Verbena: Indoor Sow or Potted Plant Annual
How to Sow and Plant
Annual verbena may be grown from seed sown early indoors, or from potted plants.
Sowing Seed Indoors:
- Sow verbena 8-10 weeks before the last frost.
- Water the seed flat the night before sowing because seeds are sensitive to high moisture.
- Sow seeds 1/8 inch deep in seed starting formula.
- Bottom heat speeds germination, keep the soil temperature 65-75 degrees F.
- Keep evenly moist.
- Seedlings emerge in about 20 days.
- As soon as seedlings emerge, provide plenty of light on a sunny windowsill or grow seedlings 3-4 inches beneath fluorescent plant lights turned on 16 hours per day, off for 8 hours at night. Raise the lights as the plants grow taller. Incandescent bulbs will not work for this process because they will get too hot. Most plants require a dark period to grow, do not leave lights on for 24 hours.
- Seedlings do not need much fertilizer, feed when they are 3-4 weeks old using a starter solution (half strength of a complete indoor houseplant food) according to manufacturer’s directions.
- If you are growing in small cells, you may need to transplant the seedlings to 3 or 4 inch pots when seedlings have at least 2 pairs of true leaves before transplanting to the garden so they have enough room to develop strong roots
- Before planting in the garden, seedling plants need to be “hardened off”. Accustom young plants to outdoor conditions by moving them to a sheltered place outside for a week. Be sure to protect them from wind and hot sun at first. If frost threatens at night, cover or bring containers indoors, then take them out again in the morning. This hardening off process toughens the plant’s cell structure and reduces transplant shock and scalding.
Planting in the Garden:
- Select a location in full sun with good rich moist organic, well-drained soil.
- Prepare the bed by turning the soil under to a depth of 6-12, inches removing any debris, and lightly raking as level as possible.
- The addition of organic matter (leaf mold, compost, well-rotted manure) benefits all gardens and is essential in recently constructed neighborhoods.
- Plant on a cloudy day or in late afternoon to reduce transplant shock.
- Dig a hole for each plant, approximately 12 inches apart large enough to amply accommodate the root ball.
- Unpot the plant and gently loosen the root ball with your hands to encourage good root growth.
- Place the top of the root ball even with the level of the surrounding soil. Fill with soil to the top of the root ball. Press soil down firmly with your hand.
- Use the plant tag as a location marker.
- Water well.
How to Grow
- Keep weeds under control during the growing season. Weeds compete with plants for water, space and nutrients, so control them by either cultivating often or use a mulch to prevent their seeds from germinating.
- Mulches also help retain soil moisture and maintain even soil temperatures. For annuals an organic mulch of shredded leaves lends a natural look to the bed and will improve the soil as it breaks down in time. Always keep mulches off a plant’s stems to prevent possible rot.
- Plants need about 1 inch of rain per week during the growing season. Use a rain gauge to check to see if you need to add water. It's best to water with a drip or trickle system that delivers water at low pressure at the soil level. If you water with overhead sprinklers, water early in the day so the foliage has time to dry off before evening, to minimize disease problems. Keep the soil moist but not saturated.
- Until plants become established, some protection from extreme winds and direct, hot sunlight may be necessary. Good air movement is also important.
- After new growth appears, a light fertilizer may be applied. Keep granular fertilizers away from the plant crown and foliage to avoid burn injury. Use low rates of a slow release fertilizer, as higher rates may encourage root rots.
- Remove spent flower heads to keep plants flowering until fall.
- Monitor for pests and diseases. Check with your local Cooperative Extension Service for pest controls recommended for your area.
- Remove plants after they are killed by frost in fall to avoid disease issues the following year.
- Deadhead or shear back verbenas after the main flush of flowers to encourage re-bloom.
- Use verbenas to add bright color to any sunny planting in dry, well-drained soil.
- Combine them with nasturtium, gazanias, blanket flowers, lavenders, achillea, sedums, purple coneflower, and yuccas.
- Garden verbenas make good edging and container plants.
- They also attract butterflies, beneficial insects, and hummingbirds to the garden.
Common Disease Problems
Botrytis: This fungus causes a grey mold on flowers, leaves, stems and buds. It thrives in cool wet weather conditions. Burpee Recommends: Remove affected plant parts, avoid watering at night and getting water on the plant when watering. Make sure plants have good air circulation. Contact your Cooperative Extension Service for fungicide recommendations.
Powdery Mildew: This fungus disease occurs on the top of the leaves in humid weather conditions. The leaves appear to have a whitish or greyish surface and may curl. Burpee Recommends: Avoid powdery mildew by providing good air circulation for the plants by good spacing and pruning. Contact your Cooperative Extension Service for fungicide recommendations.
Root Rots: A number of pathogens cause root rots of seedlings as well as mature roots. Burpee Recommends: Practice crop rotation and do not plant related crops in the same area for several years. Pull up and discard infected plants. Make sure your soil has excellent drainage. Contact your Cooperative Extension Service for recommendations.
Septoria Leaf Spot: This disease is most severe during rainy seasons in closely planted gardens. Circular spots with gray centers and dark margins appear on the lower older leaves. Fungus spores are produced and darken the center of the spots. There is a progressive loss of foliage. Burpee Recommends: Remove and destroy infected plant debris. Don't handle or brush against plants when they are wet. Rotate plantings. Remove weeds growing nearby.
Common Pest and Cultural Problems
Aphids: Greenish, red, black or peach colored sucking insects can spread disease as they feed on the undersides of leaves. They leave a sticky residue on foliage that attracts ants. Burpee Recommends: Introduce or attract natural predators into your garden such as lady beetles and wasps which feed on aphids. You can also wash them off with a strong spray, or use an insecticidal soap.
Cyclamen Mite: These mites damage plants by sucking juice from stems and leaves. They multiply rapidity in hot, dry weather. They can only be seen using a magnifying glass. Plants will look distorted and stunted, and may not bloom. Flowers will be distorted, streaked and blotched. Leaves can become cupped, curled, dwarfed and thickened. Burpee Recommends: Discard plants that are severely infested. Avoid working with infested plants. Keep plants watered in dry weather. For heavy infestations consult your Cooperative Extension Service for insecticide recommendations.
Gall Midges: Adults are tiny flies usually with long antennae resembling a fruit fly. Larvae are tiny yellow to orange maggots that can be found inside the galls feeding on the plant. Galls are distortions or lumps of plant tissue on plant leaves or stems. Burpee recommends: Removing infected leaves from the garden. If there are a lot of galls on the plant, remove and destroy the infected plant.
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage. Sanitation is important so be sure to remove all debris at the end of the season.
Spider Mites: These tiny spider-like pests are about the size of a grain of pepper. They may be red, black, brown or yellow. They suck on the plant juices removing chlorophyll and injecting toxins which cause white dots on the foliage. There is often webbing visible on the plant. They cause the foliage to turn yellow and become dry and stippled. They multiply quickly and thrive in dry conditions. Burpee Recommends: Spider mites may be controlled with a forceful spray every other day. Try hot pepper wax or insecticidal soap. Check with your Cooperative Extension Service for miticide recommendations.
Is verbena an annual or perennial? There are annual and perennial species. The verbena which is generally grown as an annual is a tender perennial.
Can I grow verbena in containers? Yes it is ideal for containers.
Are verbenas good pollinator plants? Yes they attract bees, butterflies and hummingbirds to the garden.
Why did my verbena die? Verbenas are very sensitive to wet soils and are susceptible to root rots in poorly drained soil.