Questions from Readers

After reading the March, 2021 newsletter article, “A Year of New-Home Landscaping and What I’ve Learned,” an astute reader asked the author, Susan Martin, if her position on adding nonnatives to the landscape had changed since her June, 2018 article, “Crape Myrtle–A Southern Icon Gets Even Better.” The Garden Shed staff saw this as an opportunity to open further discussion by sharing Ms. Martin’s answer. This also inspired us to launch a new feature, “Questions from Readers.” We invite you to use this forum to help us learn from one another. If you have questions about a particular topic, you can be sure that others do too! Write any questions or comments in the comments section following the article.

QUESTION:

Susan, really good article.  But in a 2018 article about Crape Myrtles, you were questioning whether or not non-natives might not have a place in our landscapes.  Now it seems as if you’ve jumped on the “All native” bandwagon.  Do you still feel that a combination of natives and nonnatives might provide a pragmatic approach to helping nature?

ANSWER:

This is a very timely comment since I’ve been thinking a lot about the question of using nonnatives in the landscape. As we know from studies on Carolina chickadees (Desirée L. Narango, Douglas W. Tallamy, and Peter P. Marra, 2018), landscapes with less than 70% native vegetation do not support the survival of chickadees or their young. When I first heard Doug Tallamy quote the minimum 70% guideline, I was relieved to think that I could indulge my fondness for plants such as lilacs (childhood memories), lungworts, leadworts, and peonies, and still be a contributing member of the homegrown national park movement. However, the chickadee study went on to show that a landscape with 94% natives is even better for chickadee survival. When I wrote the 2018 article on crape myrtles to which you referred, I was concentrating on the issue of whether that nonnative was invasive. I considered the invasive aspect of nonnatives to be a primary concern, which it is. However, I had not yet fully appreciated the longer view of building an interactive environment based on the evolutionary relationship between native plants and the native insects that support them. I’m still learning about that.

In our landscape, I can observe lots of pollinator activity on nonnatives such as crape myrtle, Russian sage (Perovskia atriplicifolia), and the annual flowering plant, gomphrena. But there are now studies that are researching differences in nectar quality. Some plants offer nectar that is more beneficial to pollinators. I don’t know if the nonnatives I mentioned are offering high quality nectar. More importantly, even if we assume that the nonnative plants are producing highly beneficial nectar, their foliage still isn’t providing food for caterpillars. All three of those flowering nonnatives, however, are deer and drought resistant, and provide late-season, long-lasting bloom which is beneficial for pollinators.

As described in this article, we had moved into a home that had the barest of landscape plantings. It was a fairly clean slate, and I wanted to plant as many natives on that clean slate as possible. Two years later, however, we’ve found that the damage from deer browsing has been severe on most of the native shrubs we planted. American beauty berry (Callicarpa americana) has been a wonderful exception. Some viburnum species are more resistant than others. We’ve had to cage our V. dentanum, but V. nudum, both straight species and cultivars, have proved acceptably resistant. V. prunifolium was largely defoliated by the second day after planting. I will keep experimenting with native shrubs to find more that are deer resistant, but the deer damage has been discouraging to date.

Except for the fringe trees (Chionanthus virginicus), the native trees have not been browsed by deer, but the survival rate has been disappointing. It’s likely that the severe drought this summer had something to do with that. But I also think that the native tree stock that’s available is not always as hardy as more commonly requested nonnative trees. The selection of native trees seems limited, and the quality hasn’t been consistent. You can easily find red maples, for example, but other trees such as hornbeams (Carpinus caroliniana) and American smoke trees (Cotinus obovatus) are more difficult to find. This will most likely change with increased demand for native trees. Another Piedmont Master Gardener, who is an expert on natives, suggested that native trees and shrubs might be more particular about where they are planted and less adaptable to less-than-ideal growing conditions as compared to nonnatives and cultivars that have been bred to be robust.

Although I am learning more about the end goals of planting natives and how to achieve these goals, the unique characteristics of our individual landscapes offer practical challenges. For example, I am limited in our landscape to selecting deer-resistant plants that can tolerate full sun, all day. There is also the challenge of finding suppliers of good quality native plants, especially trees and shrubs, of sufficient variety. Native perennials are becoming much easier to find, especially in light of the Plant Virginia Natives campaign which has been reaching out to suppliers as well as educating home gardeners. You may have seen in area nurseries the red labels from this campaign highlighting plants that are locally native. The Northern Virginia plant natives campaign has been compiling a list of cultivars of locally native plants—including shrubs and trees—that provide ecological services similar to the straight species.

My goal is to have well over 70% natives but I have the “advantage” of planting new rather than replacing. I will still keep or even add some nonnative shrubs or perennials if they are deer resistant, well-suited to our challenging landscape conditions, and bring me joy. Naturally, the “joy bar” for selecting nonnative plants becomes higher as I discover more native plants that flourish on our site.

Dear Reader, many thanks for your careful reading, and for highlighting such an important area of study.

Featured Photo:  by Hannah Wei, Unsplash