Webster defines weed as a plant that is out of place. In a corn field grass and clover are weeds; in a hay field volunteer corn or a small grain are weeds, in turf crabgrass and foxtail maybe the weeds. In most cases some type of a plant protection chemical is used to get rid of the weed. Sometimes this is only a temporary cure to improve the situation, after the effects of the treatment where off and the problem returns.
Dr. Sid Bosworth, University of Vermont, did some work and found that there are other factors that contribute to certain species of weed growth. Dr. Bosworth work is summarized in the following table.
| Weed | Conditions |
|---|---|
| Algae | Excessive surface moisture |
| Annual Bluegrass | Excessive surface moisture, compaction, mower too low, high nitrogen |
| Barnyardgrass | Poor drainage |
| Birdsfoot Trefoil | Droughty conditions, low nitrogen |
| Black Medic | Droughty conditions, low nitrogen |
| Broadleaf Plantain | High pH, compaction |
| Buttercups | Poor drainage |
| Chickweeds | Mower too low |
| Cinquefoil Species | Droughty conditions, excessive surface moisture, low pH, general low fertility |
| Clover Species | Low nitrogen |
| Coltsfoot | Poor drainage, low pH |
| Common Chickweed | Too shady |
| Common Mullein | Low pH, general low fertility |
| Corn Chamomile | Poor drainage, high pH |
| Corn Speedwell | Compaction |
| Crabgrass | Droughty conditions |
| Creeping Bentgrass | Poor drainage, excessive surface moisture, mowed too low |
| Creeping Speedwell | Too shady |
| Creeping Thyme | High pH |
| Curl Dock | Droughty conditions |
| Docks | Poor drainage, low pH |
| English Daisy | Low pH |
| Foxtail Species | General low fertility |
| Goosegrass | Droughty conditions, compaction |
| Hawkweeds | Low pH, general low fertility |
| Henbit | General low fertility |
| Hop Clover | High pH |
| Knawel | Low pH |
| Lady's Thumb | Poor drainage, low pH |
| Leafy Spurge | Doughty conditions |
| Mallow | General low fertility |
| Moss | Excessive soil moisture, mowed too low, too shady |
| Mouse-ear Chickweed | Too shady |
| Nutsedge | Poor drainage |
| Pigweed | Droughty conditions |
| Pineapple Weed | Compaction |
| Plantains | Poor drainage, mowed too low |
| Prostrate Knotweed | Compaction |
| Prostrate Spurge | Droughty conditions, compaction |
| Rabbit Foot Clover | Droughty conditions, low pH, high pH |
| Sheep or Red Sorrel | Low pH |
| Speedwell | Droughty conditions, mowed too low |
| Vetch Species | Low nitrogen |
| Wild Carrot | High pH, general low fertility |
| Wild Parsnip | General low fertility |
| Wild Radish | General low fertility |
| Wild Strawberry | Low pH |
| Yarrow | Droughty conditions |
| Yellow Woodsorrel | Droughty conditions |
Source: Bosworth, Sid. 1998. Using Plants as Indicators for Diagnosing Soil and Turf Problems. Turf Notes, Vol. 7, No. 2, p. 1-5. New England Extension Systems, Un. of Massachusetts Extension.
While there maybe other factors involved other than the ones listed, these are some general guidelines and conditions that can occur and be corrected relatively easily and inexpensively.