Scirpus: Planting, Growing and Caring

Botany

Bulrushes comprise around 110 species of perennial plants with long, slender stems, resembling grasses or particularly rushes. Some grow wild in France, typically in wetlands, along watercourses, on banks or in marshes. They play an ecological role by helping to maintain and stabilise banks, thus combating erosion, and providing a refugium for fish and amphibians. They are little known and only a few of them are cultivated in gardens.

Bulrushes are fairly hardy plants, most of them can withstand temperatures down to -20°C, except for Scirpus cernuus, which cannot tolerate temperatures below -8°C. Therefore, except in the very mild climates of the Mediterranean basin or the Atlantic coast, it is best to protect it in winter.

Bulrushes belong to the Cyperaceae family, which includes around 5,000 species. This is the family of papyrus (Cyperus papyrus), sedges and cotton grasses (Eriophorum). Scirpus species are very close to the genus Schoenoplectus, with which some bulrushes may have changed names. Thus the species Schoenoplectus lacustris and Schoenoplectus tarbernaemontani are synonymous with Scirpus lacustris and Scirpus tabernaemontani.

Scirpus sylvaticus: Botanical illustration

Scirpus cernuus is commonly nicknamed Drooping Club-rush, because its foliage gracefully trails towards the ground. This is also the translation of its species name, from the Latin cernua: “drooping”, “nodding”. In English it is nicknamed Fiber optic grass, due to its numerous thread-like stems, topped with small silvery inflorescences, which remarkably resemble fibre-optic strands. Scirpus lacustris, on the other hand, is nicknamed Common Club-rush or Grey Club-rush, because its long stems were used for chair caning and barrel making. Moreover, it is true that bulrushes closely resemble rushes, which like them bear long stems and also appreciate moist environments. However, they do not belong to the same botanical family.

Bulrushes form dense clumps of long, slender stems, particularly graphic. Some species such as Scirpus lacustris and Scirpus tabernaemontani, are rhizomatous and spread over time, potentially forming large colonies. The height of bulrushes is highly variable: Scirpus cernuus does not exceed 30 cm in height and has trailing stems, while Scirpus lacustris and Scirpus tabernaemontani form stiff stems reaching up to 1.50 m, even 2 m in height. You can therefore rely on the latter to add verticality to pond edges.

Bulrushes generally flower in summer, between June and August, bearing brown spikelets at the ends of their stems, except for Scirpus cernuus, which flowers practically all year round and bears tiny cream-white spikelets.

The inflorescences, terminal or axillary, comprise countless spikelets (between 50 and 500!) measuring less than 4 mm in diameter, and are themselves made up of tiny flowers. The perianth – petals and sepals – is reduced to small bristles (3 to 6 per flower). The flowers are bisexual: each has 1 to 3 stamens (male reproductive parts, releasing pollen) and a style (female reproductive part, receiving pollen). Pollination is carried out by the wind: it transports pollen to the style of another flower (anemogamous pollination). This explains why bulrush flowers are neither fragrant nor colourful, as these attributes aim to attract insects to ensure pollination. You will therefore never see insects foraging on bulrush flowers.

The spikelets of bulrushes, more or less branched depending on the species. From left to right, Scirpus cernuus, Scirpus lacustris, Scirpus tabernaemontani and Scirpus sylvaticus (photos: Krzysztof Ziarnek / AnRo0002 / R. A. Nonenmacher / Robert Flogaus-Faust)

Scirpus cernuus, S. lacustris and S. tabernaemontani have very short leaves, almost non-existent, reduced to foliar sheaths. It is only their stems that are visible and decorative. However, some bulrushes have true leaves: this is the case, for example, of Wood Club-rush (Scirpus sylvaticus), which bears long, slender leaves, like those of grasses.

Scirpus tabernaemontani ‘Zebrinus’ stands out with its variegated stems, green striped with yellow, giving it a very original style. As for Scirpus lacustris ‘Albescens’, it has very pale stems, cream-white – yellow. These varieties are ideal for bringing light into a water garden!

The fruits of bulrushes are tiny trigonous or convex achenes, brown in colour, measuring 0.5 to 2 mm. Each achene contains a seed.

The foliage of Scirpus sylvaticus and the decorative stems of Scirpus cernuus, Scirpus tabernaemontani ‘Zebrinus’ and Scirpus lacustris ‘Albescens’ (photos: Roland.aprent / Jerzy Opioła / Krzysztof Ziarnek / David J. Stang)

The main varieties of Scirpus

The Most Popular Varieties

Scirpus cernuus - Fibre Optic Grass

The leaning bulrush, also called nodding flatsedge, is a semi-aquatic perennial that grows on banks or slightly submerged. It forms small dense clumps, made up of stiff thread-like stems in acid green, very graphic.

• Flowering time March to December
• Height at maturity 30 cm

See the product sheet

Schoenoplectus lacustris subsp. tabernaemontani Albescens

Also called Scirpus lacustris ‘Albescens’ (synonym) or Common club-rush, this variety bears stiff stems, green with vertical striate cream-white markings, making it particularly luminous.

• Flowering time July to October
• Height at maturity 1,20 m

See the product sheet

Schoenoplectus lacustris subsp tabernaemontani Zebrinus

This Bulrush forms upright, very vertical stems, which have the particularity of being dark bluish-green, striped with cream-white. Very original, it immediately catches the eye! It is perfect in a modern, graphic water garden.

• Flowering time July to September
• Height at maturity 1,20 m

See the product sheet

Planting

Where to plant?

Scirpus species thrive in full sun, as long as the soil remains moist, but will also tolerate partial shade. If possible, position them in a sheltered spot as wind can break the stems of taller species like Scirpus lacustris.

These are ideal plants for aquatic gardens and for naturalising ponds. Scirpus lacustris and Scirpus tabernaemontani must be submerged, with their roots in water: plant them at a depth of 20 to 30 cm. Scirpus cernuus, however, can be planted under a few centimetres of water, partially submerged, but will also do well in simply moist soil, so can be planted outside the water, on the banks. It has the advantage of also adapting to container planting and can be grown indoors, for example in a conservatory or well-lit room. As its stems cascade downwards, growing it in a hanging basket really showcases its beauty.

Scirpus species are water-purifying plants, helping to oxygenate and clean the water. You can combine them with other plants used in phytoremediation, such as reeds, yellow flag irises (Iris pseudacorus), water mint, Acorus calamus, broadleaf cattail (Typha latifolia)…

Discover our advice sheet “8 oxygenating aquatic plants for ponds or pools”

When to plant?

Plant Scirpus species in spring, around April, or in autumn, during September-October. For Scirpus cernuus, spring planting is preferable so it can establish during mild temperatures, as it is less hardy than other species. In all cases, avoid periods of frost or extreme heat.

How to plant?

In a pond:

When purchasing Scirpus plants, plant them promptly or store them in a water-filled container meanwhile to prevent the root ball from drying out.

1. Before placing in the pond, we recommend planting the Scirpus in a perforated plastic basket, designed for aquatic plants, to facilitate establishment and control spread.
2. Line the bottom and sides of the basket with hessian (if available, otherwise use fabric): this retains the substrate while allowing water through.
3. Add compost to the basket. Ideally use specialist aquatic compost, or create your own mix with clay soil supplemented with some compost and coarse sand.
4. Remove the Scirpus from its pot and plant it in the centre of the basket.
5. Fill around with more compost, then firm down.
6. Cover the surface with a layer of gravel or pumice.
7. Water or partially submerge the basket, ensuring the compost is thoroughly moist before full submersion, otherwise fine particles may float to the surface.
8. Simply position the basket in the pond. Scirpus lacustris and Scirpus tabernaemontani should be submerged under 20-30 cm of water, while Scirpus cernuus thrives under just a few centimetres of water or on banks, provided the soil stays moist.

In containers:

Scirpus cernuus is best suited to container planting.

1. Soak the root ball in a water-filled container to rehydrate it.
2. Take a pot and add compost.
3. Position the Scirpus in the pot’s centre.
4. Fill around with more compost, then lightly firm.
5. Place a saucer beneath the pot, ensuring the compost remains constantly moist.
6. You can place Scirpus cernuus outdoors – it creates a stunning effect in hanging baskets on sunny terraces or balconies – but also adapts well indoors, for example in conservatories or bright rooms.

Scirpus lacustris (photo Frank Vincentz)

Maintenance

Whether planted in a pond or on the banks, Bulrushes require almost no maintenance. Both Scirpus lacustris and tabernaemontani are very hardy and do not need winter protection. We simply recommend cutting back the stems to about 10 cm in late winter or early spring. This will stimulate growth and allow the plant to renew its stems.

If you grow Scirpus cernuus in a pot, ensure the compost remains consistently moist. Always keep water in the saucer and add a piece of charcoal to prevent mould development. In spring and summer, you can apply a little fertiliser. If you notice the stems drying out, this means the compost is too dry or the temperature is too high (especially if grown indoors). In winter, if possible, place it in a cool but frost-free room, away from radiators and heat sources.

Propagation

Although it is possible to sow bulrushes, this method is rarely used and we recommend division instead, a much easier and quicker technique.

Dividing clumps

If you have a bulrush that has been established for several years and has had time to grow and spread a little, don’t hesitate to divide it to obtain several young plants, either to give away or to plant in a new location. This will help rejuvenate the clumps and give them more space. Carry out this task in spring, around April.

1. Remove the bulrush from its pot or dig it up carefully;
2. Divide the clump into several sections, loosening the rootstock and cutting it with secateurs. Each rootstock section should have a few roots and young stems;
3. Take the opportunity to remove any dead or damaged stems;
4. Replant immediately on the banks or in the pond.

Association

Bulrush is perfect for creating a very natural scene on the edges of a pond, pairing it for example with common reeds (Phragmites australis) and bulrushes (Typha latifolia). Their tall, lush vegetation will complement the bulrushes beautifully. Add brightness with the striking variegated foliage of the reed Phragmites australis ‘Variegatus’ and enjoy the opulent, finely divided fronds of ferns like Matteuccia struthiopteris or Osmunda species. For flowering plants, consider planting purple loosestrife, brook thistle (Cirsium rivulare) and meadowsweet along the banks. The slender foliage and mauve flower spikes of Thalia dealbata add elegance to any aquatic setting! In the pond itself, plant water lilies (Nymphaea sp.), whose graceful flowers will be the centrepiece of your aquatic display!

For more information and ideas, explore our advice sheets “Choosing aquatic plants for a pond or water feature” and “10 aquatic plants, submerged or floating”

Combine Bulrush with other aquatic or marginal plants. Cirsium rivulare ‘Atropurpureum’, Nymphaea, Butomus umbellatus, Scirpus tabernaemontani, Pontederia cordata and Thalia dealbata (photo Lip Kee)

You can also create a modern, graphic aquatic display with bulrush. For this purpose, we particularly recommend Scirpus tabernaemontani ‘Zebrinus’, with its green stems striped with cream. Pair it with the variegated foliage of Phalaris arundinacea ‘Picta’, the curiously spiralled stems of Juncus effusus ‘Spiralis’, and the tall, vertical stems of horsetails, Equisetum for striking textural contrast! You might also include some flowering plants like the architectural umbels of Butomus umbellatus and the delicate white plumes of Eriophorum angustifolium.