PL. —Calocedrus decurrensBotanical illustration — drop image
Calocedrus decurrens

Incense Cedar

SpringSummerFallWinter
5a8bHardiness zone
Background

Incense cedar is a large, long-lived conifer native to the mountains of California, Oregon, Nevada, and northern Baja California, growing from low foothills to elevations above 9,000 feet. In gardens it typically develops a narrow columnar to broadly pyramidal form and works well as a tall screen, windbreak, or solitary specimen on large properties.

It tolerates clay, loam, or sandy soils but requires good drainage; waterlogged conditions promote root disease. Once established it is notably drought tolerant, suiting it well to western North American summers. Growth is moderate in youth and slows with age. Bark on older trees is reddish-brown, deeply furrowed, and fibrous; the flat-sprayed, scale-like foliage is strongly aromatic when crushed. A soil pH of 5.0–7.5 is acceptable. In colder portions of its range, young trees benefit from windbreak protection during their first one or two winters.

The wood is extremely decay-resistant and is the primary material used worldwide for pencil casings—most cedar pencils are made from incense cedar, not from true cedars. Indigenous peoples of California and Oregon used the split wood for construction, bows, and stakes, and wove the fibrous bark into baskets and mats.

Care guide
SunFull sun
WaterLow
SoilWell-drained, adaptable
Spacing15–25 ft
Height40–70 ft
Zone5a – 8b
Native RegionCA, NV, OR
Frost hardy
Seasonal tasks
spring
watchExamine the root collar in spring on heavy-clay or poorly drained sites. Soft, dark bark at the base signals Phytophthora root rot; correct surface drainage and reduce irrigation frequency immediately.
cutRemove dead, broken, or rubbing branches in late winter before new growth resumes. Preserve the central leader and avoid heavy cuts into live wood; the tree needs little routine pruning.
sowPlant container-grown or balled-and-burlapped trees in early spring once the ground is workable. Dig the hole twice as wide as the root ball and no deeper; backfill with unamended native soil.
summer
watchWater newly planted trees deeply every 1–2 weeks through the first two growing seasons. Taper irrigation after establishment; mature trees rarely require supplemental water except during prolonged drought.
watchInspect foliage in late summer for dead branch tips or resin-soaked cankers on bark, early signs of Seiridium canker. Prune affected limbs 6–8 inches below discolored tissue and dispose of cuttings off-site; disinfect tools between cuts.
fall
watchApply a 3–4 inch layer of coarse wood chip mulch over the root zone in fall, keeping it several inches clear of the trunk to prevent bark decay.
Common problems

Phytophthora Root Rot

Symptoms

Wilting despite moist soil, yellowing leaves, stunted growth, and dark, decayed roots and crown tissue. Vines may collapse during hot weather.

Treatment

Plant in well-draining soil and avoid waterlogging. Remove and destroy affected vines. Improve drainage with raised beds or amended soil and avoid overwatering.

Armillaria Root Rot

Symptoms

Thinning, yellowing canopy with progressive dieback; white, fan-shaped mycelial mats visible beneath bark at or just below the soil line; honey-colored mushroom clusters appearing at the trunk base or on surface roots in autumn.

Treatment

No chemical cure exists. Improve drainage and avoid any injury to roots or trunk. Remove severely infected trees along with as much root material as possible. Do not replant susceptible species in the same spot.

Seiridium Canker

Symptoms

Elongated, sunken cankers on branches or trunk with heavy amber to brown resin exudate. Foliage above the canker turns yellow then brown and dies. Multiple cankers can girdle a branch or stem completely.

Treatment

Prune infected branches 6–8 inches below the visible canker margin and dispose of material off-site. Sterilize tools with 70% isopropyl alcohol between every cut. No curative fungicide is available; focus on reducing tree stress through proper site selection, avoiding overhead irrigation, and ensuring good soil drainage.