Myrtillocactus geometrizans – Blue Myrtle Cactus

With its striking blue-green skin, branching form, and sculptural silhouette, Myrtillocactus geometrizans is a bold addition to any cactus lover’s collection. This fast-growing species can eventually reach impressive heights and develop candelabra-like arms. While usually kept as a compact indoor plant, in the wild it can grow several metres tall. Its name comes from the small, edible blue fruits it produces – reminiscent of blueberries.

Scientific Name
Myrtillocactus geometrizans (geometrizans = ‘geometrical’, referring to its distinct ribbed structure; myrtillo = ‘little myrtle berry’)

Synonyms
None widely used, though some forms are sold as ‘Blue Candle Cactus’ or ‘Bilberry Cactus’

Common Name
Blue Myrtle Cactus, Bilberry Cactus, Blue Candle Cactus

Origin
Native to central and northern Mexico

Light
Requires very bright light and several hours of direct sun. A south- or west-facing window is ideal. Supplement with grow lights in winter if needed.

Water
Water only when the soil has completely dried out. In spring and summer, this may be every 2–3 weeks. Reduce drastically in winter – once a month or less. Avoid letting water sit near the base.

Humidity
Prefers dry air. Avoid humid environments and ensure good ventilation.

Soil
Use a very free-draining cactus mix with added grit or sand. Avoid standard compost or moisture-retentive mixes.

Food
Feed every 4–6 weeks during the growing season with cactus fertiliser. Do not feed during winter dormancy.

Temperature
Prefers 20–28°C. Tolerates as low as 5°C if kept dry. Protect from frost and cold drafts.

Pet-safe
No – mildly toxic if ingested.

Sprouts Top Tips
Rotate regularly to prevent leaning towards the light – this cactus grows fast when happy!

Extras
In maturity, it produces fragrant, pale greenish-white flowers followed by edible blue fruits.

Did You Know?
The small fruits of Myrtillocactus geometrizans are known as “garambullos” in Mexico and are traditionally eaten fresh or made into jam.