What Is A Noxious Weed?

A weed is designated noxious when it is considered by a governmental agency to be injurious to public health, agriculture, recreation, wildlife, or property. Some general characteristics of noxious weed are their ability to spread rapidly, reproduce in high numbers, and crowd out native plants. Noxious weeds also tend to be very difficult to control.

Noxious weeds can be annuals, completing their life cycle in one growing season, or perennials, having a life cycle spanning more than one growing season. Most noxious weeds were originally from other countries. Many arrived in shipments of desirable seeds, in the ballast of sailing ships, or were introduced intentionally as garden plants. Noxious weeds thrive in disturbed areas like roadsides, building sites, maintenance areas, irrigation ditches, dirt parking areas, trails, and campgrounds. Once noxious weeds gain a foothold, they can increase water and wind erosion, alter nutrient cycling, destroy wildlife habitat, reduce the usefulness of recreation areas, and decrease agricultural productivity.

Slide 1-9 are weeds. Slide 10 thru 14 are Native Vegetation.

The following list of non-native weeds are plants that pose a threat to the natural habitats of Southern California by their distribution or invasiveness, and should be removed whenever they are found. The native vegetation list outlines vegetation that needs to be thinned.

The purpose here is to identify the most common weeds homeowners might encounter but be aware that the chief danger remains in the annual grasses that appear in spring. These grasses, chiefly wild oats, quickly die back and become a fire danger.

Artichoke Thistle - Cynara cardunculus

Artichoke Thistle is a state listed, aggressive noxious weed that infests much of Orange County. It has caused widespread damage to native plant communities and ecosystems and has rendered pockets of rangeland useless. It should be removed whenever possible to prevent further infestations. The plant stands 1-2 m in height and can be identified by large spiny leaves that form a rosette pattern. It displays large flowering heads with showy purple disk flowers.

This extremely invasive perennial weed is commonly found in grasslands and hillsides. It’s leaves sport some very nasty spines. It is easily identifiable by it’s bright purple flower disks. In late summer it dies back and becomes a fire danger.

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Wild Fennel - Foeniculum vulgare

This wispy perennial is similar to the domesticated herb found in gardens. It can grow up to 8’ high, dry out, and become fire danger.

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Wild Tobacco -

Found in disturbed areas, this is highly invasive perennial weed is also quite toxic. It is usually spindly in appearance with bright yellow elongated flowers.

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Giant Reed - Arundo donax

This grass is one of the most invasive wild land pest plants known in California. It is commonly found in riparian (creek) areas.

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Black Mustard - Brassica nigra

This annual herb is found on almost every disturbed hillside and vacant lot in Orange County. It is easily identifiable by its many small bright yellow flowers. When it has taken over a large area it provides a beautiful carpet of yellow. It only real danger is that completely dries out in late summer and becomes a significant fire danger.

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Caster Bean - Ricinus communis

Native to the east Africa, the castor bean plant has become naturalized to all of Southern California. They are very common along creeks, riverbeds, and just about any area with sufficient moisture to sustain the vigorous growth. It is easily identifiable by its large seeds. They are usually bunched with each seed about the size of a nickel. The plant will typically grow from 10 to 15 feet in height. Keep in mind the seeds and beans are extremely poisonous, so keep children and pets away.

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Russian Thistle (Tumbleweed) - Salsola tragus

A rounded, bushy annual, it stands from ½ to 3 feet tall. It became common throughout the western United States in the late 19th century. It is mostly found on disturbed lands and vacant lots.

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Bromus Sp -

The Bromus species are common grasses that emerge in spring. They can be found almost everywhere up to 10,000 feet. Bromus, like most grasses, is an annual that begins to dry out in early summer until it becomes a significant fire hazard.

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Wild Oats - Avena fatua

Wild oats is an annual weed, reproducing by seed. In the mature plant, the stems are smooth, erect, and grow up to 150 cm (4 ft.) tall. The leaves are similar to tame oats. The head is an open panicle and the spikelets usually contain 2-3 florets (up to 7). The panicle may contain up to 250 seeds, ranging from black, brown, gray, yellow, to white.

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Lemonade Berry - Rhus orata

This large shrub gets to 4-5 feet tall and can spread to 15 or more feet across. It is native to the slopes above the coast.

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Coastal Sage - Artemisia california

California Sagebrush is a dominant plant in coastal sage and occurs usually below 2,000 feet. It is a much-branched shrub two to five feet tall with numerous, grayish-green leaves parted into thread-like divisions. The leaves have a clean, but bitter fragrance.

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Wild Buckwheat - Eriogonum fasciculatum

A common native perennial herb. 12-15 inches tall. It is found throughout Southern California in areas below 3000 ft. Small clusters of white flowers in spring turn to reddish brown by summer.

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Laurel sumac - Rhus laurina

Laurel sumac is a large rounded evergreen shrub or small tree growing 10' to 15' tall. Laurel sumac is commonly found on dry ridges and canyons below 3000' in chaparral and coastal sage scrub. Very susceptible to frost, it is often planted by citrus growers as a frost indicator. The dried out floral remains are sometimes utilized by train set builders as model trees. It blooms from June to July.

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Toyon - Heteromeles arbutifolia

Toyon, or California Christmas Berry, is an evergreen shrub or small tree growing 6 to 10 feet high and forming a round crown. The elliptical leaves are 2 to 4 inches long, dark green above and lighter underneath. By Christmas, the tree produces attractive red berries that add a cheerful note to the winter landscape and to provide a feast for robins, mockingbirds and cedar waxwings.

Toyon berries were gathered by many Indian tribes. The berries were roasted over open coals or boiled in a cooking basket to take away the bitter taste of the fresh fruit. Indians also made a tea from the bark to cure stomach aches. Today, this beautiful and useful shrub is planted extensively in parks and gardens.

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