Applying fertilizers, checking growing conditions, pruning, and re-potting are ways to encourage thickening in Euphorbia trigona.
Specifically, the succulent plant in question also goes by the common names African milk tree and cathedral plant, in reference to its church spire-like growth pattern. It is natural for a cathedral cactus to show thick inward- and outward-branching growth. An African milk tree that has thin branches and stems probably suffers from problems with the care or the container.
Care issues include over- or under-exposure to light, moisture and nutrients. A heat/light concern is solved by changing the orientation or the position of the plant within the room. A moisture issue needs to be addressed by checking drainage since the soil always must be slightly moist and never permitted to dry out or waterlog. A nutrient problem requires a low-nitrogen fertilizer since this particular euphorbia's growth depends more upon phosphorus, potassium and trace elements than upon nitrogen.
Micrarctia trigona was created in 1899.
Eriocraniella trigona was created in 1978.
Trigona spinipes was created in 1793.
Euphorbia haeleeleana was created in 1971.
Euphorbia herbstii was created in 1988.
Euphorbia albomarginata was created in 1857.
Euphorbia chamaesyce was created in 1753.
Euphorbia skottsbergii was created in 1936.
Euphorbia thulinii was created in 1992.
Euphorbia epithymoides was created in 1762.
Euphorbia deppeana was created in 1860.
Euphorbia antisyphilitica was created in 1832.