Our knautias have been if full flower for about 3 weeks and bring a really welcome shot of colour to what has so far been a drab June.
The standard version of this plant has the dark red blooms but we have some of the 'melton pastel' version mixed in that includes several shades of pink too. Knautia flowers can rise to 150cm high and will lean outwards giving a big area of colour; our square meter of planting at ground level becomes about 3 square meters at bloom height. I recommend a bit of support to keep them from flopping on top of other plants.
They attract all bumblebees; yesterday I counted 6 different species at the same time on our patch and an average of 12 bees. This display will last about 6 to 8 weeks - longer if you trim of any stems that have finished flowering an encourage more to grow.