It’s that time of year when we’re clearing back areas of the garden in autumn, it also gives rise to seed collection, storage, seed treatment, sowing, whatever the regime may be for a particular genus.
Acanthus comprise 30 species belonging to the family Acanthaceae from the Mediterranean and Europe.
Commonly known as Bears Breeches, as the curved bracts on the flower stalks resemble bears claws. The flowers of Acanthus spinosus are white with the purple bracts and flower from late spring and well into summer. The leaf structure of Acanthus spinosus is more deeply cut and jagged compared to that of Acanthus mollis.
Acanthus is a genus that is magnificent architecturally and invaluable within any design element of the Hardy Perennial border that has the space to accommodate it.
This clump forming perennial will thrive in most soil types, its preference that of fertile well drained loamy soil, if the soil is too dry, they are susceptible to powdery mildew, this can be very evident on the beautiful glossy leaves. Acanthus can rise at the back of the border up to 1.5 metres, with a spread of 0.5 – 1 metre. The ideal aspect is full sun, but Acanthus will also thrive in semi shaded conditions within the perimeters of a tree canopy.
I’ve enjoyed the merits of this perennial as a National Trust Gardener, BBC Gardener, Head Gardener in the Cotswolds, and here in the South Lakes, it seems to be following me, or vice versa!
Collecting and extracting the seed from species of Acanthus can be quite tricky if you don’t get the timing right. I start to collect around early October when the seed pod within the bract is still green. If you leave them too long once the stem is cut, they turn a deep brown, and the inner seeds disintegrate. If you get the timing right, the seed will extract at a riper stage. A lot will depend on weather conditions, temperatures. There draws the big comparison between gardening in the South Lakes, compared to the North Cotswolds as an example.
The seed capsules are attached to a stalk called the funicular retinacula, or retinaculum or jaculator which helps to propel them outside of the capsule.
Reference to the image, the seeds resemble a small broad bean. When the capsules are green/ turning brown, a gentle squeeze is all that’s required, and the seeds pop out. After I’ve done this, I place a small number of seeds out to dry on the glasshouse bench, or a cool outhouse / utility. After a few weeks the seeds start turning brown.
I sow the seeds directly into 9cm pots of John Innes seed compost. I trialled some seeds last autumn / winter and achieved some germination under cool glasshouse conditions. I’ve had some success and continue to grow young plants on in our cool glasshouse environment, these are in the 9cm pots.
Greater success has been achieved sowing seeds in mid spring, again under cool glasshouse conditions, but obviously as the outside temperature is warming up. Germination has been a bit sporadic, on average germination takes about 6 weeks, this would easily be accelerated under heated conditions. I’ve worked in many settings managing heated and unheated glasshouses, depending on the arrangement (you have to work with what you’ve got ! )
The young Acanthus plants (one of a number) see image is growing on in these unheated conditions.ย Although a hardy plant, from this point on, horticultural fleece protection is applied on minus temperature nights.
Research informs me that after two or three seasons’ plants should establish reasonably to first flowering.
My aim will be to grow these Acanthus on to plant into the Lakeside Garden next summer.
Kevin Line,
Kevin has been writing the HPS Blog since May 2015.
Head Gardener/ Plantsman,
Lakeside Hotel Garden, Freelance Garden Adviser, South Cumbria.
Member of The Professional Gardeners Guild.
