Family: Cactaceae
Common names: Prickly pear, Wheel cactus, Blue prickly pear, Silver dollar prickly pear
There are many species of plants commonly called as Prickly pear, like Opuntia robusta, Opuntia engelmannii, Opuntia stricta, Opuntia ficus-indica and more. My plant identification app said that this plant is Opuntia engelmanii.
But the first set of photos were taken at KEW gardens in London, and a board right below them said ‘Opuntia robusta’. And I am not one to question KEW gardens, the official plant species specialists.
So this comes with a disclaimer that these pictures could be of Opuntia robusta, Opuntia engelmanii or a mix of both. That’s what happens when you dwell deeper and deeper into the botanical names of plants, the more you try to learn, the less you realize you know.
Plant Characteristics
Prickly pear is a very common, shrubby cactus that usually grows 1-3 meters tall and wide, forming a broad, tree-like shape with age. Instead of true leaves, it has large, round to oval pads that act as stems.
These pads are thick and fleshy, often 25–40 cm across, with a bluish-green to silvery coating that gives the plant its common name. The surface is dotted with areoles bearing long, sharp spines that can prick badly and also detach easily.
The root system is shallow but wide-spreading, allowing the plant to quickly absorb moisture from light rains since they grow in arid areas. This makes it very drought-adapted but also means that they prefer well-drained soil.
Younger plants are unstable and could topple easily, but older plants develop a woody base that helps anchor the heavy upper growth.
Flowers appear in late spring to early summer along the edges of mature cactus pads. They are showy, usually yellow to yellow-green, about 6–8 cm wide, and attract pollinators in plenty.
After pollination, the flowers turn into fruits that are oval, 5–7 cm long, ripening to red or purple. These fruits are fleshy containing multiple seeds, and edible when properly prepared. Opuntia robusta is native to central Mexico, where it grows in arid and semi-arid regions.
Gardening Tips
Prickly pear cacti thrive in full sun, where the pads develop their best color and strong growth. It can tolerate light shade, but too little sun leads to weak, floppy pads.
Plant it in sandy or gritty soil with excellent drainage, as standing water around the roots can cause rot. Raised beds or sloped sites work especially well.
Water sparingly once established. During the growing season, occasional deep watering is enough, while in winter the soil should be kept almost dry.
Overwatering is a more common problem than underwatering. Space plants at least 2–3 meters apart to allow for their wide spread and to make maintenance easier.
Pruning is rarely needed, but damaged or overcrowded pads can be removed with thick gloves and clean tools. Fertilizer is usually unnecessary, since slow-growing plants like cacti and succulents are very light feeders.
Watch for scale insects and cochineal, which appear as white cottony patches, and treat early with water sprays or mild insecticidal soap.
Growing these Prickly pears are quite easy, but they are very difficult to get rid of, once they are established in the soil. So only grow these cacti near hedges or areas where you don’t want cattle to come in.
Uses of Opuntia robusta
Opuntia robusta is widely grown as an ornamental plant for its bold form and attractive blue-green pads.
It works well as a focal plant in dry gardens, desert landscapes, and large containers where space allows. Its size and spines also make it useful as a living barrier or boundary plant.
The young pads and fruits are eaten raw or cooked, and the peel is sometimes fried and consumed. Edible pads called nopales is used in Mexican dishes, especially tamales.
The flesh of the stem could be used as a poultice for cuts and inflammation. The fleshy insides of the pads are used in the treatment of diabetes and cholesterol.
The plant is high in oxalate content, and no part of it should be consumed without expert supervision. There are many species of Prickly pears and not all of them are consumed. So it is best to exercise caution.
Propagation
Propagation is through seeds and pad cuttings.
Pad cuttings are the easiest and fastest method for home gardeners. Healthy pads are cut, allowed to dry for several days until the cut end calluses, and then planted upright in well-drained soil where they root readily with minimal watering.
Photographed at: KEW gardens, London; National botanical garden, Narikala fortress, Tbilisi
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