How Cold Can Verbena Tolerate? A Guide to Growing Verbena in Chilly Weather

Verbena is a popular flowering plant that adds vibrant pops of color to gardens, containers, and hanging baskets. With its trailing and mounding habits, verbena creates visual interest and texture. But if you live in an area with cold winters, you may be wondering – how cold hardy is verbena? Can you grow verbena in chilly climates? Let’s take a look at verbena’s cold tolerance and tips for success when growing verbena in cold weather.

An Overview of Verbena’s Cold Hardiness

Most verbena varieties are best suited for warm weather and are typically classified as frost-tender annuals However, some newer verbena cultivars exhibit better cold tolerance than others Here’s a general overview of verbena’s ability to withstand chilly temps

• Most verbena varieties can tolerate temperatures down to the mid to upper 30s Fahrenheit. Once temps dip into the low 30s, damage is likely.

• Some newer verbena series like the Quartz XP and Imagination series can handle temps down into the mid to upper 20s

• Sustained freezing temps below 30°F will cause cold damage. Flowers and buds blacken, leaves turn mushy and die back.

• While verbena can take short periods of light frost or freezes, prolonged exposure to freezing will kill the plant.

• Exact cold hardiness depends on factors like location and weather. Verbena growing in ground beds may survive colder temps than container grown plants.

• In general, verbena performs best in Zones 9-11 where freezing weather is rare. With protection, you can stretch its growing range into Zones 7-8.

Tips for Growing Verbena in Cold Climates

If you live in an area with cold winters, don’t give up on growing verbena! Here are some tips to help verbena successfully overwinter:

Choose Cold-Tolerant Varieties

Select verbena varieties that are rated for colder zones like Quartz XP and Imagination. These can withstand temperatures down into the 20s. Avoid more tender varieties.

Use Sheltered Locations

Plant verbena in sheltered spots that receive warmth from southern sun exposure. This protects from cold winds. Avoid frost pockets.

Wait Until After Last Frost

Don’t jump the gun on planting. Wait until after your area’s average last spring frost to plant verbena outdoors. Planting too early increases frost damage.

Give Verbena a Head Start

Rather than sowing seeds, start with transplants. Transplants mature faster so you get more cold tolerance quicker.

Protect from Frost

When frost threatens, cover verbena with fabric row covers or frost blankets overnight. Remove covers during daytime.

Provide Excellent Drainage

Ensure beds and containers have excellent drainage. Wet soil loses temperature faster than dry soil.

Mulch Verbena

Put 2-3 inches of mulch like bark chips, straw, or leaves around verbena to insulate plant roots and crown.

Avoid Excess Fertilizer

Too much nitrogen fertilizer in fall spurs tender new growth prone to frost damage.

Bring Containers Indoors

At night, move verbena containers to a sheltered spot like a garage or patio. Return them outside daily.

What to Expect Over Winter

If verbena survives light fall frosts, expect increasing dieback as winter gets colder. Flowering will likely stop even if you protect from hard freezes. Here’s what to expect:

• Annual verbenas will eventually die from sustained freezing and frost. They lack perennial verbena’s overwintering ability.

• Dieback starts at the roots and moves upwards. Lower leaves perish first.

• Plants may go dormant but stay alive underground. Protect crowns from freezing for potential regrowth.

• In very mild winters, some sporadic winter flowering may occur. But plants lack their full vigor.

• Evergreen varieties like Quartz XP retain more foliage but don’t actively grow in winter.

• When cutting plants back in fall, leave 1-2″ of stem to protect crowns for spring regrowth.

Best Practices for Growing Verbena in Cold Climates

With smart planting techniques and protection from frost, you can enjoy verbena for an extended season even in cool climates. Follow these best practices:

• Stick with cold hardy verbena varieties rated for your zone. Quartz XP and Imagination are good choices.

• Plant verbena in beds and containers with excellent drainage. Wet soil causes cold damage.

• Give verbena plenty of sun – at least 6 hours of direct daily sun.

• Shelter verbena from cold winds which accelerate frost damage.

• Mulch verbena in fall to insulate roots from hard freezes.

• When frost is imminent, cover plants with fabric row covers or frost blankets overnight.

• Move container grown verbena to sheltered areas on cold nights.

• Avoid excess fertilization in fall that stimulates tender new growth.

• Leave some stem stubble when cutting back in fall to protect crowns.

Ideal Temperature Range for Verbena

While verbena can tolerate some temperature fluctuations, the ideal temperature range is between 68-72°F. When temps drop below or above this range, you may see stressed, stunted growth. Here are some tips:

• In hot climates, give verbena afternoon shade to prevent leaf scorch.

• Don’t overwater verbena. Too much moisture causes issues in heat and cold.

• For humid climates, monitor for signs of fungal disease and increase airflow.

• In frosty zones, plant verbena close together for added insulation.

• Stop fertilizing 6-8 weeks before your first fall frost date.

Does Verbena Freeze?

Yes, verbena will freeze. And sustained freezing temps can kill the plant. While verbena can tolerate brief temps as low as 20°F, it grows best in frost-free environments. If you want winter flowers, grow verbena in a greenhouse or bring containers indoors. But you can grow verbena solely for its spring-fall flowers if you don’t mind bare spots in winter. Just protect the roots from hard freezes.

Final Tips for Overwintering Verbena

Here are some final tips for keeping potted and in-ground verbena healthy through winter:

• Overwinter verbena indoors in a sunny window. Provide grow lights to supplement sunlight.

• Continue watering and monthly fertilization at half strength during winter dormancy.

• Prune back any dead, damaged foliage but leave lower stems to protect the crown.

• Check for pests like aphids, mealybugs, and spider mites which thrive on stressed plants.

• Transplant rootbound containers to give roots room to grow next spring.

• In spring, gradually introduce verbena to outdoor conditions over 7-10 days.

The Reward of Vibrant Verbena Flowers

While verbena won’t actively grow or flower through harsh winters, you can still enjoy months of bright blooms during the warmer seasons even in cooler climates. Just focus on cold protection strategies like planting cold-hardy varieties in sheltered microclimates and covering plants when frost threatens. With a little TLC, you’ll be rewarded with vivid verbena flowers from spring through fall.