Black haw (Viburnum prunifolium) is a white-flowered shrub that grows throughout the eastern and southern United States. Black haw bears large clusters of dark berries in early fall. These berries are consumed by all manner of wildlife – especially birds and bears.
I. Appearance and Characteristics
Viburnum prunifolium (known as blackhaw or black haw, blackhaw viburnum, sweet haw, and stag bush) is a species of Viburnum native to eastern North America, from Connecticut west to eastern Kansas, and south to Alabama and Texas.
It is a deciduous shrub or small tree growing to 2–9 metres (7–30 ft) tall with a short crooked trunk and stout spreading branches; in the northern parts of its range, it is a shrub, becoming a small tree in the southern parts of its range. The bark is reddish-brown, very rough on old stems. The branchlets are red at first, then green, finally dark brown tinged with red. The winter buds are coated with rusty tomentum. The flower buds ovate, 1 cm long, much larger than the axillary buds. The leaves are simple, arranged oppositely, up to 9 cm long and 6 cm broad, oval, ovate or orbicular, wedge-shaped or rounded at base, serrate, acute, with serrated edges with a grooved and slightly winged red petiole 1.5 cm long; they turn red in fall.
The leaves are superficially similar to some species of Prunus (thus “prunifolium”); they come out of the bud involute, shining, green, tinged with red, sometimes smooth, or clothed with rusty tomentum; when full grown dark green and smooth above, pale, smooth or tomentose beneath.
The flowers are creamy white, 9 mm diameter; the calyx is urn-shaped, five-toothed, persistent; the corolla is five-lobed, with rounded lobes, imbricate in bud; the five stamens alternate with the corolla lobes, the filaments slender, the anthers pale yellow, oblong, two-celled, the cells opening longitudinally; the ovary is inferior, one-celled, with a thick, pale green style and a flat stigma and a single ovule. The flowers are borne in flat-topped cymes 10 cm in diameter in mid to late spring.
The fruit is a drupe 1 cm long, dark blue-black with glaucous bloom, hangs until winter, becomes edible after being frosted, then eaten by birds; the stone is flat and even, broadly oval. Wherever it lives, black haw prefers sunny woodland with well-drained soil and adequate water.
II. How to Grow and Care
Sunlight
This shrub prefers to grow in full sun or partial shade, meaning it needs at least three hours of direct sunlight on most days. The best flowering and fruiting will occur in higher levels of sunlight. However, it’s ideal to provide the shrub with some afternoon shade in the hottest parts of its growing zones.
Temperature and Humidity
Blackhaw viburnum is hardy both to hot and cold temperatures. It can tolerate temperatures around 90 degrees Fahrenheit as long as its moisture needs are met. And it will survive conditions below freezing, though once frost hits in the fall is when it starts to lose its leaves for winter. Humidity typically isn’t an issue for the shrub. In very high humidity it’s important to ensure good air flow around the plant to prevent fungal diseases. And in dry conditions, a layer of mulch over the root zone can help to retain soil moisture.
Watering
Moist soil makes black haw 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
Black haw 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
The shrub will benefit from an annual feeding in the spring, especially if you have poor soil. Use a balanced, slow-release fertilizer around the plant, following label instructions.
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 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. Black haw 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
You should propagate blackhaw viburnum in early spring to create new plants. Make sure to choose a healthy plant free from disease. You can propagate blackhaw viburnum by cuttings. Here’s how:
- Take 4 to 6 inch cuttings in late fall after leaves have dropped or in spring using a sharp instrument.
- Remove leaves from the bottom of the cutting and keep the cutting moist.
- Mix one part peat and one part perlite and plant the cutting leaving half out.
- Cover with plastic. Keep the pots in indirect light and mist occasionally.
- Check for rooting in approximately four weeks.
How to Grow from Seed
Plant seeds in small pots in early spring. Make sure to keep them lightly moist and in a bright and warm spot. Once the seedlings are about one foot tall, you can transplant them outdoors. Here’s how to plant blackhaw viburnum from seeds:
- Save seeds by harvesting the fruit once it turns its black-blue color and drying the berries (with pulp) in a cool location.
- Once dry, store the seeds over the winter in a brown paper bag in a cool, dark spot.
- Plant them in small pots in the early spring in a seed-starting mix that you keep lightly moist.
- Keep the pots in a bright, warm spot as they germinate.
- Transplant the seedlings outdoors when they’re about a foot tall. Make sure to bring the young plants outside for gradually longer stretches for about a week to acclimate them to direct sun.
Overwintering
To prepare your shrub for winter, cut down watering in the fall. You can also add mulch to the base of the plant to help insulate it. Loosely cover with burlap if snow or heavy winds are expected.
How to Get to Bloom
Blackhaw viburnum blooms in late spring with small, white flower clusters which gave way to berries in the fall. Full sun and well-drained, acidic soil help encourage blooming. Make sure not to trim while dormant as you may lose the flower-producing buds. Once blooming, make sure to provide the plant with afternoon shade. Deadheading is not necessary as the flowers give way to fruit.
Pests and Diseases
This shrub is relatively easy-going, but there are a few common issues to look out for. It’s particularly prone to root rot, but this is easily preventable if you know how to properly care for it.
Root Rot
Armillaria root rot is one of the most common afflictions blackhaw viburnum is prone to. The fungus affects the roots of the plant and will turn the leaves yellow and cause them to drop. To avoid this, make sure the plant has proper air circulation and is not overwatered. Soil should also have ample drainage.
Leaf Mildew
You may notice something white and dusty on the leaves, which is known as powdery mildew. In this case, apply a fungicide. To prevent mildew, avoid overwatering and ensure adequate air circulation around the plants..
III. Uses and Benefits
- Medicinal uses
For centuries, black haw has been used for medical purposes, mainly for gynecological conditions. The bark is the part of the plant used in treatments.
The active components include scopoletin, aesculetin, salicin, 1-methyl-2,3 dibutyl hemimellitate, and viburnin. Tannin is another chemical component of black haw.
Native Americans used a decoction of black haw to treat gynecological conditions, including menstrual cramps, aiding recovery after childbirth, and in treating the effects of menopause. As a folk remedy, black haw has been used to treat menstrual pain, and morning sickness. Due to its antispasmodic properties, the plant may also be of use in treating cramps of the digestive tract or the bile ducts.
Black haw’s primary use was to prevent miscarriages. The primary use of black haw today is to prevent menstrual cramps. The salicin in black haw may also be of use in pain relief.
By specific Native American tribes
The Cherokee have several uses for the plant. They take an infusion of it to prevent recurrent spasms, use the root bark as a diaphoretic and a tonic, and take a compound infusion of it for fever, smallpox and ague. They also use an infusion of the bark as a wash for a sore tongue. The Lenape combines the root bark with leaves of other plants and use it to strengthen the female reproductive tract or use the root bark in a tonic alone. The Mi’kmaq take an infusion of the plant before and during parturition.
- Culinary uses
The Meskwaki eat the fruit raw and also cook them into a jam.
Find Where to Buy the Best Blackhaw (Viburnum prunifolium)
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