If you look at Spiraea douglasii on the RHS website it says:
"Easy to grow in most moist soils, tolerant of all but the most extreme
conditions. A rampant shrub that in time can form a dense thicket" and
"If overgrown, can be renovated by cutting back hard immediately after flowering".
So if you're a novice gardener who sees it in the garden center and think I'd better do some research you'd have no real idea that it could become a problem plant. I really think the RHS should consider putting warnings or advisories on some of their descriptions.
“Success is the ability to go from one failure to another with no loss of enthusiasm.” Winston Churchill
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