This extremely attractive Ceanothus was first planted in the Garden in the 1970s, grown from seed collected by, and presented to, the Garden by Lady Cynthia Postan. It was later named to honour Lady Postan, the wife of Peterhouse historian Sir Munia Postan, when the plant was exhibited at the RHS Chelsea Flower Show.
Lady Postan collected the seed from a plant of Ceanothus papillosus var. roweanus growing at Tilden Regional Parks Botanic Garden in Berkeley, California in the 1960s. It was however, originally identified as Ceanothus x regius and distributed as such in the 1970s. Dr Peter Yeo’s observations of the plant led to the conclusion that it was in fact a hybrid between C. thyrsiflorus var. griseus and Ceanothus papillosus var. roweanus. Yeo based this on his study of the leaf morphology of the specimen grown here and that of another seedling grown by Lady Postan in her own garden in Cambridge.
Ceanothus ‘Cynthia Postan’ forms a large, rounded shrub nearly 3 metres high and across, clothed with dark, evergreen, narrowly oblong leaves. The dense inflorescences of flowers, which emerge from reddish buds, smother the plant in rich blue flowers when in flower in May and early June. Suitable for a sunny spot, it requires very little irrigation once established.
It can be seen planted outside the main entrance to Cory Lodge and a further seedling from Lady Postan’s donated seeds graces the south elevation of Cory Lodge.