Calocedrus

( kal - oh - SED - russ )

At-A-Glance Information

Commonly called Incense Cedar or Pencil Cedar, this genus of evergreen conifer tree needs full sun to light shade and little to moderate amounts of water for best performance in the landscape. These trees are native to eastern Asia and western North America, and are known for their beautiful, soft foliage. They are commonly grown as garden ornamentals in medium to large gardens, particularly in cooler climates such as those in the Pacific Northwest. Use these trees as background plantings, windbreaks, or trim them into a screening or hedge plant.

Calocedrus species and varietals

The genus Calocedrus is a member of the plant family Cupressaceae and includes 4 extant species (and a few extinct species, as well). The genus grows best in USDA hardiness zones 5-8 or Sunset growing zones 2-12 and 14-24 (to find your zone, click here: Zone Map).

Calocedrus decurrens (Libocedrus decurrens) (California Incense Cedar, Pencil Cedar, Pecky Cedar)
These trees are native to the West Coast, from the mountains of the state of Oregon down through Baja California, Mexico. They reach between 75 and 90 feet tall and 15 feet wide, with a pyramid shape. Bark is reddish brown and foliage is green. Flat sprays of leaves are dotted with small yellow-brown to red cones. California Incense Cedars are used as specimen trees, for screening and as windbreaks. These trees are drought-tolerant when mature. Dwarf cultivars include 'Compacta' and 'Berrima Gold'.

Calocedrus formosana (Taiwan Incense-Cedar, Taiwan Cui Bai, Taiwan Xiao Nan)
Endemic to Taiwan, this species reaches between 65 and 83 feet tall when mature. Bark is greyish when mature and somewhat fissured, and foliage is green. Cones are pale purple with a whitish wax coating, and turn brown when mature.

Calocedrus macrolepis (Chinese Incense-Cedar, Yunnan Cypress, Cui Bai)
This species is native to southwest China, northern Vietnam, northern Laos, extreme northern Thailand, and northeastern Myanmar. Trees can reach between 82 and 115 feet tall when mature, and produce green foliage in flattened sprays that are whitish underneath. Cones turn brown when mature (about 8 months after pollination). These trees have been historically overharvested in their native range for their valuable wood, and are considered vulnerable to extinction.

Calocedrus rupestris (Vietnam Incense Cedar, Limestone Incense-Cedar, Bach Xanh)
This conifer species was recently discovered and is native to China and Vietnam. It forms a medium-sized tree that reaches up to 80 feet tall at maturity. This species is considered to be endangered in its native range, and a reserve has been established for their protection.

Caring for Calocedrus

Incense Cedar trees prefer to be planted in a location that receives full sun, but can also tolerate partial shade if necessary, especially when they are young. They need about 6 hours of direct sun per day to perform well. They have a moderate growth rate, putting on around 1 or 2 feet per year in garden cultivation. Plant trees 25 feet apart for individual specimens, but only 6 to 8 feet apart for a hedge or screen. Ensure that soil is well-draining before planting. They can adapt to a range of soils, including rocky, sandy, or loamy, and prefer a slightly acidic to neutral soil pH (6.0 - 7.5). Clay soils will need to be amended with sand or another drainage-increasing material before planting. Mulch around the base of the tree after installation, ensuring that there is a few inches of space between the mulch and the trunk.

To encourage a good root system to develop, water young trees regularly and deep water when mature. Avoid overwatering these trees, as they prefer soil to be on the drier end. Allow soil to dry out in between waterings to prevent root rot issues. Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Prune to remove dead, damaged, or diseased branches and avoid heavy prunings. Incense Cedars are relatively cold-hardy, and can also tolerate hot summers, surviving for over 50 years in the garden if cared for properly.

Propagation

Calocedrus can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your tree, follow the instructions below:

Propagating Calocedrus by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After a few months have passed, your cutting should be rooted. When you notice new growth on your propagated Calocedrus, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Calocedrus by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a sealable bag or other container filled partially with sand, pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds in late fall, when the female cones begin to open up and look a bit like a duck's bill. Once they have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Harvested seeds will benefit from some cold stratification before sowing to increase the rates of germination. Place seeds in a sealable bag or other container filled with moist/damp sand. Place the container in the refrigerator (or other area that stays between 37 and 41 degrees Fahrenheit) for between 30 and 60 days' time.
In early springtime, water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.