The Soap Nut Tree (Sapindus mukorossi) and How to Grow One
Soap nuts grow on Sapindus mukorossi, a deciduous tree from northern India and the Himalayan foothills. It starts producing soap nuts after about 9 to 10 years, and you can grow one from seed if you are patient.
Please note: we can no longer source or supply soap nut seeds or plants. Occasionally you might find a left over seed in one of the soapnut shells.
Soap nut tree facts
- Botanical name: Sapindus mukorossi, in the soapberry family (Sapindaceae)
- Deciduous, with leaves up to 40cm long
- Grows 12 to 20 metres tall over about 70 years, with a trunk girth of 3 to 5 metres. Smaller in cooler climates.
- Produces soap nut berries after 9 to 10 years
- Small flowers become yellow, leathery-skinned fruit that darken as they ripen and dry
- Prefers tropical and subtropical climates with 150 to 200cm of rain a year
- Likes deep clay loam soil and a sunny spot
It is a handsome tree, found through most of India and also grown in China, Hawaii and Florida. It looks a little like a large mimosa. The berries are golden when harvested and dry to a dark reddish brown. Only the shells are used for washing. The seeds contain no saponin.
The tree flowers in summer and the berries are collected over the winter months. Once harvested, the ripe berries are sun-dried, cracked and deseeded. The shells are used for washing and the seeds can be replanted.
Sapindus mukorossi, saponaria and other soapberry species
Several Sapindus species produce saponin-rich berries. Sapindus mukorossi grows in northern India and Nepal, and is the species our soap nuts come from. Its fruit and seeds are slightly bigger than those of Sapindus trifoliatus, the soapberry of southern India. Sapindus saponaria, the wingleaf soapberry, is native to the Americas.
How to grow a soap nut tree from seed
Plant seeds as soon as you get them, ideally in spring or early summer. Do not store them.
- Weaken the seed coat. Rub the seed with a nail file or sandpaper. If the coat is too tough, tap it gently with a hammer, taking care not to crush the seed.
- Soak for 24 hours. Pour hot water into a vacuum flask (not boiling, let it sit for 5 minutes first), add the seeds and leave them for 24 hours. The flask keeps the water warm, and the soak is what starts germination.
- Plant. Use good quality potting or seed-raising mix, not garden soil. Plant the seeds 2.5cm deep in a deep pot, because soap nut trees grow a long tap root. Keep the pot out of direct sun but where it can catch some rain.
- Water carefully. Water when the mix starts to dry out, but not while it is still moist, as that encourages fungus. Don't fertilise before germination, because high nitrogen can stop seeds germinating.
- Wait. Germination takes 1 to 3 months in summer, longer in cooler months. Keep the mix warm and give it plenty of light.
Over time the seed swells to almost twice its size and grows a white powdery coating. That is a good sign: the seedling is about to come up.
Caring for your seedling
Once the seedling emerges, repot it into a large container or planter bag to protect its long main root. It is a subtropical to tropical plant that loves rain, so keep it in a sunny spot and water it regularly.
Can't wait 10 years for your own harvest? Learn more about soap nuts or shop our soap nuts.