Hi Mike, how are you ? Seems you have also found a Periwinkle problem. Is yours as above in a Public or Private area ? The one I reported in Watson is on Private / Business land. I have written to Company concerned and also posted on ACT "Fix my street". Sofar no response from either.
Not sure I'm fond of these Neighbours particularly... I guess they are probably not aware that Periwinkle is invasive... we'll have to try harder on public education on this, sigh...
And yet another reason to only buy plants from a licensed vendor, thankfully Periwinkle is prohibited from sale in the ACT following the Pest plants and Animals declaration (2015). Although this hasn't always been so, I once talked to a resident in Garran who drove to Melbourne specifically to pick up seedlings for their garden, and another who prizes it for medicinal properties. Food for thought I guess. :)