Acanthus

( ak - ANTH - us )

At-A-Glance Information

Acanthus, or Bear's Breech, is a perennial flowering plant that requires either sun or shade, depending on the species, and moderate to regular water. This genus is native to southern Africa, Asia, Europe and the Mediterranean. Leaves form in a clump about three feet wide close to the ground, and have spines. Tall spikes of hooded white, rose, or purple flowers bloom in late spring or summer and have green or purple spiny bracts. These flowers can be great additions to partial shade border gardens. They can also handle full shade, though they may not bloom as profusely. The leaves of Acanthus plants were used widely in Greek and Roman art. The flowers on these plants produce nectar, which will entice hummingbirds and other nectar-feeding organisms to your garden.

Acanthus Species and Varietals

The best growing zones for Acanthus (Bear's Breech) vary depending on the species. There are about 30 species in the Acanthus genus with a variety of leaf shape and flower colors; they are part of the family Acanthaceae. The genus name is derived from the Greek term akanthos, which translates approximately to 'spiny', a reference to the toothed edged leaves of some species. For more growing information, see the descriptions below. To find your zone, click here: Zone Map.

Acanthus ebracteatus (Sea Holly, Holly Mangrove)
Best when grown in USDA hardiness zones 10-12 or Sunset growing zones 4-9, 16-23, and 26. This species has tropical origins, and is at home along ocean shorelines in mangrove swamps or forests in southern China, India, and Australia. It reaches around 4 to 5 feet tall, and leaves have sharp spines. After flowers fade, squared fruit capsules form and when they are ripe, they split open, shooting the seeds out up to six and a half feet away from the parent plant.

Acanthus hungaricus (Acanthus balcanicus)
Native to Hungary (hence, hungaricus) and the Balkan Peninsula, this species grows best in USDA hardiness zones 5-10 or Sunset growing zones 2-24, and has finely cut and toothed leaves. Flowers are pale pink to white and are enclosed in reddish-purple bracts. Flower spikes reach between 3 and 4 feet tall, and appear in late spring through the middle of summertime.

Acanthus ilicifolius (Holly-Leaved Acanthus, Sea Holly, Holly Mangrove)
This species is native to Australia, Australasia, and Southeast Asia, and grows best in USDA hardiness zones 8-11 and Sunset growing zones 4-9, 16-23, 26, H1 and H2. It forms a shrubby plant reaching 6-7 feet tall and has shallow taproots. This plant will form the occasional stilt root, as well, if conditions are right. These shrubby plants are home in mangrove situations along water shorelines.

Acanthus mollis (Sea Dock, Bear's Foot Plant, Gator Plant, Oyster Plant, Bear's Breech, Big Spinach)
Growing best in USDA hardiness zones 7-11 or Sunset growing zones 5-24, this is the most commonly cultivated species of Bear's Breech. Flower spikes can reach 4-5 feet tall and the 3-4 foot wide plant has large, spineless leaves. Popular varieties include 'Hollard's Gold' (with yellow foliage in spring and summer) and 'Summer Beauty' (a heat-tolerant choice).

Acanthus spinosus (Spiny Bear's Breech)
This native of southern Europe grows well in USDA hardiness zones 5-9 or Sunset growing zones 2-24, reaching about 4-5 feet tall. Leaves have long spines and are silvery in color. Flowers are pure white, and have reddish-purple bracts, giving them a hooded look. Hybrids of this species have pure green leaves without a silvery sheen to them.

Caring for Acanthus

Acanthus plants will do well in most gardens without any specific effort; it will tolerate any soil type as long as it is well-drained. They can be situated in full sun, where it will prioritize flowering, or in full shade, where leaves will become larger, deeper green, and more beautiful. Take care to ensure that your Acanthus isn't spreading to areas where they are not wanted; they spread by underground runners and can be invasive if not kept in check. However, this issue isn't as much of a problem where winters are cold; as the runners will not survive the cooler temperatures. If you'd like to ensure that your bed of Bear's Breech doesn't grow, it can be helpful to bury an eight-inch deep root barrier, as is done with other plants like Nandina, and take care to not disturb the dirt around the bottoms of the plants, as causing damage to the underground rhizomes will encourage new plants to sprout. Acanthus needs frequent water and will wilt dramatically if not provided with adequate irrigation.

Pruning is not necessary for these plants, though spent spires of blooms should be deadheaded. Even after the flower stalk has been removed, this plant's greenery will remain and add interest to your garden. Once the leaves wilt, die and turn brown in summer or fall, they can be cut back to just above ground level. Mulch around the base of the plant to protect the bottom of the plant and its roots over winter, and it will pop back up the following spring.

Propagation

Propagation of Acanthus is done through seed and through root cuttings. Bear's Breeches will self-sow easily if left to their own devices through dropping their seeds. If you'd like to curb the growth of new plants, it is important to remove the flower spires before seed pods break open and release their seeds. Keep in mind that your newly propagated Acanthus may not bloom until it is 2 to 3 years old, and that propagating by seed does not always guarantee a clone of the parent plant. To propagate your Acanthus, follow the instructions below:

Propagating Acanthus by Seed

Acanthus seeds are contained in seed pods when flowers have been pollinated. These seed pods will burst open, sending seeds a pretty far distance, so if you'd like to prevent this spread, it is best to cut off flower stalks before this happens. To harvest seeds, cut flower stalks off in their peak bloom (in late spring or summer). Hang them upside-down in a dark, cool place and wait for them to dry out. This will take a few months. Once they are dried (in late winter), harvest the seeds from the seed pods.
The seeds should be placed in a cool, dark place until spring, when they can be planted. Ensure that the last frost of the season has passed, and then choose your planting site. It should receive filtered sunlight. have fast-draining soil, and be moist. Soak your seeds for 24-48 hours in cool water. Amend your planting site by tilling and amending soil with a 4-inch layer of compost.
Take your seeds out of their soaking container and immediately plant them in the ground, about 1/2 inch deep and 36 inches apart. Cover seeds with loose soil, and do not pat the soil down. Spray the planting site gently with water to settle the soil on top. Keep the bed moist; adding water if the soil feels dry to the touch about an inch down. Seeds will germinate in about three to four weeks. And then, enjoy watching your new plants grow!

Propagating Acanthus by Root Cutting

In late fall or early winter, dig down to find the roots of your plant. cut a 3-4 inch section from the root (you can take more than one if you'd like!). The roots you choose should be relatively young, pale and slender. Trim off any 'hairs' or smaller roots coming off of the main root. Note that the roots will not grow if they are planted upside-down, so make sure you keep them right side up. In other words, keep track of which end of your cutting was closer to the crown. They should look like the picture shown below.
Fill your pot or tray with well-draining potting medium amended with compost. Insert the cuttings into the potting medium, bottom side down, until they are able to stay upright without help.
Keep your cuttings in a cool place that receives bright, indirect light, and wait for leaves to appear. The following spring, after the last frost has passed, plant your roots outdoors where you'd like them to grow, after tilling and amending the soil by adding about a 2-4 inch layer of compost.