. Part two, in the next issue of
ProHort, will review taxa from the other
three regions.

The Mediterranean

Of the five cool winter-rain regions, the
Mediterranean is the greatest source of
widely available landscape plants, as would
be expected from its long history of human
settlement and its natural biotic diversity.
Several landscape standards from the area
are: Arbutus unedo (marginally cold-hardy
here), Cedrus atlantica, Cistus species,
Erica arborea, and Viburnum tinus. Many
other dependable performers range from
Europe down into the Mediterranean, such
as Acer campestre, Hedera helix, Ilex aqui-
folium, Pyracantha coccinea, and Taxus
baccata.

Most interesting to me are the well adapted
plants that deserve wider use in landscapes.
Of the conifers, Pinus pinea, the Italian
Stone Pine, makes a striking specimen tree
with a roughly spherical crown flattened at
the top. Of the broad-leaved evergreens,
Quercus ilex, the Holm Oak, is a proven
performer; Quercus suber, the Cork Oak,
can have difficulty in harsh winters, such as
1988-89, but often grows to a grand, dis-
tinctive old age. Laurus nobilis, the Bay
Laurel of cooking fame, is also marginally
hardy in the Puget Sound, but has suc-
ceeded well in partly shaded locations. The
evergreen shrub species Arbutus an-
drachne, Phillyrea angustifolia, and P. lati-
folia also deserve more attention; perhaps
greater demand would inspire wider avail-
ability, or vice-versa.

Among Mediterranean deciduous trees and
shrubs, Cercis siliquastrum, Judas Tree, is a
very drought-tolerant redbud that is pre-
ferable to its more common congener C.
canadensis. Cytisus battandieri, the Atlas
Broom, is a shrub currently gaining popu-
larity for its showy racemes of yellow
flowers and broad (for a broom!) leaflets.
Two striking small trees occasionally used as
small-scale specimens are Acer monspes-
sulanum and Sorbus torminalis; rarity in the
trade is their only drawback.

PROHORT

Bookshelf

By Valerie Easton, Horticultural Librarian.

A listing of new resources available at the
Elisabeth C. Miller Library. Library hours
are 9:00 a.m. to 5:00 p.m., Monday
through Friday. For further information,
please call librarians Valerie Easton or
Laura Lipton, at 685-8033.

Andersen Horticultural Library. Andersen
Horticultural Library’s Source List of Plants
and Seeds: A Completely Revised List of
1988-89 Catalogues. Chanhassen, MN:
Andersen Horticultural Library, University
of Minnesota Libraries, Minnesota Land-
scape Arboretum, 1989.

Funk, Sue Ann. Urban Forestry Notebook,
1990. Center for Urban Horticulture, Puget
Sound Power and Light Company, and
Washington State Department of Natural
Resources.

Gerhold, Henry D., Wandell, WiletN., Lac-
asse, Norman, L., Schein, Richard D., edi-
tors. Street Tree Fact Sheets. University
Park, PA: The Pennsylvania State Univer-
sity, 1989.

Grant, John A. and Grant, Carol L. Trees
and Shrubs for Pacific Northwest Gardens.
2nd ed. Timber Books, 1990.

Hartmann, Hudson T., Kester, Dale E.,
Davies, Fred T., Jr. Plant Propagation: Prin-
ciples and Practices. 5th ed. Englewood
Cliffs, NJ: Prentice-Hall, 1989.

Heriteau, Jacqueline and Cathey, Dr. H.
Marc. The National Arboretum Book of
Outstanding Garden Plants. New York: Si-
mon and Schuster, Stonesong Press, 1990.

Jacobson, Arthur Lee. Trees of Seattle.
Seattle: Sasquatch, 1990.

Landis, Thomas D. Seedling Nutrition:
Container Tree Nursery Manual, v.4; Agri-
culture Handbook no. 674. Washington,
DC: U.S. Department of Agriculture, Forest
Service, 1989.

Tartar, Terry A. Diseases of Shade Trees.
Revised ed. New York: Academic Press,
1989.

Thompson, Peter. Creative Propagation: A
Grower’s Guide. Portland: Timber Press,
1989.

Torres, Kenneth C. Tissue Culture Tech-
niques for Horticultural Crops. New York:
Van Nostrand Reinhold, 1989.

Whitcomb, Carl E. Plant Production in
Containers. Revised ed. Stillwater, OK:
Lacebark Publications, 1988.

Other Educational
Resources

Edmonds Community College Horti-
culture Courses, Summer 1990. Sprinkler
Repair and Installation, Deciduous Plant
Identification. For more information, call
771-1679.

South Seattle Community College:

Plant Materials for the Pacific Northwest,
Recertification Review for Pesticide Testing.
Call 764-5336 for information.

PRO HORT Editorial Staff:

David L. Stockdale, Coordinator
George J. Pinyuh, County Extension
Agent, Horticulture

John A. Wott, Associate Director, CUH

Pruning and Planting
Practices

By George Pinyuh, WSU Extension Agent

There are several horticultural myths that
die hard. One concerns the frequent recom-
mendation that when trees or shrubs are
planted barerooted, they must be pruned
hard to balance the top with the reduced
root system.

Standard practice for centuries has been to
remove twenty to thirty percent or more of
the branches of woody plants to help bal-
ance out the top with the remaining root
system. Because such a large percentage of
the root system is usually left behind when a
tree or shrub is moved, it seemed logical
that a substantial amount of the potential
leaf surface should also be removed to take
pressure off the reduced root system to help
it re-establish more easily.

Since the mid-1970s, a considerable
amount of scientific research at a number of
land grant universities has consistently
shown the opposite to be true. Although the
research has largely been aimed at fruit and
shade trees, the results are just as likely to be
applicable to shrubs. The gist of all this sci-
entific effort is that pruning to compensate
for root loss at planting does not affect a
plant’s chances for re-establishment and
survival, or even for better growth.

What has been found is that the more leaf
surface a plant has, the more food it can
manufacture for itself, resulting in more en-

ergy being directed to the regeneration of
much needed new roots. Also, the terminal
buds, which are often removed in the trans-
plant-pruning process, seem to have a di-
rect effect on the growth of new root tissue.
Generally, the more terminal buds that are
left on a tree or shrub, the quicker and more
vigorously new root growth proceeds.

Furthermore, it has been reported that trees
which were not pruned at planting had
greater height and more stem diameter as
well as a significantly greater proportion of
roots than the pruned specimens after 1-2
years.

The current recommendation on pruning
and training recently transplanted woody
plants, including fruit trees, is to wait at least
one year after transplanting to carry out any
extensive renovation. All one needs to do at
transplant time is remove any broken,
crossing or obviously weak branches at
their points of origin. Do not remove termi-
nal buds by unnecessary pruning.

Most properly grown fruit, shade and
flowering trees have usually been trained to
include well branched tops.

Even if you get a tree that needs major work
to get it into shape, it’s best to allow the plant
to grow for at least a year before working it
over. In addition, heavy pruning at planting
is likely to significantly delay fruit produc-
tion on most fruit tree species.

All this presupposes that the newly trans-
planted trees will be adequately watered, at
least during the first critical growing season.
If for some reason sufficient water is not
going to be available during the re-estab-
lishment period, it might be appropriate to
thin out (not head back) severely enough to
reduce the amount of potential leaf area,
perhaps by about 25%. Presumably less
water will be given off by fewer leaves
(transpiration), so less water will be needed.

Another myth is that backfill soils must be
amended with some sort of organic matter
or coarse mineral aggregate when being re-
turned to the hole around the plant’s roots.
Several studies have shown that the practice
of amending soils is of no benefit to the
plants.

Trees seem reluctant to get their roots out
into the surrounding soil if the backfill is
amended. Roots tend to be restricted to the
planting hole if amendments are added and
often do not do as well under drought stress
conditions as those whose roots have pene-
trated into the surrounding area. The only
time organic matter should be added is if an
entire area’s soil can be amended. When
entire bed sections, or an entire landscape
or orchard area can be altered with the ad-
dition of some organic matter, results are
likely to be more positive.

It is preferable to loosen or break up the
backfill which will be returned to a hole at
least twice the diameter of the spread out
root system. However, a tree or shrub is not
likely to survive in a hole dug in a com-
pacted or otherwise impermeable soil even
if it is loosened or amended. Water drainage
must be adequate or the roots will rot de-
spite what is done to the backfill soil.

In areas where water drains out of a hole
slowly, say less than one-half inch per hour,
it may be preferable to plant on top of the
ground rather than in a hole. Dig a shallow
depression in the native soil, and surround
the roots of your plant with a more amena-
ble soil brought in from another location.
Then before installing the tree or shrub, mix
an inch or two of the good soil with the
native material in the shallow depression to
create a transitional layer between the two
radicallly different soils.

Parking

Prepaid parking is available in the Cen-
ter for Urban Horticulture lots for those
attending Pro Hort seminars. Please use
the parking lots.

Landscape Maintenance Seminar Registration

Tree Preservation Ordinances $35.00

Success with Broad-Leafed & Evergreen Trees & Shrubs in the Landscape $13.00

Plant Selection Based on Ecological Consideration $13.00

TOTAL: $

Group rates: 2-5 persons, less 20%; 6 or more, less 25%. Group registrations must be
accompanied by ONE check or purchase order, at least one week in advance.

Portion of fees may cover refreshments and speaker expenses.

Make checks payable to the University of Washington; receipts available at the door.
Mail payment and registration to: Center for Urban Horticulture/ProHort, University of
Washington GF-15, Seattle, WA 98195. For information, call 685-8033.

Name

Address

City State ZIP

Day Phone Evening Phone

Plant Palette

By Tim Hohn, Curator of Plant Collections.

Trachycarpus fortunei. The beauty of palms
in tropical and subtropical landscapes is un-
deniable. Perhaps no other plants better
exemplify the look of a “tropical paradise”
than palm trees. This may be why many
people are astonished when they encounter
the occasional palm in the Pacific Northwest
landscape. Trachycarpus fortunei, the Chi-
nese windmill or Chusan palm, is a palm
that can be planted in this region. Its survival
in the Puget Sound basin, Willamette Val-
ley, and other mild regions of the Pacific
Northwest is not a fluke; this is a hardy
species.

There are six species of Trachycarpus cur-
rently recorded from the Himalayas of
northern India through the northern por-
tion of Southeast Asia and into southern
China. The most commonly grown is 7.
fortunei, thought to be the hardiest of all
cultivated palms. There are beautiful spec-
imens of this plant at the Graham Visitors
Center, Washington Park Arboretum, and
the Carl S. English Gardens in Ballard.
Specimens of the Chinese windmill palm
can even be found growing at 50° latitude in
the British Isles.

Trachycarpus fortunei can grow as tall as 30
feet in the Northwest. The trunks are often
very fibrous and dotted with the old, per-
sistent leaf bases. The fronds are palmate or
fan shaped, relatively flat, and frequently
divided by about half their width into ta-
pered segments. The leaf stems, or petioles,
are so slightly serrated as to appear smooth.
To some, this palm looks like a smaller ver-
sion of the Washington fan palm of Califor-
nia.

The Chinese windmill palm is most suc-
cessful in Sunset Zone 5 and the warmer
areas of Zone 4. They benefit from southern
or western exposures which provide some
protection from northerly cold fronts that
occasionally plague the Northwest. This
also ensures that plants will receive max-
imum exposure in the summer for more
rapid growth and optimal production and
storage of carbohydrates, all of which aid in
the ability of plants to withstand cold. Hard-
iness of seedlings is often questionable and
it is advisable to acquire plants in 5-15 gal-
lon containers, with some evidence of trunk
development. Palms can be variable in
growth rate, but will benefit from the use of
fertilizers. Six month formulations of micro-
encapsulated fertilizers applied in early May
will satisfy the needs of these plants for the
remainder of the warm growing season.

Trachycarpus fortunei seems tolerant of a
wide range of soil types but does best in well
drained, loamy soil. It is a drought-tolerant
plant, once established, although its growth
rate is probably enhanced by summer irri-
gation.

Don’t let the fear of creating an incongruous
landscape inhibit your use of Trachycarpus.
However, realize that palms work better
with other bold or tropical-looking compan-
ions, or when used as specimens; evergreen
species make the most effective compan-
ions. Palms are also particularly striking
next to water, such as ponds or swimming
pools. Unless you are deliberately trying to
create a tropical effect, consider palms as
simply another bold, texturally interesting
landscape plant with special contextual
considerations. Trachycarpus fortunei
brings a tropical flavor to the feast of land-
scape plants available in the Pacific North-
west.

To reprint material from this publication,
obtain permission from the editor and
cite ProHort.

SUMMER 1990

University of Washington, GF-15
College of Forest Resources
Center for Urban Horticulture
Seattle, WA 98195

Nonprofit Org.
U.S. Postage Paid
Permit No. 62
Seattle, WA