It would probably look much the same. It depends on what the other plants are.

IME purple loosestrife isn't some all-conquering invader, but is quite limited in its ability to push out other plants. Like many other invasive plants, it competes best in disturbed areas. No disturbance - no outcompeting. In my swamp, it lost out to cattails.

I am actually interested to see how much it does spread for as you can see it doesn't have much "family" around right now ;).

" purple loosestrife isn't some all-conquering invader "

If that were truly the case, then it would not be a listed invasive species in all but 12 states. Each plant can produce 2.5 million seeds a year. All it needs to thrive is a somewhat moist soil and an open location

An open location that is not already occupied by another plant.

There is much, much less of it around here since people stopped messing around with the tidal flats.

" An open location that is not already occupied by another plant. "

Not according to the invasive species authorities. In fact, they state that it will cohabit happily with other wetland plants like rushes, reeds, teasel and cattails. It is also a frequent invader of meadows and unused pastures.

Nasty invasive here. Eradication progress has been made here, don't see it as much as I used to but I do still see it - usually big swaths of it in roadside ditches.

Another plant which is perfectly well behaved here in its native habitat but for some reason goes nuts in the US. It's not exactly rare here but we also don't see huge areas of it. I'm always pleased to spot it.

ETA Canada! Profuse apologies.

In this case Canada :)

It was taking over vast areas here.

This is an excerpt from Ontario.ca

In 1992, the Canadian and American governments approved the release of two European leaf-eating beetles, Galerucella calmariensis and G. pusilla. The beetles are natural enemies of purple loosestrife and feed primarily on the plant, although they occasionally eat other species of loosestrife. This biological control of purple loosestrife can reduce populations by up to 90 per cent and allow native plants to re-establish. The beetles were widely released in Ontario, and purple loosestrife populations at many of these sites have been significantly reduced.

Of course my concern is what the beetles will move on to after.

The next time you walk by it,Rouge, please pull it. i dont think it makes a good observational experiment.It did real damage to freshwater habitats on the east coast . and cost big money to remove it.

Since its spread has been better controlled by laws and mechanical removal the beekeepers have missed it. A local one said it made wonderful honey and its widespread abundance contibuted to generous honey production

In the same park I came across this (native?) plant. Can you identify it (very large leaves and when upright it can be as tall as 6 feet high).

Compare with Inula helenium or I. magnifica. Can't be certain. Neither native to you.

@floral_uk z.8/9 SW UK it does closely resemble both of your suggestions. Thanks for looking.

(I was hoping native but thinking "native" only because I see it in this wild/untended park)