Bladder Senna - Colutea: planting, pruning and care

Botany and description

Colutea, also known as bladder senna or bladder pod, is a genus of plants belonging to the Fabaceae family. Its name comes from the ancient Greek “kolutea”, which evokes the idea of hollow wood, in reference to its fruits: small inflated and translucent pods that, when dried, resemble little bladders. This genus includes around 25 species, among which Colutea arborescens, or common bladder senna, is the most widespread for its hardiness and characteristic fruits. Colutea orientalis is also appreciated, particularly for its colourful flowering and more compact form.

Colutea arborescens: botanical plate circa 1790

These bushes are particularly well-suited to dry and sunny environments. They are naturally found in Mediterranean regions, from southern Europe to the Middle East and Central Asia. They thrive in calcareous, poor and well-drained soils, and are drought-resistant, making them perfect candidates for dry gardens.

Did you know? The name “bladder senna” comes from the old French verb baguenauder, meaning “to amuse oneself with trifles” or “to stroll aimlessly”. This term was given to Colutea because of its fruits shaped like little inflated bladders, light and fun to pop between fingers, like a child’s game. Indeed, the light and translucent pods, which almost float in the air, are seen as a symbol of lightness, evoking simplicity and carefreeness.

Bladder senna is a bush distinguished by its airy, bushy appearance, reaching between 2 and 3 metres in height. Its habit is naturally spreading, with flexible, arching branches giving it an elegant yet slightly untidy silhouette. This shape makes it a beautiful bush for natural gardens or those with a Mediterranean style.

Its root system is taprooted and powerful. The plant can thus anchor well in poor and stony soils, as well as withstand periods of drought. It is a hardy plant, capable of drawing water from deep underground, making it a good candidate for dry gardens and arid terrain.

The foliage of Colutea is deciduous, composed of pinnate leaves of a lovely soft green. Each leaf consists of small oval and rounded leaflets, slightly velvety to the touch. This light foliage creates an impression of softness and complements its flexible habit well.

The inflorescence of Colutea consists of clusters of papilionaceous flowers, typical of the Fabaceae family. The flowers are generally yellow, sometimes tinged with orange or red depending on the variety. They appear throughout summer and attract pollinating insects, such as bees and butterflies, thus contributing to local biodiversity.

Graceful flowering and light foliage, and very original coppery fruits

Finally, fruiting is one of the most striking characteristics of Colutea. After flowering, the bush produces inflated pods, shaped like small translucent and hollow bladders, which take on a reddish hue as they ripen. These air-filled fruits are light and often popped by children. They remain on the plant in autumn, adding a decorative touch even after the leaves have fallen. These bladder-shaped pods, which ripen in late summer, also provide temporary shelter for certain insects, creating little natural “hiding places” where they can take refuge from bad weather or predators.

The bushy growth and flexible habit of bladder senna make it perfect for creating informal hedges, where it can integrate without the need for strict pruning. It also finds its place in naturalistic borders, where its light foliage and yellow summer flowers brighten plantings. Bladder senna integrates particularly well into dry garden borders, alongside other drought-resistant plants. In borders, it acts as a beautiful, resilient and elegant green screen, harmonising with Mediterranean or wild styles thanks to its hardiness and ease of maintenance.

The most beautiful varieties

Colutea arborescens

Colutea arborescens originates from Southern Europe and North Africa. This hardy bush thrives even in poor, stony soil. While not spectacular, the Bladder Senna offers unique, decorative fruiting throughout summer.

• Flowering time June to August
• Height at maturity 2 m

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Colutea media Copper Beauty

Colutea (x) media Copper Beauty is a hybrid variety of Bladder Senna featuring striking coppery-orange flowering, more decorative than its southern countryside counterpart known as the bladder tree.

• Flowering time June to October
• Height at maturity 1,75 m

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Planting the Bladder Senna

Where to plant?

To plant a bladder senna bush, choose a sunny spot with well-drained soil, preferably chalky or stony, as it cannot tolerate waterlogged conditions. This bush is ideal for dry or rocky gardens, and once established, it tolerates poor soils and drought conditions.

The Colutea struggles in heavy, poorly drained soils that retain water and increase the risk of root rot, a common issue for plants adapted to dry mediums. If your soil is clay-based, it’s advisable to improve drainage before planting by adding compost, gravel at planting time, and/or planting on a mound.

Colutea arborescens planted here as a wild hedge (©De Tuin-Flickr)

When to plant?

The ideal time to plant is in autumn, between October and November, as this gives the roots time to establish before spring. In regions with harsh winters, you can also plant in early spring, but be sure to water regularly during the first few weeks to help the roots settle.

How to plant?

• Dig a hole: make it about twice as wide as the young plant’s root ball.
• Gently place the root ball in the hole, positioning it so the plant stands upright.
• Fill the space around the root ball with the original soil, lightly firming it as you go to secure the plant and avoid air pockets.
• Water generously right after planting to encourage rooting, even if the soil is dry or well-drained. This initial watering helps the plant get off to a good start.
• Once established, the bladder senna requires little maintenance. Light pruning each year, ideally in late winter, will encourage a more balanced habit and stimulate beautiful flowering the following spring.

Maintenance, pruning and watering

Pruning

• When to prune?: Pruning is ideally carried out at the end of winter, before the start of new growth, usually in February or March.
• How to prune?: Carry out light pruning to maintain a balanced habit and encourage flowering. Remove dead, damaged or overly old branches, and shorten shoots that disrupt the shape of the bush. If necessary, you can also cut back more severely every 2-3 years to rejuvenate the bush, cutting back to 20-30 cm from the soil; it will regrow vigorously.

Watering

During the first year after planting, water regularly to help the roots establish, especially during prolonged dry spells. However, once well-rooted, the Colutea tolerates drought very well and hardly needs watering, except during prolonged extreme heat.

You can add a mineral or organic mulch around the base to limit weed growth and retain some moisture, especially in the first year.

Fertilisation

In principle, no fertiliser is required. The Colutea thrives in poor soils, and too many nutrients may stimulate leaf growth at the expense of flowers.

Colutea arborescens

Diseases and Pests

The Colutea is a particularly hardy and resilient plant, and it is rarely affected by diseases or pests.

However, in inadequate growing conditions, such as poorly drained soil or excess moisture, it can be vulnerable to root rot, a fungal disease that affects the root system.

In exceptional situations, it may also attract aphids, but these rarely cause significant damage and can be easily controlled.

How to propagate the bladder senna?

Sowing

• Harvest the seeds from the pods at the end of summer or in autumn, once they are fully ripe. Shake the pods; if the seeds rattle inside, they’re ready.
• Let them dry for a few days, then store them in a dry place if you plan to sow them in spring.
• Sow the seeds in pots or directly in the ground in spring, after the last frosts. For pots, use a mix of compost and sand for good drainage.
• Water lightly and keep the pots in a sunny spot. Germination takes around 2 to 4 weeks.

Propagation by cuttings

• Take semi-hardwood cuttings in summer, around July-August.
• Cut sections of 10 to 15 cm and remove the leaves from the base.
• Plant the cuttings in a mix of compost and sand, keeping the substrate slightly moist.
• Place them in a bright spot, sheltered from draughts. Roots should form within a few weeks.

And layering? Layering of the bladder senna, though less common, is possible. In late spring, select a low, flexible shoot, bury a portion of its length in the soil, and secure it with a stone or clip. Keep the soil moist to encourage root formation. Once roots appear, separate the new shoot from the parent plant and replant it in the desired location.

Successful pairings

To create a harmonious flowerbed around the Colutea arborescens, the common bladder senna, choose plants that enjoy sunny spots and well-drained soil, while providing a contrast in textures and colours. The Lavandula angustifolia ‘Munstead’, with its grey-green foliage and blue-violet flower spikes in summer, pairs beautifully with the yellow-orange flowers of the bladder senna, creating a soothing Mediterranean atmosphere. At the base of the Colutea, the compact, silvery Santolina ‘Edward Bowles’ adds structure while harmonising with its creamy-white summer flowering.

The Cistus obtusifolius, with its white flowers and yellow centres, brings a lightness that echoes the Colutea, while its evergreen foliage maintains visual interest in winter. Rosemary, with its dark green foliage dotted with tiny blue flowers, not only adds an aromatic dimension to the planting but also forms a striking contrast with the Colutea. Alternatively, Afghan sage, such as Perovskia ‘Blue Steel’, with its violet-blue flowers and fine foliage, creates visual depth that enhances the bladder senna’s bright yellow.

Finally, Thymus praecox ‘Coccineus’, used as ground cover or edging, forms a lush, evergreen and fragrant carpet that perfectly complements the Colutea’s soft, airy habit. Together, these plants create a natural, colourful ensemble, perfectly suited to dry conditions, resulting in a vibrant yet low-maintenance garden in well-drained soil and full sun.

Colutea arborescens, Lavender ‘Munstead’, Cistus obtusifolius, Santolina ‘Edward Bowles’, Rosemary, Perovskia ‘Blue Steel’ and Creeping Thyme ‘Coccineus’