Quick Facts

Quick facts

• Harrisia Cactus (Harrisia spp.) are aggressive weeds which form dense spiny thickets and can cover extensive areas.
• Once established, plants are drought tolerant.
• Fruits are succulent and contain hundreds of seeds in a fleshy pulp which is attractive to birds and animals who readily disperse the seed.
• Plants are spiny and can cause injury to humans and animals.

What Does It Look Like?

What is it?

Harrisia Cactus (Harrisia spp.) is a term used for several species of Harrisia including H. martinii,   H. tortuosa  and H. pomanensis [ H. regelii].

Harrisia martinii is the most common of the three Harrisia cacti occurring in Australia. It is a mat-like or scrambling much branched shrub forming tangled thickets from 0.3 to 2 m tall or climbing over other plants with stems to 2 to 3 m long. It has tuberous roots. Its stems are green to grey green, 2.5–4 cm in diameter, with 4 to 6 ridges. The ridges are prominently tuberculate (warty), each tubercle tipped by an areole (spots on stem segments and fruits that contain the spines). The areoles contain 1 to 4 central spines (10–35 mm long) and 3 to 7 smaller reflexed spines 1–6 mm long. Leaves are small, insignificant and deciduous (tending to drop off).

Flowers are large and showy and borne singly along the stems. They consist of many white 'petals' (perianth segments) which may turn pinkish with age, merged into a tube that is 15–20 cm long, with the outermost of these 'petals' (perianth segments) sometimes greenish in colour. These flowers usually open at night and begin to wither by the next morning.

The red, succulent fruit are 2–6 cm diameter, spiny or sometimes smooth. When ripe the fruit split vertically on one side with white flesh and numerous seed (Stanley & Ross 1983; Harden 1990; Navie 2004).

Harrisia pomanensis ( H.regelii) is similar to H. martinii  but the stems lack tubercles and have finer spines, the plants are more erect and the fruits spineless.  Whether this species is in Australia is not yet comfirmed as no authentic records of it were found in the Queensland Herbarium (Chinnock pers. comm. 2021).

Harrisia tortuosa is readily distinguished from H. martini by its thicker deep green to brownish stems 4–5 cm diameter with usually 1-3 robust grey, black tipped central spines, the longest 3–7 cm long, and 7–9 smaller radiating ones.

For further information and assistance with identification of Harrisia Cactus contact the herbarium in your state or territory.

Flower colour

White

Growth form (weed type/habit)

Shrub

Where it currently grows? Preferred habitat

Harrisia Cacti are found in subtropical semi arid shrublands with variable summer dominant rainfall especially on deep, fertile cracking clays. In Queensland it has a close association with brigalow scrub where the weed reaches it maximum development often completely covering the ground (Parsons & Cuthbertson 2001).

Are there similar species?

Harrisia Cactus can be confused with Sword Cactus (Acanthocereus tetragonus) and Moonlight Cactus (Hylocereus undatus). Sword Cactus forms a large shrub to 3 or m tall with strongly 3–4 angled stems with areoles having 6–7 (rarely up to 12) large spines 1 to 5 cm long. Moonlight Cactus differs in having 3-angled stems with areoles having 1 to 4 small spines only 2–4 mm long, much shorter than those of Harrisia Cactus (Navie 2004).

Some consider Tiger Pear (Opuntia aurantiaca) to be similar to Harrisia Cactus but it is easily distinguished by its very short rounded (terete) or flattened detachable stem segments that are rarely more than 20 cm long and the small yellow flowers (Navie 2004).

Why Is It A Weed?

What are its impacts?

Human impacts: Harrisia Cactus can cause painful injury to animals or humans who accidentally walk into or otherwise touch a plant due to the sharp spines.

Agriculture: It is a prolific seeder, spreads quickly, and has the ability to eventually take over large areas of grazing country (Tanner 2007). If unchecked, it can form dense, tangled thickets that are impenetrable to stock, can choke out pasture species and can eventually cover as much as 80 to 90 percent of the land and seriously reduce productivity. The dense thickets also interfere with mustering operations. It is not readily grazed due to its spines except during drought. 

Native ecosystems: It can be a particular problem in brigalow areas where it may completely cover the ground surface. It competes strongly in the brigalow scrub under shaded and dry conditions but will can also grow, albeit slowly, in the full sun (Parsons & Cuthbertson 2001).

How does it spread?

Harrisia Cactus, because of it use of an ornamental and its edible fruit, was spread intentionally during the early stages of it establishment in Australia. Harrisia Cactus reproduces by seed and also by fragments of the fleshy (succulent) stem segments. Dispersal of seeds is primarily by birds, other animals (e.g. pigs, cattle, foxes) and reptiles (e.g. goannas) that eat the fruit. Stem fragments may also be spread by animals and in discarded garden waste (Parsons & Cuthbertson 2001; Navie 2004; North West Weeds 2006).

What is its history in Australia?

Harrisia martinii was introduced to Queensland between 1885 and 1900 during the flourishing Mt Coolon goldfields period. It was planted as an ornamental in miner's gardens in nearby Charters Towers and on Sonoma Station near Collinsville. Later outbreaks including those at Ipswich, Mt Sylvia, Mt Morgan, Rockhampton and Rannes were thought to be the result of plants being brought south from the original plantings (Parsons & Cuthbertson 2001).

Harrisia tortuosa populations at Millmerran and Drayton districts in Queensland and at Scone and Muswellbrook in New South Wales originate from a specimen brought as a pot plant to the Western Creek Homestead near Millmerran in 1888 (Parsons & Cuthbertson 2001).

How To Manage It?

Best practice management

Non-chemical control: Control of Harrisia Cactus is difficult due to its deep underground tuberous root system. Small infestations and single plants should be completely removed as plants can grow from small sections of the tuberous root left behind in the soil (Land Protection 2007).

Fire: Burning can be undertaken for small infestations but intense heat is required to destroy underground parts (Tanner 2007).

Chemical control: is possible but must be regularly undertaken (Tanner 2007).

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Biological control: Harrisia Cactus has been recognised as a target for biological control through a cross-jurisdictional government process. This allows activities to be undertaken to develop effective biological controls. Biological control using the Stem Boring Beetle (Alcidion cereicola) has been successful in the Collinsville area. Large stem boring beetle colonies developed and contributed to the collapse of dense areas of cactus. The populations of this beetle have declined with the declining numbers of the cactus (Land Protection 2007). The Mealy Bug (Hypogeococcus festerianus) is the most successful biological control agent used on Harrisia Cactus. It is now widespread in affected areas in Queensland (Land Protection 2007). The Prickly Pear Moth Borer (Tucumania tapiacola) has also been observed attacking Harrisia Cactus (Land Protection 2006).

Does it have a biological control agent?

YES

When does it grow? (lifecycle/growth calendar)

Harrisia plants are active throughout most of the year in warmer areas. Flowering occurs mostly during spring and early summer, but may continue through until early autumn depending on conditions. The scented flowers open and night and collapse the following morning. Plants can start producing seed at age 6 months and from that age they can continue to produce fruit throughout the year. Seeds germinate after the first heavy rains of summer but the seedlings are fragile and easily destroyed by drought, trampling, grazing and cultivation (Parsons & Cuthbertson 2001; Navie 2004; Tanner 2007)

Where Is It Found?

Which states and territories is it found?

NSW, QLD, WA

What areas within states and territories is it found?

Harrisia Cactus is widespread in parts of eastern Queensland and a few scattered locations in New South Wales including West Wyalong, Sydney and in the upper Hunter valley. It also occurs in a few scattered locations in Western Australia (Harden 1990; Parsons & Cuthbertson 2001).

Where does it originate?

Harrisia martinii is restricted to the Gran Chaco area of Argentina while H. regelii [as H. pomanensis] and H. tortuosa are more widespread, occurring in Argentina, Bolivia and Paraguay (Anderson 2001).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

NSW, NT, QLD, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Harrisia spp.

Other scientific names (synonyms)?

Does it have other known common name(s)?

• Harrisia Cactus (all species)
• Moon Cactus
• Moonlight Cactus
• Snake Cactus