Ceanothus delilianus
California lilac
Common names: Ceanothus
At a glance
- Light
- Full sun
- Hardiness
- Hardy with protection
- Pruning
- Mar–Apr
- Flowering
- Jun–Aug
Photo: CC BY-SA 2.0 · Source
Description
The California lilac, botanically Ceanothus delilianus, transforms sunny garden corners from June to August into a brilliant blue. Its dense flower spikes sit on summer‑green shoots and attract bees and bumblebees almost magically. The shrub grows loosely upright, usually 100 to 150 cm tall and wide, and prefers a warm‑protected spot facing a south wall. In harsh conditions it needs light winter protection, as young shoots are sensitive to hard frost. Popular varieties such as ‘Gloire de Versailles’ provide striking accents in the bed with their strong blue hue.
Care instructions
Plant the California lilac in a full‑sun, wind‑protected location with well‑draining, somewhat lean soil; it does not tolerate wet feet. Water young plants regularly until they are established, thereafter watering only during longer dry periods. Prune the shrub in early spring, just before flush begins, cutting back heavily to promote abundant flower set in summer. In autumn, heap leaf or pine straw around the root area and wrap young shoots with fleece if needed, allowing the plant to survive colder winters between week 48 and week 10. Remove faded spikes promptly so the plant can invest energy in new shoots rather than seed production.
The care notes were machine-translated from German.
Garden year
FloweringJun–Aug
Soil & site
Soil pH
Soil type
well-drained, lean, dry, lime-avoiding
Ceanothus likes a free-draining, rather lean soil and barely tolerates waterlogging. It feels most at home in a warm, sheltered spot with sandy loam. Very chalky soils do not suit it, as the leaves tend to turn pale there; good drainage matters most of all. In heavy soils, it is worth working in a mix of sand and grit before planting.
Feeding
Light feeder
As a wild shrub from lean sites, ceanothus needs hardly any extra nutrients. A thin layer of mature compost in spring is quite enough. Overly generous feeding encourages soft shoot growth, which freezes more easily in winter.
Pruning
Prune the ceanothus in early spring, just before growth begins. Since it flowers on the current year's wood, it tolerates a hard cut-back well and rewards you with denser growth and more flowers. Remove frost-damaged and weak shoots back to healthy wood.
Overwintering
Ceanothus is only moderately hardy and needs protection in harsh locations. Horticultural fleece around the shoots and a thick layer of mulch made of leaves or brushwood over the root zone help it through the winter. Against a sheltered south-facing wall or grown in a container, it gets through cold winters much more safely.
Propagation
Methods
- Cuttings
- Layering
The most reliable way to propagate it is by semi-ripe cuttings in late summer, which you root in a bright, warm spot. Layering also works well, because flexible shoots are easily covered with soil. Seeds are rarely available and germinate unreliably as well, so vegetative propagation is the better choice.
For your garden
Grow California lilac yourself
Gartenkern tells you when frost is coming, when to sow and when to harvest, for your location.
Free, no time limit
Notes from real gardens
What other gardeners have written down about this variety, anonymous and voluntary.
No notes shared yet. Will you be the first to write one down?