Slender stems three to four feet tall hold airy clusters of purple flowers that lighten the back of a border rather than crowd it: purpletop vervain (Verbena bonariensis) is abundantly melliferous, drawing butterflies as well as bees. Give it full sun and soil that drains freely, since it fears excess water, and it blooms abundantly and self-sows year after year.
Purpletop vervain at a glance
Botanical name
Verbena bonariensis
Common name
Argentinian verbena, Purpletop vervain
Family
Verbenaceae
Type
perennial, grown either as an annual or a biennial
Bearing
disorderly, upright mound
Height
3 to 4 feet (1 m to 1.20 m)
Planting density
4 to 6 plants per sq. yard (m²)
Exposure
full sun
Soil
any type, as long as well drained
Flowering
from July to October
Its airy and vaporwave blooming bring a touch of lightness to the garden, perfect for dressing up the back of a flower bed without overloading it. It isn’t very resistant, but that’s more than made up for thanks to abundant seeds that self-sow. Discover more about Argentinian vervain!
Planting Argentinian verbena
Verbena bonariensis requires growing in full sun if you want it to bloom abundantly.
It also fears excess water. You’ll have to really make sure that the soil drains well enough.
Just like stonecrop and centaury, the Buenos Aires verbena will settle in just fine in all types of soil, so it’s often selected for difficult situations.
To plant Verbena bonariensis, it’s easiest to simply start them from seeds anytime in March, April. If ever they sprout too close to one another, thin them to a distance of about 1½ feet (40 cm): this will let each plant thrive on its own.
Argentinian verbena care
Once flowers have wilted away, cut them off above the leaves to trigger another round of blooming. If you’re trying to grow your Argentinian Verbena in pots, one point of caution is to watch soil moisture: watering should be moderate, but regular. At the beginning of spring, cut the stems back to the base. If ever winter isn’t too harsh, they’ll bud and sprout back to life in spring. If not, no worry: seeds will start sprouting, too.
Verbena, a seed-bearing perennial, can be left to set seed in late summer, its spent flower heads ripening into tiny nutlets that self-sow readily or can be collected and stored for spring sowing.
Susans, leaving faded stems standing over winter can give the crown modest insulation, supply seed for finches, and allow some self-sowing; cut them back in spring.
Once established in open ground, purpletop vervain (Verbena bonariensis) is markedly drought tolerant and needs watering only in prolonged dry spells, though it dislikes winter wet and does best in free-draining soil.
As a general rule, excess nitrogen and rich feeding encourage soft, sappy growth that is more likely to flop and need staking, so many tall perennials are grown harder on leaner, free-draining soil.
Propagation
Simple and straightforward: just let this verbena re-seed itself on its own. For that, come fall, don’t cut the last flowers off their stem. Let them form seeds instead, they’ll scatter around naturally.
Where possible, liftself-sown seedlings while they are still small and move them with a good ball of soil around the roots, since many plants establish more readily when transplanted young, though tolerance of disturbance varies by species.
You can also collect seed from dried flower heads and store it dry and cool in a paper envelope, though sowing needs vary by species: check whether yours requires stratification, fresh sowing, or spring trays.
Year-round calendar for Argentinian verbena
Slender stems three to four feet tall carry airy clusters of purple flowers that lighten the back of a border rather than crowd it: purpletop vervain (Verbena bonariensis) is highly melliferous, drawing butterflies as well as bees. Give it full sun and freely draining soil, for it fears excess water, and it blooms abundantly and self-sows year after year.
Year-round calendar for Argentinian verbena
Period
What to do
Why
March, April
Sow seeds directly
The easiest way to establish the plant
After sprouting
Thin to about 1½ feet (40 cm)
Lets each plant thrive on its own
July to October
Cut wilted flowers off above the leaves
Triggers another round of blooming
Fall
Leave the last flowers on their stems
They form seeds that scatter around naturally
Beginning of spring
Cut the stems back to the base
Clumps bud and sprout back after a mild winter
Follow this rhythm and the colony renews itself year after year with almost no effort.
Diseases and pests
Aphids are definitely fond of infesting Argentina verbena. If ever the onslaught is so severe that the plant is in danger, spray a mix of watered-down beldi soap on all the leaves.
Below, a large white (the cabbage pest butterfly) sips up nectar.
Aphids cluster on the soft growing tips and the undersides of leaves, so turn shoots over when inspecting and target the spray there, since soapy solutions only work on contact.
Spray soapy water early or late in the day rather than in full sun, and avoid drenching open flowers, so that the bees and butterflies the plant attracts are not caught in the treatment.
Overwatering and waterlogged soil are a common cause of root rot in container plants, so make sure the pot’s drainage holes stay clear and never leave the container standing in a full saucer.
Seedlings and fresh basal shoots are grazed by slugs and snails, so check around the base of clumps after rain and clear hiding places such as flat stones and dense mulch nearby.
Landscaping uses and companion plants
Highly melliferous flowers that draw butterflies as well as bees
The best way to use Argentinian verbena is to add it to flower beds, either on its own or surrounded by other companion perennials, even grasses:
It’s worth giving growing it in pots a go, but for that you must select a container that’s large enough to house all of its roots – and heavy enough that it won’t topple over when wind pulls on its long stems.
Smart tip
Argentinian verbena is an abundantly melliferous plant: this makes it ideal not only to attract bees, but butterflies, too!
