Growing wild in my son's somewhat overgrown garden
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...although some people throw their hands up in horror - it is a bit of a spreader.
It is often grown just for the lovely purple foliage; allow to grow to about two feet high, then chop off the top 4" before the flowers open. Well, that bright yellow is a bit shocking against the purple.
How to take close-ups with cheap phone and hand-lens:
Field Guides for Budding Botanists:
Lat/Lng: 52.4718, -2.0821
OS grid ref: SO945859