Soapnut Trees

The seeds from this tree may not be edible, but they are certainly a natural way to cut down on your laundry bill!

This discovery started when I was looking for a laundry detergent that wouldn’t hurt my landscape. I have a large diameter vinyl hose attached to the back of my washing machine (in summer) and I use the water to irrigate my fruit and nut trees, lawn, and ornamentals. (This isn’t legal everywhere, and isn’t necessarily a good idea, depending upon your preferred brand of laundry soap.) In my search for living a less polluting (and more cost effective) life, I stumbled upon soapnuts, also known as soapberries. Believe it or not, I was delighted to discover that these tree fruits cleaned my laundry just as well as commercial soap! Not only that, but they have natural fabric softening properties.

I don’t know how or why, but the water that came out of my washing machine when using commercial laundry soap usually contained a significant amount of clothing dye, while the soapberry loads do not. Safer, softer, and more brightly colored clothes without the use of chemical additives. In my book, it’s a total win.

Muslin bag with deseeded soapnut drupes

Mature soapnut tree (I, KENPEI) CC BY-SA 3.0

What are soapnut trees?

Soapnut trees are members of the Lychee family (Sapindus), which includes 5 to 12 different species of trees and shrubs (depending on who you ask) that all produce saponins. These saponins are found in the fruit, or drupes, of the soapnut tree (as well as in soapwort plants and sea cucumbers). Saponins are surfactants, chemicals that reduce the surface tension between molecules, allowing water to lift away grease, soil, and other impurities from your laundry. In fact, people have been using soapnuts as a sudsy cleaning agent for far longer than commercially made soaps and detergents.

The soapnuts used to clean laundry, hair, and skin nowadays are mostly from the S. mukorossi variety. This particular tree also goes by the names Sapindus detergens, Indian soapberry, Chinese soapberry, Reetha, Areetha, Ritha, and Doda, just to name a few. [If you are feeling particularly nerdly today, you can see this plant’s genetic code here.]

How soapnut trees grow 

Soapnut trees prefer temperate to tropical conditions. Some varieties are deciduous, while others are evergreen. The Indian soapberry tree, in particular, is a lovely deciduous tree that can tolerate poor soil. Trees will need the equivalent of 60 to 80 inches of rainfall each year. (San Jose, CA gets an average of 15 inches of rain, so some irrigation will be needed in the Bay Area.)

Ultimately (and under ideal conditions), your soapnut tree can reach a height of 80 feet, with a girth of 15 feet. Most trees, however, end up significantly smaller than that (12 to 16 feet tall). The tree has smooth gray bark and a semi-umbrella shape. Small, greenish-white flowers emerge in summer and fruit appears in July and August. A mature soapnut tree can produce 60 or more pounds of soapberry fruit each year.

How to grow a soap nut tree

To grow your own soapnut tree, you will first have to find a seed. This has become easier in recent years, as more people discover just how effective soapnuts are. You can search online for seeds, or you can give soapnuts a try and hope to find a seed. The drupes (pictured) normally contain up to three seeds. The seeds need to be roughed up a little (scarified) before they can germinate. It is best to plant in spring. You can use a fine-grit sandpaper to score the outer hull, then soak the seeds in warm water for 24 hours. The most common way to keep the water warm is to place the seed and the warm water in a thermos. (My guess is that these prerequisites evolved out of the natural processes of seeds being eaten and then, well, you know.) Start each seed in a large container filled with high quality potting soil, planting them one inch deep. Keep the soil moist down to at least 2 inches, but not waterlogged, and provide plenty of sunlight. It may take a long time for your seeds to germinate. Once they do, they will grow quickly. After 3 or 4 months (or when frost isn’t expected any time soon), you can place your soapnut tree in the ground. Select a site that provides partial shade or dappled sunlight, if possible, and plenty of room to grow.

Using homegrown soapnuts

Once your soapnut tree produces fruit, you will want to collect the drupes in early winter, remove the seeds, and allow the fruit to dry out. A small muslin bag with tie strings can be used to hold 4 or 5 soapnuts and tossed in the laundry. The soapnuts do not have to be removed for the rinse cycle because the normally colder water of rinse cycles does not pull as much of the sudsing saponins as warm or hot wash water. The same bag of soapnuts can be used for up to 10 loads of wash. After that, toss them into the compost pile and reuse the bag!

Other advantages of soapnuts

Besides being disease-resistant plants, soapnuts also have gentle insecticidal properties that have been shown to interfere with mosquito and lice life cycles. Whether this means that washing your clothes with soapnuts will render them mosquito-proof has yet to be shown. Did you know that soapnuts are used to clean cardamom seeds, improving their color and flavor? If you use graywater from your washing machine, soapnuts are a far better option than soaps and detergents sold over-the-counter, and they’re free!

Unfortunately, it may take your soapnut tree up to 10 years to begin producing fruit. (At least it’s faster that stone pines!) The nice thing is, soapnuts are lovely trees, long before they provide you and your family with a lifetime supply of environmentally safe laundry soap and shampoo!