for wool and Latin cereus for wax, in reference to the woolly axils of the floral tube and the waxy bloom on the stems.
Harrisia Cactus recognises the botanist William Harris and was the genus name in days past.
Other names:Moonlight Cactus because the flowers come out at night.
Snake Cactus because of its trailing habit and scaly leaves.
Summary:A night flowering, spiny, red fruited, succulent, rope like spiny cactus that forms large tangled matts to 600 mm tall.
Leaves:Small and hidden at the base of the spines.
Stems:Bright green, fleshy, cylindrical, 25-40 mm diameter and jointed every 300-450 mm. 6 lengthwise ribs with low, pyramidal humps (areoles), 50-75 mm apart. Each hump has 1-3, sharp, 10-35 mm long spines surrounded by grey felted hairs and 3-7 low lying radial 1-6 mm short spines. Spines become grey and black tipped with age.
Open at night and wither in the morning.
'Petals' - Large funnel shaped, white tinged with pink 'petals' on a 150-200 mm long, green tube.
Fruit:Red, globular, 40-50 mm diameter. Several warts with felted hairs and spines similar to the stem. Splits down one side exposing the white pulp and seeds. Attached to a hump on stem.
Seeds:400-1000, small black, sub-globular seeds embedded in a white pulp.
Roots:Shallow, fibrous roots to 100 mm deep and a large, fleshy, branched, segmented storage roots to 500 mm deep. Each segment can form new plants.
Key Characters:White flowers that open at night.
Rope like spiny cactus with globular red fruit.
Perennial. Seeds germinate after rain in early summer and grow slowly. A few establish to form a 100-150 mm long stem by the end of summer. Storage roots then develop. Growth stops during the cold, dry season and starts again after spring rains that exceed 5 mm. After 3-5 years when the stems are 600-900 mm long, the plant will flower between November and April following heavy rains. Fruit development takes several weeks. Animals and birds usually eat the fruit or it withers on the stems. Storage roots and stem segments disturbed by cultivation sprout to form new plants.
Drought tolerant once established due to thick leaves and cuticle, low stomatal density and size, mucilage cells and crassulacean acid metabolism (CAM plant).
Reproduction:By seed and vegetatively.
Flowering times:November to April in Queensland.
Seed Biology and Germination:Seeds have no after ripening period.
Remain viable for 4-5 years in storage conditions.
Require light for germination.
Germinate readily in manure.
Exposure to cold conditions improves germination.
Seedlings are sensitive to water stress.
Vegetative Propagules:Stem and root fragments.
Population Dynamics and Dispersal:
Most long distance spread is due to intentional planting in gardens as an ornamental and disposal of garden waste.
Wild pigs increase the spread by rooting out the roots and eating the fruit. Birds and cattle eat the fruit and are a major mode of dispersal. Seeds germinate readily in animal droppings.
Colonies increase in size by vegetative growth of the long trailing stems. Stem fragments broken from the parent plant readily transplant and take root wherever they contact the soil.
Origin and History:South America, Argentina and Paraguay.
Introduced to Queensland as an ornamental plant between 1885 and 1900.
Distribution:NSW, QLD, WA.
Courtesy Australia's Virtual Herbarium.
Courtesy Australia's Virtual Herbarium.
Habitats:Sub-tropical, semi-arid grasslands. Summer dominant rainfall areas. Prefers deep cracking friable clays with more than 500 mm annual rainfall.
Climate:Sub tropical, semi arid areas of variable summer rainfall of more than 500 mm per year.
Soil:Most abundant on the deep fertile cracking clays.
Occurs in low density on less fertile duplex soils.
Plant Associations:Brigalow and False Sandalwood.
Detrimental:Forms dense, prickly, impenetrable mats, 1000-2000 mm tall, preventing use of the area by stock or people. It is too spiny to be readily grazed.
Toxicity:Not recorded as toxic.
Legislation:Noxious weed of NSW, NT, QLD, and WA.
Management and Control:Thresholds:
Hexaflurate and dichlorprop are used for control, usually in conjunction with scrub clearing.
Sodium 2,4-D powder is used to treat individual plants. Tops are cut off 40-50 mm below ground level and the exposed rootstock sprinkled with powder then covered. Cut tops are crushed, treated with 2,4-D powder and burnt. Cut tops will take root and form new plants if they are not treated.
Herbicide resistance:Biological Control:
Biological control with a stem boring beetle and a mealy bug has been effective in reducing dense stands.
Related plants:Harrisia Cactus (Eriocereus tortuosus) has only slight humps on the stem ridges and areoles with longer (25-60 mm) central spines, and more (6-10) low lying radial spines that are also longer (10-30 mm).
Harrisia Cactus (Intermediate form of E. bonplandii and E. regelii) has no spines on the fruit and 4-5 lengthwise ribs with shallow humps on the stems.
Plants of similar appearance:Prickly Pear
Drooping Prickly Pear.
References:Auld, B.A. and Medd R.W. (1992). Weeds. An illustrated botanical guide to the weeds of Australia. (Inkata Press, Melbourne). P140. Photo.
Lamp, C. and Collet, F. (1990). A Field Guide to Weeds in Australia. (Inkata Press, Melbourne).
Lazarides, M. and Hince, B. (1993). CSIRO handbook of economic plants of Australia. (CSIRO, Melbourne). #515.1.
Parsons, W.T. and Cuthbertson, E.G. (1992). Noxious weeds of Australia. (Inkata Press, Melbourne). P355-359. Photos.
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