Caragana arborescens, Yellow Acacia: Planting, Growing, Care

Botany

The Caragana arborescens, commonly known as Siberian pea shrub, Yellow acacia or Siberian pea tree, is a species belonging to the Fabaceae family like the Black locust and Alfalfa. This bush is native to the cold and arid regions of Siberia and Mongolia, where it is traditionally used to form protective hedges around orchards. This function is explained by its ability to withstand strong winds and harsh environmental conditions, particularly severe winters, with an impressive tolerance to temperatures well below -20°C.

Its geographical range now extends far beyond its original areas. Thanks to its robustness and great adaptability, Caragana arborescens has spread to Europe, North America and other regions with extreme climates. The type species Caragana arborescens has given rise to interesting varieties, including the Caragana arborescens ‘Pendula’, a grafted standard variety characterised by its weeping habit, and the Caragana arborescens ‘Walker’, another weeping variety distinguished by its very fine foliage.

The Siberian pea shrub is a deciduous, thorny bush, often wider than tall, which can form a small tree with low branching composed of multiple stems. Typically wider than tall, it reaches an average of 4.5 to 5m in all directions with rapid growth. It adopts a supple, rounded habit, supported by fine, slightly trailing branches. Some varieties display a weeping habit, giving the tree an elegant and graceful appearance with branches trailing down to the ground.

Depending on the variety, Caragana has an upright or weeping habit. On the left, Caragana arborescens (type species) and on the right, the ‘Pendula’ variety (photo: Wilrooij)

Its deciduous foliage, very dense, of a fresh light green, sometimes lemon yellow, recalls, depending on the variety, that of alfalfa or ferns. The leaves are compound with 5 to 7 pairs of small oval and slightly villous leaflets, about 2 cm long. Each leaf is equipped with small thorns at the base. In autumn, the foliage turns a golden yellow hue, offering a beautiful glow before falling as winter approaches.

Flowering occurs in spring, between April and May. It is rather discreet but charming, with small clusters of pea-shaped flowers, typical of Fabaceae, of a bright light yellow, which bloom on the previous year’s shoots. Although modest, this flowering is melliferous, attracting bees and other pollinators. The flowers are solitary or grouped in short clusters, they evoke those of acacias, hence the popular name “Yellow acacia”.

After flowering, the tree produces fruits in the form of flat pods measuring about 5 cm long, each containing 4 to 6 seeds. The pods, as well as the seeds, are edible and can be used in cooking.

The flowering and foliage of Caragana arborescens

Main species and varieties

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[product sku=”219981″ blog_description=”A variety grafted onto a stem, with weeping habit, magnificent as a standalone specimen, at the centre of a small bed, or in a container on the terrace.” template=”listing1″ /]

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Planting Caragana arborescens

Where to plant the Yellow Acacia?

The Siberian Pea Bush is one of the most hardy and undemanding plants in existence. Hardy well beyond -20°C (down to -29°C), it acclimatises to all our regions. It can adapt to a wide variety of soils, whether slightly acidic, very chalky or poor. However, it does not appreciate waterlogged soils, preferring well-drained ground. Avoid therefore heavy, clay soils that retain too much moisture. Its deep root system allows it to survive in drought conditions once established. This robustness makes it a preferred choice for regions with harsh climates or for low-maintenance gardens. It prefers spots in full sun or very lightly shaded. Good exposure to sunlight will encourage more abundant flowering.

The Siberian Pea Bush suits both small and large gardens equally well. It naturally finds its place in a flowering hedge, loose or defensive in the garden’s deprived areas, or as a standalone specimen for cultivars with an attractively pendulous silhouette.

When to plant it?

The best time to plant Caragana arborescens is in autumn, in regions with hot, dry summers, or in early spring, in cool to cold regions. This gives it time to establish roots before summer heat or winter frosts.

How to plant a Siberian Pea Bush?

As it prefers poor or stony soils, overly fertile soil, as is often the case with fabaceae, would encourage leaf growth at the expense of flowering. Due to its deep root system, avoid moving it once planted. The smaller varieties are ideal for container growing, particularly in urban gardens or on terraces. However, in a container, it will need more regular watering from spring until early autumn.

• Dig a planting hole 2 to 3 times wider than the root ball and as deep as the root ball (around 40 to 60 cm). This will allow the roots to spread.
• Hydrate the root ball by soaking it in water for 10 to 15 minutes.
• Position the bush in the centre of the hole, ensuring the collar is level with the soil.
• Plant in a mixture of garden soil, coarse sand or gravel, and leaf mould.
• Backfill, lightly firming the soil to avoid air pockets.
• Water generously after planting.
• Spread a layer of mulch around the base of the bush to retain moisture and suppress weeds, avoiding direct contact with the trunk.

Maintenance and Pruning of Caragana

The Caragana arborescens is a very hardy bush requiring minimal care once well established. Maintain regular watering during the first two summers after planting to encourage good root development. Subsequently, the Siberian Peashrub will only need watering during prolonged dry spells. Its deep root system allows it to withstand drought once properly settled. It adapts well to poor soils, so regular fertilisation isn’t necessary. A light application of compost in early spring may nevertheless stimulate growth and flowering, though this remains facultative. Renew the mulch annually in spring to retain soil moisture and suppress weeds, particularly if your region experiences dry summers.

The Siberian Peashrub is highly resistant to diseases and pests. However, watch for signs of root rot if the soil is waterlogged.

Pruning isn’t essential. In spring after flowering, simply remove dead, damaged or diseased branches to keep the bush healthy. For pendulous varieties, eliminate any shoots touching the ground or crossing over to maintain an elegant shape and an airy habit.

How to propagate Caragana?

Sowing is the most common technique, but propagation by cuttings is ideal for propagating specific varieties such as pendulous forms. You will need to wait between 3 and 5 years to see the young plants flower.

Sowing

Sowing is the most common method for propagating the Siberian Pea Tree. It does not necessarily produce specimens identical to the parent plant. The tree’s pods contain seeds that can be harvested in late summer or autumn. Wait until the pods turn brown and begin to open before harvesting them. To increase the germination rate of the seeds, it is recommended to scarify them (lightly scratch their coating with sandpaper) and soak them in warm water for 24 hours before sowing.

• Sow the seeds in a mixture of light compost and sand, pressing them about 1 cm deep.
• Place the pots or sowing trays in a sunny spot.
• Keep the substrate slightly moist until germination, which occurs in about 2 to 3 weeks.
• When the young plants have 4 to 6 leaves, you can transplant them into the ground the following spring.

Propagation by cuttings

Propagation by cuttings is another simple method for propagating the Caragana, particularly for pendulous varieties. It is usually carried out in late summer (August-September) on semi-hardwood, i.e., stems that have begun to turn into hard wood.

• Choose vigorous stems about 15 cm long. Cut just below a node (the point where the leaf is attached to the stem) and remove the leaves from the lower half.
• Plant the cuttings in a mixture of sand and compost in equal parts. Insert them one-third of their length into the substrate.
• Place the cuttings in a bright spot, but out of direct sunlight.
• Maintain regular moisture (without excess). Root formation takes about 6 to 8 weeks.
• Rooted cuttings can be transplanted into the ground the following spring.

How to pair Caragana?

The Siberian Pea Bush is suitable for both small and large gardens. Versatile, it naturally finds its place in a flowering hedge or defensive hedge, in an English-style border, or as a standalone specimen in a container on the terrace, depending on the variety. Its robustness and delicate leaf make it an excellent companion for other undemanding and resilient bushes, perfect for bringing life and light to the most challenging corners of the garden.

It integrates perfectly into hedges alongside equally hardy bushes such as the Cotinus, whose purple or golden leaf creates a lovely contrast with the flowering of the Caragana, or shrubby honeysuckles (Lonicera tatarica and Lonicera fragrantissima). It also pairs well with other, less vigorous Fabaceae like the Coronilla glauca. The Caragana arborescens is also excellent for creating defensive hedges. For a striking contrast, plant it next to bushes with purple leaf such as the Berberis thunbergii ‘Atropurpurea’. The Vitex, Sophora davidii, Buddleias, Phillyrea angustifolia, and Rhamnus alaternus ‘Argenteovariegata’ are other undemanding bushes that adapt well to dry, poor soil, making excellent companions.

To highlight the Caragana, don’t hesitate to play with contrasts by pairing it with purple foliage. Caragana arborescens, Cotinus coggygria ‘Grace’, Coronilla valentina ‘Glauca’ and Berberis thunbergii ‘Atropurpurea’

The Caragana can also be planted within borders alongside small, undemanding bushes suited to drought conditions and full sun. For example, at its base, you can plant rockroses, lavenders, perovskia, and shrubby sages, which flower all summer. In a yellow and blue border, it will look stunning alongside blue rosemary, creeping ceanothus, or grape hyacinths. In small spaces or containers, it pairs well with variegated ground covers like Vinca major ‘Variegata’, ivies, or small blue-flowering sages.

Did you know?

The pods, seeds and flowers of Caragana arborescens are edible. Young pods can be harvested before ripeness, then cooked and eaten like green beans. They are tender with a slight vegetable flavour. The seeds, once ripe, can be used like peas or lentils. Rich in protein, they can be boiled or roasted. As for the flowers, they can be eaten raw. Their sweet, slightly sugary taste enhances salads. However, it’s important to note that this consumption remains marginal and it’s advisable to taste in small quantities to check individual tolerance.