Description of Scirpus cernuus (Fibre Optic Plant)

Isolepis cernua is the plant most people know as fibre optic plant. You may still see the old name Scirpus cernuus on labels. It’s a small marginal that gives you a neat, quirky texture around a bog edge or in a shallow shelf.

Appearance

It forms a soft clump of thin green stems, each tipped with a tiny pale flower head, which is where the fibre optic look comes from. It stays low, often 15 to 30cm tall, and it spreads into a wider tuft over time.

It looks tidy in baskets and also works in small pots dropped into gaps between bigger plants.

Care Guide

Keep it evenly wet. This is one that dries out fast if the basket sits too high.

• Sun: Full sun to light shade.
• Soil: Aquatic compost in a small basket. Top with grit to stop it floating.
• Water depth: Very shallow water works best. Around 2 to 8cm over the soil is a good aim.
• Tidy up: In autumn, remove messy stems but don’t scalp it right down.
• Division: Split the clump in late spring or early summer if it gets crowded.

If you grow it in a container on a patio, treat it like a plant that never wants to dry. A saucer of water under the pot keeps it happier.

Suitability for Bog Garden

This is perfect for small bog gardens because it gives you detail at the front edge without taking over. Use it to soften basket edges, hide liners, or break up straight lines where the bog meets paving.

It also sits well next to plants with big leaves, like hostas or butterbur, because it adds fine texture and makes those leaves look even larger.

In colder winters, it can look rough for a while. Leave the clump in place and it often freshens up once temperatures rise.

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