It has been a hot, dry summer across North Carolina, and only recently have we finally caught a break with some rain. Unfortunately, these sudden weather inflection points are precisely when we start noticing our landscape trees showing symptoms of decline or death.
One of the trees most near and dear to our North Carolina hearts is, of course, our state flower: the Flowering Dogwood (Cornus florida). Homeowners take immense pride in their dogwoods. We love watching them grace our yards with brilliant spring displays (technically made of modified leaves called bracts, surrounding tiny yellow true flowers!), followed by glossy red fruits in the late summer that serve as vital fuel for songbirds and wildlife.
However, we need to have an honest conversation about how we treat dogwoods in modern home landscapes that causes them to show signs of stress and decline.
Forest Natives vs. Suburban Lawns
In nature, dogwoods are forest understory and woodland-edge species. They are adapted to dappled shade, cool organic soils, and undisturbed leaf litter. They were never evolved to coexist with aggressive, water-guzzling lawn grass in full sun.
Every summer, the Extension office gets frantic calls from homeowners watching their dogwoods exhibit dieback, leaf scorch, or sudden decline. In nearly every case, the tree is suffering from major landscape mistakes:
Turfgrass Under the Canopy
Growing turf grass right up to the trunk creates a hostile, hyper-competitive environment for a dogwood. Grass roots form a dense mat in the top few inches of soil, efficiently stealing moisture and nutrients before the tree's shallower feeder roots ever get a drink.
The "Mulch Volcano" Strategy
If homeowners do try to protect their tree, they often pile wood chips directly against the bark at the base of the tree. Piling mulch up the trunk creates a perpetually damp environment that invites trunk rot, root rot, and deadly girdling roots. While meant to protect, mulch volcanoes actually compromise the tree's vascular system, making it far more vulnerable during environmental extremes like droughts or heavy downpours. The longer the volcano mulch is present, the more and more stressed these trees get.
Root Heat & Dehydration from Placement in the Landscape
Sometimes dogwoods are situated in an open area as focal points or anchors in the landscape. Many are floating out in the landscape with no mulch around their roots in poor, exposed soils. Without a natural protective layer of organic leaf litter, a dogwood’s shallow root system bakes in the summer heat. Combine hot soil with low organic matter and zero supplemental water during extended dry spells, and the tree becomes starved for basic survival resources.
Planting Too Deep
Trees need to be planted at the right depth at the time of planting to have a good chance of survival. The root flair of the tree needs to be at or above grade and needs to be free of any mulch or covering. This flair and first order root provide vital structural stability and are the gateway between the canopy and the root system. Unfortunately, trees are also incredibly forgiving and can persist for a few years before succumbing to being planted too deep; and once they do succumb, it can be nearly impossible for the tree to recover.
Landscape Fabric Usage
Landscape fabric is a misnomer of the highest order in gardening. We have known for more than 30 years that landscape fabric does not provide the benefits of mulch: building organic matter, moderating soil temperatures, conserving soil moisture, and weed suppression. I see the saddest dogwoods surrounded by landscape fabric topped with mulch. The landscape fabric exacerbates the stresses of summer: it heats the soil; keeps the moisture in when it rains but also makes it harder to moisten after it dries out; it stops gas exchange, leading to anaerobic, bacteria-supporting conditions; and ultimately does not build organic matter or provide weed suppression after mulch on top of it starts to break down.
