WE KNOW TURF: What Is A Weed?

Webster defines a weed as a plant of no value, a plant of detrimental quality, or any plant growing out of place, where it is not desired.

Most weeds possess a vigorous capacity for growth and survival under adverse conditions. Some weeds are found nationwide, while others adapt themselves only to certain areas of the country. Research has given us the means to selectively control, chemically, a large majority of these pests.

Most weeds in lawns come from seeds present in the soil. These seeds can remain inactive 50 years or more if for some reason they don't receive the conditions they need for growth. Generally, when the soil is cultivated for planting or repairing bare spots, the weed seeds then receive the warmth, light and moisture they need to germinate and mature.

Topsoils, manures and composts usually contain an abundance of weed seeds. A new crop of weeds can be expected whenever these additives are used. The possibility of introducing weeds in to the soil from sterilized soil, properly cleaned lawn seed, or fertilizer, is practically non-existent.

There are two main types of selective herbicides commonly used in lawn care. One group is the pre-emergent type that prevents the seed of annual grass-type weeds like crabgrass from growing. The other group is the postemergent type that doesn't prevent the seed from developing, but destroys the weeds after they are actively growing in the lawn.

Pre-Emergence herbicides are basically soil-applied materials that create a chemical blanket or barrier at the soil surface. These herbicides are used predominately to control annual weeds in turf grass areas. The herbicide is absorbed by the germinating seed or by the young shoot and/or root of emerging weeds.

Ideally, all pre-emergence turf herbicides should be applied one to two weeks prior to weed germination. Soil temperatures can be a reliable guide to predict the germination time of Summer annual grasses. Crabgrass germinates when soil temperatures near the surface reach 55 to 60 degrees for several consecutive nights.

Biological indicators, such as certain flowering plants, are desirable in timing pre-emergence turf herbicide applications because soil temperature and moisture conditions vary from year to year.

All pre-emergence turf herbicides should be watered into the root zone soil where weed seeds are located to minimize loss from volatilization and photo-decomposition.

Soil longevity of the pre-emergence turf herbicides is not equal. Factors such as volatilization, degradation by ultraviolet light, microbial decomposition, and chemical decomposition, which are influenced by soil type, moisture content, temperature, microflora and method of application, affect disappearance of herbicides in the soil.

Pre-emergence herbicides are effective tools that provide good weed control and good safety when used judiciously and at reasonable rates. Post-emergence herbicides such as used in Warren's 25-3-3 Weed & Feed destroys weeds after thay are growing. The materials are dry, granular formulation and are applied ideally with a drop-type spreader. These materials must be applied to the foliage of the weeds so it will be absorbed into the plants. For optimum control, apply when foliage is wet from dew or sprinkling. Warren's 25-3-3 Weed & Feed is also effective when applied to a dry lawn. It is important for the granules to stick to weed leaves rather than fall to the soil. Use when daytime temperatures are between 50 and 80 degrees. Apply with a properly calibrated spreader. Use on a calm day so granules don't drift onto flowers and shrubs. Don't apply when rain is expected within 24 hours and withhold watering for 24 hours to avoid working the particles off the weed leaves.

Don't use on newly seeded or sodded lawns. Remember, these products don't work overnight. While leaves and stems should begin to twist and curl in just a few days, actively growing weeds will die out slowly. A month or more of good growing weatner may be required for complete control.

This product will not prevent weed seeds in the soil from producing new plants. Always follow label instructions.