Source: California Invasive Plant Council


URL of this page: http://www.cal-ipc.org/ip/management/ipcw/pages/detailreport.cfm@usernumber=7&surveynumber=182.php

Invasive Plants of California's Wildland

Arctotheca calendula
Scientific name   Arctotheca calendula
Additional name information: (L.) Levyns
Common name capeweed, South African capeweed, cape dandelion, cape gold
Synonymous scientific names none known
Closely related California natives 0
Closely related California non-natives: 0
Listed CalEPPC Red Alert,CDFA A
By: Maria Alvarez
Distribution
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HOW DO I RECOGNIZE IT?
Distinctive features:

Capeweed (Arctotheca calendula) is an annual or perennial evergreen herb that, when young, forms a low-growing rosette of heavily pinnately lobed leaves, with undersides covered by woolly down. With age, it forms an extensive, dense, mat-like groundcover by proliferation of rooting stems (stolons) from rosettes. Leaves are pinnately lobed; fine, dense hairs cause stems and leaves to appear silvery. Flowers are approximately two inches in diameter, lemon yellow, and daisy-like with yellow centers. The plant is conspicuous in late spring and early summer due to its increase in size and the profusion of large yellow daisies. Plants are seldom solitary, and they spread vigorously by creeping stems (Lasca Leaves 1968).

Description:
Asteraceae. Stems: creeping or decumbent, originating from an individual rosette; succulent, hairy (tomentose), and ribbed; stems creep along or just below the soil surface, bearing fully formed leaves and reaching lengths of up to nine feet in one growing season. Leaves: pinnately lobed, 2-10 in (5-25 cm) long, upper surface finely hairy (cobwebby), lower surface densely hairy or silky (white-woolly). The woolly leaf underside is a feature distinguishing capeweed from other herbs in the absence of flowers. Inflorescence: heads 2.4 in (6 cm), peduncles scapose, 6-8 in (15-20 cm) long; outer phyllaries green, woolly tips reflexed. Ray flowers fewer than 20; ligules lemon yellow above. Disk flowers many, bisexual, also yellow. Fruit: sterile, up to 0.2 in (5 mm), covered with hairs (Hickman 1993).

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WHERE WOULD I FIND IT?

At present, infestations in California are known only from coastal Marin and Humboldt counties (Barbe 1990), but capeweed can survive in most of this state west of the Sierra Nevada. Hickman (1993) reports a probable range of coastal counties from the Oregon border to Monterey County. Capeweed grows best in full sun to light shade, can tolerate a wide variety of soils, and needs little water to persist once it is established. It is typically planted by homeowners and is used extensively in San Francisco Bay Area landscaping. It is often planted in or near urban wildlands, where it thrives in seasonally wet meadows. Capeweed also will grow in drier soils, spreading during the wet season, then becoming dormant during periods of low water availability. It is subject to frost damage, but can quickly regenerate from the crowns when the weather warms.

WHERE DID IT COME FROM AND HOW IS IT SPREAD?

A sterile, vegetatively reproducing race of capeweed was introduced to the United States in 1963 from the Cape of Good Hope in South Africa. Capeweed was propagated by Los Angeles State and County Arboretum, and it was made available to the nursery trade in 1965 (Lasca Leaves 1968). It is still available in nurseries and has been widely used in landscaping. It escapes from cultivation to wildlands. Capeweed spreads vegetatively by rooting stolons.

WHAT PROBLEMS DOES IT CAUSE?

Capeweed grows over and displaces other herbs and in coastal grasslands and riparian zones forms monospecific stands of impenetrable mats up to several thousand square feet (Alvarez unpubl. data). It is a rapidly growing groundcover, and, if planted on one-foot centers, will establish full cover within six months (Sunset 1985). Capeweed is an aggressive competitor for water and space, and it seriously threatens native plant communities by crowding out grasses, herbs, and small shrubs. Once capeweed is established, it is difficult for other plants, particularly perennials, to become established (Frey 1984).

HOW DOES IT GROW AND REPRODUCE?

Propagation or reproduction of capeweed is by vegetative means. Flowering occurs principally from March to June, but this variety does not produce fertile seed. It is a sterile race, extremely successful at spreading by sending out extensive stolons (stems) from one individual crown (rosette). These stolons are capable of rooting at each node and forming a new plant that remains attached to the runner until it is capable of making its own stolons (approximately one season). Above-ground stolons develop from the axil of a leaf at the root crown of the plant. Runners grow horizontally along the ground, and are typically about 6.6 feet (2 m) in length; some up to thirteen feet (3.9 m) long have been extracted from capeweed removal sites in the Golden Gate National Recreation Area. Stolons form principally in late winter and throughout spring until water availability decreases. Another method by which capeweed is known to spread is the mechanical removal of a piece of stem or root tuber from an established patch to a new location. Capeweed infestations are often located along roads and trails, particularly where heavy equipment operators perform routine grading, resurfacing, or fill removal activities.

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New growth can grow over other herbs and through shrubs. An old colony often has new stems growing over old stems, forming a thickened mat of mostly capeweed over time. Capeweed also can form small tubers 0.4 inch (1 cm) thick and 1.2 inches (3 cm) long. This plant will grow well in less than favorable conditions, does equally well on slopes, flat areas, or mounds, and performs best in full sun (Lasca Leaves 1973). It is hardy to a few degrees below freezing. If unchecked, a small plant can cover as much as 200 square feet (18 sq m) in a year or two (Mathias 1982). It has a shallow root system

(click on photos to view larger image)

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HOW CAN I GET RID OF IT?

Physical control:

Manual methods: Hand removal has been the primary method of capeweed removal in the GGNRA since 1987. Many tools can aid in removal, but the best found so far is a lightweight hand pick available at garden or hardware stores. A hand pick 12 to 15 in (45-53 cm) in size, with a 10 in (25 cm) head, consisting of a five-inch (13 cm) pick on one side and a five-inch (13 cm) hoe on the other has been found to be most effective. A spading fork can also be useful for loosening densely rooted capeweed prior to hand pick removal. Approach the removal of capeweed from the outer perimeter of the infestation, carefully locating the growing tips of the runners and gently prying them up with the hand pick, feeling for resistance where each node may have taken root. Strike the soil around the rooted node, or root crown and gently lift the surrounding soil upward to remove the root intact. If you are removing a well established plant, the root crown will appear semi-woody and small tubers may be left behind. Try to remove the crown and roots as intact as possible to avoid leaving tubers. Avoid breaking the capeweed stems, since stem pieces with nodes will take root if they are left behind. Dormant crowns can be located by following succulent or shriveled stem runners leading to them. The center of the infestation usually contains older, more established plants with deeper root systems. Capeweed cover in the center is also usually denser, since the runners cross each other and form a mat. In dense infestations, all capeweed crowns are not removed during one control effort, so follow-up will be needed.

Solarization: Application of horticultural grade, polyethylene landscape fabric is a successful alternative to hand removal of most large infestations. Landscape fabric is a supple black fabric that prevents sunlight from reaching the plants but allows water and gases to penetrate. Unable to photosynthesize, capeweed exhausts stored food reserves and eventually dies. A minimum of one and a half years is needed to kill 99 percent of the covered capeweed (GGNRA). Landscape fabric is far superior to black plastic, which photodegrades in the field after several months, turns brittle, and crumbles. Wildlife will also eat plastic. Landscape fabric has been re-used for at least five years. Seeds will stick to the fabric, so be sure to remove them if the fabric is to be taken to another plant community. Not all sites are suitable for the use of landscape fabric, since it must be staked down for a long period. It is difficult to maintain cover on steep, rocky, or extremely windy sites. Jute netting staples typically are used to secure the fabric; in rocky, level sites they are useless, so the edges are weighted down with heavy boards, rocks, or logs. A soil trench can also be excavated to bury the edges of the fabric. If there are still native plants in the capeweed site, holes can be cut through the fabric to preserve large native plants, but it is preferable to relocate desirable plants, if possible, to reduce fabric maintenance. Hand weeding is also critical around the edges when the fabric is first applied or capeweed will spread from the site. Straw mulch can be placed over the fabric to conceal it from vandals.

Mechanical methods: Heavy equipment can be an appropriate means of capeweed removal. A small tractor with a front-end loader was successful in removing most of a dense trailside infestation in the GGNRA by scraping the capeweed off the soil surface into a pile. Capeweed was subsequently bagged, and manual follow-up was conducted for several years. Use of heavy equipment greatly reduced the manual labor needed to eradicate the capeweed.

Prescribed burning: There are no reports of attempts to control capeweed by burning.

Biological control:

Insects and fungi: Capeweed is not known to be eaten by California wildlife or invertebrates and has no known pathogens in the central coast region of California. No effective biological control agents have been reported. Horticultural literature reports that it is occasionally eaten by caterpillars, aphids, mites, slugs, and snails but will usually sustain or recover from such herbivory without any treatment (Lasca Leaves 1973).

Literature exists on the forage value of the related fertile form of capeweed for Australian fauna (Rayner and Langidge 1985). Large established patches may experience some root rot, but plants quickly regenerate from stem nodes. An Ortho book (1977) on groundcovers claimed that capeweed is subject to fungus diseases that damage the foliage but generally not the root system, so the plant will usually recover.

Chemical control:

Herbicide application to large, dense capeweed patches can be successful in reducing the density of the infestation. Repeated application of 3 percent glyphosate may be needed to permanently eliminate capeweed. Glyphosate has been recommended for use on the related fertile capeweed. However, ten years of continual herbicide use on the fertile capeweed in Australia resulted in a herbicide-resistant biotype (Powles et. al. 1989).