Albizia, or silk tree, stands out by its slightly weeping habit and airy appearance. This small deciduous tree is very decorative thanks to its fine, dissected, delicate foliage reminiscent of mimosa, and to its summer flowering in silky tufts with pink stamens. Although hardy down to −15 °C, it grows best in warm climates with long, sunny summers. Modest in size, Albizia can be grown directly in ground in regions with mild winters, but also in a pot or large container in colder areas so it can be moved indoors or protected over winter. It particularly favours a full sun exposure, well-drained soil and a situation sheltered from cold winds. Sowing Albizia makes it possible to produce a large number of young plants, to choose from several varieties and to obtain specimens perfectly suited to local conditions. Here is how to succeed with your Albizia sowing and quickly enjoy this remarkable ornamental tree.
For everything about Albizia, discover our complete guide: "Albizia: planting, pruning and maintenance".
Why sow Albizia?
Sowing Albizia julibrissin (this is the most common species) offers many advantages. It is an economical method, allowing production of several young plants at a cost far lower than buying trees from a nursery. It is also an opportunity to discover and cultivate less common varieties, such as 'Summer Chocolate' or 'Ombrella', with distinctive foliage or flowering. Sowing is accessible to most gardeners: it requires only some preparation, notably soaking seeds to break their dormancy, and suitable heat and light conditions. By doing it yourself, you control the entire growth cycle, from germination to final planting, ensuring specimens perfectly acclimatised to your garden.
How to harvest Albizia julibrissin seeds?
If you already have an Albizia in the garden, harvest seeds from the tree; otherwise you can order them. Harvest Albizia seeds at late summer or early autumn, when pods, long and flattened, turn brown and begin to dry on the tree. Choose a dry day to avoid any residual moisture. Cut pods with a clean pruning shear, then open them gently to extract seeds. Spread seeds on absorbent paper in a dry place, away from direct light, for a few days to complete drying. Once thoroughly dry, store them in a paper bag or envelope in a cool, dry place until sowing. In good conditions, Albizia seeds retain their seed viability for two to three years.
When to sow Albizia julibrissin?
Albizia produces seeds in late summer or early autumn. That is when they should be harvested. Although these seeds are fresh and have excellent seed viability, the season is not suitable for direct outdoor sowing: temperatures fall quickly and young plants, sensitive to cold, would not survive winter.
The safest method is therefore to dry and store seeds in a cool, dry, dark place, then sow them in spring outdoors when temperatures stabilise between 20 and 25 °C. Outdoor sowing should only be done after risk of frost has passed, generally between April and May depending on region.
For gardeners with a heated greenhouse or a bright indoor space, it is possible to sow from late winter, in February or March (at 15–16 °C), provided substrate is kept warm and moist.
Where to sow Albizia julibrissin?
Albizia can be grown either outdoors in ground or in a pot, but location choice is essential for good growth. Outdoors, plant in sunniest part of garden, sheltered from cold winds, preferably against a south- or south-west-facing wall that will radiate heat. Soil should be well drained and light, not prone to winter waterlogging.
In regions with harsh winters, pot culture or large container is preferable: place containers on a sunny terrace or balcony, then move into a conservatory or bright shelter as soon as temperatures fall below 0 °C. In a pot, use a mix of potting compost, coarse sand and a few clay pebbles at the bottom to improve drainage.
Whether in ground or in a pot, Albizia needs at least six hours of direct sun per day to ensure vigorous growth and abundant flowering.
How to sow Albizia?
Albizia can be sown either under cover, in buckets or trays for optimal control of germination conditions, or outdoors in ground when spring climate is warm and stable enough.
Sowing under cover
Required equipment
- Pots or buckets
- sowing compost
- Coarse sand
- A mini greenhouse or plastic film
- A watering can with rose
How to sow Albizia under cover?
- Prepare seeds: soak in hot (not boiling) water for at least 24 hours to soften hard seed coat. Most effective method is to pour water at about 70 °C into a thermos, immerse seeds, then close. Leave overnight and sow next day.
- Scarify if necessary: make a slight nick in seed coat with fine knife or gently rub with sandpaper to aid water uptake and speed germination.
- Fill pots or buckets with a light mix of two thirds sowing compost and one third coarse sand to ensure good drainage.
- Sow Albizia seeds: place each seed 2–3 cm deep, cover with same thickness of compost and press down lightly.
- Place pots in a warm spot (at least 18 °C), bright and sheltered from cold winds.
- Cover container with plastic film or place under a mini greenhouse to maintain steady warmth.
- Keep substrate slightly moist until germination (2–4 weeks); water regularly without excess to avoid rot.
- Ventilate occasionally and monitor germination, which generally occurs within 2–4 weeks.
- Transplant: when young plants are large enough to handle, move into individual pots.
Outdoor sowing
Required equipment
How to sow Albizia outdoors?
- Loosen soil to about 20 cm depth, remove stones and unwanted weeds, then level surface.
- Sow prepared seeds (soaked and/or scarified), spacing about 10 cm apart.
- Add 2 cm of fine soil on top and press down lightly.
- Moisten soil immediately after sowing and maintain slight moisture until emergence.
- Expect emergence in 10–20 days, then gradually reduce watering to avoid waterlogging.
After sowing: care and maintenance of young plants
- In first year, in cold regions, keep young plants under cover for winter and only plant out in ground the following spring.
- Young Albizias must be protected from frost: in winter place under cover or cover with horticultural fleece.
- Repotting every two years renews substrate and supports development before final planting in garden.
- Albizia often self-seeds. If young shoots appear at base of an adult tree, lift them carefully keeping as much root as possible, then replant in a pot or at final location.
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