Acanthocereus tetragonus 'Fairy Castle'
Acanthocereus tetragonus 'Fairy Castle is a slow-growing, densely branching miniature form of the sprawling tropical cactus Acanthocereus tetragonus, selected and sold as an easy windowsill novelty. Its many short, upright green stems cluster together at different heights to resemble the turrets and towers of a tiny castle, which is where the popular name Fairy Castle cactus comes from. Unlike the wild parent, which is a large, rambling shrub, 'Fairy Castle' stays small and compact, making it one of the most common beginner cacti in garden centres.
Description
'Fairy Castle' is a mutant, monstrose-leaning selection: instead of the long, scrambling triangular stems of the typical species, it produces a mound of short, ribbed, columnar branches that arise at many points and grow at slightly different rates. Each stem is bright to mid-green, four- or five-ribbed, and edged with small clusters of pale, soft spines along the ridges. New branches keep budding from the sides and base, so a plant slowly fills out into a knobbly, multi-towered clump.
Growth is genuinely slow, and the plant may take many years to reach even modest size. It very rarely flowers in cultivation. Be aware that the brightly coloured "blooms" often seen on plants for sale are usually dried strawflowers glued to the tips — they are not real and can be gently removed without harming the plant.
Cultivation
Care follows that of the parent species, Acanthocereus tetragonus; the notes below cover the points that matter most for this compact form.
'Fairy Castle' is undemanding and forgiving, which is much of its appeal. Grow it in a free-draining, mostly mineral mix and water only when the soil has dried out completely, easing right off through the cooler months to keep the roots dry and prevent rot — overwatering is by far the commonest cause of loss. Give it bright light: plenty of sun keeps the towers tight, green and well-armed, whereas a shady spot causes weak, stretched growth (see Watering and Repotting for general technique).
Because the clump grows slowly and stays fairly shallow-rooted, it is happy in a snug pot for a long time and seldom needs frequent repotting. Keep it above freezing and away from cold, damp conditions.
As a monstrose selection, 'Fairy Castle' is maintained vegetatively rather than from seed. It roots easily from stem cuttings: remove a branch, let the cut surface callus over for several days, then set it on a barely-moist mineral mix until roots form (see Propagation - cuttings). It is not usually grafted, and named seed does not come true.
Common problems
- Rot — from overwatering or a slow-draining mix; stems soften and brown, usually from the base.
- Etiolation — too little light produces pale, thin, over-stretched towers that lose the compact "castle" look.
- Pests — mealybugs (white fluff tucked between the ribs) and the occasional spider mite; see Pests and diseases.
- Fake flowers — the glued-on dried blooms sold with many plants can trap moisture at the tips; remove them once you get the plant home.
See also
- Acanthocereus tetragonus — the parent species
- Acanthocereus — the genus overview
- Propagation - cuttings · Soil and potting mix · Watering · Repotting · Pests and diseases