There has been considerable uncertainty amongst botanists as to the best way of treating the genus Rhus, with some viewing it in a strict sense as comprising of around 35 species and electing to separate the other species into several distinct genera; whilst others prefer to view the genus in a looser sense being comprised of perhaps 250 species grouped into several subgenera. The genus is treated here in its strict sense, with many other species that have at times been included here being moved to the genera Cotinus, Searsia and Toxicodendron.

Common Name: Smooth Sumach

General Information

Rhus glabra is a deciduous shrub with a fairly sparse branch structure; it usually grows up to 3 metres tall, though occasionally reaches 6 metres. The plant produces root suckers from a dense, shallow root system, and can spread aggressively to form thickets[, ].
A multipurpose plant, it is harvested from the wild for local use as a food, medicine and source of materials. It can be used as a pioneer to restore native woodland, in soil stabilization projects, as a shelterbelt planting and is also often grown as an ornamental, valued especially for its autumn leaf display[].
Rhus glabra has a very wide distribution, a large population, is not currently experiencing any major threats and no significant future threats have been identified. The plant is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2018)[].
This plant may become weedy or invasive in some regions or habitats and may displace native vegetation if not properly managed[].

Known Hazards

The genus Rhus is being treated in its strict sense here, so it excludes the many species with highly toxic and irritant sap (these are included in Toxicodendron). Although the two genera are very similar, it is relatively simple to distinguish which is which, the poisonous species (Toxicodendron) have axillary panicles and smooth fruits whilst non-poisonous species (Rhus) have compound terminal panicles and fruits covered with acid crimson hairs[, ].
Whilst the genus Rhus in this treatment is generally seen as having a non-toxic sap there are some suggestions that the sap of some species in the genus (including this one) can cause a skin rash in susceptible people.

Botanical References

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Range

N. America - British Colombia to Quebec, south to California, northern Mexico (Chihuahua, Sonora, Tamaulipas), Texas and Florida

Habitat

Thickets and waste ground on dry soil and by streams[, , ]. The best specimens are found in rich moist soil[, ]. Open woodlands, prairies, on dry rocky hillsides, and in canyons[].

Properties

Weed Potential	Yes
Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Shrub
Height	3.00 m
Pollinators	Bees
Self-fertile	No
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Rhus glabra is a very cold-hardy plant, when fully dormant it can tolerate temperatures down to at least -25°c, especially if the wood has been fully ripened by a hot summer[]. However, the young growth in spring is more tender and can be damaged by late frosts.
Succeeds in most well-drained moderately fertile soils, growing best in full sun but tolerating light shade[, , ]. Tolerates poor sandy soils and slightly saline conditions[, ]. Established plants are very drought tolerant[].
A fast-growing but short-lived plant in the wild[]. Single-stem plants are short-lived in cultivation, but if the plants are coppiced regularly and allowed to form thickets, then they will live longer and also be more ornamental with larger leaves[]. Any coppicing is best carried out in early spring[].
A very ornamental plant, there are some named varieties[]. It is closely allied to Rhus typhina[], hybridizing with that species where their ranges overlap[, ].
The plant usually resprouts freely from rhizomes if the top growth is cut back or burnt by fire[].
Plants have brittle branches and these can be broken off in strong winds[]. Plants are also susceptible to coral spot fungus[]. Plants in this genus are notably resistant to honey fungus[].
A good bee plant[].
A dioecious species - both male and female forms must be grown if fruit and seed are required.

Edible Uses

Fruit - raw or cooked[, , ]. An acid flavour, it has been used as a substitute for lemon juice[]. When soaked for 10 - 30 minutes in hot or cold water it makes a very refreshing lemonade-like drink (without any fizz of course). The mixture should not be boiled since this will release tannic acids and make the drink astringent[, , , , , , ]. Individual drupes are rather small - they have a flattened-globe shape around 4mm long, have very little flesh and are covered with red, sticky hairs. However, they are produced on fairly large panicles and so are easily harvested.

Root - peeled and eaten raw[, ]. This report should be treated with some caution due to possible toxicity[].

Young shoots - peeled and eaten raw[, ]. This report should be treated with some caution due to possible toxicity[].

The bark has been eaten as a delicacy by children[]. This report should be treated with some caution due to possible toxicity[].

Medicinal

Smooth sumach was employed medicinally by various native North American Indian tribes who used it to treat a variety of complaints[]. It is occasionally used in modern herbalism where it is valued for its astringent and antiseptic qualities. Some caution should be employed in the use of this species since it can possibly cause skin irritations. It is best only used under the supervision of a qualified practitioner.

A tea made from the bark or root bark is alterative, antiseptic, astringent, galactogogue, haemostatic, rubefacient and tonic[, , , ]. It is used in the treatment of diarrhoea, fevers, general debility, sore mouths, rectal bleeding, uterine prolapse etc[, ].
It is used as a gargle to treat sore throats and applied externally to treat excessive vaginal discharge, burns and skin eruptions[, ]. The powdered bark can be applied as a poultice to old ulcers, it is a good antiseptic[].

A tea made from the roots is appetizer, astringent, diuretic and emetic[, ]. An infusion is used in the treatment of colds, sore throats, painful urination, retention of urine and dysentery[].
The root is harvested in the autumn and dried for later use[].

An infusion of the green or dried branches has been used in the treatment of TB[]. A decoction of the branches, with the seed heads, has been used to treat itchy scalps and as a bathing water for frost-bitten limbs[].

The milky latex from the plant has been used as a salve on sores[].

A tea made from the leaves was used in the treatment of asthma, diarrhoea and stomatitis[]. A poultice of the leaves has been used to treat skin rashes[]. The leaves have been chewed to treat sore gums and they have been rubbed on the lips to treat sore lips[].

The berries are diuretic, emetic, emmenagogue, purgative and refrigerant[, ]. They are used in the treatment of late-onset diabetes, stranguary bowel complaints, febrile diseases, dysmenorrhoea etc[, , ]. They have been chewed as a remedy for bed-wetting[, ].

The blossoms have been chewed as a treatment for sore mouths[]. A decoction of the blossoms has been used as a mouthwash for teething children[]. An infusion of the blossoms has been used as an eye wash for sore eyes[].

The plant (part not specified) is used in homeopathic remedies to treat conditions such as epistaxis and occipital headache, foetid flatus and ulceration of the mouth[].

Agroforestry Uses:

The plant has an extensive root system and is fairly wind tolerant, though branches can be broken off in very strong winds. It is planted for soil stabilization on slopes and roadsides, and is also used as a shelter screen[, ]. It can quickly establish itself in open sunny locations and so can be used as a pioneer species for establishing woodlands[].
The flowers are a good forage for bees[].

Other Uses

The leaves are rich in tannin, containing about 10 - 25%[]. Up to 31.2% has been obtained from some plants[]. They can be collected as they fall in the autumn and used as a brown dye or as a mordant[]. The twigs and root are also rich in tannin[].

A black and a red dye is obtained from the fruit[, ].
A black dye is obtained from the leaves, bark and roots[].
An orange or yellow dye is obtained from the roots harvested in spring[, , ].
A light yellow dye is obtained from the pulp of the stems[].
The inner bark, mixed with bloodroot (Sanguinaria canadensis) and the inner bark of wild plum (Prunus sp.) has been used to make a yellow dye[].

An extract of the bark is used as an ingredient in commercial cosmetic preparations as a skin conditioner[].
An extract of the bark, roots and berries is used as an ingredient in commercial cosmetic preparations as an astringent, antiseborrhoeic and skin conditioner[].

An oil is extracted from the seeds[]. It attains a tallow-like consistency on standing and is used to make candles. These burn brilliantly, though they emit a pungent smoke[]. The smooth, yellowish seeds are 3 - 3.5mm long)[].

Wood - soft, light, brittle[, ].

Propagation

Seed - best sown in a cold frame as soon as it is ripe. Pre-soak the seed for 24 hours in hot water (starting at a temperature of 80 - 90c and allowing it to cool) prior to sowing in order to leach out any germination inhibitors[]. This soak water can be drunk and has a delicious lemon-flavour. The stored seed also needs hot water treatment and can be sown in early spring in a cold frame[]. When they are large enough to handle, prick the seedlings out into individual pots and grow them on in the greenhouse for their first winter. Plant them out into their permanent positions in late spring or early summer, after the last expected frosts.
Cuttings of half-ripe wood, 10cm with a heel, mid summer in a frame[].
Root cuttings 4cm long taken in December and potted up vertically in a greenhouse. Good percentage[, ].
Suckers in late autumn to winter[].