Weed Control


One of the most time-consuming jobs in our landscapes is trying to keep our lawns and gardens free of weeds. There are a number of chemicals that are available to use to help with this pain-staking chore. Most of us do not like using any more “chemicals” around our properties than we have to, for fear of them being toxic to our kids, our pets, and the environment. Pre-emergent herbicides have been put under stringent tests by environmental organizations and no safety issues have been found with these products. If you would compare these tests with the same tests done on common table salt you would be very surprised. There are some terms we need to discuss when talking about herbicides. They are:

· Pre-emergent
· Post emergent
· Selective
· Nonselective

These are all terms to describe how synthetic herbicides work to control unwanted plants or weeds. A pre-emergent herbicide will affect the tiny first roots of seedlings thus preventing them from growing, while post emergent herbicides are used on weeds that have germinated or hard to kill weeds such as Canadian thistle. Selective herbicides are used to remove some species of plants and not others. A nonselective herbicide will kill any plants it is applied to; a good example of this is Roundup. While all herbicides help to control weeds, knowing what type of weeds you need to eliminate will help you in selecting the right products to use. Contact us at River Valley Landscaping and we can help you design the right program to achieve optimum weed control.


For best results when using pre-emergent herbicides timing is everything. These products should be applied several weeks before germination, and watered in after application so this material can move in the top inches of soil to create a weed barrier. Weed seeds will germinate when soil temperatures are consistently over 50°F. Some gardeners prefer to apply pre-emergent before the Forsythia blooms. In southeast Pennsylvania pre-emergent herbicide should be applied around the 15th of March to control spring and summer weeds and reapplied by September 15th to control fall and winter weeds.

These chemicals can be applied any time during the growing season to control ungerminated seeds. Pre-emergent products have a life of between 60 and 90 days depending on the amount of moisture and soil content. Multiple applications can be made, be sure to read the label so you are not over applying beyond the recommended rates. These products can build up in the soil if overused and can burn root system of many plants.

Preen vs. Snapshot

Preen is a pre-emergent that is found in a lot of garden centers and box stores in the area. Trifluralin is the active ingredient in Preen; it is also the active ingredient in Snapshot but at a much higher rate. Snapshot also has another active ingredient Isoxaben, which gives this product extra protection against some difficult weeds and grasses. Snapshot is the preferred choice of many nurseries and landscape companies because of its wide label. Only select dealers sell these professional products in larger quantities. If you analyze the price of the two products, Snapshot is cheaper per 1,000 square feet and has that wider label.

One of the hardest weeds to control is Nutsedge mainly because one single weed is capable of dropping thousands of seeds. Knowing how to identify this weed and its life cycle is very important in its control. There is a pre-emergent herbicide labeled just for this weed called Freehand.

Since March is not a very busy time in the garden, set aside some time to apply some pre-emergent or contact us at River Valley Landscaping to have it professionally applied for you. Pre-emergent herbicides will not control 100 percent of your weeds, but it should reduce the amount of hand pulling and the amount of more toxic post emergent herbicides you should have to use. Giving you more time to sit back and enjoy your garden.