Plant Profile: Sophora ‘Sun King’ AGM

In June this year I will have been blogging for seven years. I have completely forgotten most of the posts I wrote at the beginning of my blogging career, occasionally stumbling upon them when researching other topics I am writing about. When this happens it is rather like bumping into an old friend. I put as much thought and care into writing those early posts as I do now, perhaps more, yet hardly anyone read them. Hence I make no apology for occasionally rehashing old posts and hopefully improving on them in the process.

I first wrote about Sophora ‘Sun King’ back in May 2013, shortly after I had introduced the plant to my garden …. or rather to an unpromising corner at the back of my street-side parking space. I had seen it growing along iron railings in a Hampstead garden and immediately decided I should have one at The Watch House. Duly purchased from Burncoose Nursery in Cornwall my sophora sapling was shoehorned into a tiny pocket next to the workshop doors where it became a wild, sprawling presence, one of the only green things in the street. Long growths would occasionally flail about and get trapped in the car boot as it closed, but otherwise the sophora flourished where many shrubs would have withered and died.

New Zealanders know sophoras, or kōwhais, by the copious yellow flowers that appear in spring (kōwhai means yellow in the Māori language). The flowers are attractive to a number of native birds because of the nectar they contain. But S. ‘Sun King’ is, in fact, a plant of Chilean origin, introduced to the UK by Hillier Nurseries in the late 1990s. It turned up in Hampshire in a packet of nothofagus seed and is believed to be a hybrid between Sophora macrocarpa and Sophora cassioides, both Chilean species. The original plant can still be found in the Harold Hillier Gardens. (Charles Darwin used sophora seeds to study seed dispersal in the South Pacific because their salt resistance allowed them to colonise many islands between Chile and New Zealand.)

British birds have yet to discover the pleasures of Kōwhai, but S. ‘Sun King’ produces an unmissable show from the end of February until as late as May. Established plants are evergreen and reasonably hardy if given a sheltered, sunny, well-drained position. They can be trained against a sunny wall or fence, or simply be left to form an open shrub. During a very cold spell sophora may lose their leaves or entire branches, but these are rapidly replaced. Frosted branches should not be removed until late spring as they may reshoot.

One day, just weeks before I managed to buy the workshop adjoining my house, I returned home to discover the previous owner hacking my sophora down to ground level and grinding out the stump. I was horrified. With negotiations at a sensitive stage (let’s just say he was a very volatile gentleman) I had to bite my tongue and let him finish his murderous work. What happened next was quite miraculous since the sophora started to resprout almost immediately from the roots. Since S. ‘Sun King’ is typically propagated by grafting onto a S. microphylla rootstock I can no longer be sure if I have the hybrid or the species. I am happy with it either way.

The resulting shrub resembled something approaching a peacock’s tail, with long, unbranched, feathery shoots projecting up and out like the sun’s rays. In spring 2018 the regnerating sophora was then completely defoliated by The Beast from The East and produced no flowers at all that year.

Following a good roasting during the summer that followed, my sophora is once again flourishing, producing its acid-yellow flowers at the end of February when the photograph above was taken. Māori people used the first flowering of kōwhai to mark the last frost of the season and to start planting sweet potatoes (kumara).

Many spring-flowering shrubs have yellow flowers, and those of S. ‘Sun King’ are an exceptionally vivid yellow with a pronounced green tinge. The best comparison I can draw is with a slightly unripe banana. Combined with waxy petals this makes for an eyecatching, weatherproof bloom.

Why we don’t grow sophora more often in our gardens I don’t know. It’s pleasing to look at, flowers in advance of your bog-standard forsythia and tolerates cold and thin soils whilst offering a hint of the exotic at the same time. It can be pruned or trained and British pests and diseases pay it no heed. Perhaps the only drawback is that the flowers are not scented, but I guess we can’t have it all. Plant a sophora somewhere warm and sunny this spring and you won’t be disappointed. TFG.