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Depends I suppose what you mean by invasive? I love my lysimachia firecracker, yes it does spread, but it easily enough removed where you don't want it. Lily of the valley gets everywhere, but who could object to that? Well, I guess some folk might. The invasiveness also varies from garden to garden, I have trouble getting japanese anemones to grow at all, never mind become a problem, whereas my friend a couple of miles away finds them a dreadful pest. Artemesia limelight is a pain, but others are Ok, it used to turn up in hanging baskets but not so much now I'm glad to say. After all, Japanese knotweed was introduced as an ornamental plant - a message to ponder maybe. One mans invasive pest is another persons joy and delight - maybe some of my hardy geraniums might be considered as invasive - what a delight!
Saponaria officinalis is a real thug. and I wish Lysimachia Firecrackere WAS easy to remove. I have been trying to get rid of it from one area for 4 years now, digging it out and putting Weedkiller on every time there is a new leaf showing.
Campanula takesimana is a seed weed of the first order, deasd head it assiduously.
Forgot another one, Solidago, that also seeds itself everywhere if not cut down.
Another seed weed, if allowed is Knautia macedonica and as for Aquilegias.................I have decided that I am removing every plant of this as I can no longer keep up with the weeding. One missed seed head and the place is crawling witrh them again. And before the 'I love them brigade' jump on me, the seedlings are small flowered nondescript wishy washy coloured things.
Now Alstromeiria do not survive in our garden, too cold we think.
Another set of plants to plant with caution are any of the perennial Helianthus. They can spread widely if suited.
I'm fortunate in that my aquilegia Guiness or Magpie produce like babies and I get decent colours in the back garden where i've planted other forms. I have japanese anemone very happy in one part of the garden but struggling in another where i'd really like it to spread.
Lysimachias I'm picky with. I've recently planted an orange flowered sister of lysimachia Firecracker that I'd be happy to have make itself at home but I don't like the yellow flowers on purple foliage of Firecracker itself nor the thuggish green leaved form with yellow flowers. I really like lysimachia alba clethorides which is very happy in my garden and would like some of the Amethyst version.
Phlomis Russelliana is getting just a bit too happy so I'll be clearing some of that and not giving it away to unsuspecting gardeners even though it does look fab when it stays where i want it in my border. I have a plain pink geranium and a paheum which are spreading a bit too far and wide but am happy for Rozanne, Johnsons's Blue, a white form and macrorhizum to spread where they like.
I've been given alchemilla mollis to full some of the gaps in my borders after more losses last winter. I'll be cutting off those flowers with due diligence.
Yes, I find geranium phaeum a real thug, trying to get rid of as much as possible of that, had forgotten that one!
I've been given some of the smaller alchemilla too so have to assume it has come from seedlings. We'll see.
I'd rather have miscanthus zebrinus than bamboo as I find the ones I like with coloured stems you can strip bare to show off are always the most expensive and the rest are very ordinary and usually thugs.
I have hakonechloa aurea which is spreading nicely in a moist bed that only gets sun in summer. Happy for that to go mad as it's lovely, especially in a breeze.
Alchemilla alpina, erythropoda and faroensis I have grown and whilst they will spread from seed they are not as invasive as mollis.
Another real spreading thug is Allium ostrowskianum which comes in different names, like A. farreri and oreophilum. No matter what the name it is a SPREADER.
I'd add verbena bonariensis to the list. A great plant in many ways but seeds itself everywhere.
I spent 5 years a long time ago getting rid of a ground-cover hypericum - it was extremely persistent. As to Japanese anemones, I am still paying the price for planting just one plant some years ago - it is even trying to come up through concrete. Visiting Wisley a few days ago, I was amazed to see huge swathes of Japanese anemones in the borders near the new conservatory. They looked attractive at the time but how on earth will they be controlled? As to golden rod, I not only suffer from seedlings from the next-door neighbour's garden, but worse still, an RHS expert told me that golden rod is an eelworm host. He explained that the near-death of a 10 ft square of phloxes my side of the fence is the result of the proximity of the golden rod planting the other side of the fence.
right now my biggest problem are nasturtiums - they are every where and growing like triffids.
@Christopher - how do you get your alstormerias to take over? mine have grown too tall this year, fallen over and then the snails have had a feild day. normally i get flowers from April to October/November - aftera first flush of flowers they are really struggling to regrowm