Cyperus dives (Cyperaceae) The most conspicuous feature of the plants are the bright green, smooth, rounded culms (flowering stems) which are up to 40 mm thick at the base and may be up to 5 m tall in ideal conditions. Each is topped by a dense cluster of thin, bright green, shiny stalks, which resemble a feather duster when young. Sowing : Sow in summer in wet conditions. Locality : Pennington. Date of harvest : May 2018.