The cyathia of Euphorbia oxystegia grow on long, erect, purplish-red peduncles from leaf axils. The peduncles may branch once or produce small cymes. The long, lanceolate, adapted leaves or bracts seen here below the involucre of the central cyathium, are referred to as cyathophylls, not often seen so conspicuously present in local Euphorbia species.
The open involucre is sessile or stalkless and cup-shaped. The unopened ones are covered in whitish hairs (iSpot; JSTOR).