Plectranthus are semi-succulent, and are very easy to grow. They hold a good shape and propagate easily, too. There are over 350 species of Plectranthus, and the majority originate from areas of South Africa, Madagascar, India, and Australia, and they belong to the Mint and Sage Family (Lamiaceae).
The genera name from the Greek plektron, ‘spur’ and anthos, ‘flower’, referring to the spurred flowers. The species is named after Ernst van Jaarsveld, a South African botanist and horticulturist who first discovered the plant in the late 1970s.
The species that I grow is Plectranthus ernstii, otherwise known as Bonsai mint or Bonsai spur flower, as this has a fun striations on the bark of the caudex, which fattens quickly with watering during the summer months. However, be careful not to overwater as they can split if they grow too quickly, plus excess watering can lead to root rot.
The leaves are aromatic, and they have small blue to purple flowers with two lips on a spike, which bloom from late spring through to autumn. They do grow fairly fast and are perennials. I grow it as a bonsai, and feeding with a balanced fertiliser as this aids in maintaining a good leaf colour as well as thick fleshy leaves. They tolerate being kept on the dry side all year but the result is smaller compact leaves.
I got my first one from Derek May in 2014 and I won first place in Class 61 at the BCSS Wiltshire Branch Annual Show in 2019 and again in 2023. My plant also came first at the National Show in 2022. It has continued to grow and expand from its original size to one that requires considerably more space now.
I also keep mine behind thickened UV-protected conservatory glass inside, which allows them to grow thick, lush green leaves. So be careful if you change their conditions to full sun and ultraviolet light, as this will impact their leaf colour and growth, and their leaves may go red or purple. They will need time to adjust to such changes if you move them from being kept inside to outside, for example, in the summer months.
The leaves are heart-shaped, soft to the touch, and fleshy, and consequently can be affected by red spider mites, mealy bugs, and caterpillars, so check regularly for pests and remove any you find.
You can grow them in Akadama or a succulent compost mix. They can get quite pot-bound, so they need repotting fairly often, and this would be a good time to divide up any clumps. Keep them in a warm environment throughout the winter months in the UK as they are not tolerant of cold conditions or frosts. Ideally, they would be on a windowsill indoors or in a warm greenhouse.
They also take well from leaf cuttings and respond well to regular pruning, which helps reduce leaf size by building up the density of leaves.
Text and photos by Amelia Williams
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