Acanthus Mollis

Acanthus mollie-bear's breeches-oyster plant

Acanthus mollis- Oyster plant,Bear's breeches

Acanthus mollis- Oyster plant is prehistoric looking plant. Its a clumping perennial with very big serrated deep green glossy leaves. It sends out long flower spikes about 1.8m in late spring-summer. These flower spikes are made up of numerous purple-pink flowers that run up the length of the spike.

Carful consideration should be given as to where to place this plant as its becomes quite large. Best planted as a backdrop to other plantings. Not a good choice for small gardens. Remove flower spikes after flowering as it seeds easily.

Prefers moist well drained soil. Can be grown in  full sun, but it will wilt in hot weather, always bounces back over night. Best suited for part shade to shady areas.

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Cultural notes

Botanical name: Acanthus mollis

Common name: Oyster plant, Bear's breeches

Family: Acanthaceae

Native to: Mediterranean

Flowers: Late spring-summer

Position: Full sun/Part shade/ Shade

Height: 1.2m (Flower spikes taller)

Width: 1.5m

Can Acanthus mollis be grown in the shade?

Yes. Acanthus mollis is very versatile and can be grown in quite deep shade, semi shade and even full sun. It does perform best in shaded areas. Too much sun can cause the foliage to loose its glossy green look. Hot summer sun will also cause the leaves to wilt, although they will bounce back once the sun goes down.

Is acanthus mollis evergreen?

Yes here in Victoria the temperatures don't get low enough for acanthus mollis to go into hibernation mode.

Is acanthus mollis invasive?

Acanthus can be invasive. It can be grown from the roots and from seed. If allowed to go to seed you'll notice baby acanthus posing up all around the mother plant. To stop this happening remove the flower spikes before the seed forms.

Removing an unwanted acanthus can be difficult as it also propagates from the roots. You'll need to remove all the roots to guarantee it doesn't come back. The easiest method of removal is to dig up as much of the root system as possible and then use a weed killer on the bay plants that emerge.

I know glyphosate based weed killers have gotten a bad rap, however at time of writing it's the most effective method of killing unwanted acanthus plants, roots and all.

Another method of removal could be covering with a light and water proof cover. This would stop the plant from being able to photosynthesis and elimate moisture. A good none chemical method to try if you are patient.

Is acanthus mollis a good fire barrier?

I cant say i have any first hand experience in this matter. However many gardeners were planting them around their houses following black Saturday. I wouldn't be surprised if there is some truth in this as the leaves are so large and contain a large amount of moisture.

Pests and diseases.

Acanthus has no pest and disease problems that we have experienced. The broad leaves can provide shade and moisture to annoying pests such as snails and slugs. Throwing some pet safe snail pellets under the leaves could help eliminate these pests from spreading throughout the rest of the garden.

How do you propagate acanthus?

We use root cuttings as its quick and super easy. You could check out this article or the video below. Another method of propagation is allowing the flowers to seed. This will take longer but will provided hundreds of plants for minimal effort.