Pre-emergent question

November 19, 2008

Categories: Growing Daffodils, Planting, Soil

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Hi all (esp you Keith!),


I was asked by a Master Gardener in Atlanta about using pre-emergents in a public planting where they’re putting in daffodils.

Both liquid and granular.

I’ve heard that the liquid is problematic in very sandy/porous soil, as it may not break down before moving down the soil column and hitting the daff bulb/roots.

But, what about granular applications?

I’m assuming they’d be sprinkling in the winter here… They’re trying to dissuade the City “community service” mowing crew from weed-wacking EVERYTHING they plant, so if there aren’t any weeds, well then! There’s no reason to hit everything with the weed-eater…

The soils where they’re planting is somewhat sandy clay. Some areas may be sandy  (downhill wash), but the uplands are good ol’ Georgia clay…




3 responses to “Pre-emergent question”

  1. Mary Lou Gripshover, Ohio Mary Lou Gripshover says:
    Hi Sara,
    I use Preen granular on clay soil.  Don’t know how it would work on sandy soil.  You can get it plain, or with a 9-17-9 fertilizer which is what I’ve been using lately on my garden beds.
    Mary Lou
  2. Keith Kridler says:

    The problem with Pre-emergent weed preventers in the southern USA is that winter weeds sprout for us in August after the first rain. Most of these weed preventers are temporary and we will have another major weed sprouting event with the first warm spell in January after all of the weed preventers have been dissipated by our heavy winter rains. Most of these actually only last about 6 weeks.
    Most pre-emergent herbicides will NOT kill or prevent weed seedlings from continuing to grow that are already 2″ tall (5 CM). VERY hard to put out the correct amount evenly.
    The pre-emergent weed preventers are in two classes. One for grass species and one for broad-leafed weeds. So it depends on what types of “weeds” you expect to have problems with your daffodil plantings.
    Preen for example sells several different types of weed killers and weed preventers under the Preen label. Be SURE you check label to see what is in your bag and check to see if it is listed to be used on daffodils!
    I pulled the following off the Preen website, read the whole link to see how difficult it is to apply this correctly. Again these products are tested “safe” for the listed plants ONLY IF applied so as not to exceed the maximum rate!!

    “”Preen Plus offers superior weed control because it combines the power of two preemergent herbicides. Isoxaben (Gallery®) provides excellent control of broadleaf weeds and Trifluralin (Treflan®) controls grassy weeds. Together they combine to provide the most broad-spectrum reliable weed prevention available.””

    They list this product as being effective on 150 species of weeds. There are 250,000 weed/plant species. Again these are tested at exact application rates too much or too little or applied a few weeks too late and you have little to no protection.

    After you apply these weed preventers you cannot disturb the soil as this exposes more weed seeds or breaks the chemical barrier.

    Thick organic mulches will prevent sunlight from germinating some weed seeds. These need to be applied annually in naturalized bulb locations.

    Maybe some others will tell what works for them or what has NOT worked. It also depends on if your bulbs will be planted in flower bed type locations or if they will be planted in full sun turf grass locations. Bulbs planted under deciduous trees where there is 100 percent shade in summer will have a whole different host of shade loving weeds to deal with as compared to even areas with 50% shade in summer. Soil PH is also a factor as clover species need higher levels of lime as do certain other species of weeds. Keith Kridler Mt. Pleasant Texas where the early tazettas are coming into full bloom.

  3. Lina Burton says:


    I’ve had good luck with the corn gluten-based weed preventers.  Timing is everything in putting them down. Here at my home in northern Virginia, mid-September seems to work best for me, and has kept the sprouting of winter weeds to a minimum.  When I haven’t used the preventers, I’ve had a definite winter weed problem.  I’ve also used them in the spring, usually about mid-April to mid-May, depending on weather, to keep down the crop of spring-sprouting weeds, and it works then too.
    As you said, it lasts for about six weeks, and while rain is useful in dissolving the granules, an extraordinarily heavy rain, like from a hurricane, tends to overdo it and you need to reapply if that happens.
    I’ve chosen the safer, corn gluten solution over possibly harmful synthetic chemicals because I have a collie and my neighbor has a sheltie, both of whom meander — and sometimes run — through my flower beds at will.  Thus, I’m reluctant to use anything out there that might get on their paws and cause them harm, when they come in and lick. (Amazingly enough, even at peak bloom and at a flat-out run, these two four-footed friends have never harmed a flower.  Either they’re careful where they put their feet or daffodils are mighty resiliant!)
    Lina Burton