Nannyberry (Viburnum lentago)

Nannyberry plants (Viburnum lentago) are large native tree-like shrubs native to the U.S. They have glossy foliage that turns red in fall as well as attractive fruit. For more information about nannyberry shrubs, or information on how to grow nannyberries, read on.

I. Appearance and Characteristics

Viburnum lentago, the nannyberry, sheepberry, or sweet viburnum, is a species of Viburnum native to North America.

It is a large shrub or small tree growing upwards to 9 m (30 ft) tall with a trunk up to 25 cm (10 in) in diameter and a short trunk, round-topped head, pendulous, flexible branches. The bark is reddish- to grayish-brown, and broken into small scales. The twigs are pale green and covered with rusty down at first, later becoming dark reddish brown, sometimes glaucous, smooth, tough, flexible, and produce an offensive odor when crushed or bruised.

The winter buds are light red, covered with pale scurfy down, protected by a pair of opposing scales. Flower-bearing buds are 2 cm (3⁄4 in) long, obovate, long pointed; other terminal buds are acute, 8.5 to 12.7 mm (1⁄3 to 1⁄2 in) long, while lateral buds are much smaller. The bud scales enlarge with the growing shoot and often become leaf-like.

Like all viburnums, the leaves are arranged in opposite pairs on the twigs; they are oval, 5–10 cm (2–4 in) long and 2–5 cm (3⁄4–2 in) broad, wedge-shaped, rounded or subcordate at base, with an acuminate apex and a finely serrated margin, and a winged petiole. They open from the bud involute, bronze green and shining, hairy and downy; when full grown are bright green and shining above, pale green and marked with tiny black dots beneath. In autumn they turn a deep red, or red and orange.

Nannyberry (Viburnum lentago)
Viburnum lentago 5350059 Keith Kanoti, Maine Forest Service, USA CC BY 3.0

The flowers are small, 5–6 mm (0.20–0.24 in) in diameter, with five whitish petals, arranged in large round terminal cymes 5–12 cm (2–4+3⁄4 in) in diameter; flowering is in late spring. The calyx is tubular, equally five-toothed, persistent; the corolla is equally five-lobed, imbricate in the bud, cream-white, one-quarter of an inch across; lobes acute, and slightly erose.

There are five stamens, inserted on the base of the corolla, alternate with its lobes, exserted; filaments slender; anthers bright yellow, oblong, introrse, versatile, two-celled; cells opening longitudinally. The pistil has a one-celled inferior ovary, the style thick, short, light green, and the stigma broad; there is one ovule in each cell.

The fruit is a small round blue-black drupe, 8–16 mm (0.31–0.63 in) long on a reddish stem; it is thick-skinned, sweet, and rather juicy. The stone is oblong oval, flattened.

The roots are fibrous. The wood is ill-smelling, dark orange brown, heavy, hard, close-grained, with a specific gravity of 0.7303.

II. How to Grow and Care

Sunlight

Nannyberry 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

Nannyberry (Viburnum lentago)
2249-Viburnum lentago-DZ-8.12 Vojtěch Zavadil CC BY-SA 3.0

The optimum growth temperature range is between 5 to 27 ℃. It has good cold resistance; some native North American species can tolerate temperatures below -25 ℃. Its growth is poor at temperatures above 29 ℃, so it cannot survive in tropical summers. Germination requires 20 consecutive days of seed exposure to 24 ℃.

Nannyberry needs occasional watering during hot and dry conditions. The average plant during its first 2 years of growth needs 1.2 to 1.5 cm water bi-weekly. Once established, it doesn’t need much watering.

Watering

Moist soil makes nannyberry more vigorous. Insufficient water decreases the ornamental value of the whole plant and leads to abnormal flowering. Water management is the key to survival during transplanting. The newly transplanted plants must be irrigated continuously for 3-4 weeks to ensure that the soil is fully absorbent and closely connected with the root system.

During severe hot and dry conditions, 7 to 8 mm of water weekly is sufficient. In daily maintenance, just keep the soil moist. Too much soil moisture affects air permeability, inhibits root respiration, causes rotten roots, and even causes the plant to die in severe cases.

Soil

Nannyberry 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

Nannyberry (Viburnum lentago)
Viburnum lentago Udo Schröter CC BY-SA 2.0

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

Planting a tree/shrub seedling or small potted tree/shrub properly is important to ensure its healthy growth and development. Here are the steps you can follow to plant a tree:

  • Choose the right spot: Select a spot with adequate sunlight, water, and soil drainage. Make sure the tree has enough space to grow to its full size without interfering with other plants, structures, or utility lines.
  • Prepare the soil: Dig a hole that is twice as wide and slightly shallower than the root ball of the seedling. Remove weeds or debris from the area. Loosen the soil around the edges of the hole to help the roots grow more easily.
  • Plant the seedling: Place the seedling in the hole, making sure the top of the root ball is level with the ground surface. Gently spread out the roots and fill in the hole with soil, tamping it down lightly as you go.
  • Water the seedling: Water the tree/shrub deeply and thoroughly after planting, making sure the soil is evenly moist. This will help settle the soil around the roots and eliminate any air pockets.
  • Monitor the growth: Keep an eye on the seedling to make sure it is getting enough water and sunlight, and that it is not being attacked by pests or diseases. Prune any damaged or dead branches as necessary, and provide support if needed.

Pruning

Light pruning to remove dead or dried branches or injured parts of the plant can be done at any time of the year. Nannyberry doesn’t need severe pruning; how much depends on the type of variety and purpose of growing.

Nannyberry (Viburnum lentago)
1515-Viburnum lentago-DZ-8.12 Vojtěch Zavadil CC BY-SA 3.0

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

Planting nannyberry from seeds is not recommended. It can take 12-18 months. Soft cutting is one of the best options to grow the plant. Be sure each soft cutting contains 2 nodes for both underground and aboveground parts. Mix 1/3 fully decomposed organic matter with 2/3 dugout soil. Place the soft cuttings into a hole and press the soil gently to keep its level at the garden level. Immediate watering will make a suitable watering pit after the soil has settled.

Pests and Diseases

Nannyberry plants have no serious pest or disease problems. The only thing to watch for is powdery mildew if air circulation is poor. This disease appears in late summer, covering the shiny leaves with whitish powder. Although making the leaves less attractive, powdery mildew doesn’t damage the plant. One other issue requiring nannyberry care is the plant’s tendency to sucker abundantly as it gets older. It can form a large thicket or colony. If you do not want this to happen, make removing suckers part of your care regimen.

III. Uses and Benefits

Nannyberry (Viburnum lentago)
Viburnum lentago – nannyberry Matt Lavin CC BY-SA 2.0

As suggested by the alternative name sweet viburnum, the fruit is (unlike that of many viburnums) widely palatable. The bark and leaves were also used by Native Americans in the preparation of herbal medicines.

It is admired for its compact habit, its lustrous foliage which insects rarely disfigure, its beautiful and abundant flowers, its handsome edible fruit and its brilliant autumnal color. It readily adapts itself to cultivation, and is one of the best of the small trees of eastern America for the decoration of parks and gardens in all regions of extreme winter cold. It is easily raised from seeds which, like those of the other American species, do not germinate until the second year after they are planted.

It has been hybridized with Viburnum prunifolium in gardens to give the hybrid Viburnum × jackii.

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