Succulent groundcovers: Plectranthus species

Here are two tough Plectranthus groundcovers that prefer dry conditions.

Plectranthus spicatus typically grows predominantly in the sun on cliff-faces, with fairly shallow soils and high wind exposure. It will cover an embankment very rapidly, and is another plant that will colonise downwards on a tightly-packed retainer wall, albeit more slowly than Crassula multicava (see previous posting). Whereas C.multicava is more likely to spread via the tiny seedlings that form as the flower dries-up, P. spicatus will root from dislodged pieces - which provides the clue to rapid cover, if you have the time to do it manually.

I love its bright green, serrated (dentate) texture. It is very hardy to drought, but gets damaged by fairly light frost (it should recover in Spring, unless the frost is severe). It has a long flowering period (Autumn to early Spring), and the flowers provide curious interest at times, but on the whole it detracts from a particularly spectacular foliage. It handles much more (dry) shade than commonly assumed.

Plectranthus lucidus is typical coastal dune vegetation undergrowth. Mthatha's climate is extremely hot in summer, but with lots of cloud. Wet summers can give the area a very sub-tropical feel (but with much less humidity). A dry summer, as we're currently experiencing, has more of a harsh karoo-like or thicket feel to it, but with much more cloud. Winters are crisp (warm-to-hot at midday; below freezing at dawn), dry and sunny. This Plectranthus does extremely well here under dry shade, and does not mind the fine clays typical of the area. It spreads fairly slowly, and needs protection from frost (solid tree cover will do). It is a delicate plant in size and appearance (tough in practice), with fine texture and bright foliage. It is a great plant for contrasting alternate repetitions. I'm currently using it to some effect with a Crassula species that I received from Ryder Nash of Simply Indigenous. Unfortunately, discussions with botanists and long searches through hundreds of Crassulas have failed to yield a name. I now call it Crassula sp. 'Ryder'. I'll do a separate posting on it.

Succulent groundcovers: Crassula species

I work with several indigenous Crassula species, including the more shrub-like form plants (and great, albeit different, bonsai material) C. ovata and C. arborescens. I personally enjoy the weird leaf form and spectacular flowers of C. perfoliata, and find that C. pellucida combines well with trailing Arctotis species.

However, it is to C. multicava and C. spathulata that I turn for tough Crassula groundcovers in the shade.

Crassula multicava is pictured here underneath Plectranthus ecklonii, during late winter (when the Plectranthus is in poor shape and fairly open). It spread itself, via seeding, down the very hostile retainer wall. It is a relatively moist area, and this Crassula does enjoy some degree of moisture. However, there's a gap as wide as the blade of a knife behind each of those retainer blocks - not much more than dust settles there. Once roots grow away, they should find a bit of soil in the blocks. The aspect is also tricky - north-facing; hot sun most of the day, most of summer; virtually no sun in winter (tall surrounding walls cut the sun). The picture was taken a year after planting the Crassula on top only. It is now 2 years since the picture, and the wall is densely covered - but nutrient deficiency is starting to show, as there's a yellowing of the leaves, particular where the sun is more persistent. I definitely prefer this Crassula in the shade.

Crassula spathulata has a very similar flower, for a much longer period, and at a different time than C. multicava. I do not rate the flower, though, finding that it gives an untidy appearance. This is a Crassula that I prefer for its leaves. It handles hot sun with less scorching, and looks better in dry locations than C.multicava. It has exceptionally beautiful texture and gloss, particularly in the shade. And that is my preferred location: dry shade.

Drainage & natural adaptation - a plant for every niche

This Crassula ovata variation from the Mbashe area (where the very rare and endemic Aloe Reynoldsii grows) illustrates the basic evolutionary principle that where there is a niche, a species will adapt and thrive.

As a landscaper, I initially struggled with the concept of good drainage for water lovers - I mean, how do you expect to provide drainage in a swampy, wet environment? Observing plants in a natural environment quickly brought the answer - just look at plants rooted in gritty, compost loam on a seasonal waterfall. Indeed, there is good drainage - the water is constantly moving over the rocky substrate, and air is being pumped through the root system.

Impatiens flanaganiae

I found these growing on boulder screes amidst (or often dominating) clivias, scadoxis and cycads, in my all-time favourite ravine; a place of rare beauty where I've returned up to 6 times a year for the past 20 years. Dangerous, inaccessible and unknown - its had a persistent pull on me unmatched by any other place of great natural beauty that I've enjoyed. This Impatiens is considered rare; it grows in shade typically on sandstone; has large tubers (used in traditional medicine); and it flowers endlessly through late Spring and Summer.

Shading the precipise

This magnificent shade tree, with its bright-green foliage, is rooted just below the lip of a 100m cliff-face.