Nature’s notebook

You can ‘release’ native plants from strangling invasives

Black cohosh, ginger, false Solomon's seal and pawpaw popped up in this area after invasives were removed

T.S. Eliot claimed April is the cruelest month, but for gardeners, I’d argue it’s the busiest. In the Piedmont, it’s our last chance to plant trees and shrubs until fall. The soil is warm enough to sow cucumbers, peppers, green beans and squash, and it’s finally safe to set out tomatoes and basil. Catalogues and garden centers brim with flashy annuals and promising perennials. I always attend the spring plant sales at Wing Haven garden in Charlotte and the UNC Charlotte Botanical Gardens with a list firmly in hand. I try to stick to it – really, I do – but I always leave with plants I can’t resist, whether I have a spot for them or not.

In the midst of this frenzied activity, I took a break from my own yard to help volunteers remove invasives from a section of Charlotte’s Little Sugar Creek Greenway. Every hateful species in the Piedmont was represented – Chinese and Japanese ligustrum, English ivy, wisteria and multiflora rose. As we hacked and pulled and hauled, we discovered a few spindly branches adorned with burgundy tri-lobed flowers – the unmistakable blooms of a pawpaw tree. It now has room to grow into a veritable pawpaw patch. I left satisfied with the morning’s effort, reminded that native plants can sometimes be added to a natural area or yard without having to purchase and plant.

 Pawpaw is a native tree with a sweet, edible fruit. Photo: Ruth Ann Grissom

A “release” is a common forestry practice, usually achieved through herbicide, fire or brush saw. The goal is to maximize production by getting rid of undesirable species that inhibit the growth of trees. In the Uwharries, we also use release techniques to promote native species in our natural areas. The same principle can sometimes be employed on a smaller scale with amazing results.

An herbicide application is used to convert fescue pastures to native, warm season grass. We’ve experimented with different approaches. In some cases we spray once in the fall to kill everything and again in early spring to catch the flush of winter annuals then sow a mix of wildflowers and grasses. Some south-facing slopes already have a healthy broomstraw component, so we’ve elected not to plant those areas at all. We spray in late fall when the native grass has gone dormant but the fescue is still active, then burn the following spring. This approach encourages the proliferation of natives already present in the seed bank.

After the native grasses are established, controlled burns are used to knock back woody vegetation and clear away the thatch, giving native forbs the space to flourish among the tufts of grass. Fire is also essential for healthy stands of longleaf pine. It reduces competition from other trees, allows cones to release their seeds and removes debris from the forest floor so they can germinate.

We’ve done a brush saw thinning on a dense stand of regenerating loblolly pines that was susceptible to an infestation of Southern pine beetle. The young trees were cut and left in place, which enriched and stabilized the soil, and the additional sunlight allowed a more diverse suite of species to emerge on the forest floor. Unlike shortleaf pines, loblollies aren’t likely to resprout from the stump, so this can be a simple and effective intervention.

When resprouting is an issue, it’s necessary to add an herbicide component. A “cut and paint” involves felling small shrubs or trees and immediately treating the stump with a concentrated herbicide. Larger specimens can be subjected to a “hack and squirt,” in which a section of bark is removed to admit the herbicide. The tree slowly dies in place, creating snags that benefit wildlife. We’ve used this method to release longleaf seedlings that were struggling under a hardwood canopy. It’s also suited to large stands of privet in riparian areas where an herbicide application needs to be especially targeted.

Wild ginger, geranium, black cohosh and pawpaw popped up in this area after invasives were removed. Photo: Ruth Ann Grissom
 

In certain small-scale situations, hand-pulling can be the best option. Over the years, my sister has battled English ivy, periwinkle and creeping euonymus in a patch of woods behind her house. The task is sometimes daunting, but the results spur her on. Woodland wildflowers soon pop up in the areas she has uncovered. Bloodroot, ginger and black cohosh now create a lush and diverse herbaceous layer on the forest floor.

There’s an instant gratification that comes with planting a vegetable garden or flower bed, but don’t overlook the deep satisfaction of acquiring plants through subtraction rather than addition. A successful release might be the ultimate form of sweat equity.