Reseeding a neglected, weedy lawn
Hi there! I have a few questions about reseeding a lawn. My client's lawn is completely invaded with weeds (70%) with small patches of some tall fescue remaining (20%) with probably 10% dead space with nothing growing on the lawn. The lawn is roughly 5500 sq. ft, and I would like to completely revamp their lawn and plant new seed for them to manage for the summer. I have tested the soil and the pH is at about 5.5 and it is mostly depleted of all nutrients. I would like to use the cheapest and most efficient option of course, though I feel like there is a lot of work to be done. Where the fescue is growing it looks like there is a decent layer of organic matter-rich soil, roughly 3 inches or so. But where there are weeds the soil is almost completely what looks like your "dead" nutrient-poor Maryland red clay/silt mix. I would like to avoid having to amend the soil simply due to the input cost. If possible, I wanted to aerate or till the lawn completely and enrich the soil with granular nutrients and neutralize the pH a bit more. Then I wanted to reseed, water, and let the lawn takeover. I have a lot of knowledge of what I would want to do, but I need just a bit of directing on how to go about reseeding the entire lawn. Could you provide a few suggestions for me?
District of Columbia County District of Columbia
For lawns with about 50% or greater weed populations, it is best to simply renovate (re-do) the entire area, as is your inclination. This square footage is not so large here that the easiest approach is probably to till the weeds under (and to a lesser extent, aerate and loosen the soil) and lay sod on top. You can, certainly, wait a few days first to let the uprooted weeds desiccate if the weather will be sunny. The alternative is to rake out as much weed growth as possible and over-seed now, though that will entail more intensive weed control in the future, and pre-emergent herbicides and germinating grass seed don't mix. Sod will at least presumably start out weed-free and can then be managed, organically or otherwise, from then on to prevent their colonization or spot-treat those that do grow.
With regards to your mention of nutrient depletion, we cannot tell if you are getting those results from a lab assessment or home test kits. We recommend using a professional soil testing lab to asses the nutrient content before assuming fertilizer needs, though for the interim, a starter fertilizer would suffice to get sod/seed set up with an initial dose of nitrogen and phosphorus. If a professional test has not been done, you can use this site to view a list of area labs, bearing in mind that some may have closed temporarily due to non-essential business closures: https://extension.umd.edu/hgic/topics/soil-testing. Labs will give liming recommendations if the site is indicated to be for turf; otherwise, you will need to go by dosage recommendations (from your starting pH level) that are listed on the label of lime packages. (There are different formulations of lime, so you would need to check the label.)
Whether re-seeding or laying sod, we have tips on lawn renovations here, as well as a plethora of other lawn-care information on the associated pages: https://extension.umd.edu/hgic/topics/lawn-renovation-and-overseeding.
As is indicated in the first pages in the above link, make sure the site is conducive to vigorous lawn in the first place, or it will be a continuing struggle to maintain in good condition. Full sun, few or no tree roots, and good drainage are important.