Flower Bed and Vegetable Garden Weeds

Weed control in flowerbeds is distinguished from weed control in other areas of desert landscapes by the nature of the desirable plants. Instead of the large or woody perennial ornamentals found elsewhere in the landscape, flowerbeds typically contain small herbaceous, flowering, broadleaf species planted at high densities. The herbaceous nature of the plants and the high density makes it much more difficult to direct the spray of non-selective, postemergence herbicides and avoid injuring desirable plants. For this reason, the use of mulches for weed suppression in flowerbeds is an especially good strategy. If the number of weeds emerging in the flowerbed is small, then hand pulling of weeds or careful spot spraying of postemergence herbicides without the use of preemergence herbicides may be the best weed control strategy. This is especially true if the problem weeds are mostly grasses because grass weeds can be selectively removed from herbaceous flowering plants fairly easily.

If high weed seed populations are present in the flowerbed, the use of a preemergence herbicide is warranted. It is easiest to apply preemergence herbicides such as dithiopyr, oryzalin, pendimethalin, and prodiamine prior to transplanting desirable herbaceous ornamentals into the flowerbed. These herbicides remain near the soil surface and don't affect the roots of transplants. Alternatively, granule herbicide formulations such as Amaze (benefin plus oryzalin), Pendulum 2G (pendimethalin) or Snapshot 2.5TG (trifluralin plus isoxaben) can be applied after transplanting and incorporated using water. Granule herbicides should be applied after the soil around transplants has been watered and has settled so that the roots of transplants are not exposed to herbicide granules. In addition, the foliage of desirable plants should be dry so that herbicide granules fall to the soil surface. As discussed above, benefin, dithiopyr, oryzalin, pendimethalin, prodiamine, and trifluralin all control grasses and small seeded broadleaf weeds. Isoxaben controls many broadleaf weeds, thus, Snapshot 2.5TG herbicide may be a good choice if it is anticipated that many broadleaf weeds will emerge in the flowerbed. A granule formulation of EPTC can be used after desirable plants are established if nutsedge species will emerge in the flowerbed. EPTC also suppresses grasses and some broadleaf weeds. EPTC provides short-term (about 4 to 6 weeks) weed control because it degrades rapidly in the soil. It must be incorporated or moved into the soil immediately after application because it readily turns into a gas (i.e., is relatively volatile). All of the herbicides discussed in this section with the exception of EPTC should be applied at low rates if the flowerbed is going to be replanted within a few months. If the flowerbed is planted with seeds, preemergence herbicides should be applied after planting seeds and after the irrigation that germinates the seeds to avoid affecting the flowers.

The use of foliar-applied postemergence herbicides in flowerbeds is a challenge because flowerbeds typically contain small herbaceous, broadleaf species planted at high densities. The easiest weeds to control in flowerbeds are grasses since they can be controlled using clethodim, fluazifop and sethoxydim. These selective, foliar-applied, translocated herbicides control grasses but not nutsedge or broadleaf species so they are especially effective for removing grasses from flowerbeds without harming the desirable plants. Both contact and translocated non-selective herbicides such as diquat, glufosinate, pleargonic acid, and glyphosate must be carefully sprayed or directed so that desirable foliage is not contacted. In addition to using a sprayer, other techniques can be used to apply postemergence herbicides to weed foliage and avoid herbicide contact on desirable foliage. For example, a light-weight cotton glove worn over a rubber glove can be dipped in a solution containing glyphosate and then used to wipe weed foliage around small flowering plants. Alternatively, wearing rubber gloves for protection, a sponge can be dipped in a glyphosate solution and used to wipe weed foliage or a paintbrush can be used to apply the herbicide to weeds. These application techniques work best with translocated herbicides because complete coverage of the weed foliage is not required for control.

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