Caring for the Karoo Rose, or Lapidaria margaretae, is refreshingly easy and straightforward for a mesemb. Similar to Split Rocks, they are a fairly forgiving species that puts up with most novice mistakes. It’s the lone species in its genus, although it used to be included in Dinteranthus.
In the wild, they’re found only in a small area – as you might guess, it’s in the Karoo region, specifically the Warmbad area of southern Namibia, bleeding into the Northern Cape Province of South Africa. They are compact growing little succulents, with keeled leaf bodies that strongly resemble the quartz fields they’re naturally found in.
My Karoo Rose in October of 2019, after I’d had it about a year. You can see an older leaf being absorbed at the base of the plant.
Soil and Potting
As with other mesembs, these do best in a fast-draining, gritty soil. Wild plants grow in mineral-rich, rocky soil with high quantities of quartz and gneiss, which is a coarse-grained rock made up of mica, feldspar, and more quartz. Basically, they live in rocks.
In cultivation, you’ll want your soil mix to be fairly low in organic material. I generally take a solid succulent/cactus mix (current favorite is EB Stone), and mix it 1:1 with pumice to increase the drainage and inorganic composition. Using pumice has the added benefit of increasing the potential calcium content, and if you’re able to add other types of stones to your mix (entire optional!) the plants may benefit from additional minerals being available. You can fertilize with a dilute cactus fertilizer once or twice a year, during their main growing season in autumn, but it’s generally unnecessary. I like to add a bit of play sand into my blend, no more than a spoonful or two for a 2.5″ pot, which can help increase the grittiness and texture of the soil. If using sand, be sure to have a fine-mesh screen over the drainage holes of your pot to prevent soil and sand from simply washing out of the bottom of the pot.
Ensure that your pot is not too large; they have very small root systems, and generally benefit from being slightly under-potted rather than over potted. A shallow pot works well, and small bonsai-style pots can be quite well suited for these slow growing, shallow-rooted little mesembs.
Two blooms from my Lapidaria margaretae in October 2019
Watering and Fertilizing
As with other living stone type plants, these require very very little water, but are more forgiving of getting it than other species. Lapidarias are very opportunistic growers, and will push out growth whenever conditions are roughly suitable – usually autumn, but sometimes spring as well. Autumn is their usual growing season in cultivation, and in colder climates, that is usually the only time of year you’ll see much in the way of growth.
During periods of growth, Lapidaria will happily take water whenever the soil is dry. For my area, this can be as often as every few days during August and September, when it’s hot and dry, but it’s more common to take a week or two between waterings. No special water treatment or quality is necessary, although if you have hard water, ensuring that the soil is flushed will help prevent excess mineral buildup in the soil and on the pot.
You should withold water when the plant is dormant, which is during the height of summer heat, and often during winter when there is less available light. In San Diego, these will often continue their growth season through winter as it’s bright enough and mild enough most of the time, but in northern areas they usually stop growing until more light is available. Once you begin watering again, water sparingly, as they are very greedy and will absorb water until they split. The splits won’t harm the plant, but are generally unsightly, and until the splits scar over they are open “wounds” that pests may invade.
“How much is too much to start?” is something that usually takes a bit of just doing it and messing up to figure out, or just be extremely cautious until you get a groove going. I split mine the first couple years, and have been able to keep a better eye on our weather + refreshed the soil with a faster draining, faster drying mix (all that pumice!).
When it comes to fertilizing, these don’t much, if any. Mine occasionally get some dilute fish emulsion in late summer/early fall, when I splash it nearby on other plants, but I don’t typically try to give these any extra plant food. If you’re only watering using RO water or distilled water, then replenishing the minerals in the soil would likely be beneficial, and a dilute cactus fertilizer would be a good idea. Unless you have very soft water, however, water quality shouldn’t be too big of a worry.
You can see the developing seed pod in the Karoo rose above, which is the result of the October 2019 bloom. This photo is from March 2020.
Light and Temperature
If kept indoors, these need very bright light, preferably near a south-facing window or at least somewhere that gets several hours of morning light, and may need supplemental light in winter or cloudy climates. If you’re able to keep it outdoors, they do best in an area that gets plenty of sunlight, but is shaded during the hottest parts of the day. Without adequate light, they won’t bloom, and if light is too poor, they typically struggle to grow and divide as well.
While they prefer to have warmer winters, they can tolerate night time temperatures down to freezing if their soil is kept quite dry. In summer, they go dormant when the weather is very hot, particularly when nights stay warm. During this period, they should be allowed to dry out as well, and watered only sparingly if they look very shriveled.
My Karoo Rose as of March 2021! Beginning to divide into multiple heads, which will eventually become almost a ball-shape with very old plants.
That’s the Karoo Rose, or Lapidaria margaretae! Hardy, easy to care for, and very pretty. These are one of the few plants I’d say would do well with a Pleiospilos in a shared planting, as they are equally as forgiving with water, and have a similar growing season.