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African woodsorrel 

Invasive Species Information

Biodiversity Medium Risk 14

What Is African woodsorrel - (Oxalis pes-caprae)?

Habitat: Terrestrial
Distribution in Ireland:

Status: Established

Family name: Oxalidaceae

Common name/s: Bermuda sorrel, buttercup oxalis, Cape sorrel, English weed, goat's-foot, sourgrass, soursob and soursop

Reproduction: African woodsorrel is a heterostylous species, with at least three forms known globally. The forms are not easily cross-pollinated and are not self-compatible.

Biodiversity Medium Risk 14

African wood sorrel flower

Only the short-styled form is common in Europe, which means that plants do not produce seeds and must rely on vegetative reproduction. 

Biodiversity Medium Risk 14

Indigenous to South Africa, African woodsorrel, is an invasive species and noxious weed in many parts of the world.

Flowers are actinomorphic, with five separated or slightly fused sepals, a sympetalous corolla composed of five fused petals, an apoandrous androecium composed of ten free stamens in two ranks, and a compound pistil.

African wood sorrel leaf

A short perennial herb forming large clonal colonies reproducing by annual bulbs. Flowering takes place between January and March, and is synchronous across the colony, producing spectacular displays of 1-5 pedicels with large cup-shaped bright yellow flowers with 5 yellow petals. Plants die back by late spring. 

 

Most African woodsorrel species produce subterranean propagules. These take the form of 'true bulbs' in botanical terms, which is unusual among dicotyledons.

 

Oxalis pes-caprae produces small bulbs copiously, whereas most other African species produce fewer, larger bulbs. New world Oxalis, such as Oxalis corniculata, generally appear not to produce bulbs.

Bulbs can easily be dispersed by agricultural activity. Bulbs can also be washed along gullies in rain or stream water.

How To Identify African woodsorrel?

Biodiversity Medium Risk 14

African wood sorrel ID Guide

Leaf: Olive green with dark purple speckles and fine hairs at margin.
Flower: Bright yellow with 5 petals 
Stem
Fruit:

Seed:

Root: brown / cream coloured roots and bulbs 

Biodiversity Medium Risk 14

African wood sorrel bulbs

Biodiversity Medium Risk 14

African wood sorrel root

Why Is African woodsorrel A Problem?

African woodsorrel is an alien (non-native) invasive plant, meaning it out-competes crowds-out and displaces beneficial native plants that have been naturally growing in Ireland for centuries.

 

It can suppress other ruderal weedy species. This is a serious problem where the arable flora is of conservation value, as over much of the Mediterranean old fields. 

The leaves contain large quantities of toxic oxalates, and in grassy areas the species can therefore be a danger to livestock. Significant losses of cattle and sheep have been recorded from some pastoral regions.

 

In annual crops, it can be a significant pest, reducing yields and becoming a nuisance during harvesting.

European Communities (Birds and Natural Habitats) Regulations 2011 non-native invasive plant species A-Z (Updated 2017)

There are currently 35 invasive plant species listed in the European Communities (Birds and Natural Habitats) Regulations (annex 2, Part 1)...

 

Click on a species from the following list to find out more regarding non-native species subject to restrictions under Regulations 49 and 50.

Additional Non-Native Plant Species identified as Medium Risk on Ireland's Biodiversity List...

Common name 

African woodsorrel

American skunk cabbage

Annual bur-sage

Antithamnionella ternifolia

Barberry

Black currant

Brazilian waterweed

Butterfly-bush

Canadian-fleabane

Clover broomrape

Creeping Bellflower

Dead man's fingers

Douglas fir

Early goldenrod

False acacia

Field penny-cress

Garden lupin

Giant rhubarb

Hairy rocket

Himalayan honeysuckle

Himalayan knotweed

Holm oak

Japanese barberry

Japanese honeysuckle

Japanese rose

Leafy spurge

Least duckweed

Narrow-leaved ragwort

New Zealand bur

Ostrich fern

Pampas grass

Pitcherplant

Red oak

Red sheath tunicate

Rock cotoneaster

Rum cherry

Russian-vine

Salmonberry

Sea-buckthorn

Sycamore

Three-cornered garlic

Traveler's-joy

Tree of heaven

Turkey oak

Virginia-creeper

Warty cabbage

Water fern

Wild parsnip

Environment 

Terrestrial

Terrestrial

Terrestrial

Marine

Terrestrial 

Terrestrial

Freshwater

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial 

Marine 

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial

Terrestrial

Terrestrial 

Terrestrial

Terrestrial

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial

Terrestrial 

Freshwater 

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial  

Terrestrial 

Terrestrial 

Marine 

Terrestrial 

Terrestrial 

Terrestrial

Terrestrial

Terrestrial

Terrestrial 

Terrestrial

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial 

Terrestrial 

Freshwater 

Terrestrial

Risk score 

14

15

17

15

14

14

17

17

14

17

16

16

15

14

17

17

17

16

17

14

16

14

14

15

14

16

14

16

14

14

14

14

14

14

14

17

14

14

14

15

15

17

17

14

16

15

14

15