Bear's Breeches Plant Profile

acanthus mollis, norfolk, july
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When it comes to tall, eye-catching flowers, Bear's Breeches are great choices. Bear’s Breeches are large perennial plants with glossy green leaves and tall spikes of flowers. They are always touted as architectural plants, and their leaves are often used as a motif in moldings, reliefs, and even jewelry. Many gardeners grow them for their foliage alone, although the flowers are quite nice themselves.

  • Botanical Name: Acanthus mollis
  • Common Name: Bear's Breeches, Oyster Plant
  • Plant Type: Perennial
  • Mature Size: 3 to 6 feet tall and 3 to 6 feet wide
  • Sun Exposure: Full sun to partial shade
  • Soil Type: Rich soil with proper drainage
  • Soil pH: 6.5 to 7.5
  • Bloom Time: Late spring to mid summer
  • Flower Color: White flowers grow on tall (3 feet) flower stalks and are hooded by purple bracts
  • Hardiness Zones: 6 to 10; they can often survive winter down to Zone 5, but can be a gamble in a harsh winter
  • Native Area: Southern Europe and Mediterranean region

How to Grow Bear's Breeches

Acanthus means bract, which are modified leaves that are often more colorful than the actual flowers. They help to attract pollinators. The botanical name for Bear's Breeches comes from the thorny look of their purple bracts. Although there are about 30 species of acanthus, only a couple are commonly grown as garden plants. While they are imposing and beautiful, they can be erratic, blooming well in one year and disappointing in another.

These are wide plants and will need at least 3 to 4 feet of garden real estate each as they like to spread out. The leaves are wide rosettes of arching, shiny, dark green leaves that are deeply lobed. Because of its bold leaves, Bear’s Breeches pairs well with airy plants, like Crocosmia, Gaura, and ornamental grasses. They are so imposing, you might not notice any plants near them and can be used quite effectively on their own. Expect your Bear’s Breeches to start blooming in late spring to mid-summer and to continue blooming for 3 to 4 weeks. Bloom time depends on both your zone and the whims of the weather.

Bear’s Breeches can be aggressive growers, spreading and squeezing out neighboring plants. To keep them under control, many gardeners place a sunken border around the plants or plant them in bottomless containers, sunk into the ground.

Light

Plants will do best in full sun to partial shade. They need more protection in hot climates, but wherever you grow them, they need at least a few hours of sun to bloom well.

Soil

Bear’s Breeches like a rich soil with plenty of compost or other organic matter. Once established, they are more accommodating about poor soil, but they absolutely need good drainage, especially in winter. Sitting in cold, wet soil can cause the roots to rot and may kill the plants.

Water

Once established, Bear’s Breeches are very drought resistant. They do best with regular water. An inch a week should be plenty.

Temperature and Humidity

These plants are dependably hardy. Protect your plants during their first couple of winters with a thick layer of mulch. In Zones 6 and lower, continue this practice for the life of your plants.

Fertilizer

Bear’s Breeches are not heavy feeders. Start with a rich soil and side dress annually with compost. You can use a balanced fertilizer in spring or mid-summer if the plants look like they need it.

Propagating Bear's Breeches

There are a few ways you can successfully propagate Bear's Breeches:

  • Starting from Seed: If you can find the seed, the best time to start Bear’s Breeches from seed is in spring. You can start seed indoors or direct sow, but expect to wait several years for them to bloom. They need time to grow and establish their root system before they start to send out flower buds.
  • Division: Bear’s Breeches have long tap roots and do not like to be moved. If you want to divide your plants, the best way to do it is to thrust a shovel through the base of the plant’s roots, in fall, leaving the plant in place. The following spring, you should see several new “baby” plants that can easily be transplanted.
  • Cuttings: You can also multiply your plants by taking root cuttings in either the spring or fall.

Varieties of Bear's Breeches

  • Acanthus balcanicus var. hungaricus Hungarian Bear's Breech: The most widely adaptable species, it blooms later and is less susceptible to late frosts.
  • Acanthus mollis Common Bear’s Breeches: This is the most popular species, but it can also be the most temperamental about blooming, with buds being damaged by late spring frosts.
  • Acanthus. spinosus Spiny Bear’s Breeches: This is more adaptable than A. mollis and more thistle-like.

Pruning

In hot climates, the plants can be cut back after flowering. This will encourage fresh new foliage. Gardeners with cold winters should leave the plants standing and allow the leaves to protect the crown. Wait until you see new growth, in the spring, to cut back any damaged or declining leaves.

Pests and Problems

Insects don’t generally bother Bear’s Breeches, but those gorgeous leaves can be susceptible to a handful of diseases, with powdery mildew being the usual culprit. Good air circulation and a dose of homemade fungicide will help with that.

  • Insects: Aphids may become a problem in the thick leaves and slugs and snails will hide out and feed, if the soil is damp.
  • Diseases: Powdery mildew, other fungal leaf spot diseases, and bacterial leaf spot can be an issue.