Euphorbia knuthii
Euphorbia knuthii is a perennial succulent in the family Euphorbiaceae. It features a large, tuberous caudex that typically remains subterranean in nature, but is often raised in cultivation for its sculptural appeal. From the top of this swollen rootstock, numerous thin, sprawling stems emerge. These stems are square or triangular in cross-section and display a distinct greenish-grey color with attractive white or silver zig-zag markings.
Origin and Natural Habitat
This species is native to South Africa, Mozambique, and Swaziland. It predominantly occurs in the lowveld regions and subtropical savannas. It grows in sandy or stony soils, often partially hidden under the shade of grass or small trees.
Plant Characteristics
Euphorbia knuthii is a medium-sized shrubby species that forms a large, tuberous caudiciform root system. It is often grown with its roots raised to make an attractive ‘bonsai’ plant. The underground caudex protects the plant from the frequent bushfires and prolonged droughts characteristic of its native habitat.
Care Guide
Light
This
Euphorbia species prefers full sun, or lightly filtered sun. In cultivation, a maximum of 40% shade cloth is recommended. This encourages stronger colouration and a more compact growth form while preventing sun damage. Do not plant in shade.
Soil
Euphorbia knuthii prefers a gritty, inorganic soil medium that drains well, such as
Ibaraki Akadama or Hyuga pumice.
Water
Euphorbia knuthii must only be watered in spring and summer. This plant should receive a thorough soaking of water every 7-10 days during the active growing season, but only if the soil is mostly dry. Keep dry in autumn and winter.
Pot size
This species should be grown in a container that is about 3-5cm wider than its root system. When small, it can be grown in 10-12cm pots, but with time will need a larger pot.
Temperature
This species’ ideal temperature ranges between 20 – 30*C. It is quite adaptable and can tolerate 5 – 40*C. It is sensitive to frost and should be protected in winter.
Humidity
This species prefers dry conditions and should not be kept in areas with more than 50% humidity.
Fertilizing
Use a half-strength diluted general liquid fertilizer only during the growing season. Do not fertilize during autumn and winter. Alternatively, a small amount of slow-release fertilizer will be sufficient.
Growing Season
This
Euphorbia grows actively in spring and summer, but their growth stops in autumn and winter.
Propagation
Euphorbia knuthii are best propagated from stem cuttings or seeds.
Stem propagation: Using a sharp, clean knife, cut one of the stems from the main stem. Let this dry for 10 days, then plant it.
Seed germination: Seeds should be sown in early spring. Plant them in a mix of
coco peat and perlite, with some vermiculite, in an airtight container. Once most of the seeds have germinated, remove the lid of the container to allow airflow. Gently mist the seedlings every few days so that the soil does not dry out.
