This pretty little daisy growing oh so prettily on this wall, and it may be said, all over the place, in gardens, bits of waste ground, is on the NZ List of noxious weeds.
The Mexican daisy, Erigeron karvinskianus, has very similar flowers to the common lawn daisy Bellis perennis. It is a perennial which grows on thin, quite brittle stems, which form a thick mat. Therein lies its pestilential problem. It forms larged matted clumps which in non-urban environments smother native vegetation. As the daisy dies off it leaves large areas vulnerable to other invasive species.
It is an incredibly prolific seeder (like most Compositae). Whilst its quite easy to 'weed' it in the garden, one is on a losing wicket as unless you dig up all the roots you only encourage its spread. Naturally weeding has to be done before it seeds, which is in itself difficult as it flowers (and seeds) pretty much all year round.
And of course neighbours tend to like it because it is a pretty wee thing, and they may not realise how noxious it is. I have even seen it for sale on plant stalls at school fairs!
