Acanthus: Love & Hate

There are plants that most gardeners hate and other plants that most gardeners love. It is a rare plant, however, that provokes both love and hate in the same people.

The Acanthus is one of those rare plants.

Let’s consider why it generates strong reactions, both positive and negative.

The genus Acanthus includes twelve species. Various species are native to Europe and the Mediterranean basin, Africa. South Asia, and Australasia.

Three species from the Mediterranean basin are cultivated in many American gardens: A. mollis, A. spinosus, and A. balcanicus and are popular in Monterey Bay area, where the climate resembles the plant’s native environs.

Acanthus spinosus

Acanthus spinosus (click to enlarge)

These popular species are similar in appearance, with differences primarily in the lobes of the leaves: some have more deeply cut lobes than others. Generally, Acanthus is a clump-forming perennial plant that is grown for its attractive foliage and bold flower spikes. It works best placed behind smaller plants, to provide a lush backdrop for the landscape.

Given a favorable climate and adequate drainage, the Acanthus adapts to various soil types, and is usually pest- and disease-free, except for an occasional snail that tries to nibble the plant’s hard and glossy leaves. It prefers partial shade, but in our moderate climate also does well in full sun. It will grow in one season up to four feet high and wide, with some flower spikes reaching above the leaves.

At the end of the season, the flowers fade and the leaves wilt, and new leaves spring from the base. It’s time to cut the old growth to the ground and welcome a new cycle of growth.

Everything about the plant seems fine, right? Let’s look at the sources of ill will.

Firstly, a relatively minor concern is the plant’s prickliness. The genus name comes from the Greek word akantha, which means spine and refers to the edges of the leaves. When we encounter A. spinosus, we have the addition of the Latin term for spine, and a plant that might be called “Spiny Spiny.”

Actually, the Acanthus’ common name is “Bear’s Breeches.” I have not found an explanation for that odd name.

Secondly, the Acanthus propagates too readily. It develops creeping rootstocks and drops seeds, and has been considered invasive in some agricultural areas, but the progeny are really not difficult to control in a garden setting.

Thirdly (and this is the big negative), a well-established Acanthus is very difficult to eradicate. The smallest piece of root left behind will sprout into a new plant. Gardens change by the gardener’s design or by Nature’s plan, but the Acanthus is forever.

Given the excessive persistence of the Acanthus, we might have mixed feelings about the introduction of a new hybrid form of the plant. But the recent appearance of Acanthus ‘Whitewater’ has generated enthusiasm. This plant has variegated leaves and blossoms in white and cream, aging into pink. A mature clump of this plant in the right setting could be a knockout. (The ‘Whitewater’ photo is from Terra Nova Nurseries.)

Acanthus 'Whitewater'

Acanthus ‘Whitewater’

I have struggled to eliminate A. mollis and found A. spinosus to be better-behaved, so I’m hesitant to plant ‘Whitewater’ in my garden. It’s striking appearance, however, invites a compromise: container planting. The pot should be large enough for the roots, the right proportion for the largish plant, and in a color that complements green and white with a touch of pink. I have begun looking!

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