Invasive plants

[Lori S.]

After a brief experiment with it in the garden, plume poppy (Macleaya cordata) has earned a place very high up on my Most Invasive Plant list!   I was aware that it was considered invasive but I thought I'd try one anyway and see for myself last summer.  It didn't do much of anything at all last year and this spring, I was even wondering if it had survived... but then yesterday I noticed the distinctive leaves coming up 1-2 feet away from the plant.  Upon starting to dig, I found the roots going out even farther - truly impressive!  I wish I had a confined space for it but lacking that, it's in the composter.

A similar story with Stachys lavandulifolia in the rock garden...  Though the flowers are very beautiful, it seems to have spent most of its energy sending shoots far and wide instead of flowering, so it's been turfed too.  The roots went extremely deep and it will no doubt will keep popping up for some time.

[Jandals]

Thanks for the warning Lori . I was looking at the beautiful flowers of Stachys  lavandufolia in a catalogue .

It took me several seasons to get rid of Macleaya cordata

[Hoy]

I tried Macleya once but it didn't make it. I have spot where it could have roamed free but the slugs (as usuall) found it irresistible. Somebody who wants some slugs? They're expensive though these days as the population was depleted last winter.

[Paul]

Speaking of invasive plants, does anyone know if the biological control trials for Japanese Knotweed, Polygonum cuspidatum, in the UK have had any success?  It's a big problem here in western Pennsylvania as well.

[McDonough]

Excellent idea to create this topic.  

The single worst highly invasive plant, for which I fear I am losing the battle, is Campanula takesimana.  It is now established in parts of the lawn, in the crowns of shrubs, taking over whole areas.  It has stringy white stoloniferous roots, and if the slightest piece is left behind, it sprouts ten-fold. I haven't tried round-up on it (I don't use chemicals), but it is so horrendously aggressive, that I can easily envision it getting loose into the neighboring woodlands and becoming the next terrible invasive, so I may have to give round-up a try.  The flowers are big beautiful bells, in white, pinks, and lavenders, strongly dotted inside (the species is related to C. punctata, another terribly invasive weed).  Here are 3 color forms; don't be fooled!  In the areas shown in the photos, the Campanula came in on its own.

[Hoy]

Well, Mark, I won't ask for seed I already have it in the garden and it is behaving itself and not spreading - or to be precise, it is kept in a restricted area and makes a nice clump. No seeding around. I have some other Campanulas that is worse! (I'll show some pictures later)