How to Grow and Care for Verbena Plants

Verbena plants, also called vervain, are commonly grown as annual hybrid flower bed plants and low trailers with dark green elongated leaves with toothed edges. Historically, verbena has been used as an essential oil for its lemony scent and taste. Although verbena is edible by humans, it isn't very tasty and is mainly used as an herb.

They grow as hardy perennials, coming back year after year, in zones 8 to 11. Their colorful flowers continuously bloom from spring to fall and grow best with eight to 10 hours of full sun, moderately moist, well-drained soil, and good air circulation between plants. Learn how easy it is to grow and care for verbena.

Verbena hybrids are usually planted as potted nursery plants in the spring or by sowing seeds indoors in plant trays in late winter. They are moderately fast-growing plants that will bloom by mid-summer from seeds started indoors in winter; potted plants will grow to full size in a few weeks. Some types, like lemon verbena, are toxic to cats, dogs, and horses.

How to Grow Verbena

Here are the main care requirements and growth habits for a verbena plant:

• Plant in a spot with at least six hours of full sun; eight to 10 hours are preferred.
• Give regular water, but avoid soggy soil conditions.
• Needs moderately moist, well-drained, slightly acidic soil.
• Fertilize once per month with slow-release, balanced fertilizer.
• Allow space for air circulation between plants; grows at least 12 to 18 inches wide.
  

Light

Plant verbena in full sun. This plant requires at least six hours of sun daily; eight to 10 hours is much better. Flowering will be much reduced in shady locations.

Soil

These plants like relatively dry soil with slightly acidic to neutral pH (5.8 to 7.2). Verbena is not too particular about soil, except that it must be well-draining. Heavy clay can lead to root rot, so dig in several shovelfuls of compost or leaf mold to lighten dense soils.

Water

Many of the parent species of these hybrids are native to Mediterranean regions or dry prairies, and their water needs resemble the conditions of those regions. Once mature, these plants have average water needs (1/2 to 1 inch per week) but will tolerate short periods of drought. Keep plants evenly moist until established. Soggy plants will succumb to botrytis blight, but drought-stressed plants may attract spider mites.

Temperature and Humidity

Planted as annuals, hybrid verbenas perform suitably in virtually any climate but may decline in the hottest summer period. When grown as short-lived garden perennials, most hybrids are hardy in zones 8 to 11, but some are hardy up to zone 7.

Fertilizer

Verbenas are not heavy feeders, but they appreciate a monthly application of balanced, slow-release flower fertilizerto help them keep up the flower show, which can last from spring until frost. If grown in containers, use a water-soluble fertilizer throughout the growing season. For the amount of fertilizer to use, follow the product label instructions.

Types of Verbena

The Verbena genus has more than 250 species or lower classifications. Common verbena (Verbena officinalis) has been historically used in the folk medicine of different countries, including traditional Chinese medicine. Herb extracts contain antioxidant, antibacterial, and anti-inflammatory properties."Verbena x" or "annual verbena" distinguishes a verbena type from the native species forms. The varieties of hybrid verbena are identified by their unique flower colors. Here are some notable selections:

• 'Lanai Royal Purple with Eye' is a cultivar with bright purple flowers and contrasting white eyes.
• 'Lanai Twister Pink' has dual-tone light pink and dark pink flowers on low-trailing plants.
• 'Superbena' series is bred to resist powdery mildew, and it sometimes becomes a short-lived perennial as far north as zone 7. Flowers are white or shades of lavender.

Species Types

In addition to the Verbena hybrids that are so common as annual bedding and container plants, there are several pure Verbena species that you can try as garden perennials. These species are welcome in the butterfly garden. Tall varieties belong in the cottage garden, naturalized meadow, or back of the border. Many of these plants are more upright in growth habit and may look quite different from the hybrid trailers.

• V. hastata (blue vervain) is a North American native that grows 6 feet tall with purplish-blue flowers. It is hardy in zones 3 to 8.
• Glandularia pulchella (moss verbena)was once categorized as Verbena tenuisecta. It has delicate, lace-like foliage and low low-growing habit, only growing up to 5 or 6 inches. It blooms during late summer and early fall and is hardy in zones 7 to 9.
• Aloysia citrodora (lemon verbena) is a South American native, also known as lemon beebrush. It is grown mainly as an herb used in aromatherapy and home remedies. However, it is toxic to dogs, cats, and horses.
• V. bonariensis (purple top vervain) is a native of Brazil that grows to 4 feet with lavender flowers. It is hardy in zones 7 to 11.
• Glandulariacanadensiswas once considered a member of the Verbena genus but has now been recategorized. The 'Greystone Daphne' cultivar has lavender-pink flowers and grows to 8 inches with a sprawling habit. It is hardy in zones 5 to 8.
• V. rigida (rigid verbena) is a spreading variety that makes a good ground cover. It is hardy in zones 7 to 9. Notable cultivars include 'Polaris' and 'Stantos.'

Pruning

Pruning the plants back several times during the growing season will help prompt new blooms and extend the blooming season.

Shear back verbena plants once or twice per season to keep the plants looking full and tidy. You do not have to deadhead spent flowers, but you could if you want to encourage more blooms.

Propagating Verbena

The best way to propagate hybrid garden verbenas is by stem cuttings, which involves clipping stem segments and rooting them. Take stem cuttings to keep plants alive through the winter, root them indoors, and then pot them up to prepare for transplanting outdoors in the spring. Here's how to do it:

1. You will need sharp, sterilized pruners, rooting hormone, peat-free potting mix blended with sand or perlite, a potting container, and a clear plastic bag.
2. Cut 4- to 6-inch clippings from the ends of healthy stems using sterile pruners. Remove the leaves from the bottom one-third of the cutting, then dip the cut end into the rooting hormone.
3. Fill small pots with a porous rooting medium. Plant the cutting in the potting mix and bury the bare part of the stem. Carefully water the pots so the potting mix is thoroughly moistened.
4. Cover the pot with a plastic cover or loose plastic bag and set it in a bright but out of the direct sun location. Periodically inspect the cutting and moisten the potting mix when necessary.
5. After several weeks, begin testing the cutting by gently tugging on the stem. You'll know that roots have developed once you begin to feel resistance. When new growth is evident, the plant can be transplanted into the garden or larger pots filled with commercial potting mix.

How to Grow Verbena From Seed

Most verbenas are hybrids that don't "come true" or grow into plants that resemble their parent plants. To propagate using seeds, purchase commercial seeds bred under carefully controlled greenhouse conditions.

1. Start seeds indoors 12 to 14 weeks before your average last frost date to ensure flowers by early summer.
2. Wrap the seeds in a moist paper towel and place them in a plastic bag. Refrigerate them for seven days.
3. Plant them in cell trays filled with a commercial seed-starter mix.
4. Press the seed into the soil and barely cover it with an additional seed-starter mix.
5. Mist the starter mix to moisten it, then cover the tray and place it in a dark location out of direct sunlight at about 75°F.
6. When the seeds begin to sprout (21 to 30 days), remove the cover and bring the tray into direct light.
7. When they have several sets of true leaves, the seedlings can be transplanted into pots filled with commercial potting mix or directly into the garden.
8. Harden off seedlings before planting in the garden.

Potting and Repotting Verbena

Verbena is commonly found in hanging baskets with a mix of flowers, where they make good "spillers" trailing over the sides of the container. Use any general-purpose potting mix for container planting in any well-draining container (any material will do). You can also pot up verbena growing in the ground for overwintering indoors.

Generally grown as annuals, potted verbenas usually do not require repotting. Discard them at the end of the growing season.

Perennial verbenas have a short lifespan (two to three growing seasons) and do not make good permanent houseplants. However, potted verbenas are technically warm-climate perennials, so you can bring them indoors and keep them growing through the winter. If you bring them inside, cut them back by one-third before moving them, and give them an indoor location with as much sunlight as possible.

Overwintering

Potted verbena can be overwintered. Unpotted verbena will likely be killed off by the first hard frost (when temperatures dip well under freezing). You can pot up in-ground verbena by digging up the entire plant. Here's what to do:

1. Cut the plant back to less than half its size. Carefully dig it up, then trim the roots in half.
2. Find a container that leaves a couple of inches around the root ball and fill it with potting soil. Plant the verbena at the same depth it was growing in the ground.
3. Put the newly potted plant in the sunniest indoor spot you can find. Spray with a mist of water for the first few weeks indoors, then inspect frequently and water as needed. Also, check for pests, as indoor plants can be prone to aphids and other common houseplant pests.
4. As the last frost of spring approaches, prune back the plant to stimulate new growth. Once nighttime temperatures are reliably above 50°F, you can move the container outdoors or replant the verbena in the garden.

Common Pests & Plant Diseases

These plants are susceptible to powdery mildew and may be visited by common insect pests that can be treated with insecticidal soaps but none of these afflictions are typically fatal to the plants. The main insect pests include aphids, mites, leafminers, thrips, and scale insects.

You can minimize the potential for powdery mildew if you water at ground level rather than through overhead spraying. And giving the plants plenty of space to improve air circulation will help reduce these fungal infections.

How to Get Verbena to Bloom

Hybrid verbenas almost always bloom profusely if their basic cultural needs are met: lots of sun, well-draining soil with moderate moisture, and light, regular feeding. When a plant fails to bloom, the solution is often to give it a good "haircut" by pruning it back fairly severely, combined with a healthy dose of balanced fertilizer.

Bloom Months

Verbenas typically bloom from May to October.

How Long Does Verbena Bloom?

The flowers last for about two to three weeks. After they fade, the plant usually reblooms after being deadheaded.

What Do Verbena Flowers Look and Smell Like?

Verbena grows in clusters of tiny star-shaped flowers in many colors—red, pink, apricot, lavender, purple, blue, white, and bicolor.Most verbena do not have a scent unless it's lemon verbena, which has a citrusy fragrance from its crushed leaves.

How to Encourage More Blooms?

Deadhead spent flowersto encourage more blooms.

Deadheading Verbena Flowers

To deadhead verbena, wait until the first set of flowers fades. Then, using clean gardening shears or pruners, trim back the top quarter of the plants, lopping off the upper section.

Common Problems With Verbena

Verbena plants are easy to grow and maintain. The trickiest part with hybrid verbenas is giving them the right amount of water, which can lead to common problems if not done right.

Plants Dry Up or Die Back

When verbenas get too little water, they dry up and die back. They can tolerate short droughts and drier soil, but anything longer than a few weeks in hot weather will kill them. Usually, 1 inch of water applied weekly is adequate, but this can be too much for plants planted in poorly draining, dense soils. One strategy is to watch the plant daily and withhold water until the leaves show signs of curling, then water it thoroughly.

Plants Become Leggy

When verbenas get leggy and sparse, it could signify that the plant is growing outward, looking for more light. Make sure the plant receives at least six hours of sunlight. If the sun isn't the issue, severely prune back and feed the plant. Pruning and feeding should stimulate thick new growth and a flush of flowering.

Plants Wilt and Turn Brown

A plant with too much water or compacted soil can develop root rot. Inspect the roots. If they appear dark brown, it's likely root rot. Reduce watering frequency. Apply a fungicide to curb the disease. For best results to encourage recovery, dig up the plant, trim off any black or brown root sections, apply fungicide, and replant in fresh, well-draining potting soil.

From: thespruce