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Viburnum: A Guide to Cultivation and Care
Overview
Viburnum shrubs are popular landscape plants due to their attractive foliage, beautiful blooms, and adaptability to various growing conditions. This comprehensive guide will provide insights into the cultivation, care, and troubleshooting of viburnum plants.
Types of Viburnum
Viburnums encompass a wide range of deciduous and evergreen shrubs and small trees. Some varieties exhibit deciduous or evergreen characteristics depending on their location.
Deciduous Viburnum Varieties
- Swamp-haw viburnum (Viburnum nudum): Reaches heights of 12 feet, with white flowers and blue-black fruits. Prefers full sun to partial shade.
- Hobblebush (Viburnum lantanoides): Grows up to 8 feet tall, with white flowers and red fruit clusters that mature to blue-black. Enjoys moist shade but tolerates hot sun and dry soil.
- Nannyberry (Viburnum lentago): Can reach 12 feet in height, with creamy white flowers and attractive fall foliage. Prefers moist shade but tolerates full sun and dry soil.
- Korean spice viburnum (Viburnum carlesii): A popular flowering shrub with aromatic pink buds that bloom into white flowers. Fall leaves turn vibrant shades of red, purple, and orange.
Evergreen Viburnum Varieties
- David viburnum (Viburnum davidii): A low, compact shrub with distinctive leathery dark blue-green leaves. Pink flower buds open into creamy white flowers in spring. Can be deciduous in colder climates.
- ‘Spring Bouquet’ (Viburnum tinus): Produces dense clusters of white flowers on reddish stems in late winter and early spring. Fruits develop into metallic blue-black berries.
- ‘Emerald Lustre’ (Viburnum odoratissimum): Upright cultivar with lustrous green leaves and mid-spring white blooms. New growth has a pink tinge. Fruits transition from red to purple-black.
- Walter’s viburnum (Viburnum abovatum): A native evergreen that can reach 20 feet in height. Produces white flowers in spring. Best suited for warmer climates.
Cultivation
Planting
- Choose a planting site with well-drained soil and ample sunlight.
- Dig a hole twice as wide as the container and deep enough to accommodate the root ball.
- Gently remove the plant from the container and place it in the hole.
- Backfill the hole halfway with soil, add water, and then fill the rest of the hole.
- Add a 2-inch layer of mulch around the base of the plant to retain moisture.
Watering
- Water newly planted viburnums every 7 to 10 days during hot weather.
- Established plants generally need deep watering once a week, either through rainfall or irrigation.
- Native varieties with well-established root systems have good drought tolerance.
Fertilizing
- Most viburnums benefit from an annual application of a balanced, time-release fertilizer mixed into the soil in spring.
- Follow the product label instructions for dosage.
- Established shrubs typically do not require additional feeding.
Care
Pruning
- Trim leggy shoots in early summer to maintain the shrub’s shape.
- Avoid pruning during dormancy, as this can remove bloom-producing buds.
- Broken, dead, or diseased branches should be removed promptly.
- Tree forms of viburnum may require some pruning to achieve the desired shape.
Propagation
- Viburnum can be propagated from softwood or hardwood cuttings.
- Take cuttings in the morning and remove leaves from the lower third.
- Dip the stem in rooting hormone and plant it in a moist mixture of peat and perlite.
- Cover the cutting with plastic and keep it in indirect light until roots form.
Pests and Diseases
- Viburnum leaf beetle (VLB): A serious pest that can cause significant damage. Remove egg-infested leaves and encourage predatory insects.
- Fungal diseases: Powdery mildew, downy mildew, and fungal leaf spots can affect viburnum. Avoid overhead watering, use fungicides on affected plants, and remove infected plant parts.
- Armillaria root rot: A fungal disease that causes stunted or yellow leaves. Remove and discard affected plants to prevent spread.
- Canker: A fungal problem that affects stressed trees and shrubs. Restore plant health to promote recovery.
Troubleshooting
Why is my viburnum not blooming?
- Ensure the plant receives ample sunlight.
- Check soil drainage and avoid overwatering.
- Avoid excessive nitrogen fertilization, which can promote lush foliage but inhibit blooming.
- Do not prune during dormancy, as this can remove bloom-producing buds.
My viburnum leaves are discolored or wilted.
- Check for signs of fungal diseases and apply appropriate treatments.
- Armillaria root rot can cause stunted or yellow leaves. Dig up and discard affected plants.
- Canker can cause dead, wilted, and discolored leaves. Restore plant health to promote recovery.
Additional Tips
- Choose viburnum varieties that are well-suited to your climate and growing conditions.
- Plant viburnum in groups to enhance their visual impact.
- Use viburnum as a hedge, screen, or specimen plant.
- Enjoy the beauty and benefits of viburnum shrubs for years to come.
