Verbena hybrids are usually planted as potted nursery plants in the spring, or started indoors from seeds 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 matter of a few weeks. Pruning the plants back a couple of times during the growing season will help prompt new blooms and extend the blooming season.
Light
Plant verbena in full sun. Flowering will be much reduced in shady locations. This is a plant that requires at least six hours of sun daily, and eight to 10 hours is much better.
Soil
These plants like fairly 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. Keep plants evenly moist until established. Once mature, these plants have average water needs (1/2 to 1 inch per week) but will tolerate short periods of drought. 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 period of the summer. 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 do appreciate a monthly application of balanced, slow-release flower fertilizer to help them keep up the flower show, which can last from spring until frost. For the amount of fertilizer to use, follow the product label instructions. If grown in containers, use a water soluble fertilizer throughout the growing season.
Types of Verbena
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 a number of pure Verbena species that you can try as garden perennials, though finding them can be a challenge. 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 to 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 finely cut leaves and a very low growing habit. V. bonariensis is a native of Brazil that grows to 4 feet with lavender flowers. It is hardy in zones 7 to 11. It is sometimes known as purple-top vervain.Glandularia canadensis was 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. tenuisecta (moss verbena) has delicate, lace-like foliage and grows to 5 or 6 inches. It blooms during late summer and early fall and is hardy in zones 7 to 9.V. rigida (rigid verbena) is a spreading variety that makes a good ground cover. Notable cultivars include ‘Polaris’ and ‘Stantos’. It is hardy in zones 7 to 9.
Pruning
Shear back verbena plants once or twice per season to stimulate new blossoms and keep the plants full and tidy-looking. Deadheading spent flowers is not typically necessary.
Propagating Verbena
The best way to propagate hybrid garden verbenas is a traditional vegetative method—clipping off stem segments and rooting them. This is the tried-and-true method that works for many herbaceous plants. With verbenas, taking stem cuttings in the fall can be a good way to keep plants alive through the winter, rooting them indoors and then potting them up to prepare for transplanting outdoor in the spring. Here’s how to do it:
How to Grow Verbena From Seed
Most verbenas are hybrids that don’t “come true” from the seeds you collect from garden plants, so seed propagation should be done from purchased commercial seeds, which are bred under carefully controlled greenhouse conditions. They should be started indoors 12 to 14 weeks before your average last frost date to ensure flowers by early summer. Wrap the seeds in a moist paper towel and place them in a plastic bag. Refrigerate them for seven days, then plant in cell trays filled with a commercial seed-starter mix. Press the seed into the soil and barely cover with additional seed-starter mix. Mist the starter mix to moisten it, then cover the tray and place in a dark location out of direct sunlight, at a temperature of about 75 degrees Fahrenheit. When the seeds begin to sprout (21 to 30 days) remove the cover and bring the tray out into direct light. The seedlings can be transplanted into their own pots filled with commercial potting mix—or directly into the garden—when they have several sets of true leaves. Make sure to 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. For container planting, use any general-purpose potting mix, in any well-draining container (any material will do) You can also pot up verbena growing in the ground for overwintering indoors. Because they are normally grown as annuals, potted verbenas normally do not require repotting; they are simply discarded at the end of the growing season. But potted verbenas are technically warm-climate perennials, so it is possible to bring pots indoors and keep them growing through the winter. If you do so, cut back the foliage by one-third before moving them, and give them an indoor location with as much sunlight as possible. But be aware that verbenas have a short lifespan as perennials; they do not make good permanent houseplants.
Overwintering
Potted verbena can be overwintered. Unpotted verbena will likely be killed off by the first hard frost (when temperatures dip well under freezing) unless you pot it by digging up the entire plant. Here’s what to do:
Common Pests & Plant Diseases
These plants are susceptible to powdery mildew, and they may be visited by common insect pests that can be treated with insecticidal soaps. Such problems are rarely fatal to the plants, however. Powdery mildew can be minimized if you make a point to 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 good “haircut” by pruning it back fairly severely, combined with a healthy dose of balanced fertilizer.
Common Problems With Verbena
Gardners often have trouble getting the watering routine right when growing hybrid verbenas. Too much water and the plant can develop root rot; too little water and the plant can dry up and die back. While this plant tends to like dryish soils and tolerates short drought, extended drought that lasts more than a couple of weeks in hot weather can kill the plants. Perfecting the timing for watering these plants can be tricky. Usually, the standard 1 inch of water applied weekly is adequate—but this can be too much for plants planted in poorly draining dense soils. Successful growers often find that the best strategy is to carefully watch the plant and withhold water just until the leaves start to show signs of curling—then water it thoroughly. This approach requires daily observation. Verbenas sometimes become overly leggy and sparse. Make sure the plant receives at least 6 hours of sunlight. If sun isn’t the issue, the course of action here is to severely prune back and feed the plant, which will quickly stimulate thick new growth and a flush of flowering.
