Blackhaw Viburnum

(Caprifoliaceae - Honeysuckle Family)

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Form
• large ornamental shrub or small ornamental tree
• maturing at up to 15' tall by 10' wide
• upright oval growth habit in youth, becoming upright rounded, spreading, or irregular with age
• slow growth rate
• Culture
  • full sun to full shade
  • prefers moist, well-drained soils of average fertility in full sun, but is adaptable to poor soils, compacted soils, soils of various pH, permanently moist soils, dry soils, moderate heat, drought, and pollution
  • propagated by rooted stem cuttings, seeds, or transplanting of suckers
  • Honeysuckle Family, with no serious pest or disease problems, except for occasional powdery mildew as a leaf cosmetic disease, which sometimes occurs in late August or early September and is persistent until leaf drop
  • moderately available in ball and burlap from, and primarily sold as a multistemmed shrub, but also trained into single-leader or multi-trunked tree forms
  • the twiggiest and most dense Viburnum, resembling a shrubform Washington Hawthorn (hence the common name of Blackhaw Viburnum, with the "black" referring to the color of very old bark, and the "haw" referring to the Hawthorn-like appearance)
  • in addition to being confused with Viburnum lentago, it also shares many morphological features in common with Viburnum cassinoides (Witherod Viburnum, noted for its consistent pink and blue Autumn fruits) and Viburnum rufidulum (Rusty Blackhaw Viburnum, noted for its super-glossy dark green Summer foliage that explodes into vibrant scarlet or bright yellow hues in Autumn)

• Foliage
  • medium- to dark green, elliptical, sparsely and finely serrated (appearing entire at first glance), with a concave petiole that is is widened (subtlely winged) but has smooth (non-warty and non-undulating) margins
  • fall color is variable from dark green, burgundy, red, orange, yellow, or purple, and often a mixture thereof, and can be quite showy, especially when the shrub is sited in full sun

• Flowers
  • creamy-white, flat-topped inflorescences to 2.5" in diameter bloom in early May, effective for one to two weeks

• Fruits
  • a mixture of green, yellow, and red-pink fruits transition to blue-black or blue-pink at maturity, often bloomy when ripe and attracting wildlife (especially birds)
  • can be profusely borne from August through early December and rather attractive when viewed up-close or from a short distance

• Twigs
  • twigs are smooth, gray, and relatively thin, having a repeated branching pattern that gives them a very dense twigginess (with numerous short lateral twigs that mimic the fine-textured thorns and twigs of Washington Hawthorn, but without the actual thorns)
  • vegetative buds are valvate with two outer scales, while the prominent floral buds are swelled at the base and taper quickly to a short stubby apex with two scales
  • emphemeral pairs of small blue-green auricles (at the base of the newly emerging stems) are not long persistent in Spring, but abscisce within six weeks of bud break

• Trunk
  • multi-trunked, brown-gray, and smooth in youth, but becoming platy and gray-black with age

• ID Summary
  • multitrunked, densely twiggy upright growth habit in youth quickly becomes rounded and sprawling with age, to form an extremely dense and often ragged canopy
  • leaves are elliptical, sparsely serrated to nearly entire, lustrous, medium- to dark green, and have characteristic smooth-margined winged petioles
  • Viburnum prunifolium (Blackhaw Viburnum) and Viburnum lentago (Nannyberry Viburnum) are similar and can be easily confused, but have the following differences:
    • Blackhaw Viburnum has smooth-margined wide petioles, with nearly entire leaves that are less susceptible to powdery mildew, and have good to excellent fall color, with the emergent stems having a pair of miniature blue-green basal auricles that abscise by late Spring, with a growth habit that is more rounded and very densely twiggy with age, and plump Winter floral buds that have a very short "stalk" and short acute tip
    • Nannyberry Viburnum has warty-margined wide petioles, with larger leaves that are serrated and become significantly infected with powdery mildew, and yield average to poor mixed fall color, while its growth habit is more upright, vigorous, and less twiggy, and plump Winter floral buds occur on elongated "stalks" with a long, acuminate tip that resembles a duck's bill

• Function
  • informal hedge (can be planted densely for a barrier thicket that branches and suckers from the ground-up), deciduous screen, border, large foundation, woodland edge, embankment, or naturalizing shrub for group or mass plantings
  • often found in native sites as a forest understory shrub, where it grows in deep shade but has few (if any) inflorescences

• Texture
  • medium texture in foliage and when bare
  • very thick density in foliage and when bare

• Assets
  • showy inflorescences in Spring and semi-showy fruits in Autumn
  • densely twiggy with maturity, to the point that it can be utilized as a pseudo-thorny barrier hedge
  • wildlife refuge and attraction (especially birds, who like to rest or feed in a protective, densely twiggy canopy)
  • tolerant of dense shade
  • can be limbed up into treeform status
  • urban tolerant

• Liabilities
  • the dense, low-branching, twiggy habit with its associated shade, wildlife attraction, and pesky twigs that scratch the skin, may become a liability
  • often becomes very unkempt in appearance with age (a sprawling mass of stems and suckers to form a very non-formal shrub)
  • occasional suckers from the nearby roots at its base

• Habitat
  • zones 3 to 9
  • native as an understory shrub in the Eastern and Midwestern United States

• Alternates
  • naturalizing shrubs with good solid or mixed fall color when placed in full sun (Aronia arbutifolia, Euonymus alatus, Hydrangea quercifolia, Rhus glabra, etc.)
  • deciduous shrubs ideal for naturalized mass plantings (Cornus racemosa, Ilex verticillata, Kerria japonica, Rhus aromatica, Sambucus canadensis, etc.)
  • shrubs or trees for wildlife protective refuge, that are deciduous (Crataegus, Photinia villosa, Malus, Lonicera tatarica, etc.) or evergreen (Pinus sylvestris, Taxus x media, Thuja occidentalis, Tsuga canadensis, etc.)

• Variants
  • Viburnum prunifolium 'Summer Magic' - leaves emerge bronzed, transitioning to very dark green, leathery, and more glossy Summer foliage on a more upright shrub

• Translation
  • Viburnum is the classical Latin name for Wayfaringtree Viburnum.
  • prunifolium translates as "plum-leaved", noting the similarity of the small foliage to those of some fruiting Plums (Prunus hybrids).

• Purpose
  • Blackhaw Viburnum is a very dense shrub that is ideal as a wildlife refuge, as a non-thorny barrier hedge, or in a naturalized group planting.

• Summary
  • Viburnum prunifolium is a shrub noted for its Spring flowers, Autumn fruits, fall color, and very dense twigginess.