If there’s a plant that goes well with everything, it’s Verbena bonariensis. And if you don’t know what plant I’m talking about, that’s precisely the point.
Verbena bonariensis (also known as purple vervain or tall verbena) is the poster child for underrated plants. The horticultural equivalent of a subtle understated accessory that makes the whole outfit work, if you’ll allow my analogy.
You’ve probably seen it in city gardens and cottage gardens; in borders along walls or in open meadows; in pollinator gardens and patio gardens. You get the gist. It’s popular, yet it doesn’t overshadow its companion plants.
I’m making it my mission to convince you to bring this plant into your garden too, if you haven’t already. I may not succeed on my first try, but I can guarantee one thing: you will start noticing it everywhere from now on.
Let’s clarify which plant we’re talking about first.
Confusingly, there are three plants that we commonly call verbena in English.
First, there is lemon verbena (Aloysia citriodora), the soothing herb that you will often see as a common ingredient in tea blends.
Secondly, there’s common vervain (Verbena officinalis), a perennial herb native to Europe. It has very tiny mauve flowers on spike-like stems. You’ll most commonly find it in herb gardens, but rarely as an ornamental plant because it’s not very decorative.
Then there’s the purpletop verbena (Verbena bonariensis), the tall plant (with a thin stem and narrow leaves) that is topped by an electric-purple cluster of small flowers.
It’s this latter verbena that I will talk about in this article. Here’s what you should know about it.
1. Verbena bonariensis can grow as an annual or as a perennial.
Verbena bonariensis is native to South America (particularly Brazil and Argentina), but it has naturalized in some Southern parts of the United States.
So depending on what gardening source of information you use, you’ll either see it listed as an annual or a perennial. It falls somewhere in between, so I think it’s more accurate to call it a tender perennial. It will survive the winter in USDA zones 6 through 11, but it will most likely grow as an annual anywhere else.
Even in colder zones, it may survive some years as the winters are getting warmer. As always in our gardens, it’s also a matter of local microclimates. If you plant verbena along a wall that reflects back heat and shields from harsh cold, it may surprise you and reemerge even after a harsh winter.
Similarly, if you apply a thick layer of protective mulch in the fall, the chances of your tall verbena surviving through winter frosts get increasingly higher.
2. Verbena bonariensis is a low-maintenance plant.
Due to its origins, you may have guessed that verbena likes full sun. But don’t let that put you off. In my observations, it’s not one of those perennials that throws a fit if it doesn’t get enough sun. Verbena will be happy to tick along in the scorcher of summer or the chilly winds of fall.
It doesn’t need super rich soil either, and if you’ve seen it swaying in the wind in beachside gardens, you’ll know that it will tolerate all types of soil, as long as it’s not too waterlogged.
In fact, during a particularly droughty summer a few years ago, I noticed that it was one of the few ornamental perennials in my garden that didn’t seem to show any signs of stress. The other perennials that fared well were Russian sage (Perovskia), lavender and blanket flowers (Gaillardia).
Verbena doesn’t need fertilizer. It’s not on the menu for any garden menaces, such as slugs or deer. And it’s not bothered much by aphids or scale either.
Yes, tall verbena can occasionally get mildew, particularly during wet and cloudy summers, but since the leaves are so small and skinny, you probably won’t even notice it.
3. Verbena bonariensis is very versatile in garden design.
I know most of us don’t consider ourselves garden designers, just simply gardeners. But there’s no denying that there is an element of design theory when we choose where to plant something. And it’s really easy to incorporate purple vervain in so many different garden scenarios.
First of all, because a scattering of Verbena bonariensis creates a pleasant see-through effect. Its lankiness adds height to the garden, with most cultivars growing between 24 inches (60 cm) to 48 inches (about 1.20 meters). But at the same time it doesn’t create a wall of green that obstructs other plants from view.
In narrow beds and borders, or along walls and fences, tall and skinny plants such as verbena create the illusion of depth. The almost ultraviolet flowers have a beautiful glow against any type of background, whether it’s a warm brick, cold white wall or a stone facade.
And let’s not forget about the movement effect, like ripples on a lake surface on a breezy day.
4. You’ll only need to buy tall verbena once.
Verbena bonariensis is a very reliable reseeder. Now depending on how and where you garden, that may be a positive or a negative.
On the one hand, it’s really easy to get it started from seed. If you want to have verbena flowers ready early in the season, you can sow the seeds indoors about a couple of months before you’re ready to get them planted outside.
I found that it’s a bit too much trouble for me to separate the seeds from the chaff at collection time. In the photo below, you’ll notice that the seeds are brown and the chaff is yellow-white. But they’re virtually the same size and weight. So I store them and plant them together.
Honestly, even this process you’ll only need to do once, when you first bring verbena into your garden. In the following years, it will reseed on its own.
In my garden, I’ve noticed that the seeds don’t travel far from the verbena patch. So all it’s doing is just getting a few more family members to join. And it isn’t one of those annoying seeds that survive in cracks in pavement or between the board of the deck.
It’s a very polite reseeder, if you will.
I generally advise our readers to allow the seed heads of perennials to overwinter in the garden. You may see some small birds that snack on verbena seeds over the winter months. However, if you decide you have plenty of this plant in your garden, you can deadhead the flowers once they’re done blooming but before they’ve had a chance to dry and disperse.
In my garden, Verbena bonariensis stays in bloom until late in the fall, so I’m never in a rush to deadhead it.
There will be no more reseeding after that.
But to be honest, If I was gardening in a colder zone, where tall verbena behaves more as an annual or a tender perennial, I would still allow it to reseed.
Just in case the roots of the plant don’t make it following prolonged periods of hard (ground) frost. The small seedlings only come out in spring since they need to go through a period of cold stratification.
That’s when you can assess whether last year’s mature plants have survived. If they have, you can pull out the seedlings, share them with other gardeners or drop them in a little free plant library.
5. You can cut tall verbena back to restrict their height.
Many gardeners, myself included, plant Verbena bonariensis to add height to the line of sight in the garden. But after the first couple of years, if you think that this plant towers over the garden a bit too much, there are a couple of fixes you can do.
First of all, you can cut it back before it has flowered. If you cut back the main flowering stem in mid-spring, right above a leaf node, the plants won’t get too leggy by late summer.
And the bonus to this method is that, when they resume their growth, there will be new buds forming from the axils. So what would have been one flower head will now be replaced by two. So even if it does grow tall, it will look less sparse and more dense.
Secondly, you can opt for compact cultivars.
Some common verbena bonariensis cultivars that don’t grow as tall are:
‘Meteor Shower’ – it reaches about 20 inches (50 cm) at its full mature height;
‘Lollipop’ – another compact cultivar perfect for containers;
‘Little One’ – it reaches about 18-24 inches (45-60 cm); its flowers are a bit more pastel-pink than purple.
6. Verbena are a food source for pollinators that feed on nectar.
In my opinion, a pollinator garden is not complete without adding some nectar-rich plants. And the excellent attribute of Verbena bonariensis is that it extends the nectar season way into fall. It blooms from mid-summer until the first frost, and you’ll notice butterflies visiting as late as November.
Butterflies love tall verbena as do hummingbird hawk-moths. To take your butterfly garden to a whole new level, you can interplant it with anise hyssop, lantana and coneflowers.