Buddleias - restricting height
I have a gap I'm thinking of putting a buddleia in. I want something attractive, both to me and to wildlife, and I'm eyeing up Black Knight. One thing I'm unsure of though... according to Crocus they grow to 3m, which would be a little too big, but according to J Parker they grow to 2m which would be as tall as I'd want, but can be pruned hard to restrict their size. However, I thought you were meant to prune them hard anyway so assumed they could reach their ultimate height despite being cut hard back in spring. Would it be possible to keep Black Knight to no more than 2m - possibly just 1.80m?
If it's going to be too vigorous, could anyone suggest alternatives please? I've seen smaller ones, but they tend to be too compact.
I think if youre growing conditions are good you will struggle to contain Black Knight to that kind of height
If you prune them later than the usually recommended March, it'll stop them getting tall as well.