#630 Preventing Weeds with Pre-Emergent

Eliminate the problem before it starts

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One of the biggest problems in flower and vegetable beds, in lawns and around shrubs is the eventual presence of weeds. Fortunately, weeds aren’t inevitable! There are products available to help gardeners prevent them. These are known as pre-emergent herbicides. Using pre-emergents is the most effective way to stop weeds while posing little or no danger to desirable plants. These herbicides work to keep weed seeds from germinating or kill newly germinated seeds before they make it to the soil surface. Regular use of pre-emergents lessens the need to use weed killers (post-emergents) to get rid of actively growing plants. Raking, cultivating and aerating should be done before the pre-emergent is applied. Normal activities such as irrigation, mowing, fertilizing and foot traffic will not decrease effectiveness.



CONTROL IN FLOWER AND SHRUB BEDS: Pre-emergent herbicides are excellent for use in perennial flower beds, shrub beds and around landscape ornamentals. Using them in mixed bulb and flower beds may cause minor damage to emerging bulb foliage but shouldn’t have any lasting effects. Avoid this altogether by applying the herbicide after bulbs have come up. When using in annual flower beds, remember that pre-emergents are not compatible with seeds, including flower seeds. Use rooted transplants to fill these beds, wait a couple of weeks to establish them, then use the pre-emergent.


Benefin 1.0 (sold as AMAZE®) can provide protection up to 4 months. Apply according to package directions around listed flowers and shrubs.


Oryzalin (sold as Weed Impede™) is a liquid concentrate to be mixed and used as a pre-emergent, surface applied herbicide for label listed landscape ornamentals, bulbs and groundcovers. Prevents weed from 2-8 months depending on solution strength. Try this one under weed block fabric or landscape rock in areas you want to remain weed-free.


Trifluoromethyl combined with Dithiopyr (sold as Dura Turf) provides excellent prevention of broadleaf weeds and crabgrass in ornamental beds and lawns.


CONTROL IN VEGETABLE BEDS: Choices are limited. While another pre-emergent may control your weed problem, remember you’re dealing with edibles here. Be sure the package specifies vegetables!


Trifluralin (sold as as Preen®


CONTROL IN TURF: A wide variety of pre-emergents can be used on turf grasses. Pay close attention to label instructions for your kind of grass. A summary of these products follows:


Dimension® (Dithiopyr) does an excellent job of preventing broadleaf weeds, crabgrass and other grassy weeds in most turf grass lawns. Apply in late January through February or from mid October through November. Limit application in the same area to once a year.


Surflan® is effective up to 8 weeks for each application. Do not use on bentgrass or at the higher rate on fescue.


Trifluoromethyl combined with Dithiopyr (sold as Dura Turf) provides excellent prevention of broadleaf weeds and crabgrass in lawns and ornamental beds.


If weeds do get the upper hand in your lawn, flower beds or landscape ornamentals, see the friendly folks at any Star Nursery location for help in selecting the right product to get rid of them.