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Knob sedge

Carex inversa · Cyperaceae

The gardener's calendar

The right move for September

Ideal time to plant knob sedge: set it out when the soil is neither frozen nor waterlogged, and water generously as it establishes.

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ID card

Foliage
Evergreen, narrow and arched
Blooming
Spring to early summer (April-June)
Adult size
30-50 cm tall, compact and spreading habit
Growth
Moderate
Hardiness
Hardy to around -15°C
Origin
New Zealand
Soil type
Well-drained, prefers light to moderately moist soils

Care

Watering

Water regularly during the growing season (spring-summer) to keep the soil moist but without waterlogging. Reduce watering in winter. In containers, check substrate moisture: Carex inversa tolerates moderate dryness once established, but prefers some moisture.

Light exposure

Place this sedge in partial shade or full sun depending on your climate. In warm regions, dappled shade prolongs vigor and prevents drying out. It also accepts shaded conditions, with slightly slower growth.

Pruning and cleaning

Remove dead or damaged foliage in late winter or early spring. A light combing helps remove dead leaves without damaging the clump. No drastic pruning needed: this plant naturally maintains a compact and graceful form.

Soil preparation

Prepare light, airy and well-drained soil. Add sand or pumice if the soil is heavy or clayey. In containers, use a specialized mix for ornamental grasses or heather plants, with added drainage material.

Fertilizing

Apply balanced or light fertilizer in spring (April-May) as growth restarts. One application is usually enough for the season. Avoid excess nitrogen which would encourage soft growth at the expense of structure.

Diseases and pests

Carex inversa is generally robust. Watch for root rot if the soil stays waterlogged for extended periods: improve drainage. In overly humid and poorly ventilated conditions, leaf fungi may appear. Remove affected leaves and improve air circulation.

Did you know?

Carex inversa is native to New Zealand, where it thrives in humid forests and coastal areas. Its name 'inversa' refers to the distinctive inverted spikelets. In contemporary landscape gardening, it ranks among the most popular ornamental grasses for creating movement and lightness in shaded plantings.

Where to buy it

Plant in spring or early autumn, avoiding spells of intense heat. Pick a plant with healthy foliage and roots that are not exposed. Best time: March, April, May, September.

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Tips generated and checked by Viridia — adapt them to your local climate.