What's that lovely pink flower that's appeared all the way down the river bank? I'd never noticed it before. It's called Himalayan Balsam - yes, the flowers are very pretty. The bees seem to love it too, and it must be an easy plant to grow. Do you know where I can buy it for my garden? You can't, I'm afraid. Himalayan Balsam is a highly invasive non-native and it's not allowed to be sold. Its Latin name is a clue - Impatiens glandulifera - as is its height. It's an annual that grows taller than 2 metres! That's a lot of growing in a year. But it can't be that bad if it's good for the bees, can it? Er... well, yes actually. Japanese Knotweed is a good bee plant too! Like Himalayan Balsam, it flowers for a long time in late summer and produces great bee forage. The point is that Balsam does for every other plant trying to grow with it. That's why you tend to see it and nothing else. And if all the other plants go, so do all the animal species that depend on them. Including bees, ironically, because the earlier flowering plants will be overwhelmed too. But can't I grow it in my garden and keep an eye on it? Not really. It has an explosive seed release, which means seeds can travel several metres. Your neighbour might not be happy about getting your Balsam, and if it hops over the hedge into the field you've potentially even committed an offence! I don't really understand. I've got lots of buttercup - that's pretty invasive. Why isn't that on the naughty plant list? I sympathize! Lots of our native plants can dominate, particular in newly planted areas, but they only like particular sites and / or particular conditions. We had a plague of Mayweed last year, but this year much less and next probably none. Images licensed under Creative Commons Attribution-Share Alike 3.0 via Wikimedia Commons. "North West Wing" by Bankhall - Own work.