Merseyside,
United Kingdom 
I have a shrub which is pretty but invasive. Has a tough root system, whip like tough stems which grow to 1.5 metres, with one dusty pink, triangle shape, fluffy flower on the top.
can you help?
30 Mar, 2010
Answers
Be easier with a photograph, though if it is Spiraea, it won't be in full leaf yet, I'd imagine.
30 Mar, 2010
is it a budldea?
30 Mar, 2010
And thinking about it, that could even be lilac, especially as its invasive.
30 Mar, 2010
Triangular stems sounds like a knotweed of some kind, though lilac could be square--still gots corners!
31 Mar, 2010
I took the flower to be 'triangular' rather than the stems.
31 Mar, 2010
That's what the questioner describes as triangular, the flowers, Tugbrethil, so you're right Seaburngirl.
31 Mar, 2010
Oops! Maybe when evolve, me learn read! : /
1 Apr, 2010
It could be Spiraea douglasii?
30 Mar, 2010