LOWER LAKE, Calif. – About two dozen people joined in the 11th annual Invasive Weeds Tour hosted by Lake County Weed Management Area on Tuesday.
This year's tour, conducted at Anderson Marsh Historic State Park in Lower Lake, was the first to be presented in a single location.
Participants engaged in a 2.1-mile walk that offered identification and conversation about various invasive plants that are present throughout the area.
The tour took guests through the flatlands of the park and across the boardwalk over the marsh lands, which are currently dry, that ends along the edge of Cache Creek.
Paul Aigner, director of McLaughlin Reserve – a former gold-mining location on Morgan Valley Road east of Lower Lake – identified several plants in the pasture area in the northwest portion of the park.
He said the area is dominated by non-native species, many of which were introduced as forage when the land was used for raising cattle.
Others, Aigner said, may have been introduced unintentionally by way of contaminated hay and other livestock feeds.
Aigner said the park's 10-year adaptive management plan contains strategies to control different non-native weeds while stimulating the growth of native species.
The feathery “medusahead,” which is prominent in the northwest quarter of the park, presents considerable difficulties, he said, in that it forms thick thatches that prevent native growth underneath.
Aigner said the durability of the thatches is evident in that they remain despite control burn eradication strategies.
He said the plant's abundance contributed to a decision to postpone native seeding after the last control burn, which was conducted about a year and a half ago.
Gae Henry, president of the Anderson Marsh Interpretive Association, said she noticed an abundance of native wildflowers after the last control burn. Aigner said the trouble is there are broad categories of weeds and few tools that can be used without damaging the native species.
Aigner added the main limitation is a lack of dedicated funding. The goal, he said, is to increase the proportion of native plants and eradicate the most noxious.
Along the creek shore, guests got a lesson in blackberries, both native and non-native.
Victoria Brandon of the Sierra Club said that the Himalayan blackberry was introduced intentionally. It can be identified by its five-leaf formation compared to the native species' three.
She said the non-native plant also has more thorns than the native version. Brandon said the both species thrive where is plenty of water, such as the bank of the creek.
Brandon said the blackberries are easily spread by birds dropping seeds and other natural occurrences. She suggested eradication when the plant is small and advised against intentionally planting it.
“This is a classic example of what invasive plants do,” Katherine Blyleven of the Lake County Department of Agriculture, pointing out that the blackberries in particular impede animals' access to water.
Another species prominent in the park is perennial pepperweed, which is abundant in the west quarter of the park and non-native to the area.
Other species identified on the tour included teasel, cocklebur, reed canary grass and bull thistle.
Greg Dills, manager of East Lake and West Lake Resource Conservation District, demonstrated use of a “weed wrench” on the bull thistle, which he lifted easily from the dirt at its roots with the tool.
Following the walk through the park, guests heard a bit about aquatic weeds while they were treated to lunch.
Dills said eradication to remove Arundo, or “giant reed” throughout Lake County, has been ongoing for the past 10 years. It is a tall, green-bladed plant.
Dills also identified salt cedar, with is a feathery plant with purple flowers. He said the salt cedar not only poisons the ground it grows in but it also consumers 300 gallons of water daily.
Other aquatic species discussed included Spanish broom, French broom and tree of heaven.
Blyleven said state legislators designated the third week in July as “Invasive Weed Awareness Week.”
The program is designed to educate citizens about the undesirable effects and impacts of non-native invasive weeds.
The tour was sponsored by the Lake County Department of Agriculture, Lake County Department of Water Resources and East Lake and West Lake Resource Conservation Districts.
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