9/17/2023 4:13 pm
Architectural, easy to grow, and attractive to hummingbirds, butterflies and bees of all kinds, Verbena bonariensis is a surprisingly under-utilized perennial. True, it self sows, but it pulls out easily.
Verbena bonariensis grows up to six feet tall. It prefers part to full sun and is unfazed by dry weather. In metro Atlanta, it flowers from early summer to a hard frost, providing a bloom time few plants can match. On the downside, it is subject to powdery mildew some years, but never so much that the population is entirely wiped out. Usually it just makes for unappealing looking stems and foliage. Selective removal of stems or individual plants minimizes that problem. Depending on the time of year, cutting the plant back will lead to fresh, non-diseased growth.
Verbena bonariensis probably performs best on a hillside or in a meadow. On a hillside, it will weave in and out of other plants, self sowing downhill. The tall, flattish flower tops provide a resting spot for dragonflies and butterflies along with other insects. Hummingbirds find the flower heads, which are composed of hundreds of individual tubular flowers, irresistible. This alone is a reason to grow it! The added bonus of letting V. bonariensis self sow among shorter plants is that it increases the visibility of hummingbirds and the many insects that visit it by creating visual platforms, which makes tracking flying critters easy as they move up to perch or down to feed off lower plants.
Grown on flat land, where seeds fall straight down, three foot wide clumps are possible. These can make quite a statement in a meadow. In a garden, some folks don't like thick clumps of it. If grown on flat land that isn't a meadow, and allowed to self sow freely, it is definitely a back of the border kind of plant. But controlling it is not difficult. The seedlings are easy to pull and thin.
In Zones 7 and higher, you can often see the basal foliage of the babies the year before. The roots are shallow and they scrape out of the soil with ease if you have more than you want or they are where you don't want them. I often just leave them be until the next year until they begin to grow a stem, which provides a sturdy handle for pulling out the plant roots and all.
V. bonariensis is a South American native. But is it invasive? Not in a garden setting per any source.
It is on a "watch list" for potentially being invasive in "natural areas" -- those areas that are managed to conserve or restore the native plant communities -- in Washington State and California. It is on Georgia's lowest category of concern for natural areas, Category 4: "Exotic plant that is naturalized in Georgia but generally does not pose a problem in Georgia natural areas or a potentially invasive plant in need of additional information to determine its true status."
In researching the question of potential invasiveness, I discovered many inaccuracies in the "Invasive Plant Atlas" that purports to be a compendium of invasive plants and is often an early listed source in a Google search. It is absolutely necessary to look at the underlying referenced sources to ascertain the actual classification or level of concern about a plant. Were one to look at the Invasive Plant Atlas map on the page for Verbena bonariensis, you would believe Georgia actually has classified it as invasive. This serves as a good reminder of the importance of primary sources.
Also, many online sources confuse Verbena bonariensis with Verbena brasiliensis, the latter of which has been listed as invasive in Texas. Indeed, the plant pictured on the Washington State Noxious Weed List appears to my eye to be V. brasiliensis not V. bonariensis.
Watch list or not, given that this plant is a long blooming beneficial insect and hummingbird magnet, there seems to be no good reason to not enjoy it in your garden. I have difficulty imagining a garden devoid of it.
Contributed by Liane Schleifer