Walnut Tree's And Asclepias

I read yesterday that scientists monitoring Walnut Groves in California, found the Trees produce Aspirin when they are stressed.
I thought a perfect photo would be this Asclepius, the greek demigod of healing. It is in flower in my garden now.
This has bloomed beautifully after being really sickly looking in March after I first bought it.
Its also called Milkweed. I love the chunky yellow flowers and reflexive orange petals that curl downwards.The flower buds look like peanut M & M's....
When I'm stressed I find standing in the garden and just looking eases the daily stresses and strains.
Watching the leaves of the plants and the colourful flowers nodding in the wind. The insects buzz around, and sometimes the birds chatter from high up in the privet hedge.
I'm still trying to find the PBS documentary called "the healing gardens of New York" which I got emailed about a year ago or more. Is it available online anywhere to watch?
The BBC's article said the aspirin compound is released in the air when the plant is stressed, helping the plants immune system. Presumably it makes the other plants ready for pest attack by warning them.
Pulling weeds out, and digging the soil takes your mind off life. You cannot hold onto stress or anger. Just look at the flowers, the intricate structure of the plants, the busyness of the insects doing what comes natural to them.
I do believe gardens are great for teaching and healing. The original article is here: http://news.bbc.co.uk/1/hi/sci/tech/7624521.stm