Commelinaceae Cultivar analysis Plant naming

The Superba Group: two birds with one stone

Skip to: Many faces of ‘Superba’ // The mystery of ‘Purple Highway’ // The cultivar group solution // Conclusions // References

For the last year or two, a particular group of Tradescantia zebrina plants have left me in a tangle. They have smooth leaves with wide, glittering bands of silver. Sometimes described as “reverted quadricolor”, “silver sicilian”, or “var zebrina”, they’re widespread in cultivation but often unlabelled. There’s also an elusive legally-protected cultivar called ‘Purple Highway’ which seemed to be related.

I think I’ve finally untangled everything now. As usual, it involves a bit of classification re-shuffling. But I hope this case will be less disruptive than some more… notorious name corrections.

Many faces of ‘Superba’

Last year I wrote about Tradescantia zebrina ‘Superba’, a plant which has been in cultivation for over a century but had lost its original name. From my research, I tracked down what it was originally called. Finally we had a unique name to accurately identfy and describe the cultivar.

But since then, it’s become clear that not all ‘Superba’ plants are the same. Although they all have indistinguishable foliage, different specimens can have subtle but consistent differences in flower colour. There seem to be at least two, and possibly three or more, distinct clones in circulation.

Flowers from two subtly different ‘Superba’ clones

The flower differences make it inaccurate to consider all these plants the same cultivar. Specimens of one cultivar should be indistinguishable from each other, and that’s not the case when we can tell them apart by flower colour.

But the differences are extremely subtle. If a plant isn’t flowering, there’s no way to tell which clone it is at all because the foliage is identical. Even if it is flowering, it’s hard to judge unless you have different clones side by side and can compare their flowers directly. It seems unlikely than anyone would have a particular need to grow multiple ‘Superba’ clones, or prefer one over any other.

So they’re not the same cultivar, but they’re not really different cultivars either. I spent a long time pondering the best way to handle the situation.

The mystery of ‘Purple Highway’

In parallel with the puzzle of ‘Superba’ and its flowers, I was working on another problem.

In 2019, Eden Collection made a new plant breeder’s rights registration for a T. zebrina cultivar in Europe (Eden Collection B.V., 2019). They changed the name several times during the application process, but the one that was eventually accepted was ‘Purple Highway’. In 2020, they filed a plant patent in Australia for the same cultivar under the name ‘EC-TRADE-1809’ (Eden Collection B.V., 2020).

I spent a long time trying to track down the plant itself, because Eden Collection inexplicably never sell their patented plants under their patented names. (If you don’t make it clear that something is patented when you sell it, you would be in a very weak legal position to actually enforce the patent if someone subsequently violated it, making it rather pointless.)

Eventually I figured out that ‘Purple Highway’ is one of two zebrina cultivars that Eden Collection sell under the trade name Silver Sicilian. The other is ‘Violet Hill’, so once I got hold of a plant that definitely wasn’t that, I knew I had ‘Purple Highway’. It was immediately clear that ‘Purple Highway’ was indistinguishable from ‘Superba’ plants.

Tradescantia zebrina Superba group plant grown in full sun

This put me in a difficult position. I knew for a fact that ‘Superba’ was a very old cultivar, and definitely not newly-created as Eden Collection’s patents suggested. But I don’t have any legal power to overturn or object to the patent (at least not without spending thousands of pounds for the privilege).

But as ICRA, I have to accept names that are established in patents. That would have meant overriding the name ‘Superba’ with the new patent. Not only would that be frustrating for everyone, it would also be very misleading. Most people’s ‘Superba’ plants do not come from the legally-protected stock that Eden Collection started selling in the last few years.

I was stuck with another naming problem that I wasn’t sure how to handle.

The cultivar group solution

In the end, both problems had the same solution: the cultivar group classification.

A cultivar group is a set of plants which have some features in common, but are not indistinguishable in every way. This is an ideal way to treat ‘Superba’, with its uniform foliage and varied flowers.

Acknowledging that it’s a cultivar group rather than a single cultivar means that no-one will be confused to find that different Superba plants have subtle differences. But it still allows us to recognise that all these plants are very similar, and not really worth identifying separately.

Tradescantia zebrina ‘Purple Highway’ flower

This also means that Eden Collection’s new release can be treated as a specific member of that group – Tradecantia zebrina (Superba Group) ‘Purple Highway’. And if a plant wasn’t specifically sold with that patented name, then it can be classified as Tradescantia zebrina Superba Group in general, without causing any legal confusion.

And hopefully it’s not too much of an ordeal to update existing labels from ‘Superba’ to Superba Group!


I threw a lot of information into this article, for people who are interested in the process of my research. But if you just want to know what this means for you, here are the headlines:

  • Plants which were labelled as Tradescantia zebrina ‘Superba’ should now be called Tradecantia zebrina Superba Group.
  • This is because ‘Superba’ actually refers to multiple clones, with identical foliage but subtly different flower colours.
  • There’s a cultivar called ‘Purple Highway’ (often sold as Silver Sicilian) which is a member of the Superba Group.
  • ‘Purple Highway’ is patented in Australia and Europe, but other Superba Group plants are unaffected by the patent.


Eden Collection B.V. (2019, February 25). Tradescantia zebrina ‘Purple Highway’ [EU plant breeder’s rights registration 51415]. Community Plant Variety Office. Registration document link.

Eden Collection B.V. (2020, July 30). Tradescantia zebrina ‘EC-TRADE-1809’ [Australia plant breeder’s rights application 2020/077]. IP Australia. Internet Archive link.

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