Mahonia, Berberis, Ilex

An adventure in plants, their appearance, and their taxonomic status.

It starts with a recent visit to the Gamble Garden in Palo Alto, where I encountered this pretty small shrub, in bloom, labeled Mahonia ‘Sweet Caress’ (photo from the net):

(#1)

At first glance, not at all like the mahonia shrub my father grew in our garden when I was a teenager: this plant has bamboo-like foliage, but the mahonia in our Wyomissing Hills PA garden had leaves that looked like holly leaves, and my dad referred to it as an Oregon grape holly: grape for the blue berries on the plant during the winter, holly for the prickly Ilex-like leaves, and Oregon for its origin in the shady forests of the Pacific Northwest.

Now it turns out that the holly-leaved mahonia of my youth and the bamboo-leaved mahonia in Gamble Garden are shade-loving evergreen plants with similar yellow flowers and blue berries, and are in fact both in the genus Mahonia, very closely related to barberries (in the genus Berberis). Both Mahonia and Berberis are in the barberry family (Berberidaceae) — with nothing much taxonomically to do with either hollies (in their own plant family, Aquifoliaceae) or bamboos (in the grass family, Poaceae).

Mahonias. From Wikipedia:

Mahonia is a genus of about 70 species of evergreen shrubs in the family Berberidaceae [a new family on this blog, #75], native to eastern Asia, the Himalaya, North America, and Central America. They are closely related to the genus Berberis. Botanists disagree on the acceptability of the genus name Mahonia. Several authorities argue plants in this genus should be included in the genus Berberis because several species in both genera are able to hybridize, and because when the two genera are looked at as a whole, there is no consistent morphological separation except simple [Berberis] vs compound [Mahonia] leaves. Mahonia typically have large, pinnate leaves 10–50 cm (3.9–19.7 in) long with five to fifteen leaflets, and flowers in racemes which are 5–20 cm (2.0–7.9 in) long.

The genus name Mahonia honours the Philadelphia horticulturist Bernard McMahon who introduced the plant from materials collected by the Lewis and Clark Expedition.

The type species of the genus is Mahonia aquifolium, (Oregon grape) from the Pacific coast of North America.

Several species are popular garden shrubs, grown for their ornamental, often spiny, evergreen foliage, yellow flowers in autumn, winter and early spring, and blue-black berries. The flowers are borne in terminal clusters or spreading racemes, and may be among the earliest flowers to appear in the growing season. The berries are edible, and rich in vitamin C, though with a very sharp flavor. Although edible, the plants contain berberine, a compound found in many Berberis and Mahonia species which can cause vomiting, lowered blood pressure, reduced heart rate, lethargy, and other ill-effects when consumed in large quantities.

Several fascinating topics here: the taxonomic question, about whether to treat Mahonia and Berberis as a single genus; the connection to the Lewis and Clark expedition, a significant moment in American history; and the edibility of the berries, with, however, the drawback of the berberine in them.

On ‘Soft Caress’, from the Monrovia nursery’s plant catalog:

Mahonia eurybracteata ‘Soft Caress’ (USDA zones 7-9 [Pacific coast, the South and Southwest]; full to partial shade)

Lemon-yellow flowers stand atop the slender, thornless, bamboo-like foliage in early winter. Flowers are followed by large clusters of silver-blue berries in spring. Perfect for an Asian garden, border planting, or as a specimen. Evergreen.

Another non-holly-leaved mahonia, from the Sunset Western Garden Collection:

(#2)

‘Marvel’ Mahonia (Mahonia x media): Mahonia medias are fabuously tough landscape plants, but most get too large for smaller spaces. Marvel keeps its flower power, but on a more compact, and less prickly plant. Large flower clusters in fall and winter are followed by dark blue berries.

Then some holly-leaved mahonias. The type plant of the genus:

(#3) Mahonia aquifolium, with berries

And the leather-leaved mahonia:

(#4) Mahonia japonica ‘Bealei’, with berries

Barberries. First, the name. OED2 has medieval Latin barbaris, berberis for the shrub, of unknown origin and history (but possibly Arabic or Persian). This word was then, presumably. re-shaped in English to have the element berry (of Germanic origin) in it.

Then, the plants. From Wikipedia on the genus:

(#5) B. vulgaris, with berries and fierce spines

Berberis, commonly known as barberry, is a large genus of deciduous and evergreen shrubs from 1–5 m (3.3–16.4 ft) tall found throughout the temperate and subtropical regions of the world (apart from Australia). Species diversity is greatest in South America, Africa and Asia; Europe and North America have native species as well. The best-known Berberis species is the European barberry, Berberis vulgaris, which is common in Europe, North Africa, the Middle East, and central Asia. Many of the species have spines on the shoots and along the margins of the leaves.

Berberis vulgaris (European barberry) and Berberis canadensis (American barberry) serve as alternate host species of the wheat rust fungus (Puccinia graminis), a grass-infecting rust fungus that is a serious fungal disease of wheat and related grains. For this reason, cultivation of B. vulgaris is prohibited in many areas, and imports to the United States are forbidden. The North American B. canadensis, native to Appalachia and the Midwest United States, was nearly eradicated for this reason, and is now rarely seen extant, with the most remaining occurrences in the Virginia mountains.

Some Berberis species have become invasive when planted outside of their native ranges, including B. glaucocarpa and B. darwinii in New Zealand (where it is now banned from sale and propagation), and green-leaved B. thunbergii in much of the eastern United States.

… Several species of Berberis are popular garden shrubs, grown for such features as ornamental leaves, yellow flowers, or red or blue-black berries. Numerous cultivars and hybrids have been selected for garden use. Low-growing Berberis plants are also commonly planted as pedestrian barriers. Taller-growing species are valued for crime prevention; being very dense, viciously spiny shrubs, they make very effective barriers impenetrable to burglars. For this reason they are often planted below potentially vulnerable windows, and used as hedges.

Our Columbus OH house came with barberry bushes (B. vulgaris) along the front. Pretty shrubs, but evil to deal with: covered with spines whose wounds were not only immediately painful, but then festered afterwards. Eventually, armed with heavy gloves and a heavy long-sleeved shirt, I cut them down and rooted them out, and replaced them with friendlier shrubs. (At some point, a government agency began citing people with barberry bushes, requiring them to get rid of the plants as a vector in wheat rust.)

On the berries of B. vulgaris, from Wikipedia:

The berries are edible and rich in vitamin C, though with a very sharp flavor; the thorny shrubs make harvesting them difficult, so in most places, they are not widely consumed. [They also contain berberine.] They are an important food for many small birds, which disperse the seeds in their droppings.

… In Europe, the berries have been traditionally used as an ingredient in making jam. The berries are high in pectin which makes the jam congeal as it cools after having been boiled. In southwestern Asia, especially Iran, the berries are used for cooking, as well as for jam-making.

Unlike the mahonias, B. vulgaris is deciduous, with leaves that turn handsomely red at this time of the year before dropping to the ground.

Hollies. Finally, we turn from holly-like mahonias to actual hollies. From Wikipedia:

(#6) Ilex aquifolium

Ilex, or holly, is a genus of 400 to 600 species of flowering plants in the family Aquifoliaceae [a new family on this blog, #76], and the only living genus in that family. The species are evergreen or deciduous trees, shrubs, and climbers from tropics to temperate zones worldwide.

And on the species in #6, from Wikipedia:

Ilex aquifolium (holly, common holly, English holly, European holly, or occasionally Christmas holly), is a species of holly native to western and southern Europe, northwest Africa, and southwest Asia. I. aquifolium is the species familiar in Christmas decoration, and is regarded as the type species of the genus Ilex, which by association is also called “holly”. It is a evergreen tree or shrub found, for example, in shady areas of forests of oak and in beech hedges. It has a great capacity to adapt to different conditions and is a pioneer species that repopulates the margins of forests or clearcuts.

Note on the species name aquifolium. The folium part is just Latin ‘leaf’. You might try to see Latin aqua ‘water’ or aquila ‘eagle’ in the aqui– part, but this turns out to have a spelling variant of the stem in acus ‘needle’: ‘needle-leaved / needle-leaf’, a good nane for holly (and for holly-leaved mahonias: note Mahonia aquifolium).

On the most familiar Ilex species, from Wikipedia:

Ilex aquifolium (holly, common holly, English holly, European holly, or occasionally Christmas holly), is a species of holly native to western and southern Europe, northwest Africa, and southwest Asia. I. aquifolium is the species familiar in Christmas decoration, and is regarded as the type species of the genus Ilex, which by association is also called “holly”. It is a evergreen tree or shrub found, for example, in shady areas of forests of oak and in beech hedges. It has a great capacity to adapt to different conditions and is a pioneer species that repopulates the margins of forests or clearcuts.

… Along the west coast of the United States, from California to British Columbia, non-native English Holly has proved very invasive, quickly spreading into native forest habitat, where it thrives in shade and crowds out native species.
… Holly berries contain alkaloids, caffeine, and theobromine and are generally regarded as toxic to humans, though their poisonous properties are overstated and fatalities almost unknown… The leaves of related plants [esp. Ilex paraguariensis] are used to make a caffeine-rich beverage, yerba mate, which has caffeine in amounts equal to that of coffee. It is likely that I. aquifolium has equal amounts of caffeine in the leaves.

So here we have the Berberidaceae diverging into an assortment of forms, some of them converging with the forms of taxonomically very distant plants (grasses and hollies). Speciation here, convergent evolution there, maybe some hybridization in the middle.

 

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