Polytrichum commune

Genus & species | Common name:
Polytrichum commune | Common Haircap Moss — Named for its tall, hair-like leaves that form a “cap” over the reproductive capsule when young. One of the largest mosses, often forming dense carpets.

How to grow:
Thrives in cool, moist, acidic environments. Best suited for large terrariums, paludarium banks, or shaded outdoor moss gardens. Requires consistently damp substrate and high humidity. Avoid compacted or alkaline soils.

Growing requirements:

• a) Water: Keep constantly moist with soft or rainwater; avoid drying out

• b) Soil / substrate: Acidic (pH 4.5–5.5), loose peat-based mix or sphagnum moss over sand/loam

• c) Humidity: Very high (≥80%)

• d) Sunlight: Bright indirect to low light (2,000–8,000 lux); 5–10W grow light

• e) Temperature: 10–20 °C; prefers cool, temperate conditions

Growth habit:
Acrocarpous moss forming dense, upright tufts up to 30 cm tall

Growing season & conditions:
Active growth in cool, moist seasons; slows in high summer heat

Acclimatization on transport:
Sensitive to drying; moss should be kept slightly damp in breathable packaging

Fun fact:
Polytrichum commune mats were traditionally used as natural insulation in storage baskets to keep grains dry.