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.
Rhoeidium microphyllum (Engelm.) Greene
Schmaltzia microphylla (Engelm.) Small
Toxicodendron microphyllum (Engelm.) Kuntze
Common Name: Desert Sumach
Rhus microphylla is an intricately-branched, deciduous shrub, suckering at the roots to form thickets and able to grow up to 4.5 metres tall.
The plant is harvested from the wild for local use as a food and a source of materials.
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.
South-western N. America - Arizona to Oklahoma and Texas, south to central Mexico.
Dry rocky hillsides or gravelly mesas; at elevations from 600 - 1,800 metres[
]. Washes, canyons, and arroyos, and on mesas, desert flats, and foothills in semidesert grasslands and desert scrub[
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Rhus microphylla is native to arid and semi-arid regions of southern N. America, where it ca be found at elevations up to 1,800 metres. Temperatures can range from up to 40°c in the summer, falling sometimes below freezing in the winter. Mean annual rainfall can range from 76 -- 406mm[
]. The plant only succeeds outdoors in the milder regions of the temperate zone, and also requires hot summers in order to ripen the new growth, in cooler regions the wood does not fully ripen and then is much more sensitive to cold damage. The young growth in spring is also very sensitive can be damaged by late frosts[
Succeeds in a well-drained fertile soil in full sun[
]. Found in the wild on soils developed from sandstone, limestone, and granite[
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[
Many of the species in this genus are highly toxic and can also cause severe irritation to the skin of some people, whilst other species such as this one are not poisonous. It is relatively simple to distinguish which is which, the poisonous species have axillary panicles and smooth fruits whilst non-poisonous species have compound terminal panicles and fruits covered with acid crimson hairs[
]. The toxic species are sometimes separated into their own genus, Toxicodendron, by some botanists[
A dioecious species - both male and female forms must be grown if fruit and seed are required.
Fruit - raw or cooked[
]. A sour flavour[
]. The dried fruits can be ground up, mixed with water and used to make a jam[
]. The fruit is small with very little flesh, but it is easily harvested and when soaked for 10 - 30 minutes in hot or cold water makes a very refreshing lemonade-like drink (without any fizz of course)[
]. The hairy, red-orange fruits are quite small, around 5mm in diameter and with very little flesh, but they are produced in clusters and are easily harvested[
The plant has some potential for use in soil stabilization projects. In New Mexico it increased in cover in the absence of grazing, effectively reducing gully erosion[
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 leaves are rich in tannin. They can be collected as they fall in the autumn and used as a brown dye or as a mordant[
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[