Tips for Managing Weeds in the Landscape, Lawn and Garden

FOR IMMEDIATE RELEASE
June 23, 2008

While weeds are a fact of life for the home gardener, understanding types of weeds and how they grow can help us choose the best way to manage them more effectively.

The two major categories of weeds are broadleaf types such as dandelions and grassy weeds such as crabgrass. Either type can have an annual life cycle, meaning it grows, goes to seed and dies in one season, or it is a perennial, meaning it re-grows year to year. Perennial weeds usually sprout from an underground plant part such as a rhizome. A less common life cycle is the biennial weed that grows in one season, over-winters, then flowers and goes to seed the next spring.

Cultural weed control is done without the use of chemicals. These methods include hand-pulling and cultivation, flaming with a hand-held propane torch, and reducing weeds in the soil by avoiding introduction of weed seeds (in manure and hay) and never allowing weeds to go to seed. Barriers such as fabric, mulch and replacing soil with sterilized soil mixes in containers and raised beds can also be effective.

Chemical control of weeds focuses on stopping weed seed germination through the use of a pre-emergent herbicide such as Preen^TM or by spraying existing weeds with a post-emergent product, such as Roundup^TM. When using these products, always read the labels to determine which weeds and weed types they will control, and to determine proper application times. Proper timing is essential to achieve maximum effectiveness.

Crabgrass is an annual grassy weed that germinates in the spring when soil temperatures reach 60 or more degrees. Thus, a timely spring application is needed. If applied too soon, they will lose their effectiveness before weeds germinate. Winter annuals like henbit and chickweed in turf germinate mid-fall, as soils cool, grow slowly over winter and set seed in spring. A well-timed early fall application using a pre-emerge herbicide can prevent their becoming established.

Post-emergence products can kill on contact only or by being absorbed into the plant's system to kill underground roots. Post-emergence products can also be selective or non-selective as to type of weeds controlled, usually selective materials kill grass or broadleaf weeds.

For lawns, both grassy and broadleaf weeds can be a problem. In addition to using well-timed pre-emerge materials in spring and fall, selective post-emerge materials such as 2,4-D and dicamba can be applied to turf without injuring grass. These are often sold with fertilizers as a dry product that sticks to leaves.

In landscape and perennial beds, it is best to use cultural methods. In new beds, an application of Preen^TM can be a valuable tool. Take care if using a post-emerge product such as Roundup^TM as a spot spray; even a slight breeze can case spray to drift and damage surrounding desirable plants.

Cultural control is the best in vegetable gardens, since pre-emerge products may affect any seeds sown directly into the ground. Perennial weeds and invasive plants are especially challenging. Using Roundup^TM or 2,4D are most effective, but must be used in well-timed applications and the proper product matched to the proper weed. 2,4-D is only effective on broadleaf weeds.

Controlling weeds does not have to be an overwhelming task, and with the proper approach and tools, can be easily managed, thus maximizing the beauty of your landscape and the productivity of your garden. For more information on weed and pest control, visit the University of Illinois website http://web.extension.uiuc.edu/state/hort.html or contact your local Extension Office.