I've never used a pre emergent, but from what I understand, you don't want to dig it in. As I understand it, it creates a sort of barrier on the surface of the soil. Corn gluten meal needs to be applied pretty heavily to be effective and it also takes a few years for benefits to show. On the bright side, it's also a pretty strong nitrogen source (for organics, anyway).

If you don't get any better responses here, you might try the Soil, Compost, Mulch or Lawns forums.

Hi Nicole,

IÂve never used Preen either. Thought about it a couple timesÂbut the stuff is just so darn expensive! The best thing IÂve foundÂand definitely the least expensiveÂis elbow grease! I really works! ;-) If you stay on top of it and pull weeds out as soon as you see them, they only have the beginning seed root and are VERY easy to pull out. And the good news is that it gets easier and easier all the time. The first year I spread out the pile of soil that was next to my house, and planted my first veggie garden, it was an insane mass of weed seedlings! There had been weeds growing AND going to seed in the pile of "scrap" dirt probably for years when I moved in. The first year I actually hoed a bunch of them a couple times. But now, every year there are fewer and fewer. There are always a few seeds that blow in or are dropped by birds, but itÂs really quite manageable by now.

With flowers, even iris, I still recommend a good natural mulchÂI like small bark. Just keep it thinner around the iris. Then watch for weed seedlings and get them as soon as theyÂre big enough to get hold of. Unless itÂs an area where there have been weeds going to seed, you shouldnÂt have that much of a problem. And if you have things in there with established roots, like bindweed, Preen wonÂt help for that. I still have a couple places where old bindweed comes up, and I carefully spray just those individual plants whenever I see themÂdo that with the bindweed and the eternal cottonwood trees that are everywhere in my yard. I use Roundup for any areas that donÂt have grass, and Weed-B-Gon for anywhere in the lawn.

If you start to pull out the tiny, little seedlings, I think you may be pleasantly surprised that itÂs not as bad as you expect.

Skybird

I used Preen last year and wasn't that impressed - still got some weeds in a gravel bed. But I do believe it would be safe in your Iris bed, as my understanding is that it's only supposed to keep many weed seeds from germinating, but it shouldn't affect your Iris rhizomes.

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I've got to make my gardens more maintenance free. I can't keep up with the weeds it's too large an area I'm gardening. I'll put down the rest of this 40lb bag of corn gluten & the chemical stuff in the spring. Maybe it has to do with timing?

Thanks for the tip on "not" using preen.

I live in northern Utah and have had great luck with Treflawn (may not be the correct spelling, but that is how it is pronounced). I sprinkle it on twice a year using a broadcast system, then water it in with the sprinkler system, and that is it. I have huge beds throughout my yard, and the Treflawn does a great job of keeping the weeds in check. There are still the weed or two to be pulled by hand, but they are the rarity.

Ideally, the Treflawn should be applied in the fall of the year, and then 6 months later. That way, the barrier will be in place for the spring emergence. Since I didn't get the Treflawn applied this fall, I'll do what I did last year...wait until the snow has melted in spring 2009, and apply it then. I use the Treflawn everywhere in my beds...on iris, near trees, perennials....everywhere.

I purchase the Treflawn from my local Intermountain Farmers' Store. My landscaper taught me about Treflawn, as he used it when he landscaped the yard and planted all the trees, shrubs, etc. in the fall of 2005. I do receive lots of compliments from my neighbors about how my yard is free of weeds.

The only thing the Treflawn doesn't work on is Snake Grass. I'd give anything to know how to get rid of that noxious weed!

Hope this info helps.