Lawn rotting?

Question: What could be the cause of the damage to the grass? My townhome neighbors have only recently experienced this in the past 10 years. The only commonality is the AC unit on the lawn. Any help would be appreciated.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 25, 2023, 5:57 PM EDT
response: It's a very challenging spot for lawn and most other plants, so any number of factors might be causing dieback or plant stress. Factors may include the repetitive wind/airflow from the A/C unit, the reflected heat from the nearby wall and pavement (and maybe even added-to by the unit itself, if it warms up with prolonged use), compacted soil, occasional soil saturation from the one or two two nearby roof downspout outlets, and likely drought conditions during periods of low rain and warm weather. You mention that this seems to be a recent problem, but we suspect the underlying stressors have been present all along (or for most of that time), and only a recent exacerbation of one factor or another pushed the plants there over the edge of their tolerances, resulting in a die-off. Our spring to date has been drier than average, but it's also possible that rain deluges months ago or during last year sometime flooded too many roots while the extra water drained and compromised enough roots that what few were left afterwards weren't able to sustain the plants once dry conditions hit. This is an educated guess and just one example; it can be hard to diagnose plants that are already completely dead.  Since this is not a location that should require lawn as a groundcover (as it's the best choice for heavy foot traffic use, which we would not expect this spot needs), planting a different species of groundcover would be more practical. Or, if you prefer due to aesthetics or budget, you could try just using a bark or gravel mulch over this area and simply weed-out any tough weeds that might appear anyway in the future.  With regard to decorative plants, unfortunately you're probably limited to species that stay fairly low or narrow, both because of space constraints as well as needing to maintain good airflow around the units for their proper functioning or any repairs. We can share a few ideas for candidates of perennials or small shrubs to consider, but this is far from an exhaustive list, and you may need to make an educated guess as to which of the above conditions suggested is less likely to be a significant stressor since very few plants will tolerate them all equally well. For example, if feasible, maybe you can reposition the downspout outlet further from the building (always recommended to avoid foundation damage or leaks anyway) by burying it using a corrugated pipe extension. In either case, the plants below don't take into account any issues with deer or rabbit browsing, and also assumes the area receives at least a half-day or more of direct sun. (We think this because turfgrass doesn't do well in shade and the nearby grass doesn't look sparse enough to suggest it's very shady.) Botanical names are in parentheses if they help for internet look-ups or confirmation with plant ID tags at a nursery. St. Johnswort (Hypericum) - a variety of species and cultivars exist, but several are fairly low-growing and they have good drought toleranceSweet Flag (Acorus gramineus) - grass-like perennial, often sold as a form with yellow-green foliage, can spread but not as a weed (it'll just form a solid carpet where planted); good option if you think wetness or poor drainage is the biggest issue hereselected ornamental grassesFeather Reed Grass (Calamagrostis x acutiflora, such as variety ‘Karl Foerster') - fairly upright as grasses go and not as large and arching as mostour native Little Bluestem (Schizachyrium scoparium) is another smaller-statured upright grasswe have a few other native short grasses like Purple Lovegrass (Eragrostis spectabilis) that, out of bloom, will look not much different from a distance than the lawn, just a little taller and more arching (though don't mow them)ground-covering or low, mounding varieties of Juniper (Juniperus) - there's lots of options in this group, some of which are pancakes and spread several feet while staying a foot or less high, others of which are tuffets around a foot or two high and wide; all require good drainage and are decently tolerant of droughtHardy Plumbago (Ceratostigma plumbaginoides) - spreading groundcover that loses its leaves in winter (but with nice reddish fall foliage color first) but which is unlikely to run into the existing grass (easy to mow-down if it does); true-blue flowers in late summer scattered atop the foliage; pretty tough but might struggle if too wetStonecrop / Sedum (Sedum) - many species and varieties, some of which will be ground-hugging and others of which might reach a foot or two tall; succulent, so very drought-tolerantLamb's-Ear (Stachys byzantina) - spreading groundcover that shouldn't invade the lawn but which has great drought toleranceCotoneaster, particularly Cotoneaster adpressus variety 'Little Gem' (might be labeled with the name 'Tom Thumb' instead) or Cotoneaster dammeri variety 'Streib's Findling'Moss Phlox (Phlox subulata) - native; mostly evergreen; creeping but won't invade the lawn; needs good drainageAdam's-Needle Yucca (Yucca filamentosa) - native; perhaps not a great idea if anyone regularly walks right next to this planting spot (the leaf tips can be a bit sharp-tipped), but otherwise these evergreen plants are very tough, prefer good drainage, and can handle drought well  Miri

responder: The Question Asker Replied May 26, 2023, 2:50 AM EDT
response: Wow! All the information is greatly appreciated!!  We will try to reassess the area and incorporate one of your recommendations.

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied May 26, 2023, 9:16 AM EDT
response: You're welcome!