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Pre-emergent herbicide for perennial beds?

Posted by lilydude sunset6/z8 (My Page) on
Thu, Jul 5, 12 at 14:45

Has anybody used pre-emergent herbicide around their annuals, perennials, or veggies? Is there one that won't damage the garden plants?

Any other creative weed control ideas? I am using doug fir bark and gravel in some areas as mulch. It works OK. But the unmulched areas are taking way too much time to weed. I am also trying to control sources of weed seeds in the vicinity of the garden.


Follow-Up Postings:

RE: Pre-emergent herbicide for perennial beds?

I mulch everywhere with about 4" of compost except a few places where I want a more durable cover and use shredded wood chips. Been doing this for years. I have no weeds to speak of and absolutely no need for pre-emergent herbicide.

RE: Pre-emergent herbicide for perennial beds?

  • Posted by corrine1 7b Pacific Northwest (My Page) on
    Fri, Jul 6, 12 at 1:34

2nd the mulch & no herbicide
cut seed heads often

creative weed control ideas?
more mulch
more plants closely spaced (no soil or mulch is visible this time of year if planted closely
be creative with what works as mulch for you to cover all soil esp. during the growing season

some ideas to try
-straw, a bale goes a long way (beware if fresh will be a bit slippery if thickly spread)
-hay sweepings from the feed store (they put in a dumpster usually & let you remove free when asked. I wear a mask, gloves, & coveralls or a large jacket. I prefer to bring my my own D handle garden fork to remove it & put in garbage cans or bags. I clean up after I'm done, so it isn't an inconvenience to them. I've not been refused as long as they have a supply. Also, haven't had a big weed problem from using it mostly as a bottom layer, so cover if you're concerned about seeds.
-dried grass clippings (herbicide free) as well or mown over perennial waste from cutting back after blooming, trimming, etc. (compost seed heads separately unless you want seedlings)
-conifer needles (cedar is prolific in dropping dead needles, pines are drop a lot & slow to decompose)
-used coffee grounds (free from St*rbucks & better results if you call ahead)
-newspaper overlapping 10 sheets as a layer & flat with a light layer of other mulch to cover
-dried leaves (from maple saplings or other deciduous hedge material. I pull backward up the stem to remove maple leaves several times a growing season on big leaf maples we've cut down but stumps keep sprouting)
-if larger areas like pathways use cardboard, burlap, or upturned carpet. Might not need to top it, but can add wood chips if you have them.

Possibly you know someone with the conifers who would appreciate you raking & cleaning up the area underneath the trees. Likewise about the grass clippings. With the dry weather now the grass should dry quickly on a tarp. I spread some lightly today without drying them 1st around the zucchini plants, then later around garden edges, but it should dry just fine by tomorrow. Don't spread thick. I'll stir it a bit and keep an eye on it. I just didn't want to bother with a tarp today and was doing 3 loads from the meadow.

RE: Pre-emergent herbicide for perennial beds?

My neighbor spread fresh grass clippings about six inches thick all along his beds adjoining our property and the smell is horrific. We can even smell the rot in our house and it isn't a nice forest compost smell it is disgusting.

RE: Pre-emergent herbicide for perennial beds?

The entire point behind pre-emergent pesticides is that they won't damage or harm existing ornamental plantings, although Casoron (dichlobenil) has a somewhat different mode of action and can/does prove harmful to some established plants in full growth mode. Besides, it's nasty stuff, anyway :-)

Preen (trifluralin) is quite effective for weed prevention around ornamentals and will not harm existing plants. Its mode of action is as a seedling growth inhibitor and actually prevents seed germination. If you prefer to keep organic around edibles, Preen for Veggies is corn gluten meal, which is sold as an organic pre-emergent under a variety of labels. CGM's mode of action is slightly different - disruption of root development on seedlings - and I have not found it to be as effective/efficient as the more potent chemical products. But perfectly safe and a low grade organic fertilizer as well.

Any kind of mulch will help to suppress weed development and karchita's method is pretty much what I follow as well. Refresh the mulch as needed (compost prob more often than wood chips) and you should be good to go.

RE: Pre-emergent herbicide for perennial beds?

  • Posted by corrine1 7b Pacific Northwest (My Page) on
    Sat, Jul 7, 12 at 12:08

Yes fresh clippings smell pretty bad & are bad for plants.

However, if you dry the grass on a tarp 1st they don't. Think hay on a small scale. I usually do it a few times in spring when the clippings are plentiful and store in a garbage can in the back of the vegetable garden.

Now with summer weather it can be done in one day if not too thickly on the tarp.

RE: Pre-emergent herbicide for perennial beds?

  • Posted by botann z8 SEof Seattle (My Page) on
    Sat, Jul 7, 12 at 13:28

GardenGal, I agree that Casoron is a bit nasty. It's supposed to be used around woody plants only, and then with a mulch over it. The problem I see is maintenance gardeners spread it around and don't cover it with a mulch. Then people, dogs, and even lawn mowers track it on to lawns. Not good!

I knew a rhododendron grower on the Olympic Peninsula who spread it on the ground around his field rhododendrons without covering it. The gas produced, when it got wet, 'burned' the lower leaves of his plants. That's why a mulch is needed to trap the gas. Yeah, it's nasty.

Some landscapers use it for initial weed control for new installations, and meant as a one time application under mulch. I use to use it on landscape jobs once in awhile when I couldn't spray the weeds before installation.
Oh, and it leaches, even when covered by a good layer of mulch. That happened to me once when it leached down onto a lawn and took out a 20 ft. X 40 ft. swath in a customer's back yard. I had dug a swale to divert the seepage, but it still soaked past it. I had to remove the lawn as well as the soil and replace it. That was an expensive redo on my part. It was a long wheelbarrow trip. I should say, many trips.
Here, at home, I use woodchips for weed control and glysophate for initial control....and I still pull weeds!

RE: Pre-emergent herbicide for perennial beds?

  • Posted by bboy USDA 8 Sunset 5 WA (My Page) on
    Sat, Jul 7, 12 at 18:04

Dichlobenil said to have been identified originally as a way to keep roots from growing out of balled in burlap stock being stored in sawdust beds.

RE: Pre-emergent herbicide for perennial beds?

  • Posted by botann z8 SEof Seattle (My Page) on
    Sat, Jul 7, 12 at 23:46

Sometimes sold as Norosac, Casoron spelled backwards.
Remember Serutan?

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