South American verbena (Verbena bonariensis) is a plant that gives a great deal to the gardener. It forms beautiful, small, purple flowers on long stems that require no staking, attracting hummingbirds and butterflies as well as curious people walking by who are wowed by a plant they haven’t seen before.
Verbena bonariensis is significantly different from the verbenas that often adorn pots. This verbena is 4 to 5 feet high, with dark purple flower clusters that wave at the end of stems. Flower clusters are 2 to 3 inches wide. Native to Argentina and Brazil, it is in fact named for Buenos Aires. It can be traced back as far as 1726, when it was being grown in England.
Even though it is not cold hardy in our area (it is hardy in zones 7 to 10), in my experience once you have a handful of these plants, you will have them forever because they self-seed. Heavy seeding can sometimes be a negative trait, but these plants have tiny root balls that take up little space and do not dislodge other plants. And if you want fewer of them, it is easy to just pull them out of the ground. I have never wanted less.
One of the magical things about Verbena bonariensis is that the stems are wiry, but sturdy and self-supporting. They never tip over. The leaves are very small, so the plants are airy. You can put these plants at the front of a border and see right through them to the plants behind. Or, because of their height, you can place them at the rear of a bed. The lovely purple shade of the flowers blends with any cool color. I grow them with roses, grasses, peonies, shrubs or in clusters by themselves. They mingle well with perennials and annuals.
Verbena bonariensis has an extended season of bloom from June through September. It provides color when the rest of the garden is becoming a little tired. And butterflies, bees and other pollinators love it, too.
You can purchase this plant in pots at garden centers, but the easiest thing to do is to obtain seeds and just toss them into your garden. Either way you will love Verbena bonariensis.
Donna Mack is a University of Illinois Extension master gardener for Kane County. The “Learning to Grow” column runs weekly during warmer months of the year. Call the extension office at 630-584-6166 for more information. Feedback on this column can be sent to firstname.lastname@example.org.