National Plant Collection of Albizia

About the collection

The collection contains eight Albizia julibrissin species and cultivars, which can be found in several areas of RHS Garden Wisley, including the Old Laboratory borders, Trials Garden, the Exotic Garden and Battleston Hill. The collection is curated by RHS Horticulturist Liam Anderson.

Albizia are members of the pea family and are native

A native plant is one that originated or arrived naturally in a particular place without human involvement. In the British Isles, native plants are those that were here during the last ice age or have arrived unaided since.

to south-west and eastern Asia. They are commonly known as Persian silk trees and are valued for their late-summer flowers, varied growth habits and range of foliage colours.

When to visit

The best time to see the collection is from July to August, when the trees are in flower and at their most spectacular.

Albizia julibrissin f. rosea

History and interesting facts

The genus Albizia was named after the Italian nobleman Filippo degli Albizzi, who introduced the tree to Europe in the mid-18th century. The common name, Persian silk tree, refers to the silky appearance of the flowers, created by masses of showy stamens.

In the United States, Albizia can self-seed freely and is considered invasive

Invasive plants are those that grow vigorously, spread rapidly and can out-compete other plants. Native, non-native and cultivated plants can all be invasive.

in some areas.

Why grow Albizia?

Albizia are attractive small trees that offer several ornamental qualities:

• Late-summer flowers with a distinctive silk-like appearance
• Delicate, feathery foliage
• A range of habits, including weeping and spreading forms
• Varied leaf colours, including purple-leaved cultivars
• Suitable for smaller gardens as they do not grow excessively large

Collection highlights

Some I'd particularly recommend are the purple-leaved cultivars Albizia julibrissin Chocolate Fountain (’Ncaj1’) and A. julibrissin 'Summer Chocolate , the latter being a weeping form. Although not considered rare, these cultivars are excellent choices for smaller gardens and deserve to be grown more widely. They provide a low, wide, spreading habit, which brings a distinctive character to a garden.

Albizia julibrissin

Growing and propagation

Albizia need a warm, sheltered position and perform best in the south-east of Britain, where they receive enough warmth to flower well. They can be propagated by cuttings

A method of growing new plants from parts of an existing plant, such as sections of root, stem, leaf or bud. When prepared correctly and planted in the right conditions, they can produce roots and eventually become independent plants. There is a wide range of different methods for taking cuttings, depending on the plant and time of year.

or grafting

This involves joining the roots of one plant to the stem of another related plant, so they fuse together to form one plant. There are various methods, all requiring great skill. Grafting is mainly carried out by commercial growers to combine one plant’s qualities of flowering or fruiting (the upper section or scion) with the vigour or resilience of the other (the roots or rootstock). Fruit trees are often grafted, along with a few ornamental shrubs and trees, and in recent years grafted vegetable plants (mainly tomatoes, but also chillies, cucumbers, aubergines, etc) have become available.

.

Climate resilience

The collection has responded positively to recent warmer, drier summers, showing good resilience as  trees that enjoy hot, dry conditions.

Looking ahead

One cultivar

Gardeners often use the word variety when referring to a specific plant, but the correct botanical term is 'cultivar'. Whichever word you use, it means a distinctive plant or plants, given a specific cultivar name and usually bred to enhance certain characteristics, such as flower or fruit size, colour, flavour or fragrance, plant size, hardiness, disease resistance, etc. Additionally, it is worth knowing that, botanically, variety has another meaning - it refers to a naturally-occurring distinct plant that only has slight differences in its looks. For example, Malva alcea var. fastigiata differs from typical plants by having an upright habit.

currently missing from the collection is Albizia julibrissin Tropical Dream (‘Pos1’) which we hope to acquire in the future.

This collection demonstrates the diversity and garden value of Albizia, showcasing forms that range from graceful weeping trees to striking purple-leaved cultivars, all united by their distinctive summer flowers and elegant foliage.

Plants in the collection at RHS Wisley

Award of Garden Merit

Albizia julibrissin 'Summer Chocolate'

Award of Garden Merit

Albizia julibrissin f. rosea

Albizia julibrissin [Ombrella] ('Boubri')

Albizia julibrissin

Albizia julibrissin 'Rouge Selection'

Albizia julibrissin [Chocolate Fountain] ('Ncaj1')

Albizia julibrissin 'Evy's Pride'

Albizia julibrissin 'Shidare'