How to Grow and Care for Alligator Juniper

Alligator junipers are one of the largest species of juniper tree!

Alligator juniper tree in a field with rolling hills in the background.

 Bruce McIntosh / Getty Images

Native to Mexico and the southern United States, the alligator juniper (Juniperus deppeana) is a species of juniper tree that is characterized by its unique cracked bark that resembles alligator skin. The leaves of the alligator juniper are arranged in opposite decussate pairs, and the shoots are typically between 1-1.5 millimeters in diameter. As one of the largest species of juniper trees, alligator junipers can grow up to fifty feet tall in their ideal environment.

Alligator junipers have had practical uses for many centuries and are an important component in the habitat of many different woodland creatures in their native range. The large berries are enjoyed by several different species of birds and mammals, and can even be eaten by humans as well. The attractive, fragrant wood of the alligator juniper is occasionally milled for lumber and used to make particleboard and furniture, as well as novelty products.  

Botanical Name Juniperus deppeana
Common Name Alligator juniper, checkerbark juniper, western juniper
Plant Type Evergreen tree
Mature Size 50' tall
Sun Exposure Full sun
Soil Type Dry, well-draining
Soil pH 5.5 - 7.0
Bloom Time Winter
Flower Color Seed cones
Hardiness Zones 7-9
Native Area Mexico, southern United States
Close up shot of an alligator juniper's bark.
 carolthacker / Getty Images

How to Grow Alligator Juniper

In their native environment, alligator junipers grow on open, rocky hills and slopes that receive full sun for the majority of the day. They are considered to be generally heat and cold-tolerant trees and are known for being adaptable to a range of growing conditions. Alligator junipers are not self-fertile and male and female trees must be planted in close proximity for flowering to occur. 

When grown in their ideal environment, alligator junipers are fairly self-sustaining and do not require too much attention. However, keep an eye out for browning leaves and tips as alligator junipers are susceptible to a host of common pests and diseases. 

Light

True to its native habitat, the alligator juniper is a sun-loving tree that requires full sun in order to thrive. Alligator junipers cannot grow in the shade, and growth may be stunted in areas that only receive partial sun.

Soil

Alligator junipers thrive in sandy, well-draining soil that is slightly acidic with a pH between 5.5 - 7.0. However, they are adaptable to a wide variety of soil conditions, as long as the medium is well-draining. 

Water

Alligator junipers are considered to be drought-tolerant trees with low water needs. An established alligator juniper should not need supplemental watering, however, seedlings and young trees may require watering during dry periods. It is important to note that alligator junipers are susceptible to overwatering. Ensuring that the tree is planted in soil that is well-draining is important to prevent this. 

Temperature and Humidity

Alligator junipers are not an overly cold-tolerant species of juniper and can only tolerate freezing temperatures for a short period of time. At their extreme, alligator junipers can tolerate temperatures as low as -8 degrees Celsius (or 17 degrees Fahrenheit) when they are fully dormant. These junipers grow best in USDA zones 7 through 9.

Fertilizer

As with most juniper trees, alligator junipers do not require heavy feeding. However, once established they can benefit from annual feeding with a slow-release shrub and tree fertilizer. Alternatively, alligator junipers also respond well to organic fertilizers and soil amendments. Feed alligator junipers in the late winter or early spring as the tree is coming out of dormancy to help kickstart their growing season.

Varieties of Alligator Juniper

There are five varieties of alligator junipers:

  • Juniperus deppeana var. Deppeana
  • Juniperus deppeana var. pachyphlaea
  • Juniperus deppeana var. robusta
  • Juniperus deppeana var. sperryi
  • Juniperus deppeana var. zacatecensis 

Growing from Seed

While alligator junipers can be propagated in other ways, they are most easily grown from seed. Alligator juniper seeds can be sown directly into the garden in the fall, or cold-stratified over the winter and sown in the spring once the last frost has passed. Germination rates are notoriously poor for alligator juniper seeds so it's important to sow a large number of seeds at one time to ensure some success.

Alligator juniper seeds can be purchased online or in-store, or they can be collected directly from a mature tree in the late summer or early fall once the seeds have ripened. If you are not sowing the seeds outdoors immediately, the seeds should be thoroughly air-dried and cleaned to ensure that mold does not grow. Then, the seeds should be cold-stratified for 30-120 days at 20-40 degrees Fahrenheit.  

Common Pests/Diseases

Unfortunately, alligator junipers are susceptible to a host of common pests and diseases. Common juniper diseases include twig and tip blight, as well as cedar rusts. Fungicides can help proactively protect alligator junipers against such diseases, but they should be applied before an infection is present. Prompt pruning of any dead or diseased branches should keep these common diseases under control. 

Common pests of the alligator juniper include bagworm, spruce spider mites, and juniper scale. Insecticides are an effective way to control serious infestations of any of these common pests but the best form of control is prevention. Make a habit of checking your alligator juniper frequently for pests so that any infestations can be caught and managed early.