.01 tree replacement on Wildflower Wy
CITY OF CUPERTINO
10300 TORRE AVENUE, CUPERTINO, CALIFORNIA 95014
DEPARTMENT OF PUBLIC WORKS
Subject: Tree Replacements on Wildflower Way in front of Wildflower Village
Planning Commission Agenda Date:
Tuesdav. January 22. 2007
SUBJECT:
Staff report on the replacement trees for those removed from Wildflower Way in front of
Wildflower Village.
BACKGROUND:
In connection with its August 28 and September 11, 2007, hearings on the Bunker
development at 1357 South De Anza Boulevard, the Planning Commission requested that
Public Works report on the replacements for the trees that were removed by Public
Works in the curb bulb-out planters adjacent the Bunker development on Wildflower
Way.
One of the conditions of approval of the Bunker project (U-2003-03) required the
preservation and protection of an existing mature evergreen ash tree along Wildflower
Way. This was a large ash tree that served as a gateway tree for the neighborhood to the
west. However, Public Works staff removed the tree and a similar ash tree across the
street because both trees had caused continual damage to the adjacent sidewalk over the
last several years, requiring repeated replacement of the sidewalk. Public Works staff
was unaware of the condition placed on Mr. Bunker's development, as well as of the
gateway designation of tree site at the time the tree removal was performed. The damage
caused by the trees and the past cutting back of significant supporting roots of the trees
would have necessitated the removal of the trees, in any case.
Originally, Public Works had recommended that the evergreen ash trees that were
removed not be replaced with ash trees. The reason for this is that evergreen ash trees
have extremely invasive and fast-growing root systems that cause considerable ongoing
public expense for the repair of the damage they cause to surrounding public roadway
and roadside improvements. The roadside planting areas typically available are not
sufficient to accommodate the mature evergreen ash root system, which, as in this present
case, spreads large surface roots 25 feet or more in every direction. The necessary
pruning of these roots to accommodate the adjacent roadway and roadside improvements
compromises the long-term stability of the trees.
In order to determine the type of replacement trees that could satisfy both the desire to
reestablish an acceptable gateway and the need to limit the public expense of continual
repair of public improvements and avoid premature loss of replacement tree viability,
Public Works asked the City arb ori st to evaluate the situation and make
recommendations. A copy of the City arborist's report is attached.
/--1
DISCUSSION:
The arborist's report confirmed the problems of the evergreen ash as a street tree in the
subject location, and recommended three alternate species, including another variety of
ash whose root system is less aggressively invasive than that of the evergreen ash, as
replacements. All three are recommended as a good balance for achieving a prominent
gateway effect while extending the life expectancy of the surrounding hardscape. With
the roots of the removed trees properly ground, there will be space to plant 48-inch box
specimens of any of the three in the spaces available.
Of the three recommended replacement species, autumn purple white ash, red oak, and
coast live oak, the autumn purple white ash is the most similar in appearance to the
evergreen ash. Public Works intends to replace the trees removed with 48-inch box
specimens of the autumn purple white ash, which is similar to the evergreen ash in height
and canopy.
Prepared by: Glenn Goepfert, Assistant Director of Public Works
Enclosure: Arborist Report from Arbor Resources
i -.;<
4i...-.-~. ARBOR RESOURCES
Pro.fessional Arboriculfural Consulting & Tree Care
October 29, 2007
Glenn Goepfert
Public Works Department
City of Cupertino
10300 Torre Avenue
Cupertino, CA 95014-3255
RE: TREE REPLACEMENTS in front of Wildflower Village Condominiullls
Wildflower Way near Wildflower Court, Cupertino
Dear Mr. Goepfert:
You have asked that I evaluate the feasibility of installing two evergreen ash (Fraxinus
uhdei) of 48-inch box size to replace two previously existing ones that were recently
removed from the above-referenced location.
Observations
The trees that were removed are situated within the public right-of-way (i.e. street trees)
and are located across "'the street frolll another. The remaining stunlp to the north (below
left photograph) is located in front of the condominium development and has a diameter of
24 inches. The remaining stump to the south (below right photograph) is located within a
planter between the street and sidewalk, and has a diameter of 28 inches.
P.o. Box 25295, San Mateo, California 94402 . Enlail: arborresources@conlcast.net
p h on e: 6 5 0 . 6 5 4 . 3 3 5 1 . Fax: 6 5 0 . 2 4 0 . 0 7 7 7 . L ice n sed C on tr a c to r # 7 9 6 7 6 3
1-~3
~~,>~-"# .
~
ARBOR RESOURCES
Pro.fessional Arboricultural Consulting & Tree Care
October 29, 2007
Wildflower Way
page 2 of3
Regarding the stump along the south side of street, there are large roots that originate and
from the stulnp and protrude along the surface within the street planter, as well as the large
planter south of the sidewalk (see photographs below; the white arrows identify the roots).
Numerous cuts made to these roots for the purpose of installing a new curb/gutter and
sidewalk can also be observed.
',-'" I - - ~_ ~' ~" "I,
_ ~ ...... _ _ IT 4'..).< ~ .,.;. ~
~...
~l
P.O. Box 25295, San Mateo, California 94402 . Email: arborresources@conlcast.net
Ph 0 n e: 650.654.335 1 . Fax: '650.240.0777 . Lie ens e d C on t r a c to r # 7 9 6763
I--~
.
ARBOR RESOURCES
Professional Arboricultural Consulting & Tree Care
October 29,2007
Wildflower Way
page 3 of3
Regarding planter size, I find there is sufficient space to successfully install new trees of
48-inch box size. Prior to this being performed, however, the stumps should be ground to
a depth of 24 inches below grade for a distance of 24 inches from the stump on all sides
(3600), or to near the existing curb, whichever is less.
Discussion and Recommendations
Evergreen ash trees have an inherent aggressive and invasive root system that damages
surrounding hardscape, particularly within street settings. Evidence of this having
occurred can be observed by the remnant roots shown in the photographs on the previous
page. Pruning or severance of the roots can occur to accommodate installing a new
curb/gutter and sidewalk; however, at the close proximity of which cuts occur to the
stump, the tree's stability and longevity becomes jeopardized, resulting in an increased risk
of uprooting and premature decline.
To maXImIze the longevity of the new curb/gutter and sidewalk, I recommend an
alternative tree (or ash) with a less aggressive root system is selected to minimize the risk
or damage that would occur in the future. To my understanding, the new trees are intended
to serve as prominent gateway trees into Wildflower Way neighborhood. In my opinion,
the following trees could serve as a good balance for achieving this while extending the
life expectancy of surrounding hardscape: red oak (Quercus rubra), coast live oak
(Quercus agrifolia) and Autumn purple white ash (Fraxinus a. 'Autumn Purple').
Sincerely,
tL;>v
<t
David Babby
Registered Consulting Arborist #399
Certified Arborist #WE-4001A
P.O. Box 25295, San Mateo, California 94402 . Email: arborresources@comcast.net
Phone: 650.654.3351 . Fax: 650.240.0777 . Licensed Contractor #796763
i~5