Plant Assessment Form

Clematis vitalba

Synonyms: Anemone vitalba

Common Names: old man's beard; traveler's joy

Evaluated on: 23-Dec-16

List committee review date: 25/01/2017

Re-evaluation date:

Evaluator(s)

Mona Robison/Science Program Manager
Cal-IPC
916-802-2004
rrobison@cal-ipc.org

List commitee members

Elizabeth Brusati
Tim Hyland
Eric Wrubel
Irina Irvine
Holly Forbes

General Comments

C. vitalba has only recently been identified in California (2014). It is not included in the Jepson Manual, and in Muir Woods it was misidentified for many years as C. ligusticifolia, which may be true elsewhere in the state. These two species can only be reliably differentiated in flower.

Table 2. Criteria, Section, and Overall Scores

Overall Score? Moderate
Alert Status? Alert
Documentation? 3 out of 5
Score Documentation
1.1 ?Impact on abiotic ecosystem processes B Reviewed Scientific Publication
Impact?
Four-part score BABC Total Score
B
1.2 ?Impact on plant community A. Severe Reviewed Scientific Publication
1.3 ?Impact on higher trophic levels B. Moderate Reviewed Scientific Publication
1.4 ?Impact on genetic integrity C. Minor/Low Other Published Material
2.1 ?Role of anthropogenic and natural disturbance in establishment B. Moderate Reviewed Scientific Publication
Invasiveness?
Total Points
18 Total Score A
2.2 ?Local rate of spread with no management A. Increases rapidly Observational
2.3 ?Recent trend in total area infested within state C. Stable Observational
2.4 ?Innate reproductive potential
(see Worksheet A)
A. High Reviewed Scientific Publication
2.5 ?Potential for human-caused dispersal A. High Other Published Material
2.6 ? Potential for natural long-distance dispersal A. Frequent Reviewed Scientific Publication
2.7 ?Other regions invaded A. Invades 3 or more ecological types Reviewed Scientific Publication
3.1 ?Ecological amplitude/Range
(see Worksheet C)
B. Moderate Observational
Distribution?
Total Score C
3.2 ?Distribution/Peak frequency
(see Worksheet C)
D. Very low Observational

Table 3. Documentation

Scores are explained in the "Criteria for Categorizing Invasive Non-Native Plants that Threaten Wildlands".

Section 1: Impact
Question 1.1 Impact on abiotic ecosystem processes? B Reviewed Scientific Publication
Identify ecosystem processes impacted:

In California, C. vitalba has smothered over 1.5 acres of riparian oak-bay woodland at Muir Woods, where it forms large monocultures. The dense canopy suppresses all vegetation below by significantly reducing light availability (Wrubel, pers. comm.).

Restricts light availability for species under the canopy. Hill et al. (2001) report that, "Vines can climb the tallest forest trees, forming a dense, light-absorbing canopy that suppresses all vegetation beneath it. C. vitalba can be so vigorous that the weight of foliage and stems breaks the supporting trees, reducing once-healthy forest to a low, long-lived thicket of vines scrambling over stumps and logs". However Ogle et al. (2000) observe that the vines ascend to the canopy of forest but are unable to climb large diameter emergent trees unless shrubs and smaller trees provide a series of stepping stones to the crown of tall trees. Their study findings (study area Taihape reserve, New Zealand) indicate that the numbers and variety of understorey trees and shrubs that have been severely reduced following the infestation of C. vitalba correlates with observations of the growth habit of C. vitalba. Ogle et al. showed e.g. that not a single canopy tree species had been lost from the Taihape Reserves though 25% or so of the understorey trees and shrubs species had been lost.


Sources of information:

GISD 2005
Ogle et al. 2000
Hill et al. 2001
Wrubel, E., Personal communication.


Question 1.2 Impact on plant community composition,
structure, and interactions?
A Reviewed Scientific Publication
Identify type of impact or alteration:

In California, C. vitalba has smothered over 1.5 acres of riparian oak-bay woodland at Muir Woods, where it forms large monocultures. The dense canopy suppresses all vegetation below. Shrub and herb diversity is severely reduced under dense infestations (Wrubel, pers. comm.). This is also consistent with its behavior in Santa Cruz County (Hyland pers. comm.).

Forms dense, smothering blanket over trees. Loss of forest structure and biodiversity at ecosystem and species levels, loss of recruitment of native shrubs in New Zealand. Dense, smothering cover can block movement through trees.

It is invasive because it forms a dense smothering blanket over native trees, impeding their growth and increasing wind and ice damage. The vine rapidly climbs into the crown by its leaf tendrils. It invades forests from the edge or in canopy gaps, alters their structure and reduces the diversity of native understory species (Weber 2003).


Sources of information:

Bungard 1996
Ogle et al. 2000
Weber 2003
Hyland, T., Personal communication.
Wrubel, E., Personal communication.


Question 1.3 Impact on higher trophic levels? B Reviewed Scientific Publication
Identify type of impact or alteration:

In California, C. vitalba has smothered over 1.5 acres of riparian oak-bay woodland at Muir Woods, where it forms large monocultures. The dense canopy suppresses all vegetation below and may impede movement of humans and animals (Wrubel, pers. comm.). In Santa Cruz County the infestation is 60 acres and there C. vitalba plants also grow over trees and may block movement (Hamey, pers. comm.). The changes caused to habitat structure by the growth of vines over trees and in thick masses on the forest floor would impede the movement of wildlife and change the diversity of plants in the understory.


Sources of information:

Weber 2003
Hamey, N., Personal communication.
Wrubel, E., Personal communication.


Question 1.4 Impact on genetic integrity? C Other Published Material

C. vitalba could have the potential to hybridize with the native Clematis species (C. ligusticifolia and C. lasiantha) which overlap with its range, but there is no documentation that this is able to occur. C. vitalba has been artificially hybridized with other species to produce vigorous garden varieties such as C. x jouiniana (C. vitalba x C. davidiana or C. vitalba x C. heracleifolia) and C. 'Paul Farges' ('summer snow') (C. vitalba x C. potanini) (CABI 2015). Since C. vitalba co-occurs with native Clematis this is scored as Minor, without evidence for hybridization.


Sources of information:

CABI 2015


Section 2: Invasiveness
Question 2.1 Role of anthropogenic and natural disturbance
in establishment?
A Observational
Describe role of disturbance:

This species may occasionally establish in undisturbed areas, but can readily establish in areas with natural disturbance. In Muir Woods, C. vitalba occasionally establishes in undisturbed forest and woodland, and frequently establishes in naturally disturbed riparian vegetation (Wrubel, pers. comm.). In Santa Cruz County C. vitalba is thought to have been introduced in the town of San Vicente which was located in the San Vicente Creek watershed. This historic town was established for workers at a nearby limestone quarry and is now uninhabited (Hamey, pers. comm.).

C. vitalba is able to establish in areas with natural or human-caused disturbance, but is not known to establish in undisturbed natural areas. C. vitalba requires high light for growth and reproduction, and is tolerant of moderate shade. In seedling germination studies done in forests, C. vitalba seedlings did not survive in undisturbed forests with low light levels. It was also found that nitrogen may be the limiting nutrient resource (Bungard et al. 1998). C. vitalba is a successful weed because it can tolerate dense shade but also has the ability to grow rapidly in high-light environments, meaning it can establish in areas with very small forest canopy gaps (Baars and Kelly 1996).


Sources of information:

Bungard et al. 1997
Baars and Kelly 1996
Hamey, N. Personal communication.
Wrubel, E. Personal communication.


Question 2.2 Local rate of spread with no management? A Observational
Describe rate of spread:

Without management, C. vitalba has the potential to spread rapidly into disturbed forest edges and canopy gaps where light is available. In Marin County it is reported as spreading rapidly and the population size has doubled since management began (Wrubel, pers. comm.). In Santa Cruz County C. vitalba was first detected in 2009 or 2010, and control work did not begin until 2012. The population is now estimated to be 60 acres and is increasing in density where it occurs (Hamey, pers. comm.).


Sources of information:

Hamey, N. Personal communication.
Wrubel, E. Personal communication.


Question 2.3 Recent trend in total area infested within state? C Observational
Describe trend:

Once introduced, C. vitalba has the potential to spread rapidly into forest edges and canopy gaps. In Marin County it is reported as spreading rapidly and the population size has doubled since management began (Wrubel, pers. comm.). In Santa Cruz County C. vitalba was first detected in 2009 or 2010, and control work did not begin until 2012. The population is now estimated to be 60 acres and is increasing in density where it occurs (Hamey, pers. comm.). Given the recent detection of this species in California, and the fact that both known populations are under management, the question is scored as stable and will be changed if more information becomes available.


Sources of information:

Hamey, N. Personal communication.
Wrubel, E. Personal communication.


Question 2.4 Innate reproductive potential? A Reviewed Scientific Publication
Describe key reproductive characteristics:

Roots can resprout. Aerial shoots touching ground after cutting may become rooted. Seed production is high. An estimated 17,000 viable seeds are produced per 0.5 square meters in areas where it is a canopy species. Seed production is possible after one to three years, depending on the exposure to full sunlight. Asexual reproduction is possible after one year. (Washington State Noxious Weed Control Board). A soil seed bank is produced and seeds are easily wind dispersed. Seeds can remain on the vine over winter and well into summer. Aerial shoots touching the ground after cutting may become rooted (Weber 2003). Seed viability in California may be low: 4 of 5 seed accessions stored at UC Botanic Garden seeds were not viable (Forbes, pers. comm.).


Sources of information:

Bungard 1996
CABI 2015
Washington State Noxious Weed Control Board 1999
Weber 2003
Forbes, H. Personal communication.


Question 2.5 Potential for human-caused dispersal? A Other Published Material
Identify dispersal mechanisms:

Dumping of garden waste containing C. vitalba vines onto roadsides has been a significant cause of spread in New Zealand. This weed appears to invade along roadsides by seed, possibly aided by the turbulence created by motor vehicles (CABI).
Fragments are spread by water, and from garden cuttings (Washington 1999).

C. vitalba often grows on roadsides, and the risk of seeds being transported on road vehicles from known infestations to new sites within continents is high. In the past, ornamental Clematis species were often grafted onto C. vitalba rootstocks. It is likely that some incursions of C. vitalba have resulted from reversion of these rootstocks. The highest risk of introduction remains via intentional introduction of the plant as an ornamental, and plants and seed continue to be sold by nurseries, mail order catalogues and websites (CABI). In Santa Cruz County C. vitalba is thought to have been introduced in the town of San Vicente which was located in the San Vicente Creek watershed. This historic town was established for workers at a nearby limestone quarry and is now uninhabited (Hamey, pers. comm.). There is also a risk of inadvertent introduction and increase via seed collection and revegetation projects, since C. vitalba can be mistaken for native clematis species (Wrubel, pers. comm.).


Sources of information:

CABI 2015
Washington Noxious Weed Control Board 1999
Hamey, N. Personal communication.
Wrubel, E. Personal communication.


Question 2.6 Potential for natural long-distance dispersal? A Reviewed Scientific Publication
Identify dispersal mechanisms:

Can be dispersed by birds and animals in New Zealand. Seeds are also wind-dispersed or water-dispersed in New Zealand. Fragments are spread by water, and from garden cuttings (Washington 1999). A soil seed bank is produced and seeds are easily wind dispersed. Seeds can remain on the vine over winter and well into summer (Weber 2003).


Sources of information:

Bungard 1996
Weber 2003


Question 2.7 Other regions invaded? A Reviewed Scientific Publication
Identify other regions:

C. vitalba is also naturalized and considered invasive in Oregon, Washington, Australia, New Zealand. C. vitalba is native to Europe, from southern England and the Netherlands to North Africa, and from Spain to the Middle East and the Caucasus (CABI).

It occurs in agricultural areas, coastland, natural forests, planted forests, range/grasslands, riparian zones, ruderal/disturbed, scrub/shrublands, and urban areas (GISD 2005). More specifically, outside of its native range, this species is found in forest lands and in the margins and openings of forested lands. It is also found in riparian areas established with willows, in waste areas, and in coastal and lowland areas (GISD 2005). Infestations of C. vitalba occur in forest reserves, gardens, road margins and other places around Taihape in New Zealand (Ogle et al. 2000), infestations of C. vitalba occur in every region of New Zealand except Northland (north of Auckland).

Some of the habitat types it has not invaded in California include scrub and shrub-dominated habitats, grasslands, and broad-leaved forests such as oak woodland.


Sources of information:

CABI 2015
GISD 2005
Ogle et al. 2000


Section 3: Distribution
Question 3.1 Ecological amplitude/Range? B Observational

C. vitalba was first collected in California in 1957 from the Strybing Arboretum in Golden Gate Park. Since that is a cultivated location C. vitalba was not included in the Jepson Manual and was not thought to be naturalized in California until it was verified in Muir Woods and in Santa Cruz County in 2014 (CCH). In Santa Cruz County C. vitalba was first noticed in 2009 or 2010, and control work did not begin until 2012 (Hamey, pers. comm.). Both California locations are under management and occur in riparian and coast redwood forest edges. It is possible that C. vitalba is more widespread as it closely resembles the native C. ligusticifolia.


Sources of information:

CCH 2016
Hamey, N. Personal communication
Hyland, T. Personal communication
Wrubel, E. Personal communication


Question 3.2 Distribution/Peak frequency? D Observational
Describe distribution:

The two known locations of C. vitalba in California are in riparian oak bay woodland and coast redwood forest edges.


Sources of information:

Hamey, N. Personal communication
Hyland, T. Personal communication
Wrubel, E. Personal communication


Worksheet A - Innate reproductive potential

Reaches reproductive maturity in 2 years or less Unknown
Dense infestations produce >1,000 viable seed per square meter Yes
Populations of this species produce seeds every year. Yes
Seed production sustained over 3 or more months within a population annually Unknown
Seeds remain viable in soil for three or more years Yes
Viable seed produced with both self-pollination and cross-pollination Yes
Has quickly spreading vegetative structures (rhizomes, roots, etc.) that may root at nodes Yes
Fragments easily and fragments can become established elsewhere Yes
Resprouts readily when cut, grazed, or burned Yes
Total points: 10
Total unknowns: 2
Total score: A?

Related traits:

Insects visit C. vitalba flowers, but flowers do not appear to be self-incompatible (West, 1992), and pollination can be successful without the attention of insects.

Worksheet B - Arizona Ecological Types is not included here

Worksheet C - California Ecological Types

(sensu Holland 1986)
Major Ecological Types Minor Ecological Types Code?
Marine Systemsmarine systems
Freshwater and Estuarine lakes, ponds, reservoirs
Aquatic Systemsrivers, streams, canals
estuaries
Dunescoastal
desert
interior
Scrub and Chaparralcoastal bluff scrub
coastal scrub
Sonoran desert scrub
Mojavean desert scrub (incl. Joshua tree woodland)
Great Basin scrub
chenopod scrub
montane dwarf scrub
Upper Sonoran subshrub scrub
chaparral
Grasslands, Vernal Pools, Meadows, and other Herb Communitiescoastal prairie
valley and foothill grassland
Great Basin grassland
vernal pool
meadow and seep
alkali playa
pebble plain
Bog and Marshbog and fen
marsh and swamp
Riparian and Bottomland habitatriparian forestD, < 5%
riparian woodlandD, < 5%
riparian scrub (incl.desert washes)
Woodlandcismontane woodland
piñon and juniper woodland
Sonoran thorn woodland
Forestbroadleaved upland forest
North Coast coniferous forestD, < 5%
closed cone coniferous forest
lower montane coniferous forest
upper montane coniferous forest
subalpine coniferous forest
Alpine Habitatsalpine boulder and rock field
alpine dwarf scrub
Amplitude (breadth): B
Distribution (highest score): D

Infested Jepson Regions

Click here for a map of Jepson regions