Pruning Acanthus mollis in Spring
Published: 04/04/2018
As an architectural plant, Acanthus mollis is superb. From it's towering spikes of other-worldly flowers to it's large, bold, glossy-green leaves Acanthus is a strikingly grand plant.
Those who have Acanthus planted in their garden, or those who have had, know that as much as it is a brilliant feature, it is also a strong growing, and sometimes invasive beast!
Here is one Acanthus that needed pruning today:
The warm winter that we have had has allowed the Acanthus to continue growing, rather than dying back as it should do late in the year. Add to that, the snowfall that we have all experienced in the last week has bent the leaves and caused frost damage.
As we are, according to forecasts, free from the threat of more icy weather, and we are technically in Spring now I decided today was the day to sort out the plant.
Pruning and thinning out Acanthus mollis is important to do in Spring because the tighter and larger it grows the less it wants to flower, and you may also have to deal with mildew later in the year because the air flow between the leaves is restricted.
Giving it a good tidy up now will set it up well for the rest of the year and ensure you have a plant that is healthy and performs well.
With Acanthus there is little point in going gentle as it is a brute so the order of the day is pruning to the ground and digging out any that has spread beyond where we want it gowing.

As shown above cut I the Acanthus just above ground level on almost all the stems, just leaving the young new shoots which are identifiable by their curled leaves, almost fern-like.
Once all the old stems were cut and deposited on the compost heap I turned my attention to digging out plants that had spread.
Now, a word of caution when attempting to dig out Acanthus mollis: Treat it like Dandelion and hunt down every root you can before kick the earth back over!
The roots of Acanthus are deep and are likely to break when digging them out so ideally dig a full spade or fork's depth down and around the plant and lift the whole clump. Then dig down the same again and turn it over pulling out any roots you find. Break the clump that you've dug out and retrieve the plant and all the roots and dispose of them on a bonfire or bin. Do not compost the roots. Much like a perennial weed it has a fair chance of surviving in a compost heap and re-growing in the future.
That should then be your Acanthus pruned and ready for the year!