The Koreanspice viburnum is a medium sized deciduous shrub that produces beautiful, fragrant flowers. With its small size, dense growing pattern and showy flowers, it’s an excellent choice for a specimen shrub as well as border plant. So how do you go about growing Koreanspice viburnum in your garden? Keep reading to learn more Koreanspice viburnum information.
I. Appearance and Characteristics
Viburnum carlesii, the arrowwood or Korean spice viburnum, is a species of flowering plant in the family Adoxaceae (formerly Caprifoliaceae), native to Korea and Japan (Tsushima Island) and naturalised in Ohio, USA. Growing to 2 m (7 ft) tall and broad, it is a bushy deciduous shrub with oval leaves which are copper-coloured when young. Round clusters of red buds open to strongly scented, pale pink flowers in late spring. These are followed in late summer by oval red fruits ripening to black in autumn.
The Latin specific epithet carlesii refers to William Richard Carles (1848–1929), a British plant collector in Korea.
The cultivars ‘Aurora’ and ‘Diana’ have gained the Royal Horticultural Society’s Award of Garden Merit.
II. How to Grow and Care
Sunlight
Koreanspice viburnum in a cold environment loves to grow in full sun on slopes and edging rocks in its natural habitat. Varieties adaptable to warmer climates grow well in full sun to medium shade; long exposure to strong light should be avoided. They can be shaded by buildings or big trees. A certain amount of scattered light is needed in the flowering phase to ensure enhanced and continuous flowering in warmer climates, but overall, plants in this genus perform well receiving 5-6 hours of continuous sunlight in a day.
Temperature and Humidity
Viburnums are generally tolerant of high heat but do best with some shade during the hottest periods of summer. They prefer humid climates, but will tolerate dry conditions.
Watering
Maintain evenly moist soil with regular watering. Weekly watering—about 1 inch per week—is typical in many areas, but drier climates or seasons may necessitate more frequent watering. This plant is relatively drought-resistant once established but will perform best if it receives a deep weekly watering during dry spells
Soil
Koreanspice viburnum likes fertile, soft, slightly acidic soil with good drainage. It likes moist soil but does not grow well in waterlogged soils. It can grow in moderately fertile, fully drained soils that keep minimum moisture, but cannot withstand poor soil. The optimum soil pH range is 5.5-6.6. It can tolerate acidic media and drought with good air circulation in the root zone, which is made possible by the addition of peat moss or coco coir to the media. The best potting soil would be to mix 1 part of fully decomposed organic matter into 2 parts of garden soil.
Fertilizing
Applying organic fertilizer in a planned and reasonable way can improve soil structure, increase soil organic matter content, and increase soil fertility. Fertilization is indispensable for growth, and fertile soil promotes the overall growth of the plants. When transplanting, apply an adequate amount of basal fertilizer, and apply fertilizer every 2 weeks during the flourishing growth stage. Fertilizer should be applied when the weather is clear and the soil is dry.
To ensure normal growth, fertilization should be carried out before the dormant period or after the leaves are preparing to fall, and before the soil freezes. Don’t fertilize the soft cuttings until they start sprouting. For transplants, fertilizer rich in nitrogen is necessary to initiate vegetative growth. In the later flowering stages, it can be replaced with high phosphorus fertilizer.
Planting Instructions
The best time for transplanting is in late spring or early summer. It is best to plant them all on the same day. Take care that roots aren’t exposed to direct light and are buried deep into the planting pit.
Before planting, you need to know the height of a fully mature plant for the variety that you are growing. Generally, the role of thumb is to divide the height of the plant by 2 to determine to space. For example, if the selected variety is predicted to grow 4 m tall at full maturity, space the plants 2 m apart. Dig a pit measuring 30 cm deep and 30 cm wide.
Pruning
Light pruning to remove dead or dried branches or injured parts of the plant can be done at any time of the year. Koreanspice viburnum doesn’t need severe pruning; how much depends on the type of variety and purpose of growing.
Pruning to shape and beautify can be done in the late winter or early spring. When growing for borders and hedges, cut only 1/3 of the branches if they are severely intermingled. In other cases, pruning can be initiated right after flowering but before the setting of fruit. To avoid frost damage, don’t prune during frost or severe cold.
Propagation
One common method of propagating Korean Spice Viburnum is through stem cuttings. In late spring or early summer, select a healthy, non-flowering stem from the parent plant. Using a sharp and clean pair of pruners, cut a 6-8 inch section of the stem just below a node (the point where leaves emerge). Remove the lower leaves, leaving only a few at the tip.
Prepare a pot with a well-draining medium, such as a mix of perlite and peat moss. Dip the cut end of the stem in a rooting hormone powder (optional) to promote root development, then gently insert it into the prepared medium, ensuring at least two nodes are buried. Place the pot in a warm, bright location with indirect sunlight. You may also mist the cutting regularly to maintain high humidity.
In a few week’s time, you should notice new roots forming which indicates successful propagation.
Another propagation method for Korean Spice Viburnum is layering, which involves encouraging a stem to root while still attached to the parent plant. In early spring, select a flexible branch close to the ground. Gently wound the area where you want roots to form by scraping off some bark or making a shallow cut (cincturing technique).
Apply a rooting hormone to the wounded area, then bury it in a shallow trench filled with a mix of soil and compost. Place and anchor the wounded stem in place using a U-shaped wire or a small rock. Over time, the buried section will develop roots, and once well-established, you can cut the new plant free from the parent and transplant it to its new location.
By exploring the art of propagation, you can unlock the secrets of multiplying the beauty of Korean Spice Viburnum. Whether through stem cuttings or layering, these techniques allow you to create new plants with the same captivating blooms and intoxicating fragrance.
How to Grow from Seed
Growing viburnums from seed is not often done, as the process is lengthy, requiring as much as 18 months before the seeds even germinate and sprout. If you want to try it, collect some seeds from the dried fruits, then store them in a moist, warm environment (76 to 86 degrees Fahrenheit) for about two months. Next, they will need a winter-like period of cold stratification (you can do this in a refrigerator) for three months.
Now, the prepared seeds can be sown in seed flats (just barely covered with seed starter mix) until they sprout. When true leaves appear, the tiny seedlings can be transplanted into individual pots and grown on for at least a full season, until they are large enough for garden planting.
The entire process can take as many as three years, so it’s much more common to propagate by rooting stem cuttings.
Potting and Repotting
Not all viburnums are suitable for container culture, but smaller cultivars of Korean spice viburnum usually do fairly well. Choose a pot that is somewhat larger than the plant’s nursery container (a pot at least 20 inches in diameter is recommended). Because potted viburnum can be sensitive to heat on the roots, choose a material that does not absorb heat, such as a resin pot or one made from fiberglass.
Use a potting mix that is slightly acidic and well-draining. A mixture of standard potting soil and perlite or sand works well. A potted viburnum will need more frequent watering and feeding than an in-ground shrub. Plan on watering at least twice a week and feeding monthly.
A potted viburnum will quickly use up the soil’s nutrients, so repot it every four or five years. Rather than potting up to a larger container, remove the plant from the pot, shake off the soil, then replant it into the same container using fresh growing mix.4
Overwintering
Viburnums are very hardy shrubs that generally do not require winter protection against cold—at least if they are grown within their recognized hardiness range. With all viburnums, withhold water and fertilizer as fall progresses. Avoid allowing the shrub to soak in damp conditions over the winter, as this is an invitation to root rot.
A blanket of mulch over the root zone can be helpful if you are growing the shrub in a region where it is borderline hardy. In these regions, some growers protect the shrub with a tent or wrap of burlap for the winter to avoid winter burn. However, viburnums generally recover nicely from some winter dieback.
Pests and Diseases
Common Pests & Plant Diseases
It’s quite likely your Korean spice viburnum will never show any pest or disease problems at all. But one problem you may experience is leaf curl at the tips of branches. The culprit will most likely be aphids.5 If you can manage to catch them in action, spray them with organic neem oil. Luckily, if restricted to just a relatively small portion of the entire plant, leaf curl does no long-term harm. Prune off the affected branch tips and dispose of them properly, and the plant will be none the worse for it.
Korean spice viburnum can also be susceptible to viburnum crown borer, an insect that bores holes in the lower stems, causing die-back. Keeping the plant in good health often prevents these insects from gaining a foothold. Where crown borers are known to be a problem, pesticides sprayed on the lower 12 inches of the stems can kill borers before they damage the shrub.6
Bacterial leaf spot, powdery mildew, and Armillaria root rot are among the diseases that occasionally cause problems with this plant. Prevent these problems by giving them good air circulation by watering them at ground level, and making sure the soil has excellent drainage. Diseased plant parts should be cut away and discarded.
Common Problems
In most cases, reported complaints with Korean spice viburnum are due to pest problems and fungal diseases that cause leaf spots or branch die-back (see above). But another very common cause of leaves drying up and branches dying back is simply that the plant is suffering the effects of drought. Although this shrub is sometimes described as having good drought resistance, that reputation only holds for well-established plants and for relatively short drought periods, up to four weeks or so. It’s quite common in these days of water-usage sensitivity for homeowners to allow ground-covers and garden plants to get quite thirsty—the belief is that they readily go dormant and will quickly return once rainfall returns.
Korean spice viburnum falls into that category of plants that is drought tolerant only up to a certain point. Beyond that line, the shrub will quickly make you pay for your miserly approach to water. It’s best to water your thirsty viburnum deeply and immediately when you begin to see leaves start to dry up and turn black
III. Uses and Benefits
The ornamental koreanspice viburnum shrub can create a wonderful border and hedge in gardens, with its full foliage and attractive bunches of white flowers. It also works as a centerpiece plant in cottage gardens. In addition to its lovely looks, its flowery fragrance and showy fall berries attract both plant enthusiasts and hungry birds.
