Second softballmom's response. I planted watermint in a pot so it wouldn't get into the garden, and spent the next several years getting it all out. Next time I plant mint, it will be in a container on the patio, so it can't get away.

I have a large patch of lemon balm (over 1000 square feet) planted in fall 2007, and I've seen no evidence of it spreading by root, here in Maryland. It certainly does self-seed all over the place, but in that regard it's just one among many weeds that pop up. Incidentally, the lemon balm was originally interplanted with catnip. It was thriving last year, but absolutely none of the catnip came back this year. I'm assuming it drowned because of the unusual snow cover last winter. The lemon balm is so vigorous that I was regretting planting it with the catnip. But if I had planted only catnip, I wouldn't have anything there now.

I wouldn't read too much into some of the arguments advanced in that book. They give one view but not one I agree with and I don't think some of the arguments given are convincing. Yes - to some extent invasive plant problems are connected with bad land management and we are to blame for them. But to use this as a reason not to manage invasive plants - I don't agree. If you want to fix problems caused by forest fragmentation in lowland NZ rainforest - well you can't really unfragment a lot of it because we have put cities and farms in the way. In such cases, you need to think about managing the consequences and this includes invasive plants. That is, if you want to take responsibility keep some parts of native forest remaining (I realise some people don't really care about that, but it matters a lot to me that we preserve some parts of our world for the environments and species that were there before us). Blaming plants has nothing to do with it. Also - in NZ it is pretty obvious in terms of plants what was here before humans arrived and what wasn't (how we usually define native). Over millions of years NZ ended up with somewhere around 2500 vascular plants via natural dispersal and speciation (there would be only a handful where we arent sure whether they are native or not). Maori arrived and brought about 10 plant species. The Europeans arrived (250 years ago) and have since introduced more than 25000. It's not the process of new species arriving that is the main issue. It's the RATE that is far exceeding pre-human times and that is the problem. With a longer human history North America is more complex but the issue is the same - it's the rate that is the problem. The arguments around "invasion is a natural process" and "everything was new once and will find their balance in time" seem to miss the point to me. Rats, stoats and cats will find their "natural balance" with flightless birds that evolved in the absence of mammalian predators. But that "natural balance" would see the extinction of many of New Zealand's endemic species (it already has in fact). There is a similar picture with invasive plants although it is much slower. Personally, I'm not prepared to accept that.

Lol, why would they need to evolve, when they are already dominating their newfound ecosystems as-is? And "find a niche and become part of the ecology?" By definition, they've already found farrrrrr more than just a niche and are overwhelming the ecology, much less simply just become a part of it!