The Hop Tree, Ptelea trifoliata, with Westminster School’s Burlington Wing
The first time I came across this tree, it was growing in the Sensory Garden at Hatfield House in Hertfordshire. It was a pleasant place to sit in the shade on a warm summer day. I was with an eighty-five year old lady who could not walk far, and did not have brilliant eyesight or hearing, but she enjoyed being here, out of the house, and near to this somehow kindly little tree. It leant towards us with its springy branches, sporting generously-sized green leaves in threes and wafted over us its powerful scent. It was refreshing, not too sweet, and the kind of scent that one would not easily tire of.
The botanical name of Ptelea is the classical Greek word for elm, whose flat round seed capsules, or samara, look very similar. It actually belongs to the Rutacae family and is related to oranges, lemons and limes. If you have ever grown a lemon plant from a pip and experienced the scent of one flower in a room, you will have some idea of what the plant is prepared to do in order to attract insects. In the case of the hop tree, its pollinators are flies, who prefer a high-protein diet of raw meat. The tiny yellow flowers are tiny, held in globe-shaped clusters resembling elderflowers.
Needing something to soften and add height to a wall around the Herb Garden, I managed to source a hop tree. I had a sunny, sheltered position for it and was hoping it would enjoy sharing a bed with a lemon verbena, Aloysia trifoliata. But for some reason, possibly inadequate watering during a hot summer, the tree did not thrive at first. In fact it seemed to die after its first winter, and we saw no sign of life for three years. Then one spring it began to sprout and began to grow with confidence. That was over ten years ago. Today it is one of the star characters in College Garden.
Having such arching growth, it looks good with buildings – though very few hop trees have such a glory as Westminster School’s Burlington Wing as a backdrop! The mathematical formality of the architecture provides the perfect foil for its delicate, almost feminine habit , while the Bath stone adds a honey-toned warmth. By the same token, many of the houses at the back of the Herb Garden were destroyed in the Second World War, and their 1960s replacements are not distinguished. Here too the hop tree comes to the rescue with its generous leafy exuberance to distract the eye from the unrelieved monotony of brick walls.
Though this tree fits so well into a monastic garden setting, it is from North America, and would not have crossed paths with the monks who worked here. It did not begin to be cultivated here until the eighteenth century. However it is a useful plant both for medicine and flavour. Its bark was used to bring down fever and other parts of the plant could be taken as a tonic to increase appetite, in the same way as dandelion leaves. European settlers discovered its bitter flavour could be used to make beer – hence the name hop tree.
A graceful, easy and worthwhile tree for a small back garden, or as a specimen on a front garden lawn. The is also a golden-leaved version, ‘Aurea’. A good alternative would be Sambucus racemosa ‘Sutherland Gold’, the golden elder. Both require a sunny, sheltered position, and have a yellow/green appearance so that that goes well with white or dark pink flowers. The open growth of both trees means that they do not cut out too much light for their herbacious companions. Both are deciduous, meaning that some permanent structure behind them such as as a house or garden wall, or an evergreen hedge, is useful visually in winter.
As the Hop Tree moves back and forth in the wind, it reminds us that before these buildings were here, there were marshes and willow trees and long grass.