Polygala myrtifolia L., Polygalaceae

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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: sweet pea bush

Habit:  shrub

Description:  "An erect much branched shrub, as much as 2 m high in sheltered places, much less when exposed.  Stems glabrous or nearly so. Leaves shortly petiolate, alternate, elliptic-oblong, obtuse or acute, sometimes minutely pubescent when young, glabrescent.  Flowers few, in terminal racemes.  Bracts 3, small.  Front petal with a fringed crest; side petals with 2 dissimilar lobes, the anterior narrow and elongated, the posterior much bent.  Style flattened, sharply bent.  Stigma oblique, the stigmatic surface along the lower edge of the keel-shaped posterior lobe"  (Adamson & Salter, 1950; pp. 543-544).

Habitat/ecology:  "Heathland, riparian habitats, coastal dunes and bluffs.  A highly variable species in the native range with regard to size and shape of leaves.  Where invasive, the plant spreads rapidly and forms dense thickets, impeding growth and regeneration of native plants.  Trees and shrubs are unable to establish seedlings under canopies of this shrub and forest regeneration is suppressed.  The plant establishes well in disturbed sites and seedling density may exceed 2,000 per square meter"  (Weber, 2003; p. 337).  In South Africa, "bushy slopes, both sheltered and exposed, up to about 1,200 ft."  (Adamson & Salter, 1950; pp. 543-544).

Propagation:  "Seed is spread in soil and water movement"  (Weedbusters New Zealand).  "Seeds can remain viable in the soil for several years"  (Weber, 2003; p. 337).

Native range:  South Africa (Adamson & Salter, 1950; pp. 543-544).

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia (Pacific offshore islands) Norfolk Islands	Norfolk Island	introduced invasive	Orchard, Anthony E., ed. (1994) (p. 10) "A relatively recent arrival and potentially serious weed; probably an escape from cultivation". Voucher cited: G. Uhe 1153 (K)
State of Hawaii Hawaiian Islands	Hawaiian Islands		Owen, S. J. (1998)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Australia Australia (continental)	Australia (continental)		Owen, S. J. (1998)
Australia Australia (continental)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Owen, S. J. (1997)
New Zealand New Zealand	New Zealand (country)	introduced invasive cultivated	Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 963) "Mostly in coastal habitats, occasionally in scrubland".

Comments:  Reported to be an invasive species in New Zealand (Owen, 1997; p. 86).

Control: 

Physical:  "Plants can be killed by cutting close to the ground". (Weber, 2003; p. 337).  "Hand pull small plants (all year round). Mulch"  (Weedbusters New Zealand).

Chemical:  "Fires are used in fire adapted communities to kill topgrowth and stimulate seed germination.  Seedlings are then sprayed with herbicide"  (Weber, 2003; p. 337).

"1. Slash larger plants in regenerating shrubland (summer). Mulch. 2. Stump swab (all year round): metsulferon-methyl 600g/kg (1g/L) or Tordon Brushkiller (100ml/L) or Tordon Gold (200ml/L). 3. Spray (larger infestations): glyphosate (100ml/10L) + penetrant"  (Weedbusters New Zealand).

Additional information:
Fact Sheet from Environmental Bay of Plenty Regional Council, New Zealand.
Information sheet from Weedbusters New Zealand.

Additional online information about Polygala myrtifolia is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Polygala myrtifolia as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Polygala myrtifolia may be available from the Germplasm Resources Information Network (GRIN).

References:

Adamson, R. S./Salter, T. M. 1950. Flora of the Cape Peninsula. Juta & Co.

Orchard, Anthony E., ed. 1994. Flora of Australia. Vol. 49, Oceanic islands 1. Australian Government Publishing Service, Canberra.

Owen, S. J. 1997. Ecological weeds on conservation land in New Zealand: A database. Working draft. Wellington, New Zealand. Department of Conservation.

Owen, S. J. 1998. Department of Conservation strategic plan for managing invasive weeds. Wellington, New Zealand. Department of Conservation. 86 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.