Most lawn chickweed weeds are winter annuals, meaning they will soon die out on their own as we move out of spring into summer. They do not need herbicide treatment now, but since their seeds germinate in autumn, that is the time a pre-emergent would be most useful. Dandelions are perennials, so need to be manually removed or spot-treated with a post-emergent systemic herbicide, which will be absorbed to kill the roots.

Fortunately, neither weed tends to be a major problem in lawns that are maintained with recommended practices, so over the long term, you can avoid a reliance on herbicide by: overseeding the lawn each autumn using one or more of the recommended cultivars; core-aerating just prior to overseeding if the lawn soil is compacted; periodically getting a laboratory soil test done to know how best to fertilize or apply lime; and mowing high so the grass shades-out most weed seeds to prevent germination or establishment.

Overseeding cool-season lawns like tall fescue is best done in late summer or early autumn, not in spring. There are various reasons for this, but they include greater competition with weed seed and colder soil slowing establishment of the young grass plants. A number of pre-emergent herbicides used to prevent weed seed germination will also affect grass seed germination, so the two might not overlap well. Areas that might be too weedy to overseed, or which have developed bare patches, can have sod put down instead, since it needs a shorter establishment time and essentially gives you a weed-free patch of lawn for the first year or two (as long as it continues to grow well). Both seed and sod cannot dry out while it is establishing, though seed will need more frequent watering (or monitoring) compared to sod.

Lawns that are growing well and which were fertilized the prior autumn should not need a spring fertilization. If spring fertilizing is warranted, the chart on the page linked above produces information about how much to apply (per thousand square feet of lawn area). Maryland law limits how much nitrogen and phosphorus can be applied over the course of a year for home lawns, in order to reduce Chesapeake Bay pollution.

Miri