Is this what you are talking about if not post a photo

 

I have no personal experience, but have heard something about injecting gly between 2 specific "knuckles"
The problem if it's in a lawn of course is that you'd have to allow it to grow to a certain height in order to be able to do that.

Good luck man, that stuff is nasty.

 

http://www.uri.edu/cels/ceoc/documents/japaneseKnotweed.pdf

 

I have a few customers that have them and they like them...they are about 8' to 10' high. They call them bamboo!

The buggers can get way out of control if you let them and grow very fast. There isn't much yo can do other than trying to dig them up...good luck, if you don't get every bit of it including the roots etc, they will come back.

The customers that have them though I will say they look good at 8' high or so as part of their landscape.

 

Thanks for the link, Redsox. Gosh, the Japanese knotweed (Polygonum species) looks a bit like bamboo, but it gets so big! 10 feet is normal. And it spreads by strong underground roots and rhizomes. Of course, it dies back after frost. Knock down the dead stems in winter or spring. Next spring, keep mowing it short. Apply any good herbicide or a three way after you mow. Do not allow the green part to send food to the roots. It is not likely to spread from the mowed residue--unless it lands on freshly plowed land in wet weather. Good idea to sweep or blow off the mower, just to be sure.

 

IF you are dealing with Microstegium vimineum, commonly known as Japanese stiltgrass, Acclaim Extra will selectively control it on cool season turf.

 

you will need a stand of untreated and unmowed JK as a timing indicator. (As this is in a lawn the next step is not as important for you) Mow the stand of JK early in the season and let it regrow. When the untouched stand is flowering spray the mowed stand with triclopyr (for lawns) and glyphosate (for other situations where selective isn't necessary). Spray is most effective on mowed/recovering stands at the flowering point of the season. Systemic herbicides are best.

 

I have used glyphosate at 3 - 6 oz per gallon foliar application in e. summer when emergent stems are ~ 1-3 feet high. Revisit and repeat in later in the season around flowering for any remaining or newly emergent shoots. This scheme will help put the brakes on new growth and spread + begin moving herbicide to the MASSIVE rhizome root system in fall. Yes, systemic herbicide is key so it can be absorbed by foliage and trans located through the vascular system and ultimately to the roots.

PDK Horticultural, LLC
Vegetation and Conservation Services
Maryland

 

If it is Stilt grass, you can apply a pre-emergent in the late fall or early spring to control it as it is an annual. I had good luck this spring with the pre app...probably knocked out 80%...this lawn was loaded. I will be doing another app next year in late February or early March.

If it is not a residential lawn, you could use the old standby...MSMA. Can't use it on residential lawns unless you have the old stuff sitting around that is labeled for residential lawns. This stuff will fry it at the 1oz/m rate.

Aclaim did not do a very good job for me at the 1oz/m rate. Just way to expensive and poor results. Actually had to do two apps 14 days apart just to get decent results.

 

I like Japanese stiltgrass. it grows in the shade where grass doesn't and is pretty.

 

The picture in the second post so stiltgrass correct?

This is knotweed:

 

YES...your pic is japanese Knotweed.

Yes, stilt grass and knot weed are nowhere similar so we can pardon the confusion.

I treat Japanese knot weed same as phragmites.

The both have enormous rhizomous root systems.

Like phragmites, flowering signals the coming end of the plants cycle, building resources toward next year and reproducing. AND sending valuable nutrients to the roots.

I monitor and treat knot weed with systemic glyphosate 3-6 oz gal just prior and during flowering to maximize control.

Like phragmites, monitor the following year for re sprouts that will require treatment before they build their reserves.