Purple tree collards - Brassica oleracea var. Acephala
This perennial kale variety has been popular for many years among permaculture and forest garden folks in north America, but it is just beginning to show up in the UK.
Tree collards probably originated in the UK - they are believed to have been introduced to California during the latter half of the eighteenth century, from the island of Jersey in the English Channel where they were grown to feed cattle. You can find seeds and plants of 'Jersey kale', however, although it probably shares a common ancestor with perennial tree collards, it does not seem to be truly perennial.
We don’t have a lot of experience with purple tree collards yet, but we have been treating it much as the other perennial kales and it has responded well. It grows like a lanky Taunton Deane, although it is less robust and needs some support if exposed to wind when it gets taller. Its structure is more open than other kales, making it particularly good for under-planting with alliums and ground cover plants. It is also a very elegant plant with attractive purple leaves and stems. A mixture of this and variegated Daubenton’s at the back of a border would make a beautiful sight.
As yet, we can’t say from experience how winter-hardy it is, but reports suggest it is hardy to at least -5C. We expect plants to grow for many years, just like the other perennial kales and, as we have already discovered, like them it can be easily propagated by taking cuttings.