Arizona Cypress (Hesperocyparis arizonica)

Arizona Cypress

The Arizona cypress is a popular evergreen for its heat and drought tolerance. The needles of the Arizona cypress are soft and fragrant. It can be used for windscreens, erosion control, landscaping, and for Christmas trees.

I. Appearance and Characteristics 

Hesperocyparis arizonica, the Arizona cypress, is a North American species of tree in the cypress family Cupressaceae. Populations may be scattered rather than in large, dense stands.

Hesperocyparis arizonica is found mainly in northern Mexico in the states of Chihuahua, Coahuila, Durango, Tamaulipas, and Zacatecas. It is also found in small areas of the southwestern United States in the southern parts of Arizona, New Mexico, and Texas. In the US it is found between 1000 and 1500 meters in elevation while in Mexico it reaches as high as 2200 meters in some forests. In the wild, the species is often found in small, scattered populations, not necessarily in large forests. An example occurrence is within the Sierra Juárez and San Pedro Mártir pine–oak forests of Mexico, where it is found along with canyon live oak and California fan palm.

Hesperocyparis arizonica is a coniferous evergreen tree with a conic to ovoid-conic crown. It grows to heights of 10–25 m (33–82 ft), and its trunk diameter reaches 55 cm (22 in). The foliage grows in dense sprays, varying from dull gray-green to bright glaucous blue-green. The leaves are scale-like, 2–5 mm long, and produced on rounded (not flattened) shoots. The seed cones are globose to oblong, 15–33 mm long, with 6 or 8 (rarely 4 or 10) scales, green at first, maturing gray or gray-brown about 20–24 months after pollination. The cones remain closed for many years, only opening after the bearing branch is killed (in a wildfire or otherwise), allowing the seeds to colonize the bare ground exposed by the fire. The male cones are 3–5 mm long, and release pollen in February–March.

Hesperocyparis arizonica was given its first scientific name and described by Edward Lee Greene in 1882 as Cupressus arizonica, placing it in genus Cupressus. This description was soon after disputed by Maxwell T. Masters who, in 1896, published a journal article where he said it should be considered a subspecies of Cupressus benthamii with the variety name of arizonica. A similar classification reduces it to a subspecies as Cupressus lusitanica subsp. arizonica was posthumously published by René Maire in 1952. There also have been publications that suggested moving it as a species to a different genus such as Callitropsis in 2006 and a new genus, Neocupressus, in 2009.

II. How to Grow and Care

Consider the environment of Arizona, where Arizona cypress trees grow naturally, and you’ll be able to picture the best environment in which to grow these trees. They do well in full sun and well-draining soil and are tolerant of hot, dry conditions.

The tree is usually delivered as a young specimen that’s between 6 inches and 1 foot tall, which can then be transplanted to an outdoor site. It serves well as a windbreak and for erosion control.

Sunlight

Cupressus arizonica needs a site that provides full sun for plenty of direct light.

Temperature and Humidity

As its name suggests, the Arizona cypress is tolerant of hot and dry conditions like you would find in the American Southwest or Mexico. In areas of high humidity, the Arizona cypress might be more prone to diseases.

In the United States, the Arizona cypress tree does best in USDA zones 7 to 9.

Watering

Cupressus arizonica can tolerate dry soils, but it does need at least 10 to 12 inches of water annually. Any location chosen should offer proper drainage for optimal growth. It will grow better if it is watered regularly.

Soil

Arizona cypress trees are not particular about soil pH and can grow in acidic, neutral, or alkaline dirt. It can also tolerate clay, loamy or sandy soils. However, the soil should be well-drained.

Fertilizing

Unless there are specific and known nutritional deficiencies, it’s not necessary to fertilize an Arizona cypress tree. Fertilizer applications could increase the growth rate, which would require additional irrigation. If you need to increase how quickly the cypress tree grows, use a quality granular fertilizer.

Planting Instructions

When planting Arizona Cypress, select a site with full sun exposure and ample space for the tree to reach its mature size. Dig a hole twice as wide as the root ball and just as deep. Place the tree in the hole, backfill with native soil, and water thoroughly. Mulching around the base can help retain moisture and regulate soil temperature.

Pruning

The Arizona cypress can be pruned to form a hedge if desired. It will need little pruning otherwise unless you are removing branches that have become dead, damaged, or diseased.

Be careful if you choose to prune the tree. Cypress trees do not develop new buds on older wood, so cutting back shoots could lead to bare spots on the tree. Additionally, you should only prune right before new growth in the spring. If you need to control growth or prune for shape, you can also do it in the late spring or early summer.

Propagation

Arizona cypress can be propagated from cuttings. Here’s how:

  • What You’ll Need: Healthy plant, scissors, plastic bag, soilless potting mix, containers, rooting hormone (optional)
  • Where to Cut: Cut with scissors just below a node on a soft, green stem (cutting should be about 4 to 6 inches long).
  • Maintaining the Cutting: Remove the bottom few leaves (needles), dip the stem in water then in rooting hormone (if desired), and slide the stem about 2 inches into a container of potting mix. Keep warm and moist but not soggy.
  • When to Plant the Cutting: In 3 weeks, transplant the cutting into another pot or the ground.

Grow from Seed

This tree will grow from seed, but the process does require a bit of effort and patience. Here’s how:

  • Cut this year’s brown cones from the tree and place them in a warm, dry, shaded area. Be sure they are protected from squirrels and other seed eaters. 
  • Allow the cones to dry out until they “open” and their seeds begin to drop out.
  • Sprinkle seeds in a single layer in the bottom of a container, cover with water, and soak for 24 hours.
  • Wrap the soaked seeds in moist paper towels and seal them in a plastic bag. Refrigerate the seeds for 30 days.
  • After a month of refrigeration, plant the seeds in small nursery pots with a soilless potting mix. Press one seed about 1/4 inch deep in each pot and cover with a thin layer of packed potting mix.
  • Water pots thoroughly, keeping them moist but not soggy, in a location that receives indirect light and a temperature around 72 degrees Fahrenheit.  
  • Germination should occur one to two months after planting. Keep the seedlings in a greenhouse for the first winter, then transfer them into the ground the following spring.

Overwintering

Arizona cypress is cold tolerant and does not require special winter care. Seedlings, however, should be kept indoors as mentioned in the steps above.

Pests and Diseases

Common Pests and Plant Diseases

Cupressus arizonica is susceptible to several pests and diseases. Pests include bagworms, which will cause defoliation as these larvae chew their way through the leaves, as well as cypress bark beetles (Phloeosinus spp.), which will bore holes into the trunk and can kill the tree if you are not able to get rid of the beetles soon enough.

Additionally, mistletoes are parasitic shrubs that send roots out into the branches of the tree and steal nutrients. You should prune out affected branches when the mistletoe first forms if possible to keep it from growing and spreading.

Common Problems With Arizona Cypress

Problems with Arizona cypress are generally easy to recognize and occur as a result of improper care or environmental conditions. A few of the common issues owners might encounter include the following:

Galls

Gymnosporangium rusts occur when fungi invade. It can lead to problems like galls and witches’ brooms. These rusts are usually not too problematic except in rainy years.

Yellow or Brown Needles

Phomopsis blight will cause new growth to turn yellow and then brown as it dies. Make sure your soil offers good drainage as too much moistness can make the problem worse.

Stem Cankers

Finally, stem cankers should be pruned out as soon as you notice them help maintain the overall health of the tree.

Health & Safety

There are no known toxic or poisonous parts of the Arizona Cypress to humans, dogs, or cats. The tree is not thorny or spiky and does not typically cause contact dermatitis or other skin irritations.

III. Varieties of Arizona Cypress

Arizona cypresses come in five different types, even though some botanists consider them to be separate species.

  • Cupressus arizonica var. arizonica
  • Cupressus arizonica var. glabra
  • Cupressus arizonica var. montana
  • Cupressus arizonica var. nevadensis
  • Cupressus arizonica var. stephensonii

IV. Uses and Benefits 

Normally chosen by gardeners for its dense growth and suitability for blocking views and wind, the arizona cypress can also grow in a wide variety of soil, light and watering conditions. They are most commonly used as garden hedges, but also make great shade and specimen trees.

Arizona Cypress (Hesperocyparis arizonica) Details

Common name Arizona Cypress
Botanical name Hesperocyparis arizonica
Plant type Perennial
Hardiness zone 7a, 7b, 8a, 8b, 9a, 9b, 10a, 10b, 11a, 11b
Growth rate Fast
Harvest time Summer
Height 40 ft. 0 in. - 60 ft. 0 in.
Width 40 ft. 0 in. - 60 ft. 0 in.
Sunlight Full sun (6 or more hours of direct sunlight a day)
Soil condition Loam (Silt)
Leaf color Blue