How to Plant and Grow Acanthus

Commonly called bear's breeches, this plant is grown for its glossy, large foliage that can be jagged or spiny. Also called acanthus, it bears tall spikes of striking flowers with white petals and prickly purple bracts in late spring into early summer. Fun fact: The acanthus leaf motif was incorporated in the design of the crowns on Corinthian columns; this architectural detail can still be seen adorning pillars today.

Where to Plant Acanthus

Choose a location that is permanent because acanthus does not like to be moved. As a plant that is native to the Mediterranean and Africa, acanthus loves the sun and should be planted in a spot where it gets full sun or direct sun for at least part of the day. Due to its tall size—when in bloom, it can reach 6 feet—it is best planted in the back of the border where it is not towering over other plants and casting shade on them. Its rhizomes can spread quite aggressively; to prevent it from taking over an area, plant it in a location with root barriers, such as near a patio, pool, or walkway. or bury a large container in the ground to confine its spread.

Acanthus does not like wet feet so plant it in a location with well-draining soil with a neutral pH (between 6.5 and 7.5.).

How and When to Plant Acanthus

Acanthus can be planted in the spring or fall.

Dig a hole that is at least twice the size of the container that the plant comes in (or the root ball) and at the same depth so that the plant sits at its original growing level. Refill the hole and tamp down the soil to remove air pockets. Water it well and continue to water regularly during its first season of growth. Leave at least 2 feet distance between specimens.

Acanthus Care Tips

Light

Give acanthus full sun to ensure the best-looking foliage and flowers and to prevent any foliar diseases like powdery mildew. However, in warmer climates, this perennial can struggle in the hot afternoon sun and would benefit from planting in part shade. While you may sacrifice a few flowers in part sun, the plants will perform much better.

Soil and Water

Acanthus thrives in rich, fertile soil with plenty of organic matter; the soil needs to be evenly moist and well-drained. It will not tolerate wet roots, so make sure to plant it away from areas with standing water. Ensure your plant's happiness by amending the soil with compost before planting.

Temperature and Humidity

Acanthus is tolerant of heat and humidity, the cold-hardiness, however, varies from species to species. The popular common bear’s breeches (Acanthus mollis) requires a mild to warm winter climate, whereas spiny bear’s breeches (Acanthus spinosus) can survive winter chill as low as Zone 5.

Fertilizer

If planted in fertile soil with plenty of organic matter, the plant only needs an annual feeding of a complete slow-release fertilizer in the spring. For the amount to use, follow product label instructions.

Pruning

Cutting the stems back after flowering encourages new foliage growth. The entire plant can be cut back to the ground level in the fall or in the spring to make room for new growth.

Potting and Repotting Acanthus

Acanthus can be grown in a pot; in fact, because its roots tend to spread aggressively, planting it in a pot might be the better option to keep it contained. The plant has a long taproot that does not like to be disturbed so the taller and wider the container, the larger the plant can grow without being disturbed. Also, make sure the pot has large drainage holes and use well-draining potting soil.

Pests and Problems 

Acanthus is a not bothered by serious pests or diseases, if you discount slugs or snails that occasionally feed especially on young plants. You might also find some powdery mildew on the foliage.

The biggest problem of acanthus is its aggressive spread in areas with mild winters. Acanthus will spread aggressively by sending up new shoots from its creeping roots. Because of its large size, acanthus can easily outgrow smaller, more delicate plants and can be difficult to control.

How to Propagate Acanthus

Acanthus is best propagated by division, and it’s a two-step process (remember, acanthus doesn't like to be moved due to its long taproot). Here's how to do it: In the fall, push a shovel into the root system to slightly break it apart but leave it in the ground. By the following spring, small plants will emerge from the main plant, which you can then cut off with all roots connected to them and replant in a new location.

Types of Acanthus

Spiny Bear's Breeches

Acanthus spinosus is the hardiest type. It has white flowers with purple hoods on plants up to 4 feet tall. Zones 5-9

Common Bear's Breeches

Acanthus mollis grows to 5 feet tall and produces glossy green leaves and purplish flower stems with mauve-hooded white flowers. Zones 6-10

Balkan Bear's Breeches

Acanthus hungaricus bears white or light pink flowers with purple bracts on 2-foot-tall stems in early to midsummer. Zones 6-9

Acanthus Companion Plants

Balloon Flower

The inflated buds of balloon flowers are fun to pop. And they make great cut flowers. Cut them in the bud stage, and sear the base of the stems to prevent the milky sap from seeping out and fouling the water. Most commonly available in blue-violet, balloon flowers also come in pink and white, as well as shorter forms that are better suited for rock gardens and containers. In fall, the foliage of balloon flower turns clear gold, so don't cut the plant down too early or you'll miss the show! They tolerate light shade, but not wet feet or drought.

Pearly Everlasting

Pearly everlasting is often grown as a flower for drying, but it's so pretty growing fresh in the garden, it's hard to bring yourself to cut it and bring it indoors. This North American native looks great even in the driest of weather. Its silvery foliage and creamy white blooms make it suitable for moon or white gardens. Grow it in lean soil or divide it frequently to keep it from spreading too quickly.

Spurge

There are hundreds of different spurges, and most are valued by gardeners because they're drought-resistant and almost always ignored by deer and rabbits. Spurges are surefire picks for adding color to the garden. Many also turn gorgeous colors in the fall, enlivening the fall garden.