A member of the Apiaceae (Carrot) family Poison-hemlock is a biennial native to the Europe and North Africa and is a common weed, widespread in California. Poison-hemlock may germinate throughout the year. First year plants are low-growing and may overwinter in mild climates and plants resemble carrot plants. Stems are erect, hollow, smooth and bright green with purple-reddish blotches. Leaves grow to two feet long and are tri-pinnately compound. In late spring, robust plants reach 5-8 feet tall and produce numerous umbel-shaped clusters of tiny, white, 5-petaled flowers. Poison-hemlock grows in moist areas such as pond sides, creek
banks and flood plains. It tends to grow in dense thickets and when the plants have dried out it is very difficult to walk through and the dead canes are toxic! It is notorious for displacing other vegetation. Plants reproduce only by seed and seeds may survive to about 3 years. Each flower produces two gray–brown seeds. There are hundreds of seeds on each plant. Poison hemlock is highly toxic due the toxin coniine. Seeds have the highest concentration of coniine. All parts of the plant are poisonous. Cattle are especially vulnerable. There are limitations to controlling this plant: do not cut, burn or graze. Pulling it is one of the best options and it’s especially important to pull out the root.
A member of the Asteraceae family, bull thistle is an annual herb native to Europe and is widespread in California and listed as a noxious weed in Colorado, New Mexico, Oregon and Washington. It is found in every state in the U.S. and on every continent except Antarctica. It is a problem in some natural areas such as Yosemite National Park, California. It might have been introduced to eastern North America during colonial times, and to western North America in the late 1800s. Bull thistle is the most common and widespread of pasture and rangeland thistles in western North America. It is also found in disturbed areas such as forest clearcuts, and along roads, riparian areas, and fences. Plants can form dense thickets, displacing other vegetation. The spiny nature of the plant renders it unpalatable to wildlife. Bull thistle is usually a biennial, but can be monocarpic (flowers and seeds one time) and die. It forms a deep taproot and prefers
fertile, well drained soils and grows to 3 to 4 ft. tall. In the juvenile phase, individual bull thistle plants form a single rosette to 3 ft. in diameter. Stems have spiny wings with many spreading branches, and sometimes a single stem. Leaves are 3 to 12 inches long, deeply lobed with coarse prickly hairs on top and woolly underneath. Lobes are tipped with stout spines. Bull thistle flower heads are pink-magenta, to 2 inches in diameter, to 2 inches long, usually solitary, or clustered at the ends of shoots and branches. Large spiny bracts (modified or specialized leaves) surround the seed heads. Bull thistle fruits are achenes (a simple dry fruit), 1/16th-inch long, with a long, hairy plume that is easily detached. Plants can produce up to 300 seeds per flowerhead, with 1 to 400 flower heads per plant. The seed bank is very short lived on the surface but may last 3 years if buried. The key to successful management of bull thistle is to prevent seed production. Seedling and rosette growth stages are the most logical to target for control efforts.
The extremely invasive Foeniculum vulgare is in the carrot (Apiaceae) family. It is native to Southern Europe and is problematic in coastal California and is also present throughout the western US all the way to Texas. I’ve encountered Fennel on Santa Catalina Island and Santa Cruz Island. Clusters of Fennel may be found in disturbed areas, mostly roadsides and fields. Fennel is an aromatic perennial with a thick deep taproot and which grows to 5 to 10 ft. tall forming dense stands producing thousands of seeds that birds and rodents consume. Seeds may survive several years. Feral pigs are attracted to it and love its roots! Fennel crowds out native plant species and can drastically alter the composition and structure of many plant communities, including grasslands, coastal scrub, riparian, and wetland communities.
The cultivated varieties of Fennel are seldom invasive. The leaves are finely dissected and the plants produce yellow flowers on compound umbels. Fennel is a difficult, labor intensive plant to control. Small infestations can be dug out. Large plants are hard to dig out. Preventing seed production by lopping stems is vital so cutting Fennel repeatedly is advised. Grazing with goats can knock the plants down. Burning doesn’t work because Fennel quickly recovers, but if linked with herbicide treatment may be an effective method.
Conicosia is in the Aizoaceae family. It is a succulent perennial with a crowded basal rosette of smooth, bright green, upright, linear leaves. Clustered with the leaves are stems with brilliant yellow flowers. All this on top of a carrot like root. It’s capsule fruits are dry at maturity.
Conicosia is abundant on coastal dunes. It seems like nearly anywhere I travel in the back dunes from Oceano to Guadalupe—there they are—they’re so darn ubiquitous! Conicosia crowds out native plants and is a prolific seed producer.
Do not step on a plant with dried capsules: the seed will stick to the bottoms of your shoes! Due to a thick root it is hard to pull. If one snaps off the leaves on the soil surface it will grow back, therefore a shovel is best. Chemical control is best achieved by spraying a liquid mix containing 1.5% glyphosate 1.5% surfactant. It is best to spray before flowering. (We caution that the use of glycophosate is under legal challenge as a possible carcinogen.)
Brassica tournefortii is in the Mustard family. It is native to the desert areas of the Mediterranean region of Europe. It has expanded its distribution in the sandy soils of Los Osos, most probably spread during the sewer project, and can rapidly overtake other plants and form a monoculture. (more…)
Dittrichia graveolens is in the Asteraceae family. It is native to the Mediterranean region of Europe. Stinkwort is erect, growing to 2.5 feet. It typically has a conical shape but can have a round appearance. It’s sometimes confused with Russian thistle (tumbleweed). It ﬂowers from September to December and produces tiny seeds. Stinkwort’s foliage has sticky hairs covered in resin that truly stinks and sticks to and stains skin. (more…)
Sahara mustard is annual from the Mediterranean and has been spreading rapidly into coastal San Luis Obispo County. It is in Los Osos, Grover Beach, Oceano, the Nipomo Mesa and the Santa Maria River. Sahara Mustard first appeared in North America in 1927 in Coachella Valley and has spread throughout the Sonoran Desert. It grows in disturbed areas: mainly roadsides, dirt roads and construction sites. Locally it has spread from sticky seeds on pick-up truck tires, construction equipment, rodents and from wind. One of the awful qualities about this weed is that it out-competes native plants, especially annuals, simply because it grows very densely.
Basal rosette (David Chipping)
The 3 to 12 inch deeply lobed leaves exist as a rosette which is low, only several inches above the ground. The small, pale yellow flower stalks may reach 4 feet and produce zillions of seeds (actually up to 9,000 seeds) that are viable for more than 3 years.
Controlling Sahara mustard may be done by hand pulling. It is easier to pull than Black mustard. Sahara mustard is prolific and annoyingly often grows amongst tree and shrub plantings: pulling is the only option in this instance. It is best to pull when they are emerging. Once seed pods develop, the plant will set seed after it has been pulled, so it should be removed from the site.
When away from native plants monotypic Sahara mustard may be sprayed with Telar, Milestone, Garlon 3A or Transline (they are all broad leaf herbicides). Grazing is not a good idea because there is are toxic compounds in the seeds.
Coffeeberry Frangula californica – Images courtesy of Marlin Harms Way back in 1992 the Watershed Education Program for San Luis Obispo County, in conjunction with U.C. Extension and the Soil Conservation Service (now Natural Resources Conservation Service)...
There is an intense infestation of Jubata grass on the California coast. As almost everyone knows it mars the most
beautiful places such as Big Sur. On their web site California Invasive Plant Council (CalIPC) describes that Jubata grass is native to northern Argentina, Bolivia, Peru Chile and Ecuador. It was grown in France and Ireland from seed collected in Ecuador. It may have come to California from France and was first seen in 1966. Jubata grass has been called the “marriage weed” as honeymooners dragged the plumes behind their cars in Big Sur. Oy! What a mess!
Jubata grass flowers from late July to September. No pollination is necessary for reproduction. Flowers are female
only, which produces viable seed. Each plume may contain 100,000 seeds! Plants may have 1 to 30+ plumes. I started removing Jubata grass in the mid 1990’s with Jack Biegle and John Nowak, just north of Oso Flaco boardwalk.
I’ve been at it ever since and removed hundreds from the Guadalupe-Nipomo Dunes, San Luis Obispo, Cambria and
Vandenberg. I’m happy to report that from the many hundreds that were in the Guadalupe-Nipomo Dunes there are only about twenty remaining.
I’m pleased to start an Invasive Species Watch column to Obispoensis. I’ve been in the invasive species removal business since 1999 mainly working in the Guadalupe-Nipomo Dunes and San Luis Obispo Creek. Those that know me many not think of me as a warrior however many people (thanks CCC’s!) and I have been battling bad guys such as Arundo, jubata grass, veldt grass, European beach grass, Russian wheat grass (some of the most insidious weeds are grasses!) cape ivy and ice plant for a long time. The satisfaction of this work arrives when a formerly infested area is re-taken by native plants. The best memory I have is from 2002 when a heavy veldt grass infestation was sprayed out at the then Tosco Buffer (now Phillips 66) which was followed by a lush wildflower display of goldfields, dune larkspur, owl’s clover, baby blue eyes, blue dicks, sky lupine, and fiddleneck. I’m still working on the same weeds and I’m seeing progress: Russian wheat grass and jubata grass have been nearly eradicated from the Dunes! In future pieces I’ll be describing specific invasive species and what’s being done to control them.