Unidentified growing object!
This plant reaches about 1m high, then in summer produces large spherical heads of flowers purple out side and lilac within, which have the scent of hyacinths. In its earlier phase it looks like a weed, and is extremely invasive. It spreads by runners and one plant could colonise the average suburban garden in a season! One problem which arises when gardening in a new country is that many of the weeds are different - for a long time I was not sure whether this was a weed or not! I have asked many local people if they recognise it without any luck, including my professional colleaues at the local market where I sell my plants, so I assume this is not a local weed or someone else would have it! The previous owner produced water plants and was fond of the rare. It survives frosts of -20°
Can any body help?