We all make mistakes. There was a small clump of Verbena bonariensis seedlings growing just inside the boundary when I put the polytunnel up. Decided to leave them and pot them up later but forgot.
(http://downtheplot.com/images/verbena.jpg)
Pretty mistake though! Now you will have them in there for ever.... ;D
bring the insects in ? ;D
Verbena bonariensis is what I would term a 'borderline' thug. It readily seeds itself all over the garden, but the insects, ie butterflies, hoverflies, etc love it. Wouldn't be without it. ;D ;D
valmarg
I usually pot up and sell 2-3 dozen a year to cover my seed expenses. With them growing under cover there is the added bonus of the sweet scent when I get to the polytunnel each evening.