Vegetation Maintenance Inspection and Recommendations - VTA

16 January 2012
MEMORANDUM
TO: Ann Calnan (Valley Transportation Authority)
FROM: Joe Howard and Carrie Jensen
PROJECT #2995-04
CC: Lani Lee Ho (Valley Transportation Authority); Max Busnardo, Dan Stephens,
Matt Quinn (H. T. Harvey & Associates)
SUBJECT: Wrigley Creek Improvement Project, Vegetation Maintenance Inspection
and Recommendations
H. T. Harvey & Associates’(HTH) Carrie Jensen visited the Wrigley Creek Improvement Project
on 10 January 2012, to perform a vegetation maintenance inspection and assess weed control and
soil moisture. This memorandum summarizes her observations and HTH’s maintenance
recommendations.
Overall the site was well maintained, weed cover was low, and the soil moisture was sufficient
but quickly diminishing. The basins were well maintained with sufficient mulch levels and
wooden stakes. The majority of container plants had high health and vigor and some had new
growth. Weed cover averaged less than 6" high, and weeds are being actively controlled across
the site. The dense patches of nonnative, invasive herbaceous species observed during the last
maintenance inspection had died back, presumably from herbicide treatments; these species
included cheeseweed (Malva sp.), wild radish (Raphanus raphanistrum), bristly ox tongue
(Picris echioides), and wild beet (Beta vulgaris) (Figure 1). The stands of nonnative, invasive
barnyard grass (Echinochloa crus-galli) in the channel had been mowed/weed whipped. There
were numerous native wetland plant species in the floodplain such as iris-leaved rushes (Juncus
xiphiodes) and flatsedges (Cyperus eragrostis) and several native species in the uplands
including mugwort (Artemisia douglasiana) and yarrow (Achillea millefolium). Care had been
taken to avoid these native species during weeding events.
A few noxious/invasive species were observed on the site. There were still a few scattered
stinkwort (Dittrichia graveolens) individuals with seed on the west bank (Figure 2). English ivy
(Hedera helix) was overhanging into the project site on some sections of the eastern fence line
(Figure 3). There was one Canary Island date palm (Phoenix canariensis) also along this eastern
fence line (Figure 4). Soil moisture was variable and followed a gradient from saturated soils
along the channel to drier soils in the upland planting zones. All areas had at least some moisture
at depths of 4 inches or greater; however, in the absence of rain, this moisture will quickly
diminish.
983 University Avenue, Building D Los Gatos, CA 95032 Ph: 408.458.3200 F: 408.458.3210

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Dense weed
patches have
died back.
Figure 1: On the southwest top of bank dense patches of weeds have died
back.
Stinkwort
Figure 2: Stinkwort gone to seed on the west bank near the additional
outfall structure.
H. T. HARVEY & ASSOCIATES

Figure 3: English ivy hanging over the eastern fence into the project site.
Figure 4: Canary Island date palm and English ivy along the eastern fence
line.
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H. T. HARVEY & ASSOCIATES

Discussion and Recommendations
The following are our recommendations for compliance with specification Section 32 95 00
Plant Establishment Period and Long-term Landscaping Maintenance.
1. All noxious/invasive plants shall be removed from the planting area limits, including
stinkwort, Canary Island date palm, and English ivy. The few remaining stinkwort
individuals with seed should be bagged and removed from the site. The one Canary
Island date palm individual should be removed. The English ivy that is encroaching into
the site over the eastern fence should be pruned off of the project’s side of the fence
before the berries mature in the spring; care should be taken to avoid damaging the fence.
All material of these species should be removed from the site and properly disposed off
of the site because even small pieces of remaining material may re-root if left in contact
with the soil.
2. Due to the lack of rain and decreasing soil moisture on the site, the VTA may want to
consider adjusting the irrigation schedule per the specifications to provide sufficient
water to maintain plant health. We will continue to monitor the forecast on a weekly basis
and follow-up with recommendations on the appropriate timing of winter irrigation
events, if necessary.
Please feel free to contact Joe Howard at jhoward@haveyecology.com or 408.458.3224 or
Carrie Jensen at cjensen@haveyecology.com or 408.458.3234 if you have any questions.
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H. T. HARVEY & ASSOCIATES