Sea Spurge

Euphorbia paralias L.

Synonyms -

Family: Euphorbiaceae

Names:

Euphorbia is the name given by Juba, the king of Mauritania, to an African species in honour of his Greek physician Euphorbus who discovered some of the medicinal properties of the plant.

Other Names:

Summary:

Sea Spurge is an erect, sea side, leafy perennial to 0.6 m high, whose stems exude an irritant, sticky, milky sap when damaged. The crowded stalkless leaves are somewhat fleshy and bluish green in colour but may become yellow or red when the plant is under stress. The elliptic stem leaves are 5-18 mm long and 2-7 mm wide, but the egg-shaped floral leaves are much broader and up to 18 mm wide. The inflorescence is composed of yellowish-green petal-less flowers in clusters of heads. Each head is a cup-shaped structure with crescent-shaped glands and contains 1 female flower and several male flowers. The male flower has 1 stamen and the female flower a single 3-lobed ovary with 3 styles which are forked. The fruit is a small capsule 5 mm across, which splits to release 3 smooth seeds.
Native to western and southern Europe, it is now a common weed of coastal dunes and beaches and flowers from spring through to early winter.

Description:

Cotyledons:

Two.

First leaves:

Leaves:

Alternate, Crowded and overlapping. Green to red with a waxy bloom. Exudes a bitter, caustic, sticky, milky sap when damaged.
Stipules – None.
Petiole – None.
Blade – Green to blue-green to red with a waxy bloom, 5-30 mm long x 2-15(18) mm wide, thick or somewhat fleshy, lower leaves oblong to egg shaped, middle leaves elliptic to oblong, Upper leaves egg shaped. Leaves of fertile branches circular to kidney shaped, Tip pointed. Sides parallel to curved and entire. Base tapering. Hairless.

Stems:

1-9, slender and branching from a woody base, dividing into 3-6 fertile branches, each dichotomously branching up to 3 times. 200-700(1000) mm tall x 2-5 mm diameter. Exudes a bitter, caustic, sticky, milky sap when damaged. Hairless

Flower head:

Yellow-green flat topped cluster (umbel) with a whorl of floral leaves at the base of the 3-6 primary rays. Each ray usually forked several times and with a pair of opposite floral bracts at each fork.
8-15 male and 1 female flower enclosed in a cup shaped floral structure (involucre or cyathium) composed of 5 overlapping almost circular bracts resembling a calyx. The involucre with 5 small membranous teeth alternating with 4 thick, spreading, crescent shaped with short dividing horns, honey bearing glands. Cyathia, yellow green, 1.5 mm long on a single distinct stalk (pedicel).

Flowers:

Male and female flowers in the same head.
Ovary – 3 celled. 1 ovule in each cell.
Styles – 3, slender and forked to the middle.
Sepals – None.
Petals – None.
Male flowers
Stamens – 1. Articulate filament with a membranous bracteole at the base.
Anthers - 1

Fruit:

Capsule 3-6 mm long x 4.5-6 mm diameter. Granular surface. Deeply furrowed. Wrinkled on the keels. Hang out of the floral structure. Three 2 valved fruitlets with one seed each. Seed is explosively propelled up to 2 metres from the capsule at maturity.

Seeds:

Pale grey to whitish, egg shaped to globular, 2.5-3.5 mm long, smooth. Very small outgrowth near the base of the seed (caruncle). Floats in water.

Roots:

Deep taproot with many fibrous roots.

Key Characters:

Perennial
Leaves narrow, sessile, alternate, crowded, imbricate.
Stem woody near base.
Flower heads in umbels, with a whorl of floral leaves at the base of the primary rays, each ray usually forked several times and with a pair of opposite floral bracts at each fork.
Bracts sub triangular to sub orbicular.
Glands with a horn at each end so as to appear lunate (crescent shaped).
Seeds ovoid, carunculate(tiny)

Biology:

Life cycle:

Perennial. The seed germinates after heavy rain and the seedling grows rapidly producing a long taproot. If it is buried the plant continues growing until it runs out of nutrients stored in the stem or reaches the surface to produce new leaves. It flowers from spring to autumn and explosively releases the seed up to 2 m from the mother plant. Forked flowering branches die off after flowering but may often remain on the plant for a year. Root fragments that are moved by wave action or earthmoving will re-establish where they are dumped. Seed that is washed out to sea will float and survive for several years and may form new infestations if returned to the beach.

Physiology:

Drought, salt, sea spray, sand blast and sun tolerant.
Unpalatable to stock and insects.

Reproduction:

By seed and root fragments.

Flowering times:

October to June in WA.
September to May in NSW.

Seed Biology and Germination:

Seed survives in salt water with 50% viability after 2 years and dropping to no viable seed after 6 years.
A single plant can produce 5000 seeds per year.
Germination usually occurs after heavy rain.

Vegetative Propagules:

Root fragments.

Hybrids:

Allelopathy:

Population Dynamics and Dispersal:

Long distance spread was usually by planting for dune stabilisation or movement between beaches by recreational craft, camping equipment and towels. Medium distance spread is by ocean currents. Local spread is by wind erosion, explosive release of seed from the parent plant and root fragments spread along the beach after storms.

Origin and History:

Western Europe, Mediterranean, Black Sea, Siberia.
In SA it was initially reported on Yorke Peninsula opposite Wardang Island and has since spread along most of the SA coast.

Distribution:

NSW, SA, TAS, VIC, WA.
Along the coast from Lancelin, north of Perth to the West Australian border east of Esperance.

Courtesy Australia’s Virtual Herbarium.

Habitats:

Coastal dunes extending inland to the permanent vegetation.
Primary coloniser. Tolerates slow burial by sand.

Climate:

Cool temperate, warm temperate.

Soil:

Sands, white beach sand.

Plant Associations:

Marram grass (Ammophila arenaria)

Significance:

Beneficial:

Used for dune stabilisation.

Detrimental:

Environmental weed invading dunes, sandy island shores and changing dune shape.

Toxicity:

Possibly toxic but cases of poisoning rare and unconfirmed as stock are not usually exposed to it and it is unpalatable.
Sap may harm eyes

Symptoms:

Skin irritation. Eye irritation.

Treatment:

Wash contaminated skin with methylated spirits.

Legislation:

Prohibited entry to Australia.

Management and Control:

Prevent denudation and grazing (including rabbit grazing) of susceptible areas.
Hand weeding and mechanical removal are usually ineffective.
Preferentially use selective herbicides like triasulfuron to avoid having bare areas after Sea Spurge is removed. If necessary, plant stabilising species into the infestation before control work is started.

Thresholds:

Eradication strategies:

Spray until just wet with 10 g metsulfuron600 in 100 L water.
In bushland areas 50 g/ha triasulfuron will provide more selective control.
500 mL glyphosate450 in 100 L water also provides control but tends to leave the area bare and prone to reinvasion.

Seedlings can be hand pulled but older plants that have been buried usually break off and regrow. Wear gloves because the sap is corrosive and irritating. Cultivation is usually not appropriate as Sea Spurge tends to grow on erosion prone dunes. Spray until just wet with a mix of 40 mL glyphosate(450g/L) plus 0.2 g metsulfuron(600 g/kg) plus 25 mL Pulse® in 10 L water any time the plant is actively growing. For overall spraying use 2 L/ha glyphosate(450g/L) plus 10 g/ha metsulfuron(600 g/kg) plus wetting agent in non-selective situations. Where contacting companion plants can’t be avoided, 40 g/ha triasulfuron(750g/kg) (0.8 g triasulfuron(750g/kg) in 10 L water for hand sprays) is preferred.
Mowing is ineffective.
Plant stabilising species to reduce the risk of erosion following control.

Herbicide resistance:

None reported

Biological Control:

Related plants:

Asthma plant (Euphorbia hirta)
Bottle tree Caustic (Euphorbia stevenii)
Caper Spurge (Euphorbia lathyrus)
Caustic weed (Euphorbia drummondii)
Climbing Caustic (Euphorbia sarcostemmoides)
Cypress Spurge (Euphorbia cyparissias)
Desert Spurge (Euphorbia tannensis ssp. eremophila)
Dwarf Poinsettia (Euphorbia cyathophora)
Dwarf Spurge (Euphorbia exigua)
Eyebane (Euphorbia maculata)
False Caper or Geraldton Carnation Weed (Euphorbia terracina) is a serious weed of agricultural land, road verges, coastal heath and woodland. It differs in its narrow stem leaves which are minutely toothed towards their tips.
Garden Weed or Short-stemmed Carnation Weed (Euphorbia segetalis) is a weed of coastal heath at Esperance and has narrower leaves and pitted seeds.
Gascoyne Spurge (Euphorbia boophthona)
Hairy Caustic Weed (Euphorbia australis)
Mexican Fire plant (Euphorbia heterophylla)
Naked Lady (Euphorbia tirucalli)
Petty Spurge (Euphorbia peplus), is occasionally naturalised in disturbed shrub land, heath and woodland and differs in its stalked leaves that don’t have serrated leaf tips and deeply pitted seeds.
Plains Spurge (Euphorbia planiticola)
Poinsettia (Euphorbia pulcherrima)
Red Caustic creeper (Euphorbia prostrata)
Red Caustic Creeper (Euphorbia thymifolia)
Sea Spurge (Euphorbia paralias)
Sickle leaved Spurge (Euphorbia falcata)
Snow on the Mountain (Euphorbia marginata)
Sun Spurge (Euphorbia helioscopia), which is occasionally naturalised in coastal peppermint woodland, differs in having a hairy stem and broader spoon-shaped leaves.
Tree Spurge (Euphorbia dendroides)
Euphorbia dentata
Euphorbia hyssopifolia

Plants of similar appearance:

References:

Black, J.M. (1965). Flora of South Australia. (Government Printer, Adelaide, South Australia). P509.

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

Blood, K. (2001). Environmental weeds: a field guide for SE Australia. (CH Jerram & Associates, Australia). P144-5. Photos.

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

Harden, Gwen J. (1991). Flora of NSW. (Royal Botanic Gardens, Sydney). Volume 1. P426. Diagram.

Hussey, B.M.J., Keighery, G.J., Cousens, R.D., Dodd, J. and Lloyd, S.G. (2007). Western Weeds. A guide to the weeds of Western Australia. (Second Edition). Plant Protection Society of Western Australia, Perth, Western Australia. P148. Photo.

Lazarides, M. and Cowley, K. and Hohnen, P. (1997). CSIRO handbook of Australian Weeds. (CSIRO, Melbourne). #411.19.

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

Paczkowska, G. and Chapman, A. (2000). The Western Australia flora: a descriptive catalogue. (Wildflower Society of Western Australia (Inc), the Western Australian Herbarium, CALM and the Botanic Gardens & Parks Authority). P246.

Wheeler, Judy, Marchant, Neville and Lewington, Margaret. (2002). Flora of the South West: Bunbury - Augusta – Denmark. (Western Australian Herbarium, Bentley, Western Australia). P613. Diagram.

Acknowledgments:

Collated by HerbiGuide. Phone 08 98444064 for more information.