Viburnum odoratissimum Seeds | Sweet Viburnum
LATIN NAME: Viburnum odoratissimum
COMMON NAME: Sweet Viburnum
Plant Profile
A generation ago this plant was a member of the honeysuckle family. Molecular work moved the genus, together with the elders, into the small family Adoxaceae, whose type is a modest woodland herb rather than a shrub, and the change is now routine in every modern flora. Structure supports the move in its own way. The snowball viburnums get their look from a ring of sterile, enlarged florets around the outside of the head, whereas the panicles of sweet viburnum are entirely fertile, so every flower in the truss can turn into fruit.
The worst pest of the genus in eastern North America is Pyrrhalta viburni, a European beetle that arrived without its natural enemies. The larvae hatch in spring and strip the leaves to a lace of veins, and the adults then lay their eggs in the tips of young twigs, which kills the shoots they use. The practical response is to inspect the twig tips in winter, cut out and destroy the ones carrying the characteristic row of egg pits, and repeat the search on regrowth, since the beetle has several generations and a hedge can be defoliated more than once in a season.
The species can reach ten metres in the wild, but in a garden it is normally held at two or three as a clipped screen, and it takes hard shearing without sulking. Shear soon after flowering if a tight surface matters more than berries, and leave the tips alone for the rest of the year if the fruit is what you are growing the hedge for. Set the plants sixty to ninety centimetres apart and the line closes within a couple of seasons.
Science & Biotechnology
The leaves carry the vibsane diterpenoids, an unusual family of diterpenes built on an eleven-membered ring and named after the genus itself. These compounds have drawn steady interest from pharmacology laboratories, where they have been screened for cytotoxic and anti-inflammatory activity, and they appear across several viburnums rather than in this species alone. The genus also produces the iridoids typical of its order.
Uses & Benefits
The botanical name uses the superlative of the Latin word for fragrant, so the plant is literally labelled the most sweet-scented viburnum of its genus. Each floret is tiny, five-lobed and white, with five stamens, and the florets are packed into a pyramidal panicle at the end of the shoot. The scent is not a daytime display; it peaks in the evening, which points to moths as the pollinators in the native thickets rather than to bees.
The flowers are followed by oval drupes that begin red and darken towards black-purple as they ripen, each holding a single stone. The fruit is for the birds, not the kitchen, and a hedge left unclipped will be stripped by wintering thrushes, which deposit the stones along fence lines and under trees. Gardeners who want the berries should prune with a light hand, because the flower buds for the following year are carried at the tips of the current growth.
Along the coasts of southern Japan and the Ryukyu Islands the plant takes a different shape, with thicker, glossier leaves whose margins curl back slightly and whose surface sheds salt spray. That form, treated as a variety and often sold under its own name, is the one to use for a sea-front hedge, though it is a little less hardy than the mainland plant and wants the mildest position available.
Growing from Seed
Gather the drupes once they have darkened and softened, rub off the pulp, and sow the stones in a gritty, humus-rich mix, covering them lightly. The endocarp is hard and the embryo inside is slow, so a cool, damp season before warmth is the reliable route; keep the trays shaded and never let them dry out. Plant the young plants out at hedge spacing when they are about forty centimetres tall, and water them through their first summer while the roots are finding their way.
Deep, moist soil suits sweet viburnum, and once established it tolerates a dry spell better than its glossy leaves suggest. It is a plant for mild winters only, roughly the warmer half of the temperate zone, and young plants benefit from a mulch over the root run in their first cold season. A balanced feed in spring is enough; over-feeding produces soft growth that the leaf beetle prefers and that shears badly.
Our Take
For a screen that smells of summer, this is the viburnum I plant first, and its autumn berries make a fine contrast with the red-fruiting linden viburnum. Where the ground is colder, the weatherproof foliage of leatherleaf viburnum is the safer bet, and for a spring show of sterile white balls rather than scent, the Chinese snowball viburnum is in a class of its own.
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