End of 2017 Field SeasonThe ISED Team has completed our surveys for the 2017 field season, wrapping up the second full round of surveys of roads and trails in the SFAN Network. This season, we surveyed over 180 miles of roads and trails and recorded 1348 new assessments of priority invasive plant patches. Special thanks to our interns Amber Antonison, Sarah Inman, Cheyenne Liddicote, and Julia Hedelman and to our volunteers Alex Wong and Kathleen Feinblum, without whom this monumental task would not have been completed.
Noteworthy Early Detections
Spiny plumeless thistle is a biennial thistle that grows taller than the more common bull thistle (Cirsium vulgare). The leaves of spiny plumeless thistle are deeply lobed with long spines and the stems have spiny wings. Spiny plumeless thistle has a roughly spherical inflorescence, distinguishing it from Italian thistle (Carduus pycnocephalus) and a pappus of barbed bristles (not plumose), distinguishing it from Cirsium spp. Spiny plumeless thistle tends invade disturbed areas and form tall dense patches that are unusable by humans and wildlife alike.
When thistles such as plumeless thistle outcompete native grasses, long fibrous grass roots are replaced with a single taproot, which leads to erosion and subsequent sedimentation. Plumeless thistles have a very high reproductive ability; a single inflorescence can produce up to 1500 seeds. Seeds are transported by wind, but usually remain within 100 meters of the parent.
USDA Field guide for managing invasive thistles
Spiny plumeless thistle NPS article
Poroporo is a soft-wooded shrub characterized by deeply lobed leaves, blue-violet flowers, and round, green fruits that turn bright red-orange as they mature. Each fruit contains hundreds of seeds. This perennial plant can reach up to 12 feet in height. Like many other plants of the Solanaceae, the unripe fruits and leaves of this species are toxic to humans and animals.
Poroporo, also known as New Zealand nightshade or kangaroo apple, is native to the east coast of Australia and New Zealand. It has been introduced to other regions of those countries where it is now considered an environmental weed. In the US, its invasion potential is largely unknown. Currently, Poroporo has been introduced to Oregon and California; in Hawaii, it is considered to be an invasive plant. In Marin, plants have been found in Point Reyes NS on Limantour Road and in Golden Gate NRA at Muir Beach and scattered patches from Stinson Beach to Mt Tam. We have also mapped substantial populations in the San Francisco Presidio. It is typically found in loose soils and heavily disturbed areas.
Some controversy remains about the identification of this species in California. In their native New Zealand and southwestern Australia, there are two closely related poroporo species, Solanum laciniatum and Solanum aviculare. Recent correspondence from New Zealand taxonomists calls the attribution of the Calfornia plants into question. Of further ecological interest, S. aviculare is in decline in New Zealand while S. laciniatum remains widespread there.
USDA Plants Profile
Black locust grows as a shrub or tree which is distinguishable by its paired thorns. Black locust leaves are pinnately compound in sets of 7-20 leaflets, which are round and 3-4 cm in length. Black locust have large drooping clusters of white flowers.
Black locust is native to parts of the US including the Southern Appalachian and Ozark Mountains. It has been planted in all of the Lower 48 states but has been noted as invasive in as wide ranging ecosystems as pine barren, sand prairie, and black oak savannah communities, in as varied climates as the Mid-Atlantic, Midwest, West Coast, and Texas. Black locust grows best in full sun and well drained soils. Where invasive, black locust forms dense clonal forests which shade out competitors and alter nitrogen, calcium, and phosphorus cycling. This disruption of nutrient cycling has in some cases led to the establishment of other problematic invaders, such as cheat grass (Bromus tectorum).
Fire Effects Information System Plant Profile
Common cocklebur is an annual herb that is believed to be native to North America. It has become weedy due to the fact that it competes strongly in agricultural and disturbed areas. It is highly invasive elsewhere in the world where it is not native, including Africa and the Middle East. Cocklebur’s weediness stems in part from the way its various subpopulations adapt quickly to changes in the environment.
The distinctive fruits of common cocklebur are distinctive ellipsoid burs covered with hooked prickles. Two unusually large prickles mark the tip of each bur. The leaves are triangular to ovate with jagged edges and weak lobes.
Blais, P., and Lechowicz, M. (1989). Variation Among Populations of Xanthium strumarium (Compositae) from Natural and Ruderal Habitats. American Journal of Botany, 76(6), 901-908.
James M. Lee, & Michael D. K. Owen. (2003). Dry Matter Yield Differences of Five Common Cocklebur (Xanthium strumarium) Biotypes Grown at a Common Site. Weed Science, 51(2), 186-190.
Bugwood Wiki article
Weird Wildling Waifs
From time to time, landscape plants choose to scale the garden wall and live as “free folk”, growing as weeds in the wildlands. Species that only sporadically escape are known as waifs. Recently, the ISED team found and removed three new waifs that were growing in disturbed areas.
Global Compendium of Weeds Profile
Garden Guides profile
Gardening help from Missouri Botanical Garden
Pacific Island Ecosystems at Risk
Last updated: October 10, 2018