NC State Extension Publications

Description

Knawel is a winter annual which, when it first germinates, may go unnoticed because of its grasslike features. It closely resembles parsley-piert and lawn burrweed. It is a freely branched plant with spreading stems. Leaves, clasping the stem, are opposite, linear, less than 1 mm wide, and sharp-pointed. The very inconspicuous flowers are clustered in the leaf axils. They are small, green, lacking petals, and somewhat spiny to the touch.

Cultural Control

Winter annual broadleaf weeds germinate in the fall or winter and grow during any warm weather, which may occur in the winter, but otherwise remain somewhat dormant during the winter. They resume growth and produce seed in the spring and die as temperatures increase in late spring and early summer. They quickly invade thin turf areas especially where there is good soil moisture. Shade may also encourage growth. Many have a prostrate growth habit and are not affected by mowing. A dense, vigorous turf is the best way to reduce the encroachment of winter annual weeds. First, select adapted turfgrass cultivars for your area and then properly fertilize, mow, and water to encourage dense growth.

Chemical Control


Herbicide and Formulation Amount of Formulation per 1,000 sq ft Amount of Formulation per Acre Pounds Active Ingredient per Acre
Preemergence and Postemergence Control
mesotrione, MOA 27 (4 SC) (Tenacity) 0.092 to 0.183 fl oz 4 to 8 fl oz 0.125 to 0.25
Precaution and Remarks: Use on residential turf, golf courses (not greens) and sod farms for pre- and postemergence weed control. Tolerant turfgrasses include St. Augustinegrass, centipedegrass, tall fescue, fine fescue, Kentucky bluegrass, and perennial ryegrass. Add a nonionic surfactant and repeat application after 2 to 3 weeks for improved postemergence control. Tank mix with prodiamine 65 WG for extended preemergence grassy weed control. Can be applied at seeding to all tolerant grasses except fine fescue. After turf germination, wait 4 weeks or until turf has been mowed twice before making a postemergence application. Also controls henbit, chickweed, dandelion, white clover, Florida betony, Florida pusley, ground ivy, oxalis, wild violet, creeping bentgrass, and yellow nutsedge.
[sulfentrazone + prodiamine], MOA 14 + 3 (4 SC) (Echelon) 0.184 to 0.826 fl oz 0.5 to 2.25 pt 0.25 to 1.125
Precaution and Remarks: For use in residential and institutional lawns, athletic fields, sod farms, golf course fairways and roughs, roadsides, utility right-of-ways, railways, and industrial areas. Apply to turf following a second mowing if a good root system has been established. Apply up to 12 fluid ounces per acre to bentgrass at 0.5 inch or higher, fine fescue, and perennial ryegrass. Apply 18 to 24 fluid ounces per acre to perennial bluegrass, tall fescue, and all warm season grasses except St. Augustinegrass (do not apply) and bermudagrass (apply 18 to 36 fluid ounces per acre). For sod production, apply 6 months after establishment, and do not harvest within 3 months. Do not apply with adjuvants or surfactants. [Sulfentrazone + prodiamine should not be applied to cool-season turf with N-containing fertilizers unless some short-term discoloration is tolerable.​
Postemergence Control
dicamba, MOA 4 (4 SL) (various brands) 1 to 2 tsp 0.5 to 1 pt 0.25 to 0.5
Precaution and Remarks: Apply as foliar spray to growing weeds. Prevent injury to ornamentals. Avoid rooting zone of shallow-rooted trees and shrubs.​
diglycolamine, MOA 4 (4 SL) (various brands) 1 to 4.5 tsp 0.5 to 2 pt 0.25 to 1
Precaution and Remarks: Do not exceed 1 pint per acre on bentgrass, carpetgrass, buffalograss, and St. Augustinegrass. Apply to newly seeded grasses after the second mowing. Do not exceed 0.25 pint per acre on extended sensitve plant roots on sandy soils and 0.5 pint per acre on clay soils.​

Species Data

Knawel growth habit.

Figure 1. Knawel growth habit.

Knawel growth habit.

Figure 2. Knawel growth habit.

Knawel growth habit.

Figure 3. Knawel growth habit.

Knawel growth habit.

Figure 4. Knawel growth habit.

Knawel growth habit.

Figure 5. Knawel growth habit.

Knawel growth habit.

Figure 6. Knawel growth habit.

Knawel growth habit.

Figure 7. Knawel growth habit.

Knawel growth habit.

Figure 8. Knawel growth habit.

Knawel growth habit.

Figure 9. Knawel growth habit.

Knawel growth habit.

Figure 10. Knawel growth habit.

Knawel leaflet number.

Figure 11. Knawel leaflet number.

Knawel leaflet number.

Figure 12. Knawel leaflet number.

Knawel leaflet shape.

Figure 13. Knawel leaflet shape.

Knawel leaflet shape.

Figure 14. Knawel leaflet shape.

Knawel leaflet shape.

Figure 15. Knawel leaflet shape.

Knawel leaflet shape.

Figure 16. Knawel leaflet shape.

Knawel leaflet shape.

Figure 17. Knawel leaflet shape.

Knawel flower color.

Figure 18. Knawel flower color.

Author

Professor and Extension Turfgrass Specialist
Crop and Soil Sciences

Publication date: Nov. 21, 2017

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