Harrisia cactus

Native to South America, harrisia cactus is a spiny perennial plant. Harrisia cactus was introduced to Queensland as a pot plant in the 1890s and is now found in a number of sites across the state. It can infest pastures and reduce them to a level unsuitable for stock.
Description
- Spiny perennial plant with fleshy-jointed stems that form tangled mats about 0.5m tall.
- Stems are ribbed lengthwise with 6 ribs.
- Ribs have low, thick, triangular humps at regular intervals.
- Humps have cushions of grey felty hairs, 3-5 short spines lying flat, and 1-3 erect, stiff, sharp spines 2.5-3cm long.
- Flowers are large, funnel-shaped, pink with tinge of white.
- Flowers grow singly on slender, scaly, grey-green tube 12-15cm long.
- Fruit is round, 4-5cm across, bright red, with scattered bumps, hairs and spines.
- Seeds are small, black, embedded in fruit's white, juicy pulp.
- Shallow feeding roots are up to 3cm thick and 30cm-2m long, growing mostly horizontally off a crown, up to 15cm below ground level.
- Swollen tuberous storage roots descend 15−60cm.
Life cycle
- Bears bright red fruit containing 400-1000 small black seeds. Fruit and seed are readily eaten by birds and to a lesser extent by feral pigs. Plants are easily established from seed dropped by these animals. Seeds germinate soon after rain.
- Seedlings quickly produce swollen tuberous food storage root that develops as plant grows. Branches take root where they touch ground, and new plants will grow from broken branches and sections of underground tubers.
- Counts of tubers in dense cactus infestations have shown more than 125,000 per hectare. Each plant houses many dormant underground buds that are all capable of reshooting when tip growth dies; any small portion of tuberous root left in soil will grow.