9 Natural soap plants for making lye-free soap

An introduction to plants that you can use as soap without lye. Includes a list of nine natural soap plants rich in saponin and how to use them

Years ago, I taught myself how to make handmade soap, and ever since have shared ways that you can make it too. I remember how difficult it was to learn that way and the number of batches that failed, and my many questions that just weren’t clear enough in books at the time. That’s why I began sharing tips on how to make soap here on Lovely Greens. A lot of people are interested in making soap too, but after a little research, feel hesitant about using lye.

It is possible to make bar soap without having to handle lye, but it’s a little bit of a cheat. The main way is by using melt and pour soap, which you melt in the microwave, stir in scent and color, and then pour into molds to harden. It can be made using lye, but that step is done for you before it arrives in your hands. There’s another way to make a soap-like substance, though, and one that doesn’t require lye or any other harsh chemicals. You make it with saponins naturally present in plants.

Surfactants and Saponin

Soap as we know it has been around for thousands of years, and though the way we make it has changed, the principle is the same. You combine fats and oils with a powerful alkali that we call lye, and at the end, have a substance that’s a salt of a fatty acid. It’s natural chemistry, and soap cleans because it’s a surfactant.

That’s a scientific way of saying that soap pulls oil and grime away from solid surfaces (our skin, plates, floors, etc.), and the water we use it with washes it away. Without soap, oil sticks, and you can’t remove it as easily. Soap isn’t the only surfactant out there though, and some plants produce another in such high amounts that we can use it as soap. This other surfactant is called saponin.

Use soapwort’s leaves, stems, flowers, and roots to make a sudsy soap-alternative

Natural surfactants from plants

Cultures around the world have used simple plants to clean, and some of us still do. I sometimes use soap nuts for washing clothes, and if you’ve tried them too, you’ve had experience using a saponin. Just like soap, saponin is a surfactant and pulls oil and grime from surfaces. It can also create the bubbles that we associate with soap.

The chemistry may be a lot to wrap your head around, but basically, saponins are a natural plant compound that can dissolve in water, and latch itself to oils. Then the saponin, along with the oil, is washed away by water.

Soap nuts are the saponin-rich dried fruit of shrubs in the Sapindus genus

How to extract saponins from plants

Because saponins dissolve in water, it’s relatively easy to extract them from plants. All you need to do is soak or boil the plant material, fresh or dried, in water. The amount of plant-material to water isn’t exact, and you base it on how much saponin the plant has. With soap nuts, you tend to use five ‘nuts’ (actually fruit) for a load of laundry, but you can reuse them too. They still contain saponin even after being used a couple of times. My soapnut sachet is usually pretty full since I don’t take them out often and just add a new nut for each load. Warm water dissolves the saponins in the soap nuts and also washes the dirt and saponins away from your clothes. Some plants are higher or lower in saponins, so the amount you use for each type will be different.

I’m using the example of soap nuts because a lot of people use them as they’ve become more readily available in health food shops and online. They’re a fruit that grows on a group of shrubby trees in the Lychee family, but when dried, look a lot like nuts. These Sapindus species shrubs grow in tropical and sub-tropical places like India, so they’re not something that everyone can grow. Fortunately, there are saponin-rich plants that will thrive in temperate climates too.

Saponin rich plants

The most well-known saponin rich plant is soapwort, native to Europe but now found all around the world. The whole plant is rich in saponins, but it’s most concentrated in the roots. Here’s a list of plants that people around the world have used as soap and the parts most rich in saponins. If you decide to try it out for yourself, make sure that you don’t introduce the soap into open water sources such as lakes and streams. Saponins are poisonous to fish and other marine life. Also, please do not eat any of these plants as some are poisonous if taken internally:

• • • Buffaloberry Shepherdia argentea (berries)A wild shrub that grows in the western and north-western USA and Canada. The red berries (sometimes yellow) were collected by Native Americans to make a type of foamy dessert and in medicinal teas. It was only ever eaten in small amounts since buffaloberry can give you an upset stomach due to its saponins content. To use, you can mash the fresh berries together on their own or with water. There’s a video showing it in use just above.
    • California soaproot Chlorogalum pomeridianum (bulb)A wild, low-growing plant native to California and Oregon in the United States. It has long blue-green leaves that die back in winter, and a tall flower-stalk that can emerge after the plant is mature, at five to ten years old. The part high in saponins is a fist-sized bulb with a fibrous brown exterior and a white interior. The crushed bulb interior, or its juices, create a soap-like lather when added to water and agitated. Another similar species, Narrow soap leaf plant Chlorogalum angustifolium was also used as soap by Native Americans.
    • English ivy Hedera helix (leaves)Finely chop about sixty of the leaves and boil them for five minutes in 4 ½ cups of water. Next, take it off the heat and allow it to cool to hand-hot. Squeeze the leaves and agitate the water to disperse the saponins. Strain the liquid and use it in laundry and in cleaning home surfaces. Use a cup at a time with laundry and store the rest in the fridge for up to a week.

   

   

  • Horse chestnut Aesculus hippocastanum (nuts)The conkers that children collect in autumn aren’t edible, but they do have a hidden use – soap. Crush half a dozen horse chestnuts by wrapping them in a towel and bashing them into small pieces with a hammer. Simmer them with a cup of water for five minutes, take off the heat and allow to cool. The milky liquid has enough saponins to wash a single load of laundry.
  • Shikakai Acacia concinna (fruit pods, leaves, and bark)A climbing shrub native to Asia, especially India, with bark, leaves, and fruit pods rich in saponins. You can sometimes purchase the dried powder to use in shampoos, but it’s made by drying the plant material and pulverizing it. Use by mixing 1-2 teaspoons of powder into half a cup of warm water. Agitate it, pour over your hair, and leave it on for a minute before rinsing out. There are small bubbles in the liquid but don’t expect shampoo-like foam while using it.
  • Soap bark tree  Quillaja saponaria (dried, powdered bark) The inner bark of the soap bar tree has high levels of saponins and to this day is used as an emulsifier and foaming agent. Native to Chile, it can grow in other parts of the world due to it being both drought and cold-tolerant. To use, shake a small amount of the dried and powdered bark in warm water. It’s touted to be a gentle foamy skin cleanser.

• • Soapbush tree Alphitonia excelsa (leaves) A native Australian tree that has leaves rich in saponins. The video above shows how easy it is to extract the foamy soap-like substance by just using fresh leaves and cold water. Please don’t use saponin plants so close to water sources though since adding it to water has the potential to kill fish.
  • Soapnut trees Sapindus (fruit shells and pulp) The most well-known of the saponin-rich soap plants is the soapnut or soapberry tree. Native to warm-temperate to tropical places, especially India, this group of up to a dozen different species of shrubby trees produces saponin-filled berries. They’re then dried and resemble brown nuts. You can use them to make liquid detergent, but it’s easier to put them in a small cloth bag and then in with your laundry. Soap nuts are readily available to purchase.

• Soapweed yucca Yucca glauca (inner parts of the roots) A wild plant native to the prairies and great plains of North America, soapweed yucca produces foamy saponin-soap. This plant has high amounts of saponin in its roots, which are crushed and either soaked or simmered in water. The bubbly liquid has been used as a natural shampoo and cleanser.
• Soapwort Saponaria officinalis (whole plant, especially the roots) A wild and cultivated plant from Europe, soapwort is rich in saponins from it’s scented flowers to its stems and leaves. Its roots are exceptionally high in saponin content and can be dried and used throughout the year. You can use the entire plant to scour pans and surfaces or make a green-ish infusion by simmering a cup of fresh, chopped plant parts (or half that amount dried) with two cups of water. Cool, strain, and use in cleaning hair, skin, and for household cleaning purposes.