Poison-hemlock Conium maculatum
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.
-Mark Skinner, Invasive Species Chair
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.
Mark Skinner: Invasive Species Chair
Cirsium vulgare: photo by David Chipping
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.
– Mark Skinner
Photos courtesy of David Chipping
INVASIVE SPECIES REPORT
Conicosia pugioniformis Narrow leaf iceplant
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.)
Britton and Brown’s 1913 Illustrated flora of the northern states and Canada Public Domain: Wikipedia
Ailanthus altissima is in the Quassia family. It is native to China. It grows in disturbed areas including riparian areas and may tolerate extremely harsh conditions. It forms dense thickets that outcompete native vegetation and reduce wildlife habitat. The female trees produce fruit at several years of age. One tree can produce 325,000 seeds or MORE annually! However, it does not produce a consistent seed bank. Tree-of-heaven also reproduces vegetatively from creeping roots. New shoots can sprout up to 50 ft. away from the parent tree. It is present in many places in San Luis Obispo County, especially riparian areas. It is difficult to control. Tarping seedlings may work. Small trees can be weed wrenched. The whole plant has to go: stump and roots. Ideally a chemical application on a cut stump should consist of 20% Garlon 4 Ultra with 80% crop oil.
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…)
INVASIVE SPECIES REPORT by Mark Skinner
There is a weed removal initiative underway called the South Central Coast Invasive Species Eradication Project. Funded by the Wildlife Conservation Board and matching partners the $600K project joins CalIPC with multiple partners in a merged region of San Luis Obispo County and Santa Barbara County with help from the Weed Management Area of San Luis Obispo County. This effort is targeting weeds with a realistic chance of eradicating 95% of their populations in five years.
The weeds selected for removal include:
- Limonium ramosissimum – Algerian sea lavender
- Limonium duriusculum – European sea lavender
- Elymus farctus ssp. boreali-atlantucus – Russian wheatgrass
- Cirsium arvense – Canada thistle
- Linaria dalmatica ssp. dalmatica – Dalmation toadflax
The sea lavenders are at threat to Cordlylanthus maritimus ssp. maritimus – salt marsh bird’s beak and Suaeda californica -California seablite. They have appeared along the boardwalk in Morro Bay State Park In the Guadalupe-Nipomo Dunes. Russian wheatgrass can take over areas that are habitat for Atriplex leucophylla – Saltbush, Beach-Bur, Red Sand-Verbena and Dunedelion.
The agencies eradicating the weeds will track their progress through CalWeedMapper that CalIPC arranged. Partners will meet annually to report on progress.
Spiny emex (Emex spinosa)
Mark Skinner (firstname.lastname@example.org)
Spiny emex is in the Buckwheat family (Polygonaceae) and is an up and coming invasive species in California’s south coast. It’s from the Mediterranean region of Africa infesting disturbed areas especially coastal areas with sandy soils. Spiny emex spreads rapidly, crowding out native species. It has simple lime green or yellowish bronze leaves which looks like dock (which is relative) or spinach. The plant is usually two to twelve inches in diameter and produces seeds with a hard, prickly casing and spines that project from the corners. It is easy to dig out of the ground with a fork. Older plant with lots of seeds can easily shred plastic bags. Handle gingerly with tough gloves. For large monotypic infestations, Telar is an effective herbicide.