Whether from rainfall or from your hose, the average lawn requires one inch of water per week. Most lawns receive far more than that, resulting in a lack of oxygen for the roots, disease and weeds. In fact, overwatering your lawn is like sending an engraved invitation to some invasive plants.
This plant loves moisture. It's a creeper with clover-looking leaves in either green or maroon. The flowers are tiny, yellow stars that bloom all year long. The seeds of the creeping woodsorrel are sticky so they will cling to clothing and machinery and are thus easily spread. According to researchers at the University of California, the best way to manage creeping woodsorrel is to hand pick the weed and use a preemergent herbicide on the seeds.
Speedwell is an annual plant with small, blue flowers that likes shade and moist soil. Speedwell has a prolific tendency, with the average plant producing 2,000 seeds and large plants bearing up to 7,000 seeds. Raising the mowing height may help to control speedwell as will additional exposure of the plant to the sun. Herbicides, for large infestations, may be required.
A veritable seed-production machine, annual bluegrass thrives in wet soil and grows very quickly, to 15 inches in height. At the top of the stalks rests the white seed heads. This plant prefers cool weather and will die back when it gets hot. The seeds, however, lie dormant until the moisture level of the soil increases, when they will germinate and take over once again. Annual bluegrass is a tough weed to fight. Try limiting the amount of water you give the lawn. If that fails to work, seek the advice of your area cooperative extension agent.
Herbicides can be toxic. Read and follow all information on herbicide labels.