The Double Cone Quarterly
Window to the Wilderness
Spring Equinox 1999 || Volume II, Number 1

Invasive Exotic Plants in the Wilderness
a series

Cape Ivy, Another Problem Plant for the
Ventana Wilderness

by Dave Nelson

Cape Ivy (Delairea odorata)

Right now the yellow blossoms of French broom are electrifying the coastal views in the Big Sur area. The pampas grass is slightly less noticeable than in late summer because winter winds have knocked down the tall plumes.

In a drive down the coast you may also notice bright, homogeneous green patches here and there - some down along streams and rivers - some up high in isolated brushy hillsides. This is Cape ivy (Delairea odorata) - formerly known as German Ivy (Senecio mikanioides) and it's invading undisturbed wildlands in a slow-motion explosion. In Monterey County it's received less attention than other severe problem plants like pampas grass and French broom but poses an equal threat with its ability to spread readily to undisturbed wildlands.

Cape ivy is in the sunflower family and native to South Africa where it's a well behaved non-invasive component of its ecosystem. But the climate, soil, plant competitors and herbivores aren't the same here and Cape ivy, brought here in the 19th century as a potted parlor plant, spreads rapidly in riparian areas and over coastal scrub in full sun locations at low foggy elevations in Big Sur. It's proliferating in California from Del Norte to San Diego county as well as Oregon, Hawaii, Maui and Australia. Though it is moving to drier inland areas in Southern California I've only seen it in coastally influenced places below 1000 feet in Big Sur.

Look high above the homestead at Soberanes Point or inland from Bixby or Garrapata bridges. It's in numerous lower riparian areas of Big Sur - more the nearer you are to Carmel. There are more patches farther south; some are along the lower Big Sur River by the highway in Andrew Molera State Park where the Parks Department is attempting control with a combination of mechanical removal and herbicide; more are in the Ventana Wilderness near Lucia. Check out the entire watercourse at Julia Pfeiffer Burns State Park between the footbridge and the highway (an easy place to learn it up close). This plant is spreading rapidly on public and private lands and crowding out the native vegetation and the animals that depend on it, thus diminishing the biodiversity of the area.

Besides impacting ecosystems and disrupting terrestrial habitat functions, Cape ivy contains potent alkaloids including pyrrolizidine, which is toxic to aquatic organisms. It is suspected to be toxic to fresh water shrimp as well as salmonids, including threatened steelhead and coho.

Cape ivy is the number one vegetation management concern in the Golden Gate National Recreation Area, covering 162 acres of the 75,000 acres. It spread in the Marin headlands from 8.8 acres in 1987 to 67.3 acres in 1996 (765% in 9 years). The GGNRA and adjacent Point Reyes National Seashore were awarded a National Park Service grant of $600,000 over 3 years to contain this plant. The California Exotic Pest Plant Council (CalEPPC), a non-profit organization which deals with problem plants throughout the state, puts it on its A-1 list of Most Invasive Species. No systematic assessment of the spread of Cape ivy has been done in Big Sur but long term observers will tell you that it is rampant.

Cape ivy spreads primarily by vegetative means. A two inch piece including a leaf node will sprout readily - even after sitting on dry ground for months. Pieces transported by flooding can be seen growing along the Big Sur River. Uprooting Cape ivy is harder than it might sound. The stems break off easily creating re-rooting pieces and leaving purple runners under leaf litter.

It doesn't set seed readily and preliminary tests show poor germination but hard frosts appear to stimulate seed set. Local observers noticed an increase in new patches after the 1991 hard frost and we recently observed abundant seed formation at Molera and J.P Burns State Parks in January after this winter's repeated low elevation frosts. True to their Composite family ties, seeds have wispy pappus (like dandelions) making them easily airborne. More testing is needed on these subjects.

There is little you can do to control Cape ivy on a backpack trip through the Ventana. Because of its quick rooting nature, you run the risk of dropping some and spreading it! If you stuff Cape ivy in a plastic bag and bring it down, dispose of it in a container you're sure is going to a landfill. I've heard of heaps sealed in plastic garbage bags in a closed car that were still viable after many weeks.

Some control can be achieved by labor-intensive mechanical removal right down to the roots (a 'scorched earth' approach). But follow-up is necessary. A combination of two fairly benign herbicides at low concentration is also effective. Follow up spraying is necessary. A combination of mechanical removal followed by herbicide treatment is also effective and can decrease the amount of herbicide used.

These control techniques are not appropriate in the Ventana but may be useful in other areas. A more thorough discussion of Cape ivy control techniques can be found by perusing the Newsletters in the CalEPPC web site or by visiting the Cape Ivy Working Group.

The greatest promise to stop the spread of this plant in the Ventana Wilderness may be biocontrol. CalEPPC and the USDA Agricultural Research Service are cooperatively heading biocontrol research in South Africa. The first year was very successful having isolated three insects - two moths and one beetle - which control Cape ivy in its native range. Extensive testing is needed to be sure these insects won't attack native plants or cause other problems if released in California. $68,000 in funding is sought for the second year. To contribute or for any questions regarding the Cape ivy biocontrol project contact:

Greg Archbald
Golden Gate National Parks Association
Fort Mason, Building 201
San Francisco, CA 94123
415-561-3034 x 3425
x 3010 fax

The USFS Los Padres National Forest-Monterey District is creating a Weed Management Area plan to coordinate the invasive weed efforts of public agencies and private landowners. Cape ivy is a target species at Sycamore Canyon/Pfeiffer Beach named in the District's 1999 Invasive Weed Control Environmental Assessment. To express your support for these projects and more information contact:

Jeff Kwasny, Resource Officer
USFS Los Padres N.F.
Monterey Ranger District
406 S. Mildred
King City, CA 93930

Supporting biocontrol research and organized volunteer work are also important ways to fight this pest. The Monterey chapter of the California Native Plant Society often sponsors field trips that include manual Cape ivy removal (as well as less strenuous wildflower viewing) where it threatens native flora. Though most trips aren't near Ventana Wilderness proper, we would do well to keep Cape ivy controlled anywhere in the area because it doesn't know legal boundaries. Further information on how you can help can be found at the statewide California Native Plant Society website.

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