Propagating Acanthus ilicifolius (Holly Mangrove)

How to propagate the brackish holly-leaved mangrove Acanthus ilicifolius from stem cuttings and seeds for emersed paludariums and coastal biotope displays.

Overview

Acanthus ilicifolius, also called sea holly or holly mangrove, is an erect shrub of mangrove habitats that reaches up to about 2 metres tall, with stout, mostly unbranched, glabrous stems. Its oblong leaves carry margins bearing a few large spines, giving them a holly-like look. It occurs across Southeast Asia, Indochina, Indonesia, the Philippines and northern Australia.

Propagation Method

Two routes work for this shrub: vegetative stem cuttings and sexual reproduction by seed. The fruit is an elliptic capsule about 2.5 to 3 cm long containing four flattened, light yellow seeds, so collected seed can be sown directly. Stem cuttings root readily in a warm, saline, humid setting and are the faster way to clone a chosen plant.

Step-by-Step

1. Choose a healthy, firm stem and cut the top 5 to 10 cm just below a node using clean shears.
2. Strip the lower leaves from the cutting, taking care of the spiny margins, leaving a couple of upper leaves.
3. Insert the base into a brackish, water-saturated mangrove substrate so at least one node sits below the surface.
4. Keep the cutting emersed in high humidity and warmth until new shoots and fibrous roots establish.
5. For seeds, sow the four capsule seeds into damp brackish substrate and keep them warm and humid until germination.

Conditions for Healthy Growth

Provide brackish water, bright light, and warmth in the 22 to 30 C range, matching its native mangrove swamps. Grow it emersed with its roots in saturated substrate and its foliage in air. CO2 injection is not required for this terrestrial-emersed shrub; instead it relies on a stable saline environment and strong illumination.

Trimming & Maintenance

As a slow-growing background shrub, trim roughly once a month to shape it and remove damaged growth. Cuttings taken during trimming double as propagation material. Wear protection when handling the spiny leaf margins.

Common Challenges

• Attempting to grow it fully submerged in freshwater, which it does not tolerate.
• Insufficient salinity, since it is adapted to brackish coastal swamps.
• Low light slowing an already slow grower.
• Injury from the spiny holly-like leaf margins during handling.