Prostrate Knotweed (Polygonum aviculare)
Prostrate knotweed is a summer annual that is low-growing and does well in compacted high traffic areas like shortcuts across a lawn. The flowers of prostrate knotweed are very small and white.
Soil conditions that favor growth:
- Acid (low pH)
- Compacted or heavy
- Soil test (adjust soil acidity up with lime, based on PH reading)
- Thicken lawn by planting grass in any thin or bare lawn areas
- Aeration, compost topdressing
Remedy: Post emergent control in spring when actively growing.
Prostrate knotweed is a broad leaved, slow growing annual. The weed germinates early in spring and branches widely on ground. They may extent a foot or more in length, and can extend to 2 feet in length. The weed features a thin and white root. Leaves are small, oval shaped and blue green in color and the stems are wiry branched. A small papery sheath is attached to stem at same point where leaf is attached.
Hard, compacted and poorly aerated soil facilitates the weed growth. The weed is common to sunny areas in lawn. Prostrate knotweed is basically a salt tolerant weed.
To control Prostrate knotweed you need to care fully implement the cultural practices. Soil tests and soil compaction are very important. A Pitchfork or spading fork can be used to relieve soil compaction. The ground should be neither dry nor soggy. Push the fork in about 6 inches to 12 inches in the ground. For large area, plugger or core aerator should be used to remove plugs. You can take help of lawn services firm to do the work for you. To aerate soil best time is from 20th August to 15th September.
Mowing in hot conditions and deep watering can reduce knot weed growth. Try to fertilize the soil before the fall season. The herbicide use to control the weed is a mix of 2-4,D and MCPP. Dicamba can also be used as herbicide to kill the weed. This is recommended to spray knotweed in spring and to get a better result, spray when wind is calm, temperature is between 500c to 800c. Pre-emergent herbicide like isoxaben can is highly effective to kill the weed.