Rose Pelargonium

Pelargonium capitatum (L.) L'Her.

Synonyms -

Family: Geraniaceae

Names:

Other Names:

Coastal Pelargonium.

Summary:

Rose Pelargonium is a straggly, aromatic, greasy, perennial herb or small shrub, softly hairy with broad almost circular leaves which are irregularly, quite deeply lobed and have tiny pointed teeth around the margin. The pink to mauve flowers with darker markings are in dense stalked clusters. Each flower is almost stalkless and has 5 petals. There are 10 stamens but only 3-8 of them fertile, the others reduced to antherless filaments. The fruits are long and beak-like, separating at maturity into 5 fruitlets with softly hairy awns which are curved or spirally twisted. Originating from South Africa, Rose Pelargonium is a garden plant which has become a weed in disturbed areas, particularly on sandy soils near the coast. Other garden varieties may persist around old buildings. It flowers from July to October.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Alternate or opposite. Greasy to touch
Stipules - Membranous, brown, broadly egg shaped, 6-10 mm long x 6-12 mm wide and tapering to a pointed tip.
Petiole - Yes.
Blade - Broadly egg shaped to almost circular, 20-80 mm long x 20-80 mm wide, rather thick and wavy with 3-7 lobes and indented at the base. Base notched. Hairy.

Stems:

Straggly, up to 1000 mm tall. Hairy, with long soft spreading hairs that may have an oil gland.
Flower stem - Hairy.

Flower head:

Compact umbrella like head (Umbel) usually with 8-10 flowers. 25-40 mm across.

Flowers:

Stalkless below the nectary spur.
Bracts - egg shaped and densely hairy.
Ovary - Hairy.
Sepals - egg shaped, 8-9 mm long, joined at the base. The tip is blunt with a fine point. The back sepal has a spur that is joined to the stalk.
Petals - 5. Pink or white with darker markings. Spoon shaped, 10-20 mm long, smooth edges, narrowly clawed at the base. The back 2 are larger than the front 3.
Stamens - 10 with (3)6-8 fertile.
Filaments - Elliptic and irregularly joined into a tube at the base.
Anthers - Oblong in outline

Fruit:

The fruit is long and beak-like, separating at maturity into 5-6 fruitlets with softly hairy awns which are curved or spirally twisted. It breaks up elastically from the base at maturity.

Seeds:

Elliptical, hairy, 2-6 mm long, with 2 shallow depressions on either side of the base of a long corkscrew awn that is 25-35 mm long. The awns are hairy with long hairs on the inside and almost hairless on the outside.

Roots:

Taproot and many long, stout, shallow and somewhat elastic lateral roots.
Cream coloured.

Key Characters:

Leaves reniform, cordate, shallowly lobed, not deeply dissected, thick, densely villous, margin with tiny pointed teeth.
Flowers sessile below the nectary spur.
Posterior sepal with a spur.
Stamens connate towards the base into a tube and usually 6-8.
From Judy Wheeler, Flora of the Perth Region.

Biology:

Life cycle:

Perennial.

Physiology:

Reproduction:

By seed and regrowth from damaged crown.

Flowering times:

July to October in Perth.

Seed Biology and Germination:

Vegetative Propagules:

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Perennial.

Origin and History:

Introduced from South Africa.

Distribution:

ACT, NSW, TAS, VIC, WA.

Courtesy Australia's Virtual Herbarium.

Habitats:

Climate:

Temperate frost free areas.

Soil:

Common on coastal dunes.

Plant Associations:

Coastal heath.

Significance:

Beneficial:

Ornamental.

Detrimental:

Weed of disturbed coastal areas and dunes.
Unpalatable.

Toxicity:

Not recorded as toxic.

Legislation:

None.

Management and Control:

Agricultural areas.
Spray large bushes with 1 L/ha 2,4-D amine plus 0.25% Pulse® Penetrant. Spray-graze pastures annually in winter with 500 mL/ha 2,4-D amine to prevent seedlings establishing. Plant or encourage vigorous pastures and fertilise adequately. In arable areas, cultivation and the establishment of crops usually provides control.
Bushland
Spray large bushes until just wet with a mixture of 10 mL or 2,4-D amine plus 25 mL Pulse® Penetrant in 10 litres of water. Most native plants will survive this mixture. Spray a test area to determine if there are any particularly sensitive species in the area to be treated. Plant or encourage trees and shrubs to increase the levels of shade. This will help to reduce the risk of re invasion. Hand weed seedlings in the following season or apply the same mixture in densely infested areas. Prevent seed set.

Thresholds:

It generally doesn't persist in well managed agricultural situations.

Eradication strategies:

Remove large plants and hand weed seedlings to prevent seed set for at least 3 years. Cultivation or blade ploughing provides effective control.
In bushland situations, 1 L/ha of 2,4-D amine(500g/L) or 20 mL 2,4-D amine(500g/L) plus 25 mL wetting agent in 10 L water provides reasonably selective control.
For small areas, spray the bushes and a 5 metre buffer strip with 100 mL of Tordon®75-D plus 25 mL Pulse® per 10 L of water. This will control seedlings for a year or two after spraying. When seedlings appear, repeat the treatment until no more seedlings emerge. This treatment has little effect on grasses so the area is not left bare, but it will damage or kill most broad-leaved species in the sprayed area. Grasses can be planted in the area before or after spraying. Introduce broad-leaved species two seasons after the last spray.
Isolated plants can be sprayed with a window washer sprayer using a mix of 1 part glyphosate(450g/L) plus 2 parts water and applying 3 mL of solution per square metre of weed.

Herbicide resistance:

None reported.

Biological Control:

None.

Related plants:

Native species of Geranium or Pelargonium (Pelargonium species) can be distinguished by their undivided or very shallowly divided leaves whose margins have tiny rounded teeth. The flower clusters are also looser than those of Rose Pelargonium, with each flower on a distinct slender stalk. Native species of Cranesbill (Geranium species) all have deeply dissected leaves and fewer flowers, usually with only two flowers together.
Garden Pelargonium (Pelargonium x domesticum) is an introduced ornamental.
Rose Geranium (Pelargonium x asperum) is an introduced ornamental.
Pelargonium alchemilloides is a low lying, introduced ornamental with white flowers held well above the foliage and rhizomes
Pelargonium fragans is an introduced ornamental.
Pelargonium littorale is a native species that flowers slightly earlier, has stalked flowers and thin almost hairless leaves.

Plants of similar appearance:

Geranium
Erodium
Mallows

References:

Bodkin, F. (1986). Encyclopaedia Botanica. (Angus and Robertson, Australia).

Burbidge, N.T. and Gray, M. (1970). Flora of the Australian Capital Territory. (Australian National University Press, Canberra). has diagram of similar P. australe P235.

Everist, S.L. (1974). Poisonous Plants of Australia. (Angus and Robertson, Sydney).

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (1997). Western Weeds. A guide to the weeds of Western Australia. (Plant Protection Society of Western Australia, Perth, Western Australia). P166. Photo.

Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #755.2.

Marchant et al (1987). Flora of the Perth Region. (Western Australian Herbarium, Department of Agriculture, Western Australia). P500.

Moore, J.H. and Wheeler, J.R. (2008). Southern Weeds and their Control. (Second Edition). Department of Agriculture and Food Western Australia. P192-193 Photos.

Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta - Denmark. (Western Australian Herbarium, Bentley, Western Australia). P623. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 or www.herbiguide.com.au for more information.