Taxonomy and Botany of Korean Spice Viburnum
Plant taxonomy classifies Korean spice viburnum shrubs as Viburnum carlesii. These bushes are also called "Korean spicebush." However, be careful not to confuse them with other plants that have a similar common name:
- Lindera benzoin is known as "spicebush."
- Calycanthus occidentalis is called "California allspice" or "California spicebush."
Korean spice viburnums are deciduous flowering shrubs.
They are in the moschatel family of plants, another member being elderberry (Sambucus). A popular cultivar is 'Aurora.'
Shrub Characteristics and the Cross-Pollination Problem
Korean spice viburnum shrubs reach 4-6 feet in height at maturity, with a similar spread. The 'Compactum' cultivar is sometimes referred to as a "dwarf" type, because it stays a bit smaller (3-4 feet). Rather showy pink buds precede the flowers in spring; the latter, although white, retain hints of that earlier pink color. The white flower clusters, which are nicely rounded, are very fragrant.
Red berries replace the blooms in summer if a compatible cross-pollinator is present (that is, these bushes are not self-pollinating). In autumn, these berries mature to a dark color (almost black). But if you are looking forward to fall color, count more on the fall foliage of the leaves than on the berries. In the opinion of Ohio State University, the berries (drupes) are usually "ornamentally insignificant" -- even when cross-pollination does take place.
Fall leaf color starts out reddish but can morph into a purplish color.
If you still wish to try for berries, you will be faced with the cross-pollination problem. Why is it a "problem?" The difficulty here is twofold:
- The pollinator plant cannot be of the same cultivar. So, for example, you cannot pollinate an 'Aurora' with another 'Aurora.' Instead, you would have to pair your 'Aurora' with another viburnum from the same species (a hybrid bred from the same species will also work).
- The pollinator plant must also come into bloom at the same time as the plant from which you are trying to get berries. This trait is tough to research successfully online, since plants bloom at different times in different areas.
One possibility is to pair a V. carlesii with a V. x burkwoodii 'Mohawk,' since the latter is a hybrid cultivar, with one of the parents being V. carlesii. But before you buy, inquire at the garden center as to whether the two plants come into bloom at the same time in your area. Better yet, if you will be shopping for the two at the same time, buy them only if both are blooming.
Planting Zones, Sun and Soil Requirements, Care
Grow Korean spice viburnum shrubs in planting zones 4-7.
Plant them in full sun to partial shade. These bushes grow best in moist but well-drained ground that has a soil pH on the acidic side. Note that furnishing what seems like sufficient irrigation will not necessarily satisfy this requirement for a moist soil. If you grow the bush under a large Eastern white pine tree, for example, it may well fail to bloom very much. Large trees sop up a lot of water from the surrounding soil. If it is too late to follow this advice and you have already installed your bush under such a tree, consider transplanting it.
The result could be a vastly improved flowering display each spring.
Another problem that you may experience in caring for this bush is leaf curl (at the tips of branches). The culprit will most likely be aphids. If you can manage to catch the little buggers in action, you could spray them with the organic herbicide, Neem oil. But they can come and go very quickly, leaving a damaged leaf behind. Luckily, leaf curl, if restricted to just a relatively small portion of the entire plant, does no long-term harm: It is problematic only on an aesthetic level, marring the appearance of the foliage during that summer and fall. Prune off the affected branch tips (disposing of them properly) to get rid of them, and the plant will be none the worse for it.
Outstanding Characteristics, Landscaping Uses
No doubt, the single most outstanding feature of Korean spice viburnum shrubs is their aromatic quality.
Their blossoms are among the landscape's most fragrant flowers. Another plus is that these plants are among the flowering shrubs that bloom in early spring, satisfying our craving to see landscape color as soon as possible once winter ends. Honorable mention goes to the color of their fall foliage. In fact, they are undoubtedly one of the best shrubs for fall color.
Korean spice viburnum bushes certainly merit specimen plant status in the spring landscape. Due to their exceptional fragrance, you should include these bushes in your entryway landscaping or as foundation shrubs, so as to be able to appreciate their aroma more fully. Given their impressive attributes, it is surprising that this plant is not grown more widely than it is: It may be one of the best plants of which beginning gardeners are generally unaware.
Wildlife Attracted to Korean Spice Viburnum Shrubs
These bushes are among the many plants that attract butterflies. Specifically, the caterpillars of spring azure blue butterflies use Korean spice viburnums as a food source. Wild birds are also attracted to the shrubs, to feed on the berries (if present). As to a certain unwanted visitor from the Animal Kingdom, one can list them among the rabbit-proof flowers with some confidence.
Origin of the Names
The "Korean" part of the name is straightforward enough, since Korean spice viburnum shrubs are indigenous to Korea. But what about the reference to "spice?" Rather than referring to a culinary use, "spice" here is an attempt to describe the complexity of the plant's aroma. The fragrance is sweet but much more than just sweet. There is a sharpness to the fragrance, and some say the smell reminds them of cloves.
V. carlesii is named for William Richard Carles (1848 – 1929) one of those British plant collectors known for bringing home specimens from China and the surrounding region.
More Shrub Care Tips: Pruning
Buds for Korean spice viburnums form on the prior season's growth. Therefore, if you wish to prune the plants back in order to shape them and/or restrict their size, do your pruning just after they have finished flowering.
Just cut the tips to promote branching and a bushier look. In addition, remove any dead branches and/or branches rubbing against each other.