Viburnum (Viburnum)

The Viburnum genus consists of more than 150 evergreen, semi-evergreen, and deciduous woody plants from the Caprifoliaceae family. Native mostly to Northern temperate zones, some viburnums also hail from South America and Southeast Asia. Various species are frequently planted in Mediterranean areas such as Sonoma County.

Structure and Seasonal Beauty

Viburnum shrubs easily contribute to garden structure with interesting foliage, seasonal flowers, colorful fruits or berries, and, in many cases, stunning fall color, all of which become highlights in seasonal landscapes.

Leaf texture varies from species to species; some are soft and toothed while others are leathery and glossy with smooth margins.
Blossoms also vary from species to species and may be lace cap, domed, or snowball-shaped clusters, white or creamy white to pink-flushed.
Some varieties need another viburnum pollinator close by to produce a good showing of berries that may be dark red to blue to black, all appealing to wildlife.
Many viburnumsgrow 4-6 ft. in height with about a 4 ft. spread, although some, such as Viburnum sargentii and Viburnum opulus, can reach nearly 20 feet or the height of a small tree. A few dwarf varieties, such Viburnum opulus ‘Nanum,’ are less than 3 ft.

Landscape Anchors

Several viburnum shrubs serve as the key element in garden structure and permanence. While evergreen species are often considered superior in these roles, many deciduous shrubs can be just as valuable.

Because of their substantial size and ornamental features, viburnums deserve a featured site with plenty of space in landscapes and gardens.
Viburnums are not fussy. They can be grown in sun or part shade; however, sunny sites are preferable for flower and berry production.
Most prefer moderately fertile and moist, well-drained soil.
They are not drought tolerant and require adequate moisture during hot, dry summers.
Viburnums do not require regular pruning, but it is wise to cut back vigorous shoots for preferred balance and shape in early- to mid-summer.
Do not deadhead or the plant will not produce its charming berries.

Selected Species

Many species are quite resilient and do not require regular attention or maintenance. Periodic checks on irrigation during summer dry spells are important, however, since shrubs are not drought-tolerant and will suffer with inadequate moisture.

Viburnum tinus ‘Spring Bouquet’ is aptly named, as its blooms are most abundant in late winter and early spring.
- Note that ‘Spring Bouquet’ is a lower-growing cultivar of the plain species, Viburnum tinus, that grows much taller, to 10 ft. or more.
- ‘Spring Bouquet’ blossoms begin as pale pink buds that open into tight, 2-4 in. clusters of tiny, fragrant white flowers. Small lavender-to-deep-purple berries accompany the flowers which bloom periodically throughout the year.
- It is this succession of buds, blooms, and berries that is so attractive to birds, bees and butterflies. Thus, if the viburnums are threatened by an infestation of aphids, to which they are often prone, the birds can be of help in removing them.
- With a heavy infestation, spray aphids with a strong stream of water or give them a dose of Neem oil. This viburnum species is deer resistant.
- Because of its dense foliage compared to other viburnums, Viburnum tinus—or laurustinus as it is often called—makes an excellent hedge, foundation planting or even a single specimen.
Long-blooming Viburnum plicatum tomentosum ‘Summer Snowflake’ or double file viburnum has a mature height and width of 4-8 ft. tall and wide.
- The 1½-to 2-in. lace cap clusters of white flowers are perched along the shrub’s horizontally tiered branches from June through September.
- Berries age from red to black; foliage changes from deep orange to burgundy-red in autumn.
- Other cultivars of double file Viburnum plicatum tomentosumare truly show-stoppers with their graceful, outstretched spread of horizontal branches.
  - ‘Mariesii’ is a deciduous shrub with a moderate growth rate, green oval leaves that turn red in the fall, and large flat-headed white flowers.
  - ‘Shasta’ has abundant, large, white, lace cap flowers, bright red fruit and maroon foliage in the fall.
  - Both of these cultivars, however, have shorter bloom periods and are twice the size of ‘Summer Snowflake.’
- Viburnum macrocephalum (syn. m. ‘Sterile’), Chinese snowball, is evergreen or semi-evergreen with clusters of large snowball-shaped flowers in spring, lime green initially before turning pure white.
  - This shrub likes sun to partial shade, well-drained soil, and grows eventually to 12 ft. or more.
- Viburnum carlesii, Korean spicebush, is deciduous and grows to 4-6 ft. high and wide. Snowball-like clusters of waxy flowers emerge pink, then gradually fade to white.
  - Korean spicebush is noted for a heady, intoxicating fragrance, hence the common name.
  - In late summer to fall, the red berries turn black. Viburnum carlesii is tolerant of adverse conditions and is generally trouble-free.
- Viburnum x burkwoodii is a hybrid between carlesii and V. utile. Often semi-evergreen in cooler microclimates of Sonoma County, it matures at about 6-8 ft. tall by 4-6 ft. across.
  - Red or pink buds open to highly fragrant white flowers tinged with pink in mid-spring or earlier.
  - Clusters of berries change from green to red to black by early autumn. Fall color varies from brilliant red to dull burgundy.
  - This viburnum likes full sun to partial shade and prefers moist, well-drained, slightly acidic soils, but it is quite adaptable to poor soils and does withstand low water in a shaded site. Flowering is heaviest in a sunny site.
- Viburnum davidii is one of the few smaller evergreen viburnums, 3-4 ft. high and wide at maturity. Its 4-6 in. deep green leaves curve downwards to reveal handsome etched veins.
  - Foliage nearly covers all stems to impart a mounding effect. Bluish black fruits follow spring flower clusters.
  - This species enjoys morning sun only and will burn in hot afternoon conditions.

September 2023