Beverly nods as they walk. "Depending on the size of the plant and the root system," she explains. "If the roots overlap too much, they'll compete for water and nutrients and the plants above ground will fight for sunlight. They each need the right amount of space so they don't have to fight each other."

Her approval of Wanda's movements is easy to see. Wanda is a good student, willing to learn, and she seems happy to do so. If Beverly has to correct her or explain something, she does it gently, making sure that Wanda knows how good a job she's doing.

The next question gets a soft sign from Beverly. "Not exactly. It's mostly to treat insomnia. I might be able to make you a mixture to help, but it won't be a cure."