Swamp Verbena Growing, Planting, Facts & Care (Verbena hastata)
Verbena hastata is a lovely herbaceous perennial for adding height and texture to the moist or wet areas of the garden. Ideal as an edge or border plant for backyard ponds and streams, it is commonly referred to as swamp verbena, blue vervain, wild hyssop, simpler’s joy, and ironweed. It is a member of the Verbenaceae, or vervain family, which largely consists of flowering tropical species. One of about 150 species in the Verbena genus, its populations are found throughout North America.
The species’ appearance is alluded to by its scientific epithet, hastata, which means “spear-shaped”. Each shoot is able to produce a wealth of spiky inflorescences from summer to fall. The tiny blossoms are noteworthy for their bright lavender and purples hues. The blooms gradually open, starting from the bottom of each inflorescence. This results in a lengthy flowering period.
The clusters of inflorescences are borne on a branching shoot that may resemble the shape of a candelabra. The shoots can grow quite tall, contributing to this species’ maximum height of about 5 feet (152 cm). Lance-shaped and distinctly serrated foliage appear as opposing pairs and are spaced out along the stems.
Facts, Benefits & Uses of Swamp Verbena
Swamp verbena is perfect for wildlife gardens or ponds as it attracts many pollinators. Its flowers appeal to many types of bees, which gather their nectar and occasionally collect their pollen. Some types of wasps, beetles, and flies are also known for visiting the summer blooms of this species. Its foliage, on the other hand, serves as a vital food source and larval host for the caterpillars of the common buckeye butterfly and the verbena moth.
Though bitter, the plant’s foliage may occasionally attract hungry rabbits. However, most grazers prefer to avoid its leaves due to their bitter taste. Unsurprisingly, the bitterness is associated with a wealth of ethnobotanical uses for internally or externally manifested disorders. Several types of birds, including the swamp sparrow, cardinal, slate-colored junco, and song sparrow, benefit from the nutritional contents of its seeds.
As this species has a knack for thriving in degraded wetland regions, its hardiness and ease of care make it a great substitute for invasive plants. It can be used to quickly add color and dimension to a landscaped area, though the substrate must remain moist for proper root establishment.
Swamp Verbena Growth, Hardiness & Climate
In the wild, swamp verbena favors conditions in persistently moist habitats, such as along the edges of creeks, ponds, lakes, streams, and ditches. It can also survive in meadows, woods, and thickets as long as the substrate is frequently moistened by a natural water source. When its environment becomes damaged, it is quick to adapt given optimal ambient conditions. Brief flooding periods are also tolerated as the roots can persist under a few inches of standing water.
Swamp verbena usually spreads on its own via rhizomatous growth. It may also occasionally self-seed if pollinators are abundant. Though it has a moderately fast growth rate, it is not particularly known to be an invasive or pest plant outside of its native range. This plant should be situated in areas that receive full sun and have slightly acidic substrates. Partial sun is also tolerated, though this may result in shorter flowering periods and less bushy plants.
How to Plant Swamp Verbena
This species can easily be propagated via seeds or stem cuttings. If you intend to start your plant from seed, you can make use of those in seed packets or collect them manually from nutlets. Nutlets should be gathered by early fall at the latest before they can break open. Set them aside in a dry, indoor location. After a few days, they should be dry enough to break open and release their seeds. To increase their rate of successful germination, they will need to be cold-stratified for a few months prior to being sown.
Once the seeds are ready, prepare a slightly porous germination mixture (with sand comprising about 1/3 of the mixture). Distribute the seeds on the surface and then cover them with about 1/8 inch (0.3 cm) of soil. You can lightly press on the surface to secure the seeds. Store the setup in a sunlit area, preferably with ambient temperatures ranging from 15 – 21˚C (59 – 70˚F). Once seedlings are large enough to handle, they can be transplanted.
If you wish to propagate verbena using cuttings, aim to collect them in early spring. Cuttings should be obtained from the tips of healthy stems. Each one should measure around 3 – 4 inches (7.6 – 10.2 cm) long. Remove any leaves around the base of the cutting to expose the nodes. Gently plant each one in a few inches of a perlite-based rooting medium. In a moderately lit and consistently moistened setup, new roots should begin to appear in just a few weeks. Once the cuttings are well-established, they can be planted outdoors.
How to Care for Swamp Verbena
Many horticulturists recommend deadheading or pinching off the tops of verbena shoots to encourage them to develop a bushier habit. This practice also prevents the plant from self-seeding, making its spread easier to control. As its foliage and shoots are fairly pest-resistant, they will seldom require treatment with pesticides. Nonetheless, it would be best to manually remove any suspected pests as soon as they are spotted.
Swamp verbena tends to have a high tolerance for nutrients, silt, and salts. It is known for being quite low-maintenance as, despite its preference for moist substrates, it can also survive through short droughts. The soil around each shoot should receive regular moisture to ensure proper growth and a full flowering period each year.
How to Winter Swamp Verbena
As V. hastata is native to wetland regions experiencing cool winters, it need not be brought indoors as temperatures drop. Instead, prepare the base of the plant for winter by cutting down the shoot. This will naturally die back if left uncut once temperatures begin to drop. The plant should naturally enter a dormant state that can be sustained as long as temperatures don’t drop severely. You may opt to mulch the crown to protect the roots from temperature fluctuations.
Despite its preference for moist substrates, swamp verbena should be watered sparingly throughout winter. Excess moisture in the cold may damage its root system. Resume regularly watering the plant in spring, when new growths should begin to appear.
Is Swamp Verbena Invasive or Toxic?
Though swamp verbena has the tendency to grow rapidly and self-seed, it is not particularly aggressive and may have restricted colonies in the presence of other competitors. If you’re concerned about this species overgrowing your area, you can limit its growth to within large pots or containers. Deadheading its blooms as soon as they are spent would ensure that self-seeding does not occur.
When tissues of V. hastata are ingested in large quantities, mild toxicity symptoms may occur. Small amounts are usually safe for human and animal consumption, though most mammals will avoid the plant at all costs due to its bitter taste.
Consumption in the right quantities can actually lead to many pharmacological benefits to relieve a wide range of symptoms. Studies have shown that leaf extracts from this species have antimicrobial and antidiarrheal effects, among others.
Is Swamp Verbena Edible? Do Animals Eat it?
Verbena leaves are generally known for being unappealing due to their bitter taste. They are not regularly consumed as food or for flavor, but they may be ingested in poultice or extract form to treat medical ailments (including psychological disorders). The leaves can be used in infusions or incorporated into more complex dishes that may mask their strong taste. The dried seeds may be ground up or roasted, and are in fact the primary edible components of the plant.
In the wild, rabbits and birds may feast on the foliage and seeds of the plant. Some types of birds tend to rely on the seeds as a food source in the fall. Mammals seldom graze on swamp verbena leaves unless they are desperate or stressed. They are unlikely to hone in on verbena species if there are more palatable plant choices in the garden.
Where to Buy Swamp Verbena & Seeds? (UK & US)
Verbena hastata is usually sold as seeds, though some potted individuals may be available in nurseries or garden centers throughout North America. If located elsewhere, you may have more luck obtaining seeds through online plant portals. Keep in mind, however, that your area may have heavy restrictions or requirements for the legal importation of plants. This species readily hybridizes with its closest relatives, so always double-check the label or consult with the seller before making a purchase.