Among the world’s most famous cultivated Aeoniums, ‘Zwartkop’ holds a unique place.
Its near-black foliage, spectacular tree-like habit, and ability to form large rosettes atop long stems have made it—for several decades—one of the most widely grown and easily recognizable Aeoniums.
Yet the significance of ‘Zwartkop’ extends beyond its ornamental appeal.
This cultivar has also become one of the most important parent plants in the horticultural history of Aeoniums. Many famous hybrids have been derived from it or are attributed to it, and several variegated Aeonium lineages also appear to trace their origins to this plant.
However, despite its global fame, the story of ‘Zwartkop’ remains shrouded in some mystery.
AEONIUM ‘ZWARTKOP’
NAME: Aeonium ‘Zwartkop’
FAMILY: Crassulaceae
GENUS: Aeonium
TYPE: horticultural cultivar / hybrid of uncertain origin
ORIGIN: unknown with certainty
PLACE OF DISCOVERY: Leiden, Netherlands
DATE OF PUBLICATION: 1959
AUTHOR ASSOCIATED WITH THE NAME: B.K. Boom
The cultivar has been documented since the 1950s. It was reportedly discovered in a nursery in Leiden, Netherlands, before being named by the Dutch botanist B.K. Boom.
The first published reference to this cultivar appears in the journal Succulenta, volume 38, number 6, page 85, in 1959.
This information constitutes one of the best-documented historical facts regarding ‘Zwartkop’ today.
An origin that long remained a mystery
For many years, ‘Zwartkop’ was widely sold under the name Aeonium arboreum ‘Zwartkop’.
This name led to the belief that it was simply a particularly dark selection of Aeonium arboreum.
However, the reality may be more complex.
Some specialists now consider ‘Zwartkop’ to be a hybrid, rather than a simple cultivar of Aeonium arboreum.
A hypothesis now being put forward suggests that ‘Zwartkop’ is a cross between Aeonium arboreum and Aeonium korneliuslemsii. This lineage is notably reported by Aevriel Scarlett.
An Aeonium that has traveled the world
The success of ‘Zwartkop’ is easily explained when looking at a mature plant.
Its growth habit is tree-like and highly architectural.
The stems rise gradually and branch out, bearing large rosettes at their tips.
With age, the plant can form a veritable small tree covered in rosettes.
This silhouette is one of the key features that have contributed to its immense horticultural success.
In regions with mild climates, mature specimens can reach over a meter in height—or even more when grown in the ground under particularly favorable conditions.
Almost black rosettes
It is, of course, the foliage color that has made ‘Zwartkop’ famous.
In bright light, the leaves take on a very dark purple color that can appear almost black.
The contrast between the dark rosettes and the lighter stems gives the plant a particularly striking appearance.
However, this coloration is not entirely constant.
As with many heavily pigmented *Aeoniums*, it changes throughout the year depending on:
- light levels;
- temperatures;
- water availability;
- the plant’s growth cycle.
During growth periods, the center of the rosette may notably show more green.
Conversely, during periods of high light and slowed growth, the red and purple pigments become much more intense.
It is therefore quite normal for the same ‘Zwartkop’ to appear almost black in summer and more purple or greenish at other times of the year.
A rosette that changes with the seasons
The seasonal behavior of ‘Zwartkop’ is particularly interesting.
During the hot, dry season, the rosette can tighten significantly.
The outer leaves turn upward, and the heart of the plant becomes more compact.
When temperatures cool and conditions favor a return to growth, the rosette gradually opens up.
The outer leaves may then spread out, creating a much more dramatic shape.
This seasonal transformation explains why two photographs of the same cultivar can sometimes give the impression of showing two different plants.
A majestic, tree-like habit
The growth habit of ‘Zwartkop’ is particularly distinctive.
The stems elongate gradually and produce secondary branches.
Each tip can bear a rosette, allowing the plant to eventually form a veritable cluster of rosettes.
Vegetative propagation is also relatively easy via stem cuttings.
This ability to rapidly produce numerous branches has likely contributed significantly to its worldwide distribution.
Coloring that explains its name
The name Zwartkop is of Dutch origin.
It literally means « black head » :
- zwart = black;
- kop = head.
This name refers directly to the very dark appearance of the rosettes.
Consequently, the cultivar is known by various translations or adaptations depending on the country.
These include:
- ‘Zwartkop’ ;
- ‘Schwarzkopf’ ;
- ‘Blackhead’ ;
- ‘Tête noire’ ;
- ‘Black Rose’.
The name ‘Schwarzkopf’, widely used in some older collections, is therefore a linguistic variant of the name ‘Zwartkop’ rather than necessarily a different cultivar. The International Crassulaceae Network database lists ‘Blackhead’, ‘Tête noire’, and ‘Schwarzkopf’, among others, as synonyms for ‘Zwartkop’.
A major parent of modern Aeoniums
The importance of ‘Zwartkop’ in the horticultural history of the genus is considerable.
Its dark color has been highly sought after by hybridizers.
When paired with *Aeonium* varieties featuring large rosettes, velvety foliage, or contrasting colors, it has yielded hybrids with particularly spectacular combinations of traits.
Several widely known cultivars today are considered to be directly or indirectly derived from ‘Zwartkop’.
Lineages often associated with this influence include *Aeonium* varieties such as:
- ‘Velour’;
- ‘Blushing Beauty’;
- ‘Garnet’;
- ‘Zwartkin’;
- and numerous other modern hybrids.
Why are there so few ‘ Zwartkop‘ variegata?
This is arguably one of the most surprising aspects when studying this lineage.
Given the global popularity of ‘Zwartkop’, one might expect to find a vast number of documented variegated mutations.
Yet, the number of forms clearly attributed to ‘Zwartkop’ remains surprisingly limited.
LIST OF VARIEGATED AEONIUMS DERIVED FROM ‘ZWARTKOP‘
ZWARTKOP BIG BANG
KNOWN NAMES : ‘Big Bang’ (the most common name), though it is preferable to call it ‘Zwartkop BigBang’ because there are different ‘Bigbang’-type mutations, such as ‘M Brushed’.
CREATION DATE / CREATOR : Circa 2020 (South Korea).
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DARTH VADER
KNOWN NAMES : Zwartkop variegata, « M », Red Soul, 墨法师锦. Its name, « Darth Vader, » refers to the *Star Wars* character, who is dressed entirely in black and wields a red lightsaber—two colors that characterize this *Aeonium*.
CREATION DATE / CREATOR : Commercial release around 2021.
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