Plant Portraits: Aeonium arboreum ‘Zwartkop’

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Succulent plants are not everyone’s cup of tea, but one which attracted a lot of admiring glances when we opened our garden for the National Gardens Scheme was Aeonium arboreum ‘Zwartkop’. It’s hardly surprising given its height (hence arboreum, meaning ‘tree-like’) and the colour of the fleshy leaves, which are quite unlike the average houseleek. The glossy, purple-black rosettes which top each stem lend the plant its common name ‘black rose’, rather nicer than the direct translation of ‘Zwartkop’, which is ‘black head’.

A. 'Zwartkop' is readily propagated, so you can be sure of a supply of small plants to replace or give away
A. ‘Zwartkop’ is easily propagated, so you can be sure of a ready supply of small plants to use or give away

Anyone who’s made a trip to West Cornwall or The Isles of Scilly will recognise Aeonium ‘Zwartkop’ from the mild coastal gardens in this part of the UK. When we visited the island of Tresco in April, the sub-tropical Abbey Gardens were full of mature, well-branched plants topped with chunky panicles of bright yellow flowers. These appear only in the most favoured locations; those with the greatest similarity to the Aeonium’s native Canary Islands and North Africa. Hardiness is an issue elsewhere in the country, so even in balmy Broadstairs I keep my plants indoors when there is any chance of frost.

Mature plants grown in mild gardens will produce panicles of golden yellow flowers
Mature plants grown in mild locations should produce panicles of golden yellow flowers

Despite its tenderness, A. ‘Zwartkop’ is happiest outdoors in a sunny, well drained spot. Even if overwintered indoors it can be bedded out during the summer. At The Salutation aeoniums are used as a striking accent plant in Lutyen’s white garden. I keep my plants in pots and use them to punctuate a mass of dahlias, lilies and gingers by the front door. If grown indoors A. ‘Zwartkop’ needs the brightest spot you can offer, and even then the leaves will rarely be as richly coloured as they are outside. Keep a close eye out for tiny green caterpillars which can destroy the centre of the rosette in late autumn.

Mixed pots, The Watch House, July 2014
When allowed to grow tall, A. ‘Zwartkop’ mixes well with other tender exotics

Happily A. ‘Zwartkop’ is extremely easy to look after, needing very little water in winter (perhaps a drop every fortnight) and a weekly drink in summer. Aeoniums like dry air, so are quite happy in a centrally heated room. Propagation is equally straightforward. Leaf rosettes with a few inches of stem can be cut cleanly away from the plant with a knife and the cut surface left for a week or two in order to callus over before potting into in a gritty, well-drained compost. The drying stage is essential to avoid rot setting in and to encourage rooting from the sides of the stem. Within a month or two the new plant will be growing away strongly whilst the old one produces a number of new rosettes, helping to create a well-branched bush. This process can be carried out several times, meaning lots of spare plants to give to your envious friends. If you are selfish like me, plants can be allowed to grow tall and lofty, perfect for making a statement in the garden.

For Aeonium arboreum ‘Zwartkop’ and a great selection of other choice, named aeonium varieties, visit Trewidden Nursery’s website.

Him Indoors, seated as usual, basks in the sort of sunny position that aeoniums love
Spot the black head! Him Indoors soaks up the sun in Tresco’s Abbey Gardens







Categories: Container gardening, Cornish Gardens, Flowers, Foliage, Plant Portraits, Plants, Tropical Gardens

Posted by The Frustrated Gardener

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18 comments On "Plant Portraits: Aeonium arboreum ‘Zwartkop’"

  1. Thanks so much for this post – I am now enlightened! I saw these ‘Zwartkop’ at Oxford Botanical Gardens in June and was fascinated by them, but I did not know their name. Love your blog and the beautiful photos.

  2. Thanks for that interesting piece on Aeonium ‘Zwartkop’. I’ve got one at home and was wondering if it would ever flower as it seems very happy this year. Your blog answered my question and allowed me to view the flower which I’ve never seen before so thanks for that. I’m now resigned to the fact that it won’t flower this year. Boo hoo! Helen

  3. I’ve never had a problem growing these in central coastal california, but mine have never flowered, altho others in this vicinity do. I have them in various locations, full sun, morning sun, afternoon sun. Makes no difference. I seldom water them and they are otherwise very healthy. Can you advise?

  4. Hi there, love your blog, mine however is a question – that’s if you don’t mind! I have beautiful aeoniums but they are now beginning to get “chunks” bitten out of them! Have you any idea what could be causing this and if so how can I treat them. Love them and hate seeing them being attacked like this. Thank you.

    1. Hi Joan. I’d put my money on either tortrix moth caterpillars or adult vine weevils. Both are a pest in my own garden. Tortrix moth caterpillars in winter and vine weevils in summer. Either spray them with insecticide or be vigilant and pick them off by hand. I do a combination of the two. Dan

      1. Hello again, many thanks for coming back to me so promptly. Are the tortrix moth caterpillars visible, as on checking the plant there is nothing to see that could be biting chunks out of the “leaves”! Vine weevils I’ve heard of and believe they are located in the soil, if this is so presumably I should re-pot. It’s such a shame they are being eaten this way as they are so attractive. Strangely enough I have the green variety (not sure of correct name) and these are unaffected! Strange. Thanks again, Joan

      2. Tortrix moth caterpillars are bright green but good at hiding. You can often tell they’ve been active as they leave little black ‘droppings’ on the leaves. Vine Weevil adults tend to come out at night so go out after dark and check for them with a torch. Only the larvae will be in the soil – like little white maggots – they are very easily spotted. Repotting only works if you can be sure you have removed them all from around the roots. Use sharp grit on the surface of pots to stop adults laying more eggs. Dan

      3. Extremely helpful tips – many thanks. Getting the torch out ready for tonight!!!

  5. Hi, what are your thoughts on repotting large plants? I was lucky enough to be given a cutting back in 2013 and after wind blew over the plant around 2015 and snapped a branch I now have 2 beautiful big plants but one is now nearly 5 feet tall and getting too heavy to repot easily. Would you suggest I get a group of people together and a very large pot for it (meaning I will struggle to cover it on winter so a custom greenhouse will be in order) or should I do the horrible thing of cutting it into multiple plants and having lots of smaller plants?

    1. Hello. If it were me I’d keep it as a large plant, mainly because I don’t have room for lots of little ones but also because they can be quite sculptural as large plants.

      Even at 5ft you will find your aeonium has a very small root ball. The pot might be large but it will not be filling it, I can guarantee. So provided you can keep it stable, keep it in the smaller pot so you can move it around. I used to have a very large plant and it went into nothing bigger than an 8” pot every winter.

  6. Hello, I have aeoniums for the first time and love them. I live in the Midlands UK, temperature gets to around 7 at night at the moment. We have lots of rain so I cover them with plastic shields. Because frost will only be now and then in winter, can I move them in and out or is it best just to keep them indoors? Will they do OK in a unheated bedroom with north facing window, or better in living room?

    1. Hi Ann. I would not recommend leaving your aeoniums outside between now and May. An unheated room with a decent amount of bright daylight, a porch or conservatory is best. They don’t need watering over winter and will become dormant. If they lack light they can become pale and drawn. Hope this helps a little. Dan

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