I am going to try to grow a soapnut bush at home this year (indoors so I don't disturb the native plants) so fingers crossed there.... I have tried using acorns and bouncing bet (other plants with saponins traditionally used for washing) and I have heard that there are many other plants out there that are useful for cleaning, but honestly, the acorns turned my whites brown and when I tried using bouncing bet (soapwort) I had to dig out a lot of the roots of the plant. To be frank, the soapnuts are practical and actually do a good job cleaning dirty diapers too.
I don't have a washing machine in my tiny apartment, so I have to go to the laundromat once a week, which is actually a nice activity, gets me out for a walk, and plus it means I can't just throw a couple towels in for a whole load and waste energy and water doing that. I call it slow laundry because it takes me all afternoon to get it done.
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