California lilacs (Ceanothus) are well-known for the masses of intensely blue flowers produced in April, May and June. A good blue is a rare commodity in the garden, which is why California lilacs are so prized.
North and Central America have 55 different ceanothus but the most spectacular, bright-flowered, evergreen species grow close to the sea in California, high up in the scrubby chaparral. Used in early American gardens, they first came to Britain from France when the famous Hackney nursery, Loddiges, imported C. azureus from Empress Josephine’s Malmaison garden.
The intense blue flower of Ceanothus ‘Concha’ is heightened by a backdrop of crisp, dark evergreen leaves. It was originally found in a Welsh garden in Nantyderry and won an AGM in June 1986. It’s a great plant for a wildlife garden, as it will attract bees, butterflies and other pollinators. Plus, with the right variety and training, they can form a floriferous and highly attractive small tree.
Evergreen ceanothus vary in habit from the lanky, tree-sized C. arboreus, commonly called the Catalina Mountain Lilac, to the dense, mound-forming C. thyrsiflorus var. repens from California and south Oregon. They tend to be short-lived, succumbing in really hard winters and need to be trained against a warm wall. In Britain ‘Concha’ is one of the few varieties that is hardy to -10C and looks far more impressive as a specimen shrub, with its arching branches.
Ideally gardeners should emulate the drier sunnier conditions in native California for ceanothus to really work well. They prefer good drainage and a sheltered position and are happy in free-draining alkaline or acid soils away from chalk and wet clay – though drainage can be improved by adding coarse grit to the ground.
I’m a big fan of the blue and lime green combination and my favourite plant to accompany ceanothus would definitely be a euphorbia of some kind. If you have space then maybe Euphorbia characias Wulfenii, if space is a little restrictive then Euphorbia x martini. The yellow of Anthemis tinctoria ‘E C Buxton’, and Phlomis russeliana also look good and they all prefer the same drier conditions too.