With its majestic appearance, large divided leaves and spectacular flower spikes, acanthus occupies a prominent place in art and gardening history. This plant, known scientifically as Acanthus, has inspired artists since Antiquity, as shown by its depiction on Corinthian capitals of Greek temples. Today, this perennial continues to captivate gardeners with its beauty and ease of cultivation. Two categories of acanthus are distinguished: soft-leaved acanthus or Acanthus mollis, the most common in our gardens, and spiny acanthus or Acanthus spinosus. Growing up to 1.50–2 metres tall, it flowers between June and September, producing white, pink or purple flowers. Vigorous, it is hardy to −15°C. It thrives in both sun and shade in deep, rich, well-drained soil that stays cool in spring and autumn. It is also easy to propagate. There are two main methods to propagate it: sowing and propagation by root cuttings. This tutorial details each method step by step and lists necessary equipment to carry out acanthus propagation operations.
By sowing
Acanthus self-seeds. You can also harvest its seeds and dry them to propagate acanthus. Unlike propagation by root cuttings, sowing rarely produces plants identical to parent plant.
When and where to sow?
Sowing acanthus is ideally done in spring, once risk of frost has passed.
A bright spot, but out of direct sun, is ideal for sowing.
How to sow?
- Fill pots with moistened seed compost.
- Scatter seeds over compost, spacing them a few centimetres apart.
- Lightly cover with compost.
- Moisten compost carefully using a spray bottle.
- Cover pots with plastic film or a clear plastic bottle cut in half to retain moisture and warmth
- Keep compost moist, ensuring it is not waterlogged
- Seeds should germinate in one to four weeks.
- Lift seedlings as soon as first leaves appear and plant out in final position, since acanthus does not like being moved.
Equipment needed
- Acanthus seeds
- Seed compost
- Pots or trays
- Spray bottle
- Plastic film or a plastic bottle cut in half
Propagation by root cuttings
To obtain plants identical to parent plant, propagation by root cuttings is the best method.
When to take root cuttings?
Acanthus root cuttings are preferably taken in autumn or late winter, periods when plant is dormant.
How to take root cuttings?
- Choose a healthy parent plant at least 3–4 years old.
- Carefully expose part of its roots using a digging fork
- Cut root segments about 5–8 cm long.
- Place each cutting in a pot filled with a well-draining mix of compost and sand and lightly cover with the mix
- Place pots in a greenhouse or room with temperature between 15 and 20°C
- Water regularly to maintain steady humidity without saturating the substrate
- Cuttings will develop new roots in four to five weeks.
- When root system is sufficiently developed, pot up cuttings or plant out in ground in a well-drained medium
Equipment needed
After propagation
After propagation, whether by sowing or cuttings, providing appropriate care is essential to ensure acanthus growth and flowering.
Here are some tips:
- Acanthus prefers a sunny to semi-shaded position.
- Water acanthus regularly, avoiding overwatering.
- Apply fertiliser or compost in early spring.
- Remove faded leaves and flower spikes after flowering to encourage new growth.
- For more information, find all our planting and care advice for acanthus in our dedicated sheet.
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