|Official Plant Name||Albizia julibrissin / Acacia dealbata|
|Common Name(s)||Mimosa, Pink Silk Tree, Silver Wattle, Blue Wattle|
|Native Area||Ethiopia, Iran, Japan, China, Australia|
|Toxicity||Some edible uses|
|Foliage||Deciduous / evergreen|
|Flowers||Yellow / pink blooms|
|When To Sow||April, May, June / September, October|
|Flowering Months||March, April / July, August|
|When To Prune||May / October|
4 – 12M
2.5 – 4M
March-April / July-August
Loam or sand
Any / Acidic-Neutral
The name Mimosa is most commonly used to refer to two non-native tree species – Albizia julibrissin and Acacia dealbata, though, confusingly, neither of these is actually classified currently in the Mimosiae genus.
Online and in books, you will frequently hear horror stories about these plants, which can be hugely invasive in some areas.
You may also read, however, about how they can help in sustainable design and ecosystem restoration…
However, the pros and cons of these trees very much depend on where they are grown.
While they certainly can bring serious issues for local ecosystems where they become invasive, this is typically not an issue in UK gardens, where these trees are much harder to grow.
Still, though they can bring certain benefits, there are a number of reasons why they may not be the best choices for many UK gardens (which have nothing to do with their potentially invasive nature).
Read on to learn a little more about the pros and cons of both of these mimosa trees:
The Pros of Albizia julibrissin
Albizia julibrissin, also known as pink silk tree and commonly referred to as mimosa in the US, certainly is an attractive flowering tree.
It is a deciduous tree with rose-pink fluffy flower heads which open in the summer months, and interesting and exotic looking bipinnate leaves.
This plant is native to Ethiopia, Iran to Japan and China, though it has extensively naturalised elsewhere.
One of the main reasons why this can be a very useful plant in many regions is that it is a nitrogen-fixing plant, which can cope with a huge range of different soil and climatic conditions.
This can make it a useful pioneer plant, which can be used to reclaim degraded landscapes and as a key species in forest gardens and agroforestry schemes.
The variety ‘Rosea’ is hardier and more compact than other cultivars, and is the best choice for the UK.
This tree is H4 hardy and can be grown in some UK gardens with sufficient sun, warmth and shelter. However, in the climate of the British Isles, it rarely sets seed.
This means that it is not as problematic as an invasive as it can be in parts of the US, and other areas.
In southern, sheltered gardens, this can be an interesting option to consider. The tree is a suitable size for small gardens so can work well in some sheltered urban plots, and it is ideal for training against a sunny south-facing wall, or for container growing.
One other interesting plus point of this tree is that it is notably resistant to honey fungus. So for gardeners who have had issues with this fungal disease, it could be a good choice.
Aside from its ornamental appeal, Albizia julibrissin also has edible uses. The young leaves can be cooked and used as a pot herb. The flowers can also be cooked and eaten as a vegetable. Dried leaves are sometimes also used as a substitute for tea.
The Cons of Albizia julibrissin
Even ‘Rosea’ really only succeeds in the very mildest parts of the British Isles without protection, or being brought under cover during the winter months.
If you do not have a particularly warm, sunny and sheltered garden then this may not be the easiest plant to grow and lower maintenance alternatives may be a better choice. Remember, this is a non-native plant and native options can often be better for your garden.
Alternating spells of mild and cold weather can damage the top growth, and though these can and do often regrow from the ground when damaged by frost, the damage can be unsightly.
It is also worth noting that though it is notably resistant to honey fungus, it can be affected by other diseases, such as verticillium wilt.
Though the plant will not usually set seed in the UK, it can still spread.
Plants often produce suckers and send up saplings, sometimes quite far from the parent tree. The strong root system can make these difficult to remove.
The strong root system can crack concrete pavers or driveways, damaging the infrastructure in your garden. Though of course, this is not an issue when grown in containers.
Mess below the tree is also a concern to some. Flowers dropping off the tree can be a problem for some very neat and tidy gardeners.
The Pros of Acacia dealbata
Acacia dealbata, also known as mimosa, silver wattle or blue wattle, is also sometimes grown in the UK. It is native to Tasmania and parts of mainland Australia.
This plant is H3 hardy, but where it can be grown, this is another useful nitrogen-fixing plant.
Remember, nitrogen-fixing plants have symbiotic relationships with bacteria in their root nodules which can turn nitrogen from the air into nitrogen in the soil.
Some of the nitrogen is used by the plant itself, but some may also be taken up by other plants in the vicinity.
Like the above, this is a good pioneer plant for some climate zones. It is drought tolerant and may be a good choice for lower rainfall areas. As a nitrogen fixer, it can improve the soil for sustainable planting schemes.
This tree also has an extensive root system, which helps prevent soil erosion. So it can be a useful addition in areas with poor, light soils which can easily be eroded.
Like the above, this mimosa is also a good choice for small spaces. It can also be grown in containers, or trained against sunny, south-facing walls.
The flowers of silver wattle are fragrant, so can be pleasant when located close to windows or seating areas, and the flowers are edible too. They are sometimes turned into fritters, for example.
The Cons of Acacia dealbata
Like silk tree, silver wattle can only be grown without protection in milder parts of the British Isles. So again, it is not the most low-maintenance choice and you may find many of the same benefits with other much lower maintenance trees and plants.
It is also worth noting that while Acacia dealbata can work well in many different conditions, it is not suitable for heavy clay or limey soils.
Remember, as an H3 hardy plant, this tree must usually be moved under cover in winter unless you live in a particularly mild and warm part of the British Isles. They really do need hot, sunny summers to mature and flower successfully.
Mature specimens sucker very freely, just like the Albizia julibrissin, so this too can be a plant that can spread and pose a problem in your garden.
Mess dispersed below this tree may also be annoying for neat and tidy gardeners.
While both of these mimosa trees can bring benefits, neither may be the right choice for most UK gardeners. Here are some alternatives to consider:
Other Flowering Trees To Consider Instead of Mimosa Trees
- Flowering Cherries
- Crab apples
Nitrogen Fixing Trees For UK Gardens
Some good options for growing in the UK include:
- Common Laburnum
- Laburnum x watereri
- Laburnocytisus Adamii
- Caragana arborensis
Trees With Edible Yields
As well as the usual range of fruit trees including apples, pears, plums, cherries and more, you can also consider growing trees with edible leaves, such as:
- Lime/ Linden
Even if mimosa trees are not the right choice for your garden, you should still be able to find other trees which provide many of the same benefits, without the cons mentioned above.
A permaculture garden designer, sustainability consultant and freelance writer, Elizabeth works as an advocate for positive change. She aims to inspire others to reconnect with nature and live in a more eco-friendly way. She also tries to practice what she preaches as she tends her own forest garden, polyculture beds and polytunnel. See her personal website here.