When you’re looking for a landscape shrub with nice ornamental features, you should consider Rhus glabra, commonly known as smooth sumac. Interestingly, it has separate male and female flowers. These yellowish-green flowers bloom in the early summer, with the female flowers appearing smaller compared to the male flower.
I. Appearance and Characteristics
Rhus glabra, the smooth sumac, (also known as white sumac, upland sumac, or scarlet sumac) is a species of sumac in the family Anacardiaceae, native to North America, from southern Quebec west to southern British Columbia in Canada, and south to northern Florida and Arizona in the United States and Tamaulipas in northeastern Mexico.
Smooth sumac has a spreading, open habit, growing up to 3 m (9.8 ft) tall, rarely to 5 m (16 ft). The leaves are alternate, 30–50 cm (12–20 in) long, compound with 11–31 oppositely paired leaflets, each leaflet 5–11 cm (2–4+1⁄4 in) long, with a serrated margin. The leaves turn scarlet in the fall. The flowers are tiny, green, produced in dense erect panicles 10–25 cm (4–10 in) tall, in the spring, later followed by large panicles of edible crimson berries that remain throughout the winter. The buds are small, covered with brown hair and borne on fat, hairless twigs. The bark on older wood is smooth and gray to brown.
In late summer it sometimes forms galls on the underside of leaves, caused by the parasitic sumac leaf gall aphid, Melaphis rhois. The galls are not harmful to the tree.
Rhus glabra is a perennial deciduous shrub that is dioecious – which means it produces separate male and female plants. Thus, to get the fruits, you will need to have at least one male and one female plant. Both male and female plants exhibit yellowish-green flowers, with the female flowers appearing with a three-parted style in the center; the male flowers are larger and have five yellowed stamens.
Individual flowers of the male shrub don’t have a long bloom time, and the female flowers are replaced by large panicles of dark red fruit called drupes. The fruit ripens in the late summer and turns to seed in the late fall and winter. The flowers are loved by butterflies and other pollinators, while the berries and seeds provide food to birds throughout the autumn and winter.
II. How to Grow and Care
Sun and Temperature
An average of 6-8 hours per day of full sun is ideal for the best flower production and beautiful fall foliage. However, it will tolerate partial shade but may not showcase the nice ornamental features as exuberantly. The ideal USDA growing zone is 3-9, which means it is hardy enough for the cold winters and will survive summer heat. Since we find it in many areas of the United States, it can withstand dry climates as well as humid.
Since the yellowish green flowers spring into bloom in the spring, you may want to plant it in a protected area if you live in a climate that surprises you with frost so you can enjoy the fruit from the flowers later in the season.
Water and Humidity
Younger plants need to be watered once per week until established. Water from the bottom of the tree and allow the water to seep in and hydrate the roots. The best time of day to water is in the morning, so the shrub is hydrated for the heat of the day. There is no need to water in the winter when the plant is dormant.
Once smooth sumac is established, it is drought tolerant and will only need 18-20 inches of water per year. As a mature shrub, it does not like to be overwatered and thrives in dry soil.
Soil
Well-drained soil will keep your plant healthy and vibrant. It can grow in a variety of soil types, from clay loam to sandy loam, as long as there is no standing water near the base of the plant, and it actually prefers dry soil. It will survive in poor-quality soil and is adaptable to a wide pH range of 5.5-7.5.
Fertilizing
Upon planting your Rhus glabra, apply compost or a balanced slow-release fertilizer. After that, there is no need to fertilize this plant. You can fertilize in the fall, just before the shrub goes dormant, but keep in mind too much fertilizer will make it susceptible to pests and diseases.
Pruning
It is good practice to prune any dead, diseased, or overgrown branches and twigs in late winter or early spring as long as it is before the plant comes out of dormancy. This deciduous shrub requires medium maintenance to keep its shape by trimming lower and side stems. To prevent your plant from being invasive, trim off any root suckers that pop up frequently.
Propagation
You can propagate smooth sumac using root cuttings. Propagating it this way has the highest success rate. Here’s how:
- In the early spring, before the leaves emerge, take a 6-inch cutting from a healthy smooth sumac.
- Fill a 4-inch pot with loose soil mixed with sand or perlite. Dip the cut end in rooting hormone and insert it in the pot about halfway deep.
- Place the pot in a bright spot but away from direct sunlight.
- Keep the soil moist but not wet. After roots have started to form and the sapling has leafed out, let it grow for at least one summer in pots, watering it well, before transplanting it in the landscape.
How to Grow from Seed
Starting sumac from seed is better left to nature. The germination of the seeds is enhanced by acidification when the seeds pass through the digestive system of rabbits, pheasants, and quail, as well as by wildfires.
Potting and Repotting
Due to its size, smooth sumac is not suitable to be grown in a container. For potted sumac, choose a small variety of staghorn sumac such as Rhus typhina ‘Tiger Eyes’.
Overwintering
Smooth sumacs are very hardy plants that don’t require any overwintering measures. During the winter, they go into dormancy and will not suffer from low temperatures. However, saplings grown in pots should be winterized to protect their roots against frost damage.
Pests and Diseases
- Common Pests
Pests
Aphids are found on many ornamentals, and unfortunately, the smooth sumac species can be attacked by an aphid called the Sumac gall aphid (Melaphis rhois). These aphids produce bladder-like galls (that incubate a new aphid population) on the underside of the leaves along the mid-vein and near the stems. The gall is light green and can measure up to ½ to 1 inch in size. The gall may cause early coloring and shedding of the leaves but doesn’t affect the overall health of the shrub.
You can remove and destroy any stems that exhibit galls, but the best course of action is to rid your shrub of the aphids. These tiny green or brown insects hang out on the underside of the leaves and feed on the juices from the shrub. Attract beneficial bugs such as lady beetles and parasitic wasps. Neem oil, diatomaceous earth, and pyrethrins are good choices for controlling a large aphid population.
Broad mites are related to ticks and spiders, and they feed on chlorophyll in the leaves, causing them to discolor and die. They can show up mid-summer when the weather turns hot. These pests are difficult to see and are only about the size of the period at the end of this sentence. They have a sac-like body with no distinct head and eight legs.
Use a magnifying glass to identify, and you will also notice eggs, webbing, and stippling. To control mites, it is best not to use chemicals because this kills the beneficial bugs that keep the mite population under control. Instead, introduce predatory mites and blast the shrub with water to remove the mites.
- Common Diseases
Leaf spot and rust on Rhus glabra are caused by fungi. Dark spots form on the leaves, and you may notice raised areas on the affected leaf if affected with leaf spot. With rust, you will see masses of spores on the infected leaves. For both diseases, the leaves may fall prematurely and it rarely causes damage to a healthy shrub.
It’s best to prevent fungal diseases from attacking by removing any debris on the ground surrounding the shrub and to water from the base. Having well-drained soil will also prevent fungi from growing in standing water. Fungicides are not recommended unless a severe infection has affected all the leaves several years in a row.
- Common Problems
The primary concern when growing Rhus glabra is the root suckers that spread aggressively. This is nice when you want to form thickets and shrub borders, but not so on other occasions. To prevent this deciduous shrub from becoming invasive, you will need to remove any suckers that show up. Just lob them off the young shoots with shears or dig them up. This will be a yearly process but one that doesn’t take a significant amount of time.
III. Uses and Benefits
- Ornamental uses
One of the showiest native shrubs or small trees of North America, smooth sumac is known for its compact size, attractive branching and canopy shapes. However, the most decorative are the bright orange and crimson red autumn leaves and red, cone-shaped fruit clusters produced by female trees that last through most of the winter, even when the tree has lost its leaves. It is usually planted as a specimen tree. Note that it produces suckers that tend to form thickets. Its spreading habit needs to be controlled in a garden setting, making it unsuitable for shrub borders, but a great choice for soil stabilization.
- Other uses
Native Americans ate the young sprouts as a salad. The fruit is sour and contains a large seed, but can be chewed (to alleviate thirst) and made into a lemonade-like drink. Deer forage the twigs and fruit. In 2020, archaeologists unearthed a pipe at a dig in Central Washington state, showing chemical evidence that a Native American tribe had smoked Rhus glabra either alone or in a blend with tobacco, perhaps “for its medicinal qualities and to improve the flavor of smoke.”
IV. Harvesting and Storage
Collect smooth sumac seeds in the fall when the fruits turn red. Collect, wash, and dry the seeds and store them in a dry, cool place.
Find Where to Buy the Best Smooth Sumac (Rhus glabra)
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