Purple Foliage?

Weird Question of the Day

Woman called me concerned about her yard. She planted some lily bulbs in her front yard and the leaves were green, but the bulbs planted in her backyard? Deep purply-green leaves. Then she noticed a mimosa tree in her backyard also had deep purply foliage. Everything else in the backyard seems normally pigmented.

There is a septic system but the tank and lines are in another part of the yard and nowhere near the purple plants. Her neighbor has a swimming pool but no noticeable run-off across her land. Elmore County, Alabama - Currently in a Mild Drought - Not an old industrial or farming site. Normal loamy soil but the seems to be a line of crumbly soil straight between these two plants.

She’s lived at this house for 11 years and just noticed this and can’t afford to have her soil tested. So she calls the county extension agent wondering if vegetables grown in her yard would be safe to eat. The extension agent went so far as to tell her to plant tomato plants around her yard and see how they grow. If they don’t grow, don’t plant anything else back there. Then he promptly calls me with the State Environmental Office. Our answer was a combined, “Uhhhhh I dunno about that…”

So now I pass this along to you. What could cause typically green foliage to grow in purple?
(Also: I passed the agent along to the nearby agricultural university and haven’t heard back yet.)

In tomato plants, that might be a phosphorus deficiency. In lilies?

I wonder if she’s taken samples of the leaves to the front yard and compared them in the same light. It’d be funny if she painted the old shed purple and is discounting the reflected light.

WAG: Potassium deficiency (plants)