Hello DebbieSue!

Preen will not work on grass. Grass is propogated via root systems...Preen is a pre-emergent - it will keep seeds from germinating, but it will not kill or hamper any of the grass, weeds or clover that spread via roots. Irises should be weed free with plenty of light and air. Use Roundup before you plant to kill all weeds through their roots, mow with a mulching or vaccuum mower to avoid tossing seeds in your irises, find a wand or sponge to 'pat' roundup on the weeds closest to your irises - but do not drip, smear, or pat roundup on the iris fan or rhizome...it can kill irises. Once you have your iris bed weed free, keep it that way with regular applications of Preen for seeds and
Roundup for weeds. If you have wild onions, mix some dish-soap with the roundup and make sure you lavish special attention on their green stalks.

Old fashioned pulling weeds and hoeing out the beds is also
effective.

s

Preen is a pre-emergent and won't work on any existing weeds. It also won't work on grass that spreads by rhizomes and runners. It will, I believe, prevent new grass seeds from sprouting, if properly applied.

I think the iris-safe, grass-specific herbicide that is most often recommended by folks here is Poast. Someone please correct me if I'm wrong. I've not tried the stuff.

Laurie

Laurie,When we visited Iris City Gardens a couple of years back, I believe we were told that they use Poast to keep the weeds at bay.
Personally I don't use any thing to keep the weeds out except for old fashioned hand pulling. I have found that if I want peace and quiet, I can find it there. The kids don't dare come out to the beds, they are afraid I would put them to work.

littlebit

I'm with "littlebit". I get up half an hour early most days and take my coffee down to the iris. I weed, clean up dead leaves, check the rhizomes, watch the wildlife, etc. A nice quiet way to start my day.

Neil

LittleBit.......VERY good answer. Sometimes, there are things to be said about "old fashioned" ways, right!

Like Neil says, it's a nice, quiet way to start the day.

David

I've used POAST on grasses that have gotten out of hand.
It is a post emergence selective grass killer, which means it only kills grasses. Will not harm healthy and established iris. Poast is very slow acting, like 2 weeks to kill the grass. Bill B on another list said he has doubled the dose and the grasses died much faster.
Ortho also makes a similiar product, but you have to look for the word Selective, which means it is selective in what it kills.

Randy

Ortho's Grass b Gone works very well. I used on the old garden bed here in front of the farm house. The bed hadn't been weeded in many years. Once I cleared the grass the rest was easy. Does work real slow but didn't bother anything but grass. Was less overwhelming once the grass was gone.
Doesn't work on sedges, did make them a bit sick. A little paint brush with a dap of roundup finished the nutgrass and other sedges off.

Don't confuse it with weed b gone which kills everything but grass.