May 27, 2017
You dodged a specific question that a writer posed recently in the letter beginning "Emergency!" The issue is about iris beds and whether Roundup will kill the bulbs. Although you mention daffodils in your column, please correct your silence concerning irises. It's a question I've been hoping you'd answer for some time. Is there any other product that could be used in iris beds? Recommending a hoe to a letter-writer who has conceded that she/he no longer has the physical capacity to weed was also something of a dodge!
I did not mean to dodge. I did say: I don’t recommend spraying Round-up on anything other than what you want to kill. Round-up should not be used in contact with iris rhizomes or foliage. If you choose to use Round-up you would need to shield the desirable vegetation while spraying. Although Round-up may not always outright kill an iris if it got sprayed, it would do damage and can distort the foliage. There are some pre-emergent herbicides that are fairly effective on annual broadleaf weeds. They must be applied before the weeds emerge in the fall or early spring for winter and summer annual weeds. Surflan and Treflan are both labeled for iris. There is nothing that will prevent perennial weeds or grasses. Bermuda grass tends to be one of the worst weed problems in iris beds and the post-emergent grass killers – Poast and Fusilade do a good job, but should be applied before the grass has thoroughly taken over.
With the warm weather, we have healthy winter weeds and tops of tender bulbs and other perennials coming up. Is there a herbicide that will kill the weeds and not hurt the perennials?
Anything that will kill the broadleaf weeds will also kill or damage your emerging perennials and bulbs, so either use a hoe, or spot spray, making sure there is no contact between herbicide and desirable plants. Round-up or a glyphosate product will work, if you can shield the desirable plants. I prefer the hoe or hand pulling to avoid damage.
What can I spray in my iris bed to get the grass out? What can I use in other flower beds to control grass and/or weeds ? How do I determine what it can''t be sprayed on?
You can spray a grass specific herbicide such as Vantage, Grass-b-gone, Ornamec or etc. This should be used earlier in the season as the grasses begin establishing themselves. While these products do come with a list of plants that have been tested for their use, there is no way they could test the product on every ornamental plant available. therefore, for any plants not listed on the label, do a small test plot first, before randomly applying it.
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