Vol. 10, No. 1

Winter 1992

PROHORT seminars for professionals are planned and conducted cooperatively by Urban Horticulture, University of Washington
and Cooperative Extension Service, Washington State University. Edmonds Community College and South Seattle Community
College also assist cooperatively.

PRE-REGISTRATION
REQUIRED FOR ALL
PROHORT SEMINARS

PROFESSIONAL PRUNING
SERIES

Proper pruning techniques and timing
are necessary to maintain fruit trees in
healthy, productive condition. Learn
to correctly prune those assorted fruit
trees often encountered on client's
properties. Observe field demonstra-
tions of proper pruning techniques.

II. Conifer Recognition

Review specific characteristics and
work on identification skills with fresh
specimens and slides of landscape-
appropriate conifers.

III. Field Practice

Class Sizes Limited

I. PRUNING SMALL TREES

Please specify section when registering.

Section A: Tuesday, February 4, 8 to
1 1 a.m.

Graham Visitors Center, Washington
Park Arboretum (WPA)

$21

Section B: Tuesday, February 4, Noon
to 3 p.m.

Graham Visitors Center, WPA
$21

Instuctors: Chip Kennaugh, Paul
Wiltberger

A short lecture followed by field dem-
onstrations will provide insight regard-
ing pruning small landscape trees.
Learn to assess pruning/training needs,
types and timing of cuts.

III. JAPANESE STYLE
PRUNING

Section E: Tuesday, March 12, 8 to
1 1 a.m.

CUH & a University area home
$21

Instructor: Doug Tanaka

Part art, part philosophy, and part sci-
ence— study and then observe demon-
strations of this distinctly different style
of pruning. Observe steps necessary to
restyle neglected plants, or correctly re-
fine and maintain existing specimens.

CONIFER ID

Class size limited

Thursday, March 26, 9 a.m. to 4:30
p.m.

Graham Visitors Center, WPA
$35, includes lunch

II. PRUNING FRUIT TREES

Please specify section when registering.

Section C: Thursday, February 20,
8 to 1 1 a.m.

Center for Urban Horticulture (CUH)
& a University area orchard
$21

Section D: Thursday, February 20,
Noon to 3 p.m.

CUH & a University area orchard
$21

Instructor: Bess Bronstein

Instuctors: Dr. Clement Hamilton,
Associate Professor, CUH; Dr. Ray
Maleike, Extension Horticulturist,
WSU-Puyallup.

I. Principles of Plant
Recognition

Learn the basic descriptive terminol-
ogy of plant parts and the biological
basis for taxonomic plant classifica-
tion in cultivated plants.

Registration information
See page 3

Reviewand practice identification skills
utilizing Washington Park Arboretum
collections. Work to identify over 30
taxa of landscape-appropriate coni-
fers.

IV. Review

Review basic characteristics of the
day's studied conifers in this lecture/
slide overview.

V. Review Quiz

An optional short field quiz will help
you monitor your progress in learning
to identify Northwest conifers.

PLANT PALETTE
LECTURES

THE TRUE FIRS

Saturday, January 1 8, 9 to 1 1 a.m.
Leave from Graham Visitors Center, WPA
$5, payable at the door

Robert Van Pelt of Washington State's
Big Tree Program leads this in-depth
field study of the Arboretum's diverse
collection of Abies (true firs).

WINTER WONDERLAND

Saturday, February 1 5, 9 to 1 1 a.m.
Leave from Graham Visitors Center, WPA
$5, payable at the door

Landscape designer Micheal Moshier
directs this field examination of land-
scape plants with intriguing bark col-
oration and texture, unique branching
patterns, and colorful winter fruits,
flowers or foliage.

OTHER EDUCATIONAL
RESOURCES

Association for Women in Landscap-
ing/CUH Progressive Design Series
Presents:

DESIGN PRINCIPLES

Three part class, January 13, 20, 27;
6:30 to 9:30 each night
Center for Urban Horticulture
$40, pre-registration required (payable
to UW)

Instructors: Betsy Fitzgerald, Sandra
Hasegawa, KrisSargent, Mae Waldron

This short course will address basic
design principles. In addition to lec-
tures and examples, evaluations of
participant projects will be included.

JOHN BROOKES:
DEVELOPMENT OF THE
ENGLISH GARDEN

March 2, 7:30 to 9 p.m.

Center for Urban Horticulture, NHS Hall
$10, PRE-REGISTRATION REQUIRED

John Brookes is an internationally
known garden designer and lecturer
from England. He has authored such
classic books as Cardens for Small
Spaces, The Carden Book, The Coun-
try Garden, and many more. He will
share with us the history of develop-
ment of the "English Garden," from
early estates to small cottage gardens,
including examples from his recently
published book John Brookes' Garden
Design Book.

To reprint material from this pub-
lication, obtain permission from
the editor and cite ProHort.

PACIFIC NORTHWEST
COMMUNITY TREES
CONFERENCE

This two-day conference will be held
February 28-29 at the World Forestry
Center in Portland. Seminar sessions
will focus on urban tree selection and
management. For further information,
contact Paul Ries, Oregon Department
of Forestry, at (503) 373-7854, or Rick
Zenn, World Forestry Center, at (503)
228-1367.

EDMONDS COMMUNITY COLLEGE
WINTER COURSES: Conifers, Soils,
Pruning, Pest Management, Sprinkler
Design, Design I, Landscape Materi-
als, Container Gardening, Crafting,
Hedges, Winter Plant ID, Plant Propa-
gation, Herbs. For registration infor-
mation, call 771-1679.

SOUTH SEATTLE COMMUNITY COL-
LEGE WINTER COURSES: Call
764-5336 for registration information
about these upcoming courses: Coni-
fer ID, Landscape Design II, Soils &
Plant Nutrition, Pruning, Plant Propa-
gation, Drainage & Irrigation.

PROHORT BOOKSHELF

by Valerie Easton

New books at the Miller Library of inter-
est to landscape professionals. Library
hours January through June 8, 1 992, are
9 a.m. to 8 p.m. Mondays, 9 a.m. to
5 p.m. Tuesday through Thursday.

Booth, Norman K., and Hiss, James E.
Residential Landscape Architecture.
Englewood Cliffs, NJ: Prentice Hall, 1991 .

California Department of Forestry and
Fire Protection, Urban Forestry Pro-
gram. Torestry & Tree Education Cata-
logue. Sacramento, CA: 1990.

Conservatories for the 21st Century,
Symposium Proceedings, October 15-
1 7, 1 989. Lucy E. Jones, ed. New York:
Brooklyn Botanic Garden, 1990.

Programs in the United States and
Canada. 1 st Ed. Alexandria, VA: 1991.

Paul, Teresa. New Flowers: Growing
the New Garden Varieties. New York:
Harry N. Abrams, Inc., 1990.

Professional Grounds Management
Society. Grounds Maintenance Man-
agement Guidelines. 4th ed. Cockeys-
ville, MD: 1991.

URBAN FORESTRY
COUNCIL FORMED

The Washington Community and Ur-
ban Forestry Council (WACUFC) is
dedicated to working to help improve
and maintain our urban forests. Cre-
ated in 1 990 by the Washington State
Department of Natural Resources, the
Council consists of an executive advi-
sory committee to the State Forester
and a general membership.

Almost 60 persons from around the
state attended the October, 1991, gen-
eral membership meeting held at the
Center for Urban Horticulture. At that
meeting, members were invited to re-
view the final draft of the Council's
Strategic Plan and committees worked
todevelopand initiate long-range goals
relative to urban forestry. Currentgoals
include: Promote strong commitment
to increase the number of communi-
ties with urban forestry programs; De-
velop programs to support, preserve,
plant and maintain community and
urban vegetation resulting in an in-
creased number of trees in our com-
munities; Develop long-term funding
from multiple sources including both
public and private sectors, locally and
nationally; Build a clearinghouse of
information and inventory the state's
community and urban forestry needs
and resources; Develop an educational
program which stresses a consistent
educational message for municipali-
ties and the public, especially youth
and technical experts.

Himelick, E. B. Tree and Shrub Trans-
planting Manual. 2nd revision. Urbana,
IL: International Society of Arbori-
culture, 1 991 .

Master Gardeners International Cor-
poration. Directory of Master Gardener

PROHORT Editorial Staff:
Dave Stockdale, Coordinator, CUH
Dr. John A. Wott,
Associate Director, CUH
George Pinyuh, WSU County
Extension Agent-Horticulture

RESEARCH REVIEW

by Dave Stockdale

Root Growth and
Development

Two recently published research re-
view articles by Dr. Edward Gilman of

The Center for Urban Horticul- I
ture iscommitted toexcellence in I
research, teachingand publicser- I
vice in urban horticulture.

the University of Florida should be
recommended readingforanyonewho
wants to learn about or reinforce their
understanding of tree roots. Research
is reviewed on tree root form, spread,
depth, periodicity, response to cul-
ture, response to management and re-
sponse to planting — with many refer-
ences related specifically to urban trees.

For instance, root form is dictated not
only by plant genetics, but by soil
texture, compaction, depth to the wa-
ter table, fertility, moisture content and
more. Root morphology on planted
trees is also affected by nursery pro-
duction practices, age at planting,
planting method and post-planting
cultural practices. Research indicates
that pre- and post-planting cultural
practices influence root morphology
more than species differences.

The author thoroughly reviews the re-
search describing early root develop-
ment, includingtheformation and func-
tions of tap, oblique, lateral, and fine
roots. Discussion is also given to older
tree root development, includingdeep,
lateral, sinker, and fine roots.

Research findings are cited to demon-
strate that root spread is usually well
beyond the tree dripline. Studies have
indicated that the ratio of root spread to
branch spread on nursery-grown trees
is highly species dependent. Usingdata
on root-spread ranges for a variety of
trees, many researchers have been able
to reasonably predict root spread of
certain tree species based on trunk
diameter or branch crown radius.

Interesting data is available on the
seasonal periodicity of root growth.
The period of maximum root growth is
influenced by species, soil moisture
and nutrient content, stage of shoot
development, soil temperature, root or
top pruning, tree age and more. How-
ever, of all the environmental condi-
tions, soil temperature and moisture
appear to have the greatest influence
on root growth.

Of importance to landscape managers
and urban foresters are the effects of
management practices on tree root
development. For instance, grass is
most competitive with tree roots if
mowing is conducted infrequently
since this results in deeper, denser
grass root development. Numerous
findings are reviewed.

Other cultural practices greatly influ-
encing root development are irrigation
and fertility programs. The addition of
nitrogen will increase the root density
only in the area where it is applied — so
even application is required. However,
most trees are unable to utilize more
than 80 ppm nitrogen in the soil solu-
tion, so excess application is wasteful.

Other literature citations relate that
root development following transplant-
ing varies with species, physiological
status, environmental conditions, time
of year, type of root system and cul-
tural practices. It is important to note
that soil type and texture are not men-
tioned. Studies have indicated that soil
amendments in the backfill were inef-
fective for enhancing root weight, plant

survival or shoot growth in a variety of
soils. Also not shown to improve woody
plant root growth in transplants were
root ball slicing or teasing roots from
the periphery of the root ball. How-
ever, where possibilities exist for gir-
dling root development that may affect
later development of the plant — such
practices are still recommended.

For more details on the above-men-
tioned data and other relevant infor-
mation, I would suggest reading the
two review articles cited below (avail-
able in the Miller Library at CUH).
Based on information from over two
hundred sources, these articles repre-
sent an excellent starting place for
understanding or review.

Gilman, Edward F. Tree Root Growth
and Development. I. Form, Spread,
Depth and Periodicity.). Environ. Hort.
8(4):21 5-220. December, 1990.

Gilman, Edward F. Tree Root Growth
and Development. II. Response to
Culture, Management and Planting.
J. Environ. Hort. 8(4):220-2 27.
December, 1990.

PLANT PROFILE

by Tim Hohn

Hamamelis vernalis
'Purpurea'

I've liked witch hazels ever since my
first encounter with Hamamelis
virginiana, the eastern witch hazel, in
a wooded state park outside of Detroit.
Their rather small stature, distinctive
foliage, and perhaps most of all, their
unusual flowers were very captivating.
Since moving to Seattle, however, I've
developed a new respect for these
undemanding and showy cool season
performers. Although the closest wild
growing witch hazels are back east in
the Ozarks, locally grown plants often
out-perform their wild brethren with
prolonged winter blooming periods
and pleasing scents.

There are four species of Hamamelis:
H. japonica, H. mollis, H. vernalis,
and H. virginiana. Hamamelis japonica
contains two varieties, arborea and
flavopurpurascens, with the usual
amount of debate surrounding their
legitimacy. Like so many other genera,
these species are distributed exclu-
sively in eastern North America and
Eastern Asia, glacial refugees of a once
more ubiquitous temperate flora. H.
mol I is and H. japonica can be found in
the wooded uplands of China and
Japan, respectively, and the others are

PROHORT Seminar Registration

Pruning Small Trees $21 .00

Pruning Fruit Trees $21 .00

Japanese Style Pruning $21 .00

Conifer ID $35.00

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 expense.

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.

Company Name

Address

Citv

State

Zip

Da\ Phone

Evening Phone

inhabitats of the eastern deciduous
forests of North America. The oriental
plants hybridize in cultivation and have
been the source of many outstanding
garden selections under the name
Hamamelis x intermedia , and I'm cer-
tain you'll recognize the cultivar names
Diane, Jelena, and Arnold Promise.
But, there is an uncommon selection
of a less popular species that merits
particular attention.

Hamamelis vernal is grows in thickets
along the rich, forested streambanks of
the lower midwest, particularly in the
Ozark regionsof Missouri, Oklahoma,
and Arkansas. It is more shrubby in
stature than the larger, more easterly
distributed H. virginiana. Although the
vernal witch hazel is often only 6-10
feet tall, it can be twice as wide with
wild populations showing a wide range
of diversity in growth form and other
characters. Its natural suckering habit
appears to be minimal in cultivated
plants at the Arboretum.

Like its more common North American
relative, the foliage of the vernal witch
hazel turns a crisp, clear yellow before
dropping inthefall.Theflowers, likethe
plant, are the smallest in the genus with
petals sometimes only 4-5 mm long.
However, what it lacks in size it makes
up for in quantity, cold hardiness, and

color. Flower petals can be seen unfurl-
ing in the most miserable of January and
February weather. They appear in
shades of light yellow, orange, and
copper from flower buds that thickly
stud the branches. This warm haze of
color is punctuated by a pleasant yet
indescribable aroma. Hamamelis
vernalis is a popular plant in colder
climes than ours, its flower petals curl-
ing up in a warm huddle on frigid days
and rollingout unscathed under balmier
conditions.

Of all the new hybrid selections of
witch hazels, none has yet been devel-
oped with a flower color as striking as
H. vernalis 'Purpurea.' Like the spe-
cies, the flowers are small but plentiful
and of the most unusual color, a sort of
Peruvian violet. This selection fills a
unique niche in the available color
spectrum, not only among witch ha-
zels, but winter blooming plants in
general. Its one of those colors that
reignites color perceptions in the gar-
den that are as dormant as some of
the plants. As a bonus, H. vernalis
'Purpurea' produces some of the most
outstanding fall color available in the
garden. Yellows, oranges, scarlets, and
pi urns appear on the same plant, some-
times on the same leaf!

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

Winter 1992

The purple ozark (or purple vernal)
witch hazel is small like the species,
attaininga mature height of 1 0feetand
just as wide in a broad, vase shape. It
is best planted in a well-drained, mois-
ture retentive soil in part shade, similar
to the conditions under which they are
found in the wild. Many witch hazels,
particularly those with blossoms in the
yellow color range, should be sited in
front of dark backgrounds for maxi-
mum effect. However, H. vernalis
'Purpurea,' as well as copper and ma-
roon-colored hybrids, are most effec-
tive if they can be viewed with back
lighting to magnify their intensity. A
good combination of witch hazels for
a long season of winter bloom (60 - 90
days) would include the hybrid culti-
vars Arnold Promise, Diane, Jelena,
and Winter Beauty; H. mollis and, of
course, H. vernalis 'Purpurea.' In a
small setting, H. x intermedia 'Arnold
Promise' together with H. vernalis
'Purpurea 'would make a striking Feb-
ruary color combination.

A limited number of scions of
Hamamelis vernalis 'Purpurea' can
be obtained by contacting Barbara
Selemon, Propagator, Center for Ur-
ban Horticulture. Plants can also be
purchased from Gossler Farms Nurs-
ery in Springfield, Oregon.

NONPROFIT ORG.

U.S. POSTAGE
PAID

Seattle, Wash.

PERMIT NO. 62