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Euphorbia squarrosa (Euphorbia squarrosa)

Euphorbia squarrosa is a spiny succulent Euphorbia with an underground swollen fleshy root and a short underground main stem topped by a ring of green branches.

LightSources differ: it can grow in full sun to bright partial sun and tolerates strong sunlight, but a plant previously grown in shade should be exposed to stronger light gradually to avoid sunburn.
WaterSources differ on watering details: water regularly during active growth without allowing water to collect around the roots, while keeping it very dry or stopping routine watering during winter dormancy; it tolerates dro
HumidityIt is reported to need moderate airflow.
TemperatureSources differ, but the reported minimum is about -6 °C. Sources differ on its USDA hardiness zone. It is reported to tolerate brief light frost and to have high heat tolerance. It is reported to drop its leaves and go d
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Euphorbia squarrosa illustration

Overview

Euphorbia squarrosa is a spiny succulent Euphorbia with an underground swollen fleshy root and a short underground main stem topped by a ring of green branches.

Origin and habitat

It is native to South Africa's Eastern Cape, with some accounts specifically listing Albany, King Williams, and Fort Beaufort in the Cape Province. It is reported to suit warm, sunny conditions, can be grown outdoors in frost-free climates, and has some cold tolerance.

Characteristics

Sources are few, but mature height is reported at about 0–30 cm. It is reported to grow slowly, with moderate water, warmth, and fertilizer during active growth increasing its growth rate. Euphorbia has cyathia, with highly reduced male and female flowers consisting mainly of stamens and pistils respectively; its fruit is generally a capsule that splits open when mature. Euphorbia squarrosa has a swollen root and is reported to reach a limited mature height.

Light

Sources differ: it can grow in full sun to bright partial sun and tolerates strong sunlight, but a plant previously grown in shade should be exposed to stronger light gradually to avoid sunburn.

Watering

Sources differ on watering details: water regularly during active growth without allowing water to collect around the roots, while keeping it very dry or stopping routine watering during winter dormancy; it tolerates drought but performs better with regular water during active growth when drainage is good. The reported winter watering interval is 90–150 days. Withhold water while leafless.

Humidity and airflow

It is reported to need moderate airflow.

Temperature and dormancy

Sources differ, but the reported minimum is about -6 °C. Sources differ on its USDA hardiness zone. It is reported to tolerate brief light frost and to have high heat tolerance. It is reported to drop its leaves and go dormant, with dormancy triggered by cold; a specialist source gives a minimum of about -6 °C, though evidence is limited.

Growing medium and mounting

It needs a highly aerated, fast-draining medium based mainly on inorganic materials such as clay granules, pumice, and volcanic gravel, with only a small amount of peat or leaf mold, and the container needs ample drainage holes. It is reported to need a very fast-draining mix.

Feeding

Sources differ, but feeding in summer is described with a high-potassium cactus and succulent fertilizer containing a full complement of microelements and trace elements, or with a slow-release fertilizer.

Propagation

It can be propagated by seed or cuttings; seedlings more readily form a symmetrical swollen root, while ordinary cuttings may not form one, although topping again can encourage its formation. Cuttings should be allowed to dry and callus before being placed in the medium to reduce the risk of rot.

Common problems

Rot is reported as the main cultivation problem, with risk reduced by appropriate watering and airflow. A medium that stays too wet, water collecting around the roots, or planting cuttings before they have adequately dried and callused can promote rot; abruptly moving a shaded plant into intense full sun can cause severe sunburn. It is reported to tolerate heat and some cold, but maintaining good plant condition requires more warmth and sunlight, and frost-free conditions are considered more suitable.

Identification

The branches are creeping to semi-erect, dark green, often twisted, and typically angled, while the tuberculate margins bear gray spines; underground is a large swollen fleshy root. Compared with the similar-looking Euphorbia stellata, Euphorbia squarrosa can be distinguished by its typically three-angled branches rather than the bilaterally flattened, two-angled branches of Euphorbia stellata.

Photos

Euphorbia squarrosa
📷 Frank Vincentz · CC BY-SA 3.0 · source
Euphorbia squarrosa
📷 Frank Vincentz · CC BY-SA 3.0 · source

Sources