Carpetweed attacking iris bed

BPinWV(6)October 19, 2013


I'm new to Gardenweb, and I'm new to any trouble with my irises. My mother planted them many years ago, and they've never required the first minute of maintenance or worry. They have produced tall and spectacular blossums, I've seen many colors from red and blue, to yellow, and purple, and even a brown one (once).

So now I'm trouble and am seeking help.

Last summer a family member (well meaning) thinned out the irises, thinking this would be a good thing. It was not a good idea.

Two things happened, the first is the irises stopped blooming, and the second is an invasive weed has attacked the iris bed.

I believe the invader is called a Carpetweed. And it growns so dense that even grass can't survive it.

Is there any advice on how to eliminate this weed and not kill the irises. I have three humble iris beds.

The irises seem to be coming back since I've been pulling up the carpetweed. This summer when the carpetweed was at its worst, the poor irises were in really bad shape. They were probably 90% lost.

I've attached a photo. You will not be able to see any of the Carpetweed because I yank them up when I see them. But it grows so aggressively that if I don't get around to it for a few days, it is right back and thriving.

Thank you,

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iris_gal(z9 CA)


Firstly, bearded iris often skip a year or two after division. Not at all unusual.

As to killing the carpetweed without damaging the beardeds . . . . hand weeding is about the only solution.

I have used Roundup near beardeds by shielding their foliage with a box (on a still-air day). My weed is bindweed. Any Roundup on iris foliage will distort next year's flower.

    Bookmark   October 19, 2013 at 5:28PM
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Thank you iris gal for the insight. I've been afraid to use any herbicide such as Roundup. I could easily keep the Roundup off the foliage, since my bed is so small, but the carpetweed is growing right next to the Iris roots.

The Irises roots are somewhat exposed.

I've been under the impression that the Roundup would kill the Irises if it gets on the roots.

Did you protect the roots or just the foliage prior to using the Roundup?

Thank you for your message, this is a start for me.


    Bookmark   October 19, 2013 at 6:29PM
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iris_gal(z9 CA)

Roundup travels from the foliage to the roots and 'suffocates' them. Glyphosate is the key ingredient.

I'm not sure if exposed roots can absorb glyphosate.

People have reported on 'drift' from their neighbor's spraying and didn't lose any beardeds but had weird looking flowers the following year. The year after that they were back to normal provided there was no more spraying.

If you have the patience you can paint the glyphosate on the weed foliage only -- tedious, it works tho. I have taken a small jar of glyphosate and put the bindweed runners into the jar. Worked great since I didn't spill the jar. Again, tedious. I also experimented using a cone made from heavy paper and sprayed into the wide end down to the bindweed when it was close to the rhizomes. That worked. Of course the bindweek eventually reappears.

I looked up carpetweed. Said a summer annual and pictures showed strands coming out from the center plant and forming new plants at intervals along the stems. Maybe the 'cone' method would work?

Your patch looks very weed free.

My iris roots are not exposed. The top of the rhizome is.

    Bookmark   October 21, 2013 at 10:22PM
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