I live near a pond (on a commons area) and just found a few loosestrife plants growing down near the water this year. I have to get down there and yank them. I also walk in the subdivision and a couple people have them growing in their yards. I'd like to give them the picture that I'm linking and beg them to please shovel prune before our very shallow pond turns purple.

Google your state's list of invasive species to confirm that what's growing in your garden bed is either prohibited or else otherwise extremely limited for purchase. The botanical name is Lythrum salicaria.

If you're looking for something similar to plant in its place once you remove it, check out Liatris spicata/spiked gayfeather which is also blooming now and isn't invasive.

And hats off to you for recognizing that you were likely growing an invasive species.

2. Is my garden variety (cultivar) of Purple Loosestrife safe?
No. Originally many garden varieties of purple loosestrife such as Morden Pink, Morden Gleam or Dropmore Purple were considered to be sterile (did not produce seed), safe horticultural cultivars. Recent scientific studies have shown that these varieties are indeed capable of pollen and seed production. These plants can readily cross pollinate with other garden varieties, as well as wild loosestrife populations. In a Manitoba study, Morden Pink cultivars were planted near a wetland with purple loosestrife and six months later all Morden Pink plant produced viable seed. The majority of wild infestations of purple loosestrife are the result of garden escapes.

The Manitoba study involved experimentally planting 'Morden Pink' along natural waterways. In other words, it indicates, but doesn't prove that purple loosestrife cultivars planted in garden situations can be prone to this problem.

Below; actual proof.
Picture; Nov 7, 2011.
The garden is in King City, Ontario.
The cultivar ('Rosy Gem') has been cut down, prior to removal.
You can see the line of purple loosestrife seedlings below the edge of the lawn.

So far, I've only seen this in gardens with sprinkler systems or which were otherwise kept well watered; matches the waterways bit.

That Liatris spicata or it's cultivars are a match for the show put on by (or I'd say the beauty of) various purple loosestrife cultivars is, as far as I'm concerned, a joke.
On the other hand, garden-generated evidence for avoiding the use of horticultural purple loosestrife (where legal) is in.

Sorry bees.