Q: My lilacs look like death-warmed-over this time of year. Do you know what’s wrong, and is there anything I can do at this point?
A: Lilacs are sadly not very well-suited to our Mid-Atlantic conditions. We’re at the southern edge of their heat tolerance, so while they weren’t among the best flowering shrub choices to begin with, climate change is only going to worsen their prognosis. Several types of leaf-spotting fungi and bacteria, plus general heat stress (which also increases their vulnerability to borers), results in foliage that looks quite beat-up by late summer. Brown spots, crispy leaf edges and bare stems from premature leaf drop are all typical. You can explore lilac ailments and their management on our lilac diagnostic page.
No fungicide will reverse these symptoms once they appear, and while they might work as a preventive if applied before bud-break (and reapplied repeatedly well into the summer), it’s simpler to just grow something else if a plant is going to be that much of a hassle. This is especially true if the treatments don’t work and the plant still winds up looking horrible. Fungicides also carry the risk of harming other organisms.
For now, you can rake up and dispose of any fallen leaves, though this isn’t a foolproof way of removing a source of infectious spores. Cut down the oldest, thickest stems this winter (they tend not to bloom well at that age anyway) and open up the canopy by selectively removing some stems that contribute to foliage crowding. You can do this thinning after bloom next spring.
For anyone really wanting to grow lilac despite these challenges, try cultivars with above-average disease resistance and heat tolerance. While not immune to problems, they perform much better, even if they don’t look exactly the same or have blooms as large or heavily perfumed. Miss Kim is a round, compact-growing cultivar with pale lavender-purple flowers that’s been around for decades. Other varieties are now available with pink or deeper purple blooms, some of which even rebloom a bit, sporadically producing flowers into summer and early autumn, though high heat could still hamper that.
All lilacs, but especially the traditional, classic French types, should be planted in a location with great air circulation (so, not up against a fence or wall) so wet leaves dry quickly after rain, dew, or irrigation. Wet foliage is more easily infected by diseases.
The main perk of growing lilacs is fragrance, so if you want a scented replacement, consider: winterhazel (corylopsis), Koreanspice viburnum (viburnum carlesii) and its hybrids, summersweet (clethra), seven-son Flower (Hhptacodium), Carolina allspice (calycanthus), various deciduous azaleas (rhododendron viscosum and several others), mock orange (philadelphus), and fragrant abelia (abelia mosanensis). Their scent characteristics, flower colors, mature sizes, and preferred growing conditions may differ from lilac, but nothing is going to be an exact substitute. Plus, several of these species will offer the additional bonus of showy autumn foliage or (for the native ones) better wildlife value. These are just some shrub ideas; there are also fragrant perennials and, if you have the room, several fragrant trees.
Q: I know we should ideally be growing alternatives to lawn, but for now I need to rehab a section of turf until I can figure out what to convert it to. Is this too early to begin fall lawn care?
A: Actually, now’s a great time to start the rehab process for fescue-based lawns. Begin with a laboratory soil test if it’s been a few years since your last one (or have never done one), so you know what the soil characteristics are in terms of acidity and nutrient levels. Mid-August through September is when conditions are preferable for overseeding or seeding/sodding areas that need to be stripped and reestablished due to heavy weed infestation.
Core-aeration can be done just prior to seeding for better seed-to-soil contact and to lessen compaction, and applications of starter fertilizer and lime (if needed) can be made at the same time you seed/sod. Give careful attention to watering since germinating seeds and establishing lawns are intolerant of drying out.
This is the one of the rare scenarios where watering method goes against the “deeply, infrequently” recommendation, since you’ll need to irrigate lightly but more frequently. As the grass matures, wean it off that pampering to the typical technique of only watering thoroughly once the top few inches of soil becomes relatively dry. This encourages deeper rooting for a more self-sufficient lawn, conserves water, and reduces the risk of disease from frequently-wet foliage.
You can find a plethora of pages about lawn care on our website. A good starting point is the collection of page links under our Lawn Care and Maintenance tag.
University of Maryland Extension’s Home and Garden Information Center offers free gardening and pest information at extension.umd.edu/hgic. Click “Ask Extension” to send questions and photos.