Opuntia humifusa (Raf.) Raf.

I acquired this from a garden centre, where it was sold as a hardy plant, and was remaindered as a result of lack of interest from the buying public. Their loss!

The Opuntia group is a ‘Marmite’ subject. Their flowers are among the best of the family (Fig. 1), but some growers dislike the plants because they often grow large and can be painfully sharp.  They have a range of cunning spine designs, including a unique type of barbed hair, the glochid, which dislodges easily from the plant, and less so from your finger.  So, some care is needed, but the flowers are worth it, and some species (like this one) grow easily outside in the UK without shelter!

A low-growing species (the name means ‘ground-hugging’), Opuntia humifusa typically has flat pads, between 5 and 10cm across, lying horizontally on the ground. A few pads stick up into the air, but the plant does not develop any significant height and, in time, these pads often become prostrate too.

O.humifusa comes from a wide range of habitats across the northern and north-eastern USA and up into Canada. As a result, it is one of the easiest cacti to grow outdoors in the UK. Near Bristol, I give it no protection from the weather and it has grown and flowered well over the last decade.

For the container, I drilled some holes in an old pot saucer, 45cm in diameter and 7cm deep. The ‘compost’ consists of 60% 6mm pea gravel, 30% finer potting grit and 10% loam. I repot when it outgrows the pot, which is usually every three or four years.

Watering… when it rains! Actually, if there is a dry spell, I give some additional water. Also, if it has not been repotted recently, I water with some balanced fertiliser, with a range of trace elements. The compost is not very rich, so it needs help.

In winter, the plant looks rather bedraggled (Fig. 2), though in cold conditions the pads take on a nice red tinge. In spring, it starts to absorb water, plumps up and, in my south-facing aspect, develops a good supply of bright yellow flowers, about 8–10cm in diameter (Fig. 3).

I find two main problems in cultivation. First, controlling its spread. I prune it and every few years I take a cluster of pads to replant at a reduced size. It roots down from the horizontal pads so there is plenty of rooted material and any cuttings root very easily. New growth tends to grow away in one direction, so I usually pot it to one side of the tray, allowing space for the new growth on one side. I use 30cm long ‘tweezers’ and bamboo sticks to manoeuvre the plant safely, but this is one of the less aggressive opuntias and is easy to move and repot.

For me, the second issue is garden weeds. Dandelions and other interlopers love getting in between the pads and are difficult and/or painful to extract!

David Lambie

No part of this article may be reproduced without permission. Copyright BCSS & the Author 2021

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