Verbena Canadensis [vur-BEE-nuh, kan-uh-DEN-siss], also known as trailing Verbena, has a unique appearance with small spikey flowers and leaves which are sometimes hairy.
This plant will have blue, white, purple or pink flowers.
The underside of the leaves may show traces of powdery mildew.
Although the perennial Verbena plant originated in North and South America, the species are now also found in some Asian regions.
It’s part of the Verbenaceae family which is known for its different types of tropical flowering plants.
Verbena x hybrida goes by different names, some pertain to the different types of the plant:
- Common verbena
- Purpletop (or homestead purple) vervain- also known as verbena bonariensis
- Blue vervain- also known as Verbena hastata
NOTE: Verbena canadensis has been renamed Glandularia canadensis.[source]
Growing Trailing Verbena Care
If you’re planning on growing trailing verbena plants in your home garden, there are some factors you need to consider before getting started.
Remember not all types of verbena are the same and therefore require different care tactics.
You’re in luck since trailing verbenas are annual verbenas.
Size & Growth
Verbena plants may greatly vary in size.
The trailing verbena and the ground skimming moss verbena may grow to a height of 1′ foot or less but will have a ground cover of around 2′ – 5′ feet.
If you’re growing Purpletop vervain or blue verbena, they may grow to a height of 4′ – 5′ feet, but will only reach a width of around 1′ – 2′ feet.
They grow at a moderate to fast pace and are likely to bloom well within the first season of planting them.
If the plants grow beyond their designated boundary, they may be trimmed back without suffering any damage.
Flowering and Fragrance
Although verbenas feature different colored flowers if you grow different types together, they don’t really have a distinguishable fragrance.
Their flower colors are bright and spruce up any space, especially rock gardens.
Light & Temperature
Ideally, verbena should be planted in spring or early summer after the last spring frost date if you live upstate or in the plateau regions.
If you live by the coast, fall is the ideal season.
A quick pinch to the tips of the plant will encourage thicker foliage.
They require full sun for proper growth.
The USDA hardiness zone for verbena is 9 through 10.
Watering and Feeding
Verbenas grow best if they are not watered from above.
They will be alright if they receive around an inch worth of rain, but if not, they need to be watered at least once a week during their blooming phase.
Established plants are drought tolerant. However, expect slower growth and fewer blooms when plants experience dry spells for long periods.
Soil & Transplanting
Verbenas require well-drained soil.
They may suffer if they are grown on overcrowded soil with poor ventilation, shade or in too wet of soil.
In fact, if your verbena isn’t growing properly, the problems are most likely due to improper growing conditions.
Verbenas should initially be kept in moist soil until the roots have grown enough to spread to the surrounding soil.
At no point should the soil be too dry.
Although verbenas may survive drought to some extent, their growth is stunted and their appearance is affected over time.
Apply a thin layer of slow-release fertilizer in mid to late spring.
Repeat this if you’ve trimmed the plants to bring them back in bloom.
If the soil is too coarse and poor, you may need to fertilize a little more frequently.
A controlled-release fertilizer or liquid plant food is the best option.
Grooming and Maintenance
If blooming is slow during the summer, trim around 1/4th of the plant, including both the height and width.
Make sure to provide enough water and a bit of fertilizer.
Within 2-3 weeks, it will be back in bloom.
Dead-heading of faded verbenas is crucial to allow the rest to flourish.
Give the verbena a light trim in the fall, but don’t go overboard since new growth begins in spring.
Too much pruning will make the plant susceptible to destruction during a cold winter.
They do not have a very long lifespan and may need to be replaced after 2-3 years.
How to Propagate Growing Trailing Verbena
Some long-blooming verbenas re-seed very well.
Verbena may be propagated by seeds or cuttings.
To propagate by seed:
- Dead verbena flowers will leave behind a brown seed pod.
- Wait for it to dry out, then rub it to release the verbena seed.
- In the spring, spread out all your seeds over moist soil and leave them uncovered.
- Over time, they will start to germinate on their own.
To propagate by cuttings:
- Ideally, use summer cuttings for this process.
- Take a cutting which is at least 3″ inches tall and has no flowers.
- Remove all leaves except the top ones and place them in a pot of moist soil.
- After a few weeks, its roots will start to grow.
Growing Trailing Verbena Pest or Disease Problems
This plant is susceptible to pests of which some are a mere annoyance while others could cause irreversible damage.
These pests include:
- Mealy Bugs
- Gall Midgets
- Foliage-Feeding Caterpillars
Before going straight for an insecticide read the usage instructions to prevent damage to your plant.
Pests such as aphids or mealybugs are removed using a blast of water or removed with a cotton swab.
Another option is to introduce beneficial predators to your garden such as the praying mantis.
For serious infestations please consult your local gardening center for more details.
When it comes to diseases trailing verbena can have a few and these include:
- Botrytis Blight
- Powdery Mildew on plants
- Pythium Root Rot
With Botrytis Blight you’ll notice tan spots on the leaves or established plants rotting around the crown.
To manage Botrytis Blight maintain low humidity levels and improve air circulation around the plant.
Also, remove dead or dying flowers and leaves and to protect healthy plants apply a fungicide.
Powdery Mildew will show as white fungal growth on the surface of leaves or on flower petals.
Apply a fungicide to protect plants from powdery mildew.
For Pythium Root Rot you’ll have dark brown roots and plants will appear wilted and yellowed.
To avoid this do not over-water plants.
To manage the root rot pot in pasteurized media and keep hose ends off the ground.
Protect healthy plants by applying a fungicide.
Is This Plant Toxic or Poisonous?
Although most types of verbena are safe for everyone, the purple top verbena is poisonous for animals.
Is This Plant Invasive?
Verbena takes time to spread, and although it may grow beyond its intended space, it may be trimmed since this doesn’t affect its growth.
Suggested Trailing Verbena Uses
Verbena grown close together give a colorful, lively, blanketed effect.
Flowers in pink, purple and other colors cluster at the top.
They attract butterflies and may be grown in hanging baskets for another pop of color.
They create an attractive appearance in your house when grown in window boxes.