Plant of the Month (December) : Sourberry – Rhus trilobata/ Rhus aromatica ~ Tk-123456

Sourberry (Rhus trilobata/Rhus aromatica) - Mother Nature's Backyard

Seeds
are germinating, bulbs are emerging, but very few flowers can be found in early
December. So we were pleasantly
surprised to see our Sourberry (Rhus
trilobata/Rhus aromatica) coming into bloom, just in time to be our Plant
of the Month. The scientific name is
pronounced roos try-lo-BAY-tuh (roos air-oh-MAT-ih-cuh).

Sourberry
is known by a number of common names including Three-lobe sumac, Three-leaved
sumac, Basket bush sumac, Oak-leaf sumac, Skunk bush and Lemita. It belongs to
the same genus as our common Lemonadeberry (Rhus
integrifolia) and Sugar bush (Rhus
ovata). It’s a ‘cousin’ to the local
Laurel sumac (Malosma laurina) and
Poison oak (Toxicodendron diversilobum). All are members of the Sumac family (for more
on the Anacardiaceae see: http://mother-natures-backyard.blogspot.com/2014/12/plant-of-month-december-lemonadeberry.html.

Sourberry (Rhus trilobata/Rhus aromatica)

Like many other plants, the taxonomy of this
species is currently being revised.
Previously, Rhus trilobata was
considered a western N. American species; Rhus
aromatica was viewed as a related
eastern species. It now appears that both
may be the same species (Rhus aromatica),
though much of the western literature – and the nursery trade – still refers to
R. trilobata. For clarity we’ll use both names, but focus
on the natural history of this plant in the West (which is most relevant to
California gardeners).

Rhus trilobata (aromatica) is native to western North America, from Alberta
and Saskatchewan south to Texas and California – even into Mexico. It grows in prairies and shrub lands, on a
variety of sites including sandhills, seasonal stream beds, canyons and dry,
rocky slopes. In S. California, it can
be found in the canyons and washes of interior valleys, in coastal sage
scrub, chaparral and southern oak woodland, mostly below 3500 ft. elevation. It grows in the Santa Monica Mountains and
in the foothills of the San Gabriel Range.

Sourberry (Rhus trilobata/Rhus aromatica) - low-growing form

Sourberry
is a winter-deciduous shrub that varies in growth habit across its Western range. In some situations it’s a low (2-3 ft. tall)
mounding groundcover (above). In other places,
it grows as a rounded, upright shrub which may reach heights of 6-8 ft. and
similar spread (see photo below). In
moist conditions, plants spread by rhizomes, sometimes forming a thicket. In drier S. California, plants will often
remain as solitary shrubs for many years.
Plants have a lifespan of perhaps 30-40 years; they grow most rapidly
during their first five years.

Sourberry (Rhus trilobata/Rhus aromatica) - taller form

Sourberry (Rhus trilobata/Rhus aromatica) - foliage

The
foliage of Rhus trilobata (aromatica) is
medium-green to blue-green most of the year, turning yellow to orange in fall -
if temperatures are cold enough. In the
western L.A. Basin, fall leaf color is variable from year to year. Plants lose
their leaves in fall (usually November in our area) and leaf out again in
spring (often as early as February in milder climates). The plants leaf out quickly, from pre-formed
leaf buds. Plants often don’t leaf out
until after flowering.

Sourberry (Rhus trilobata/Rhus aromatica) - leaves, young bark

Sourberry
leaves are three-lobed, glossy, leathery, 1 to 1 ½ inches across. They look somewhat like those of Western
poison oak (Toxicodendron
diversilobum), though not as shiny and a smaller size. For good
pictures comparing the two species see reference 1 (below).

The young bark of Rhus trilobata (aromatica) is often a
medium red-brown, but may be as light as a pale gray-brown, with pale hairs. Older bark is gray-brown, mostly smooth and
fissuring with age. When branches are
broken (or leaves are crushed), they release an aroma that is skunky-smelling
to some (hence the common names ‘Skunk brush’ and ‘Stink-bush’).

The roots of Rhus
trilobata (aromatica) are well-adapted for climates of the American Southwest, including California. Plants have both a deep taproot and a network
of fibrous, shallower roots. This
combination allows them to make optimal use of intermittent rains, as well as tap
into deep groundwater reserves during dry periods. Because of the deep taproot,
plants resent being moved once established in the ground.

Sourberry (Rhus trilobata/Rhus aromatica) - flower

buds, flowers

Sourberry (Rhus trilobata/Rhus aromatica) - close-up

of flowers

Sourberry blooms in early spring (February-April)
in much of S. California, though flowers may appear in winter at lower
elevations. Plants may be dioecious
(separate male and female plants). More
commonly, plants contain both unisexual and bisexual flowers on the same
plant. Male and female flowers are both small (~ ¼ inch
across), with yellow petals. Male flowers cluster along yellow catkins (like a
willow) and are slightly paler in color, while female flowers occur in dense,
brighter clusters at the ends of short branches. Flowers are primarily
bee-pollinated. We’ll try to update our
close-up pictures of flowers – hopefully with pollinators - soon.

Sourberry (Rhus trilobata/Rhus aromatica) - green fruits

Sourberry (Rhus trilobata/Rhus aromatica) - ripe fruits

Those familiar with the fruits of Lemonadeberry and
Sugar bush will immediately recognize similarities between the three
species. The fruits are small (about ¼
inch; 5-7 mm), sticky drupes that contain a single seed with a hard seed coat
(a nutlet). Fruits are initially green,
becoming a dark red when ripe (see above).
Fruits ripen in late spring/early summer (June/July) at lower elevations
in S. California; they may ripen as late as early fall in colder climates. The fruits are loved by birds and animals –
including humans!

Like Lemonadeberry, the fruits are covered with a
sticky, sweet-sour secretion that tastes like lemon or lime. In fact, the most common edible use for the
fruits is to make ‘Rhus-ade’, a lemonade-like drink. Some Native Americans
still grind dried Sourberry fruits and use them as flavoring for puddings, mush
or bread. In fact, the fruits can be
used as a flavoring or seasoning in more ways than you might think. For additional ideas for using the fruits
see: http://mother-natures-backyard.blogspot.com/2015/05/california-gourmet-cooking-with.html

Sourberry (Rhus trilobata/Rhus aromatica) - in garden.

Mother Nature's Backyard

Sourberry is an undemanding plant. It tolerates pH from 6.0 to at least 8.0, and
grows fine in soils ranging from very sandy to clay. If your soils drain very slowly, consider planting
Rhus trilobata (aromatica) on a slope
or atop a small berm (it’s intolerant of standing water). While it can be found growing in full sun, it
seems to do better in our area in part-shade.
If you have a hot, inland garden, plant it where it gets some afternoon
shade.

Rhus trilobata (aromatica) is very drought tolerant. However, it looks (and produces) best with
occasional summer water. Let the soils
dry out between watering, then give the shrub a deep, slow soaking. In many areas of the West, this plant
experiences occasional summer rains.

Sourberry (Rhus trilobata/Rhus aromatica) - young plant

Sourberry (Rhus trilobata/Rhus aromatica) - mature plant

While Rhus
trilobata (aromatica) develops a nice natural shape over time, the
best-shaped shrubs are given a yearly pruning to stimulate fullness. Branches should be pruned back by ¼ to 1/3 of
their length in fall (after leaves fall) or early winter. This pruning simulates the animal browsing that
shrubs experience in the wild. Some
individuals are mildly sensitive to chemicals produced by the foliage of plants
in this genus. We suggest wearing long sleeves and gloves
when pruning (at least until you know you’re not affected). Wash hands/arms after handling the foliage.

If you desire straight stems for basket-making or
other crafts, you’ll need to cut some or all of the stems back to the ground in
early winter (coppice). While native traditions involve cutting or
burning an entire stand every few years, we wonder if just cutting back 1/3 of
the oldest stems might not work as well.
We’ll try this and report back.

Sourberry (Rhus trilobata/Rhus aromatica) - rest stop

planting, Utah

Sourberry is often used as a large shrub, either
shaped or natural, in garden plantings. It contributes to the woodsy, natural
look that some gardeners prize. It can
also be used as a hedge plant, remembering that it is winter-deciduous. It does well on slopes, often getting by with
little supplemental summer water once established. It is widely used for
erosion control on slopes and in riparian areas. And Rhus trilobata (aromatica) is becoming more common in commercial
plantings, due to its drought tolerance and low maintenance.

Sourberry can be grown in a large container – even used
as a bonsai plant. The lower-growing
forms are useful as a woody groundcover under trees. The cultivars ‘Autumn Amber’ and ‘Gro-low’, which
are available commercially, grows less than 2 ft. tall, and are popular as groundcovers.

Sourberry (Rhus trilobata/Rhus aromatica) - used as ground

cover. Rancho Santa Ana Botanic Garden, Claremont, CA.

Of the many shrubs planted in S. California gardens,
Rhus trilobata (aromatica) has some
distinct advantages. First, it is a
great habitat plant. Its size, many
small flowers, dense foliage and edible fruits make this a good choice for bird
and insect habitat. If you don’t use the
fruits yourself, don’t worry; plenty of fruit-eating birds will be glad to
remedy the situation.

If you are a basket-maker, planting Rhus trilobata (aromatica) insures a
ready source of the straight stems needed for your craft. [2] This has always been an important basketry
plant, wherever it grows. If you need it
for your craft, grow it.

Sourberry, along with the other local Rhus species,
is also a useful plant for the natural dyer.
Leaves, prunings, ashes and fruits can all be used to mordant yarn or
fabric prior to dyeing. The plants are
high in tannins, and tan-brown dyes can be obtained from leaves, bark and
roots; pink-tan dyes are possible from the fruits.

Sourberry (Rhus trilobata/Rhus aromatica) - green foliage

provides nice contrast in the summer/fall garden

Another good reason to grow this plant is its
medicinal properties. As always,
medicinal plants should be used with caution – particularly those from families
with known toxicities, like the Sumacs. For more on precautions see: http://mother-natures-backyard.blogspot.com/2015/10/garden-of-health-making-tincture-for.html

Fruits of Rhus
trilobata (aromatica) were traditionally sucked or chewed as a treatment
for toothache, mouth sores or as a mouthwash.
Fruits ease the pain, in part due to their astringent chemicals. A decoction of the fruits is also
traditionally used for stomach problems, as well as a hair tonic.

The leaves are astringent, diuretic, emetic and hemostatic;
infusions made from leaves have several traditional uses, including to treat head
colds and soothe skin itches. Dried, powdered leaves have been used to create
soothing salves for mouth sores. For
more traditional uses of this plant see reference 3, below.

Sourberry (Rhus trilobata/Rhus aromatica)

In summary, Rhus
trilobata (aromatica) is a shrub with much to recommend it. We’re surprised is isn’t used more often in
the garden setting. So if you’ve got the
space – even room for a large pot – you might want to consider this pretty and
useful native.

For a gardening
information sheet see: http://www.slideshare.net/cvadheim/gardening-sheet-rhus-trilobata

For more
pictures of this plant see: http://www.slideshare.net/cvadheim/rhus-trilobata-web-show

For plant
information sheets on other native plants see: http://nativeplantscsudh.blogspot.com/p/gallery-of-native-plants_17.html

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