Invasive Plants of California's Wildland

Conicosia (Conicosia pugioniformis) is a short-lived succulent with prostrate to ascending shoots and a central, thickened taproot. The taproot intergrades with a short, thick root crown, allowing for shoot growth after inundation with sand. Leaves are slender, bright gray-green to green, somewhat irregularly scattered along stems, and clustered near stem tips. Flowers are large and solitary with numerous shiny, light yellow petals. The fruit is a cone-shaped capsule that splits open when drying and is easily dispersed by wind, spilling seeds as it tumbles. Conicosia is easily distinguished from highway iceplant (Carpobrotus edulis) and sea fig (C. chilensis) by its narrow, long, bright green leaves, lack of rooting along trailing shoots, and absence of large clonal mats.

Aizoaceae. Perennial, usually short-lived. Roots: taproot, 1.6-3.3 ft (0.5-1 m) in length, swells extensively, especially in first year. Caudex: 0.8-8 in (2-20 cm) in length and up to 2 in (5 cm) in diameter, vertical growth apparently related to burial; intergrades with taproot. Stems: above-ground shoots decumbent, 1.66-5 ft (0.5-1.5 m) in length, moderately branched. Leaf arrangement: basal leaves form a loose rosette; cauline leaves alternate but somewhat irregularly arranged along stem.

Leaves: narrowly linear to cylindrical, rounded triangular in cross section, 6-8 in (15-20 cm) in length and 0.4-0.6 in (1-1.5 cm) in diameter. Inflorescence: 1-flowered axillary peduncle, <4.8 in (<12 cm) in length. Flowers: bright in appearance; 2-3.2 in (5-8 cm) in diameter; the 5 sepals irregular, succulent to papery; the several dozen petals shiny yellow and linear; multiple stamens; ovary +/- inferior, many chambered, multi-ovulate. Fruit: cylindrical capsule with conical top, dehiscent, with ovary chambers opening individually and capsule sometimes separating into individual valves; dried capsule dispersed easily by wind. Seeds: smooth and round, approximately 0.04 in (1 mm) in length (description from Hickman 1993). < /FONT>

Conicosia is found in coastal dunes and adjacent disturbed areas from the San Francisco peninsula to Point Conception, California. It is locally abundant, with particularly large populations occurring at Vandenberg Air Force Base and in the Guadalupe-Nipomo dunes. It is most abundant in open patches on dunes and in recently disturbed areas (e.g., along trails, roads, and railroad rights-of-way) with sandy soil. It seems to require well drained, sandy soils. It colonizes foredune, dune scrub, and, to a lesser extent, coastal scrub, coastal prairie, and maritime chaparral communities.

Conicosia invades disturbance corridors within coastal scrub or maritime chaparral and has the potential to inhibit regeneration of native species in restoration sites. It colonizes recently disturbed sandy areas, forming high-density populations that can preclude establishment of other vegetation. In addition, it readily invades openings in foredune and dune scrub communities, often becoming established under shrubs and alongside subshrubs, graminoids, and herbs. It is likely that this results in interference with the growth and establishment of native plants. Individual conicosia plants produce many seeds in fruit capsules that are easily dispersed; thus, once established in an area, it is difficult to stop further colonization. Conicosia also may invade maritime chaparral following fire (Odion et al. 1992). Other invasive members of this family have been shown to alter soil chemistry (Vivrette and Muller 1972, D’Antonio 1990a). It is not currently known if this plant can influence soil chemistry.

Flowering occurs in late summer through autumn. Plants may flower in the first year, but flowering often begins in the second year. Plants can live ten years or longer (Bleck, pers. comm.). Reproduction occurs by seed. Plants flower in summer or fall of their first or second year and every subsequent year. As capsules dry, tissue from the upper surface of individual valves pulls away, allowing seeds to drop. Capsules separate from the plant when dry. Whole dried capsules are readily moved by wind. Individual capsules produce tens to hundreds of seeds. Plants can resprout from the buried root crown after above-ground tissue is removed.

Conicosia plants can grow to several feet in diameter in a single growing season. Seeds from dense populations can spread rapidly into adjacent areas. There are currently no known studies of the physiological ecology of this species. Seedlings appear to devote much of their photosynthate to the thickened taproot; young individuals may have a taproot of one to three centimeters in diameter but only a few small leaves.

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Removal of live plants is easily accomplished by either mechanical or chemical means. Eradication of the species from any large area, however, is complicated by the wind dispersal of seeds and the propensity of conicosia to colonize disturbed areas. A critical component of any control effort will be follow-up removal of seedlings.

Manual methods: Plants are killed either by hand pulling or by slicing the taproot with a shovel, pulaski, pick and hoe tool, saw, or knife. Hand pulling is easy when plants are small (<0.5 m diameter) and soil is loose and/or moist, but can be difficult on large plants or in dry and/or compacted soils. Resprouting from basal shoots is possible, so care must be taken to ensure that the thick underground root crown is severed. Removal is recommended before fruits have set (Theiss 1994).

Prescribed burning: Because of the high water content of shoot tissues, burning live plants is not an effective method of control.

Insects and fungi: There are no known studies of biological control, and iceplant scale (Pulvinariella mesembryanthemi, P. delottoi) has not been observed on this plant. Plants at Vandenberg Air Force Base have appeared to be killed by dodder (Cuscuta sp.).

Grazing: Because of the astringent and often salty quality of the succulent tissue, grazing is not likely to be a control option.