Thelocactus hastifer can be immediately recognised by its elongated stem, which may be erect or lie along the ground (‘decumbent’). This elongate stem is a unique character among the species of this genus, and even young seedlings can be easily distinguished from other Thelocactus species by the elongate rather than rounded growth. Individual plants have a swollen root and a thin stem, about 5.5 centimetres in diameter, which is divided into 13 to 18 ribs. In older individuals, the stem branches from the base. The main body of the plant has a very thin collar between the root and the upper part of the stem, which is unable to bear the weight of the stem, so that it eventually grows lying on the ground. The spines of this cactus are straight and needle-like, and consist of 20 to 25 ‘radial’ spines, which are white in colour and measure up to 1.5 centimetres long, and 4 to 5 ‘central’ spines, which are longer, at up to 2.6 centimetres, and whitish to black in colour (4).
- Height: up to 40 cm (2)