Plants

San Pedro Creek Native PlantsThe San Pedro Valley has one of the longest histories of European settlement in the central coast region. Accordingly, extensive habitat alterations have taken place along San Pedro Creek for over two centuries. Over half of its streamside (riparian) vegetation has disappeared due to creek undergrounding into storm drains and erosion control activities along exposed channel reaches within Pacifica's neighborhoods. Of its remaining riparian vegetation, many creek segments still retain sufficient streamside habitat to support steelhead trout and numerous other increasingly rare species. Preservation of this remaining habitat is critical to maintaining the biodiversity of San Pedro Creek, however, preservation alone will not suffice. Human disturbance of the San Pedro Creek watershed has introduced a host of non-native invasive plant species (NIS), particularly of aggressive non-native plants, and these species are known to pose clear threats to the health of creekside ecosystems.


Native Plants

The San Pedro Creek riparian ecosystem contains a variety of California native plant species. These species provide essential habitat for numerous fauna that depend on a healthy and diverse assemblage of species. Below is a list of some of the most common native trees, shrubs, and forbs in the San Pedro Creek ecosystem. The plants listed below are some of the most common native species found in the riparian area.

Scientific Name
Common Name
Alnus rubra
Salix lucida
Salix lasiolepis
Salix sitchensis
Achillea millefolium
Cornus sericea
Iris longipetala
Lonicera involucrate
Sambucus racemosa
Scrophularia californica
Rubus parviflora
Equisetum telmateia
Heracleum lanatum
Oenanthe sarmentosa
Marah fabaceous
Rubus ursinus
Rhamnus californica
Scirpus microcarpus
Juncus effuses
Juncus leseurii
Juncus patens
Red alder
Shining willow
Arroyo willow
Sitka willow
Yarrow
Creek dogwood
Coast iris
Twinberry
Red elderberry
Bee plant
Thimbleberry
Giant horsetail
Cow parsnip
Pacific oenanthe
Valley manroot
California blackberry
Coffeberry
Panicled bullrush
Pacific bog rush
Salt rush
Spreading rush

San Pedro Creek - Native Plants

Illustration by Susan Riedley


Non-native Invasive Plants

San Pedro Creek also contains numerous non-native invasive plant species that have detrimental effects on California native vegetation and reduce the diversity of the vegetation system. Non-native species are fierce competitors which out compete and displace native plants. These invasive species change the dynamics of the ecosystem and severely degrade the health of the system. Below is a list of the most invasive species in the San Pedro Creek watershed.

Scientific Name
Common Name
Delairea odorata
Hedera helix
Cortaderia selloana
Arrundo donax
Conium maculatum
Vinca major
Raphnus sativa
Genista monspessulana
Picris echioides
Rubus discolor
Brassica rapa
Foeniculum vulgare
Malva parviflora
Cirsium vulgare
Nusturtium aquaticum
Euphorbia peplus
Geranium dissectum
Fumaria parviflora
Phalaris aquatica
Cape ivy
English ivy
Pampas grass
Giant reed
Poison hemlock
Periwinkle
Wild Radish
French broom
Bristly Oxtung
Himalaya berry
Wild mustard
Fennel
Mallow
Bull thistle
Watercress
Spurge
Cutleaf geranium
Small flowered fumitory
Harding grass

San Pedro Creek Non-Native Plants

Illustration by Susan Riedley

The San Pedro Creek Watershed Coalition has carried out a survey of NIS infestations in the watershed. Cape ivy (Delairea odorata) and English ivy (Hedera helix) were the most frequent and widespread NIS plants of concern. Infestations of pampas grass, French broom, poison hemlock, fennel, periwinkle and giant reed (Arundo donax) were also much in evidence. The upper and lower slopes of the San Pedro Creek watershed historically lacked conifer forests that are otherwise characteristic of other places in the Santa Cruz Mountains. Based on historical accounts, the upper San Pedro Creek watershed vegetation was dominated by various assemblages of grassland, coastal scrub and chaparral. Although a large portion of the watershed has been extensively altered due to urban influences, the surrounding slopes still support a rich and varied representation of the original biodiversity found in this area.


Summary Of The San Pedro Creek Watershed
Riparian Vegetation Survey
Summer 1999




 
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