Whirlpool Plant - Petrocosmea 'Keystone's Barnswallow' - Welsh Grown

Compact, symmetrical, and wonderfully textural, Petrocosmea are miniature rosette-forming plants known for their soft, velvety leaves arranged in perfect spirals – often described as “whirlpool-like.” With their naturally low growth habit and love of high humidity, they’re ideal for terrariums, cloches, or shaded shelves, where they quietly thrive in stable, filtered light. Grown in Wales and perfect for small-space styling, Petrocosmea bring a calm, contemplative quality to your plant collection – and may even reward you with tiny violet-like blooms when happy.

Scientific Name
Petrocosmea spp. (Petrocosmea = from Greek, meaning “rock hair”, a nod to their growth on mossy stones in the wild)

Common Name
Whirlpool Plant, Rosette Violet, Petrocosmea

Origin
Native to the cloud forests of China and surrounding regions, where they grow on moist, mossy rocks in cool, shaded conditions.

Light
Prefers bright, indirect light. Avoid direct sun, which can scorch their soft leaves. Suitable for north- or east-facing windows, or filtered terrarium lighting.

Water
Keep the soil evenly moist but never soggy. Water from the base or carefully at the edge of the rosette to avoid crown rot. Reduce watering slightly in winter or if kept inside a closed terrarium.

Humidity
Thrives in high humidity (60–80%), making Petrocosmea ideal for terrariums, bell jars, or other enclosed setups. In open air, increase humidity with misting or a pebble tray.

Soil
Use a light, well-draining mix – African violet compost with added perlite and fine bark works well. Good drainage is key to prevent waterlogging in humid conditions.

Food
Feed sparingly every 6–8 weeks during spring and summer with a diluted houseplant fertiliser. These plants are slow-growing and don’t need heavy feeding.

Temperature
Best kept between 15–22°C. Avoid cold draughts and hot, dry air.

Pet-safe
Yes – Petrocosmea are non-toxic to pets and humans.

Sprouts Top Tips
These gentle plants are happiest when left undisturbed in a stable environment. They’re perfect for terrariums or low-traffic spots where they can quietly shine. Clean leaves gently with a soft brush to keep them looking their best.

Want to encourage flowering?
Many Petrocosmea varieties produce dainty violet-like blooms in spring or summer. To encourage flowering, provide steady light, slightly cooler nights (around 12–15°C), and a diluted high-phosphorus feed in early spring.