Ask Mr. Smarty Plants

The US Forest Service has an interesting article online about the plants that have significant levels of saponins to make lather and which have historically been used for making soap.

Many native plants, especially those with waxy cuticles, contain saponins which are steroids that dissolve in water and create a stable froth. Saponins are named from the soapwort plant (Saponaria) whose roots were used historically as soap.

The earliest evidence of soap use dates back to 2800 BC in ancient Babylonian clay. Egyptians (1500 BC) bathed regularly with soaplike substances made from plant saponins combined with animal and vegetable oils. Handmade soaps are often made using fats such as olive oils with lye. Animal fat mostly in the form of tallow is still a major component of many soaps, but plant oils have become more important in soap production. Two palms, the coconut palm and the African palm, provide the bulk of the plant oils currently used.

Soaps made from plant oils often dissolve very quickly and produce excessive lather, so tallow has been used to create hardness in some mass-produced soaps. Palm oil has been found to be very similar chemically to tallow and can be used to replace the animal fat. Plant oils such as cedar wood, rosewood, and rose are often added to soaps to impart their scents.

The fruits of several native North American plants contain sufficient levels of saponin to produce lather and can be used as soaps or shampoos. This group of plants includes:

• Atriplex roots,
• Sapindus fruits,
• Mojave yucca root,
• Soapwort root (European species), and
• Buffaloberry fruits.

Of these listed, most are native to the SW region, but Atriplex prostrata and Shepherdia canadensis (Russet buffaloberry) are two that are native to Pennsylvania and can be found in our Native Plants Database.