Browningia hertlingiana
| Light | Very bright light to full sun; the blue "bloom" develops best in strong light |
|---|---|
| Water | Moderate in the growing season; let the soil dry between waterings, keep dry in winter |
| Soil | Fast-draining mineral mix (see Soil and potting mix) |
| Temperature | Keep above freezing; roughly USDA zones 9b–11 |
| Propagation | Seed; cuttings from mature or branched plants |
| Toxicity | No specific toxicity to cats or dogs is documented; the stiff spines are the main hazard |
Browningia hertlingiana is a tall, columnar cactus from the dry inter-Andean valleys of central Peru, prized above almost all others for its intense turquoise-blue skin. Young plants and fresh growth are coated in a waxy, powdery bloom that turns the whole stem a striking chalky blue-green, making it one of the most vividly blue of all cacti and a firm favourite among collectors. It belongs to the genus Browningia, and was long known by the older names Azureocereus hertlingianus and Azureocereus nobilis, a reference to that unmistakable azure colour.
Description
Browningia hertlingiana is a large, slow-growing columnar cactus that in habitat becomes tree-like, developing a distinct trunk and branching into several upright arms with age. The stems are stout and ribbed, and it is the surface colour that sets the species apart: a heavy, glaucous wax coats the newest growth in an almost metallic turquoise-blue that gradually greens and greys as the skin ages lower down the column.
The ribs are prominent and carry closely set areoles bearing stiff spines that are yellowish at first and darken toward brown or black with age; spine length and density vary from plant to plant. Mature specimens eventually produce nocturnal, funnel-shaped white flowers, but flowering is uncommon on cultivated plants and generally only occurs on very old, large specimens.
Distribution and habitat
The species is native to central Peru, where it grows on rocky slopes and in the arid, cactus-rich inter-Andean valleys such as the Mantaro valley, at moderate to fairly high elevations. These are dry, sunny, well-drained habitats with warm days, cool nights and a pronounced dry season — conditions worth keeping in mind when growing the plant.
Cultivation
Browningia hertlingiana is an undemanding grower for a columnar cactus, asking mainly for strong light and sharp drainage. Give it the brightest position you can — full sun suits it well once acclimatised — as intense light is what encourages the thickest, bluest waxy bloom. Handle plants gently, since that powdery coating rubs off easily and leaves permanent green marks where fingers or leaves have touched it.
Grow it in a very free-draining, mostly mineral mix and water moderately through the warm months, allowing the mix to dry out between waterings. Keep the plant dry and cool over winter to avoid rot; it tolerates only light, brief frost at best, so protect it where temperatures drop near freezing. Being naturally slow, it responds well to a warm position and occasional feeding in summer. See Watering and Repotting for general technique.
Propagation
Seed is the usual method for this species, germinating on a warm, moist mineral surface in the same way as other columnar cacti; see Propagation — seed. Cuttings are also possible from branched or mature plants — a removed segment should be left to callus for a week or two before being set on dry mix to root. See Propagation — cuttings for the full method. Cutting-grown plants can also be used as scions or stock in grafting.
Common problems
- Rot — the commonest cause of loss, almost always from overwatering, a slow-draining mix, or cold wet conditions in winter; the stem softens and discolours.
- Lost bloom — the prized blue coating rubs away permanently on contact and does not regenerate on old skin, so handle plants by the pot and site them where they won't be brushed.
- Etiolation — too little light produces thin, pale, un-blue growth that leans toward the light.
- Pests — mealybugs (white fluff in the areoles) and red spider mites (fine webbing, bronzed skin) are the usual offenders; see Pests and diseases.
See also
- Browningia — the genus overview
- Soil and potting mix · Watering · Propagation — seed · Propagation — cuttings · Repotting · Pests and diseases