How to Plant, Grow, and Care for Rhus Glabra

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. 

The fruits from female sumac form into drupes, and these reddish brown clusters contrast nicely with the dark green leaves. It also exhibits beautiful golden and red fall foliage that brings attention to any landscape.

Smooth sumac can form thickets that many bird species and small mammals use for protection. For example, the red-banded hairstreak butterflies and wild turkeys use the smooth sumac as a food source. The fruit is much-needed food in the fall and winter for countless bird species. You can even make your own sumac spice from the edible fruit and yellow dye from the inner bark. 

Rhus glabra is native to many wild areas and open woodlands across the Northeastern United States to the west and even north to southern Canada. This species isn’t affected by many disease problems, and it’s considered a medium-maintenance shrub that loves full sun and will tolerate dry soil as long as it is well-drained. This growing guide will help you determine if the smooth sumac is the best species for your landscape. 

What is Rhus Glabra?

The botanical name for sumac is Rhus glabra. There are many other species of sumac, but this guide focuses on the smooth sumac. Other common names for the smooth sumac are common sumac, Rocky Mountain sumac, red sumac, scarlet sumac, wild turkeys, and western sumac. 

Native Area

We consider this plant a pioneer species, and it is native to southern Canada, Mexico, and the lower 48 states – excluding California. However, it’s most common in the Northeastern United States. 

Characteristics

Rhus glabra is a perennial deciduous shrub that is dioecious – which means it produces separate male and female shrubs. Thus, to get the fruits, you will need to have at least one male and one female. They both 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 yellow 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 fall and winter.

Other identifying features are the dark green alternate oblong-lanceolate compound leaves that are odd-pinnated with 9-31 leaflets. The tree has a single trunk with multiple major branches and twigs, and its extensive root system helps it form thickets, making it ideal for shrub borders. Small twigs are smooth, while mature bark is horizontally fissured, brownish-gray, and slightly warty.   

Planting

To plant Rhus glabra, choose a location with full sun to partial shade and well-draining soil. Dig a hole about 12 to 18 inches wide and 10 to 12 inches deep to accommodate the root system. If planting multiple shrubs, space them six to ten feet apart to allow for proper growth.

Place in the hole, ensuring the root crown sits level with the surrounding soil. Backfill with a mix of native soil and compost, then gently firm it down. Water thoroughly after planting and provide about one inch per week until established. Add a two- to three-inch layer of mulch around the base to help retain moisture and suppress weeds.

How to Grow

Rhus glabra is an easy shrub to grow because it tolerates many types of conditions. By providing it with ideal moisture, sunlight, temperature, nutrients, and soil, you’ll have a healthier and more vigorous shrub with plenty of bloom time for the butterflies to enjoy.  

Light

An average of six to eight 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.

Water

Younger Rhus 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 it 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 shrub 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, 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. 

Temperature

The ideal USDA growing zone is 3-9, which means it is hardy enough for cold winters and will survive summer heat. Since we find it in many areas of the United States, it can withstand dry and humid climates. 

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.  

Fertilizing

Upon planting your Rhus glabra, apply compost or a balanced slow-release fertilizer. After that, there is no need to fertilize. 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. 

Maintenance

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 it comes out of dormancy. This deciduous shrub requires medium maintenance to keep its shape by trimming lower and side stems. To prevent your shrub from being invasive, trim off any root suckers that pop up frequently.  

Propagation

Smooth sumac can be propagated by seed, root cuttings, and divisions. Since it will spread aggressively once you have one shrub, you can easily separate them. Just dig up the sucker in the fall and transplant it to another location. 

Stratify and scarify the seed before planting in the late spring. Or you can sow the seed outside in late fall or early winter to give it the stratifying period it needs to germinate. Provide water as needed to keep the soil moist until germination and place them in a spot to receive the warmth from the sun. 

Cuttings from stems are the most reliable and easy method that gives you a larger shrub in a shorter amount of time. In the early summer, cut a healthy branch that is at least six inches long and has leaf nodes on the bark, then place it in a prepared area outside or a pot with potting soil. Keep the soil moist until roots have formed. 

Common Problems

Overall, the smooth sumac is easy to grow and you won’t run into many concerns. However, there are a few you should know because they are susceptible to leaf spot, rust, aphids and mites. This troubleshooting section should help with any disease problems. 

Growing 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. 

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 a half to one 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, or diatomaceous earth, 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. 

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.

Frequently Asked Questions