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Pre-M on flower beds

Discussion in 'Pesticide & Herbicide Application' started by turfcare, Feb 18, 2003.

  1. xpnd

    xpnd LawnSite Senior Member
    Posts: 378

    Some types of pre-emergents such as simazine, can not be put down on beds with evergreen shrubs. Simazine will burn the foilage of larger shrubs and will outright kill smaller ones if applied at the high end of the app rates. The label will indicate weather it is restricted to dormant plant/turf apps only.
  2. greenman

    greenman LawnSite Addict
    Posts: 1,405

    Yeah, forgot about simazine. Simazine, as well as Atrazine are, I thought, more commonly used for poa annual control and winter weeds, not as a pre-m for spring application. I meant like pendimethalin or dithiopyr, the more commonly used.
  3. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    Treflan is trifluralin; works OK on a couple of dozen, mostly grassy, weeds. Snapshot is trifluralin + isoxaben, controls over 100 grassy and broadleaf weeds. Not much of a difficult choice, LOL.

    And if you know how to mulch or renew mulch properly, a preemergent under the mulch is a wasted application in most cool season areas.

    UTM-PIKE LawnSite Member
    Posts: 65

    I was wandering what you meant by applying mulch properly. Do you mean 3-4 inches instead of 1-2 ??? I was getting ready to apply and mulch in middle Tennessee and didnt want to if not needed, but this is the transition zone betw/ warm and cool season. Please elaborate.
  5. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    It used to be that you got hardwood shredded bark mulch composed basically of tree bark, stripped off of logs at lumber mills. This product was true shredded bark, with very little wood content. In fact, specifications of national bark and soil manufacturers had a rule that product could not be labeled "shredded bark" if wood content was more than 15%. And today they grind up wood pallets and call it mulch, LOL.

    When you applied this product (shredded bark) on a new site, on bare soil, you applied at 3" deep. This would smother any weed seeds; once they germinated, they could not get light to grow. By the following spring, decay had reduced bark depth to 2" or less, and weeds seeds had blown into beds from summer weeds in the fall, thus sitting on top of the bark. So you would renew in spring with 1" to 1½" of new shredded bark. Following years spring renewal was 1", and you watched to make sure bark depth did not exceed 3". If the 1" was applied EVENLY, no weed seeds would be able to grow, because they do not have energy to grow up 1" before getting sunlight. Only things that would grow were tree seeds, because they have energy to grow up 4" to 8" thru a carpet of leaves in the forest. A preemergent was a waste then, if you applied your shredded bark properly.

    Now remember, shredded bark and mulch are not synonymous. A mulch is just a cover over bare soil. You can mulch with shredded bark, wood chip refuse from a tree service, gravel, pine straw, or many other products. BUT, in using coarser products, like gravel or ground up wood pallets, you do not get the blocking of sunlight to the weed seeds you are covering. Enough light can filter through 4" of coarse gravel to allow weeds that deep to survive. I do use a lot of Snapshot in gravel beds in parking lot islands.

    In the last 20 years, the availability of true shredded bark has just about vanished. Many suppliers will call their product "shredded bark", but in fact is is mostly wood, not bark. And wood chunks will not give you the compact, light stopping quality of shredded bark, or other finely ground products. During the late 80s and all thru the 90s, the price of "shredded bark" here did not go up at all. What was happening was that the bulk suppliers were just cutting more wood refuse into it each year. In some cases whole trees, or large limbs, are ground up for mulch.

    To me, a proper mulching is using a product that will block sunlight as I noted above. And the persons spreading it have to spread it evenly to get the effect of weed control from that mulch. For the last 10 years, the only way I have been able to get the mulch product I want is to buy bulk "shredded bark", and then grind it myself to the consistency I want for mulching my beds. (And I spend a lot of time looking for product with least amount of wood in it.) Our city organic waste recycling grinds brush to use for mulching. This product, at $4/cuyd, is much more effective than the $23/cuyd junk that is fobbed off on the green industry here.

    You just have to look around at what is available, and I guess even then you might be stuck with using a pre-emergent along with your mulch. But if you can find a proper mulch, to be effective at the depth you are applying, and you can apply it evenly, a preemergent is not necessary.
  6. turfcare

    turfcare LawnSite Senior Member
    Posts: 276

    Hey Guys,
    I appreciate all the helpful information, you have been a big help!
  7. Trav

    Trav LawnSite Member
    Posts: 56

    Does anyone know the sq ft coverage of snapshot and ronstar per 50lbs bag? thanks
  8. goose

    goose LawnSite Member
    Posts: 177

    Snapshot!!! 17,000 sq ft per 50 lb bag
  9. GroundKprs

    GroundKprs LawnSite Bronze Member
    Posts: 1,969

    For chemical coverage, go to http://www.cdms.net/manuf/acProducts.asp or to http://www.bluebooktor.com/asp/free_b.asp to read it right off the labels. Rates vary with location and desired use.

    And it can be beneficial to switch chemicals after a few years. Most all chemicals are degraded by soil microbal activity. If you use the same chemical, or chemical family, year after year, you are increasing the population of the specific microbes that degrade that chemical. And you are then accelerating the breakdown of your future applications.

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