Indian Bean Trees flourish in the relatively warm, dry summers of Cambridge. The focal point of the Rock Garden is a Catalapa x erubescens ‘Purpurea’, a mesmerising sight in full flower and intoxicating in its scent. The Rock Garden was developed around a small specimen in the 1950s, which is now a champion tree.
The spreading, dome-shaped crown provides shade to part of our national collection of European saxifrages. The flower stalks and buds are a wonderful papal-purple that also floods the new leaves, whilst the throats of the enormous frilly, white, foxglove-shaped flowers, held in loose panicles, are dusted with the same colour, but also striped with gold. The long, slender pods that give rise to the common name, persist well into winter.
Another striking Indian Bean Tree is the specimen of Catalpa speciosa growing rather too close to Cory Lodge. This North American species is late into leaf and flower, making it a valuable and striking addition to the landscape. The flouncy flowers are borne 15-20 to each panicle and are white and frilly with deep throats marked with gold and dusted purple. The leaves are very large and heart-shaped.
A collection of Catalpa has also been established in the eastern part of the Botanic Garden. Two more specimens of the 'Purpurea' selection are responsible for the rich scent that billows over the nearby Chronological Bed throughout June and into July. They can be contrasted with a neighbouring Catalpa bignonioides ‘Aurea’ with particularly floriferous panicles held upright against golden, heart-shaped leaves. Although fabulous in foliage and flower, the fragrance is weak. Also represented is Catalpa ovata, from China, which has much smaller, rather yellowish flowers, spotted, rather than dusted, with purple, from which develop clusters of skinny bean pods. The heart-shaped leaves of this species have pointed lobes.