Genus of about 55 species of deciduous and evergreen shrubs, more rarely small trees, mostly from W. North America, in particular California, but also from E. US and Mexico, occurring from the coast to the mountains, usually in scrub and woodland on dry slopes. They have opposite or alternate, usually toothed leaves, and are cultivated for their small but profuse, blue, white, or pink flowers, to 3 mm across, borne in terminal, lateral, or axillary cymes, racemes, or panicles. They are suitable for growing in a shrub border or against a sunny wall. Low-growing or prostrate species and cultivars are excellent as a groundcover or in a large rock garden.
California lilac (also known as wild lilac), puts the world of “blue” at your disposal. Individual flowers are tiny, but they group into dense heads or spikes that transform these shrubs into blue beacons during early to mid-spring. You’ll find them much more arresting than true lilacs; in comparison, all these flowers lack is fragrance. Numerous species, ranging in habit and size from ground cover spreaders to those of treelike habit and bulk, grow wild on California’s hillsides.
Between those extremes are many that fall into the 5 to 12 foot height range, a size well suited for contemporary gardens. Details vary a bit from one to another, but all have fairly small, glossy leaves that make a dense foliage cover. Plants generally are bushy and rounded, with a greater width than height; in youth, they may be rather angular before growth fills in. Most may be trained against a wall, where they can reach twice the height they would in an open site. As a group, California lilacs are short-lived in the landscape; expect 5-10 years for a typical lifespan.
When to grow
Plant container grown California lilacs in fall, after the weather cools, and in winter; this gives roots a chance to grow into your garden soil before warm conditions return.
Where to grow
Grow in fertile, well- drained soil in full sun, sheltered from strong, cold winds. California lilacs are lime tolerant, but may become chlorotic on shallow alkaline soils. Select locations that have full-sun exposure. These are good shrubs for planting on slopes and hillsides.
How to Grow
Dig a planting hole about 2 inches shallower than the plant’s root ball and twice as wide. Then dig deeper around the edges (leaving a firm plateau in the center) at the hole’s bottom and roughen its sides; this encourages roots to penetrate into your garden soil. Set the root ball into the center of the hole so its top is I to 2 inches higher than the soil outside the hole. Return soil to the hole around the root ball, firming it with your fingers, then water well.
Sow seed in a seedbed, or in containers in an open frame, in autumn; most species hybridize readily. Root greenwood cuttings of deciduous plants, and semi-ripe cuttings of evergreens, in mid- or late summer.
How to care
Though many of the wild species won’t tolerate summer watering, our favorite selections are primarily hybrids developed for better tolerance of typical garden conditions. In general, give these plants well-drained soil and little to moderate watering during the warm period from mid-spring to mid-fall. Prune plants to shape them after flowers have finished, but avoid heavy cutting back. To shape plants, pinch or lightly cut back young branch tips during the growing season.
Pests and diseases
Dieback, powdery mildew, mushroom root rot, fungal leaf spots, and Verticillium wilt are somewhat common. Caterpillars, scale insects, lacebug, and mealybugs occur.
- Blue Jeans: Flower color: Pale powder blue, It grows to 9 feet high and wide. It tolerates heavy soil and either drought or summer water.
- Concha: Flower color: Dark blue. It grows to 7 feet tall and 8 feet wide, tolerates some summer watering.
- Dark Star: Flower color: dark cobalt blue. It reaches 6 feet high and 10 feet wide, and is covered in tiny dark green leaves.
- Frosty Blue: Blossom: white-tipped deep blue flowers. It grows to 9 feet high and 1 feet wide.
- Julia Phelps: Blossom: intense dark blue. It grows to 7 feet high and 9 feet wide.