Did you sow seed, or did they set themselves? A little history can help. Have you seen flowers?

Persicaria lapathifolia can have dark leaf stains, distribution I'm not sure about.

http://www.agroatlas.ru/en/con...

http://www.aphotoflora.com/d_p...

The map shows it to be all over North America.

http://luirig.altervista.org/f...

Janet, those were sent to me as nameless cuttings in a plant swap. I stuck them in the soil and they took off. I do believe the flowers were pale pink or maybe white, but I don't remember for sure. I'm sorry I don't have a picture of those. I have several other types of Persicaria and knew it belonged to that genus.

The plant you ID'd looks very much like it in some of the photos. I had seen something similar labeled as Persicaria maculosa which is also listed as a synonym some places. But I think those two are distinct species?

Persicaria maculosa is accepted on the Plant List ..

http://www.theplantlist.org/tp...

So is Persicaria lapathifolia..

http://www.theplantlist.org/tp...

How to separate the two?

http://de.wikipedia.org/wiki/D...

The next link calls P. maculosa 'Redshank', look at the leaf photo, they look shorter and broader.

http://www.aphotoflora.com/d_p...

The leaves look to vary, the stems in general look to be very red but not always.

http://www.wnmu.edu/academic/n...

http://keyserver.lucidcentral....

Both seem to be variable, altough P.maculosa appears to have pink or red flowers where Persicaria lapathifolia ' Pale Persicaria' are generally pale (how many photos are correct anyway, unless there's regional variation.) The brown blotch on maculosa looks to be further towards the leaf tip.

Persicaria maculosa ..

This is a very common weed which is found in wet places, fields, waste ground and even growing out of the crack between pavement and wall. A late summer flowerer it is usually the pink colour in the left but the unusual red form shwon was in every other respect a normal P. maculosa.

http://www.ukwildflowers.com/W...

Persicaria lapathifolia ..

The diagnostic for this plant is the presence of small glands on the flower stem and on the perianth (sepals) but I first look out for a pale greenish flowered Persicaria often growing with P. maculosa (Redshank) and P. hydropiper (Water Pepper). In my experience a healthy plant will often be larger and more straggly than Persicaria maculosa which can have confusing pale forms. I haven't yet seen any pink forms of P. lapathifolia as illustrated in Stace's DVD.

http://www.ukwildflowers.com/W...

http://www.naturespot.org.uk/s...

The leaf venation appears to be closer on Persicaria lapathifolia too, yours looks to be close. Persicaria maculosa "generally" has a more lax habit.

http://www.invasive.org/browse...

Yes, I agree. The habit of this plant is not as lax appearing at P. maculosa. It stands much more upright. I am fairly content that is it P. lapathafolia. It is just very much more upright appearing as in this photo below (except with the dark markings on the leaves)

http://en.wikipedia.org/wiki/F...


(photo in the public domain)

Here is a good reference site for it too:
http://biology.burke.washingto...

By the way, thank you for helping me ID this. Much appreciated.

You're welcome Tee.