By Matt Gibson
There are around 60 different species of Juniper plants that range from low-growing ground covers that reach heights of only six inches, small, medium, and large shrubs and bushes, to full-size trees that can grow as high as 130 feet. Juniper plants, shrubs, and trees grow naturally all over the Northern Hemisphere from icy arctic climates to sweltering deserts. This cypress family member has been cultivated for centuries because it is easy-to-grow, incredibly hardy to practically every region, and provides gardeners with a year-round ornamental interest for their landscape.
Junipers come in various shades of green, steel-blue, silver, bronze, and gold. These coniferous evergreens have leaves that start out rough, prickly and needle-like, but soften as they mature into flattened, scale-like foliage. In the springtime, junipers produce tiny, yellow or green flowers. Some juniper varieties self pollinate, producing both male and female blooms, while other varieties require a male and female juniper tree in order to pollinate.
Male flowers also produce what looks very similar to a pinecone, while female flowers produce the coveted berries that are used for medicinal purposes, and are by law, the predominant flavor of any spirit classified as Gin. Juniper berries start out green and turn blue as they mature. The juniper cones produced on male trees are either yellow or tan. Juniper berries have culinary, medicinal value, and are also used in aromatherapy, though they are most commonly cultivated for gin production. Despite their mild toxicity, juniper berries are also a food source for birds and other wildlife.
Though there is some variation based on species, most junipers are hardy to USDA zones two through 10 (the majority are hardy to zones 4-10). Junipers can have an upright, spreading, or weeping habit and can range in size from six inches to 130 feet tall with a one to 25 foot spread. Junipers have an attractive shape, lovely color, interesting-looking foliage, small flowers, cones, and berries. Even the bark is attractive on many juniper trees and shrubs, and some varieties have oddly-twisted branches, which gives them a strange but undeniable ornamental appeal.
Types of Juniper
There are a wide variety of junipers to choose from. Here, we break them down into four different types based on size and function. Then we delve a bit deeper into specific species and varieties of juniper plants. Here are the four types of junipers:
Ground Cover Junipers – Ground cover junipers grow up to one and a half-feet tall. Most of these plants are creeping junipers that have a wide spread and short height. They are perfect for ground cover, rock gardens, containers, and border edging plants. These junipers are commonly grown on hills and slopes, and anywhere where soil erosion is a factor.
Dwarf Junipers – Dwarf junipers grow up to four feet tall. These junipers are commonly used as foundation plants and are often planted around gardens, ponds, and as bonsai trees.
Small Junipers – Small junipers grow up to six feet tall. These junipers are either medium to large shrubs or small trees. They are often used as foundation plants and are commonly grown in gardens and landscapes.
Large Junipers – Large junipers are trees that grow 25 feet and higher. Some varieties grow between 60 and 130 feet tall. These junipers are typically found in the forest or woods.
Varieties of Juniper
There are hundreds of varieties of Juniper growing around the world, ranging from small ground cover plants that are great for ornamental additions to the landscape and erosion control, to massive trees, which can grow up to 130 feet tall. Instead of dissecting each of our favorite varieties, we decided to break down the most commonly cultivated species. Most of our favorite juniper varieties fall under one of the species listed below. We listed some of our favorite varieties and some of the more popular cultivars beneath the species they belong to.
Alligator Juniper (Juniperus deppeana)
Also called checkerbark juniper, oak-barked juniper, thick-barked juniper, western juniper, and mountain cedar, the Alligator juniper got its name from its characteristic bark, which is rough, checkered and similar to alligator skin. Cultivars from this species are either large shrubs or small to medium sized trees, depending upon the growing conditions provided. These junipers can grow as high as 60 feet, but are usually around 20 to 40 feet tall instead. Alligator junipers are good choices for warm, arid, rocky environments. There is not much published information on the different varieties of Alligator Juniper, but the most popular cultivar is the McFetter variety, which is a large shrub that is especially well-suited for landscaping. Alligator Junipers are native to Mexico and the Southwestern United States and are hardy to USDA growing zones seven through nine.
Popular varieties include: McFetter Juniper
California Juniper (Juniperus californica)
California Junipers are typically large shrubs that grow throughout the Southwest United States, though some varieties can grow to medium-sized trees. The California junipers produce blue, scale-like leaves with brownish-red cones. Used to offer erosion protection on particularly dry slopes. California junipers are also used to create wildlife habitats and miniature California junipers are used to make bonsai trees. These Southwest US natives grow to around 10 to 15 feet, though they can potentially reach heights of up to 35 feet and higher in zones eight through ten.
Popular varieties include: California Juniper, California White Cedar, Desert White Cedar.
Chinese Juniper (Juniperus chinensis)
There are over 100 different varieties of Chinese Juniper, and the wide variety is also widely varied in different shapes, colors, leaf-type, environmental preferences, height, and more. The majority of Chinese junipers are hardy to USDA zones four through nine. When Chinese Juniper leaves are young, they look like needles, but as they mature, they start to look like scales. The Toruloso variety, which is also known as the Hollywood juniper has oddly twisted branches and is commonly used as a specimen plant. Chinese junipers tend to work well in urban environments, and tend to grow poorly in overly wet soils. Most Chinese junipers are groundcovers or shrubs, but there are a few small trees as well. Chinese junipers are native to China and Japan.
Popular varieties include Gin Fizz, Gold Lace,Montana Moss, Pfitzer, Toruloso, Blue Point, and Spartan.
Common Juniper (Juniperus communis)
Common Junipers get their name from being commonly found all over the globe. Common juniper varieties are highly adaptable and tolerant of different environmental conditions, soil types, and climates. There are common juniper shrubs that grow to 15 feet tall, as well as trees that reach up to 30 feet tall. Common juniper cultivars are hardy to USDA zones three through eight. Shrubs range from ground covers to small trees. Common juniper varieties have needle-leaves, unlike most juniper species, which have scale-like leaves.
Popular varieties include Gold Cone Juniper, Common Pioneer Juniper, Golden Flat Juniper, Green Carpet Juniper, and Compressa Common Juniper.
Creeping Juniper (Juniperus horizontalis)
As its name implies, the Creeping juniper species consists of groundcovers that are adaptable to various soils and environmental conditions. There are upwards of 100 varieties of Creeping juniper, most appearing throughout the northern US, as well as Canada and Alaska. Creeping junipers grow up to between one and two feet tall in zones three through nine.
Popular varieties include Blue Rug and Good Vibrations.
Drooping Juniper (Juniperus flaccida)
In USDA zones eight B through eleven, Drooping juniper tree varieties grow to between 35 and 40 feet tall. Native to Texas, Mexico, and Guatemala, these trees get their name from how their branches and foliage seem to droop down low. Drooping juniper trees have dirty red or grey bark that falls off in long strips.
Popular varieties include Poblana and Flaccida.
Eastern Red Cedar (Juniperus virginiana)
Red cedar Junipers are among the most fragrant juniper varieties. These upright trees typically have deep aqua-green foliage and gray to brownish-red bark that shreds into strips. Most Eastern Red Cedar cultivars have fluted trunks. These trees can grow as high as 65 feet tall, but are commonly found between 30 and 40 feet tall. Unlike most junipers, Eastern Reds have a good moisture tolerance, and can handle its roots being wet, as long as they are not sitting in boggy soil. Keep varieties of Eastern Red Cedar away from apple and crabapple trees, as it is a common carrier of cedar-apple rust fungus. Native to the Northeastern region of the United States and hardy to zones two through nine.
Popular varieties include Grey Owl and Blue Arrow.
Greek Juniper (Juniperus exelsa)
Greek Junipers are large shrubs or trees from the Eastern Mediterranean region and commonly grow near stinking juniper (J. foetidissima) cultivars. These junipers look similar to the stinking juniper, but have lighter green foliage. These hardy trees are found in zones five through nine, and are even known to grow on the sides of cliffs. These trees can be pretty large, growing to heights between 20 and 65 feet, with massive trunks that can grow up to six feet in diameter.
One-Seed Juniper (Juniperus monosperma)
Also called single-seed junipers or cherrystone junipers, this species consists of large shrubs or small trees (usually six to 20 feet tall) with multiple stems and a dense circular crown. This species was named for its single-seed bearing cones (or berries). Native to Mexico and the Southwestern US and hardy to zones three through seven, these varieties have almost vanished from the countryside of Mexico, but have become a popular site in the Southwestern US states. One-Seed Juniper wood is commonly used to make fence posts.
The most popular variety of One-Seed Juniper is the Blue Star Juniper.
Rocky Mountain Juniper (Juniperus scopulorum)
Native to the Rocky Mountains, this small to medium-sized tree has a pyramid-like shape, growing five to 15 feet high normally, but can reach heights up to 60 feet in the wild. Rocky Mountain is a close relative to the Eastern Red Cedar Juniper species, and like Eastern Reds, Rocky Mountain Junipers are very susceptible to the fungal infection called cedar-apple rust. Hardy to USDA zones three through eight.
Popular varieties include Skyrocket Juniper and Tolleson’s Blue Weeping Juniper.
Utah Juniper (Juniperus osteosperma / J. utahensis)
Native to the Western US and hardy to zones three through seven, these shrubby 10 to 20-foot-tall trees grow all over the state of Utah, and are particularly well-suited to alkaline soil types. Hardy to USDA zones three through seven, you won’t just find Utah junipers in the state of Utah, as some varieties of the Utah Juniper grow as far south as Arizona, where it is called desert juniper, or bigberry juniper instead.
Bonsai Juniper (Juniperus procumbens)
A close relative of the Chinese Juniper, the Bonsai Juniper species produces low and slow-growing evergreen trees which are commonly made into bonsai trees.
Popular varieties include Nana Juniper, Bonin Isles Juniper, and Variegated Juniper.
Western Juniper (Juniperus occidentalis)
Also known as the Sierra juniper, the Western juniper produces berries that are food for a variety of birds and other animals in zones five through eight. The 15 to 30 foot tall shrubs or small trees produce wood that was commonly used during the pioneer times. Rarely cultivated, western Junipers grow naturally in the mountainous regions of California, Idaho, Nevada, Oregon, and Washington.
Popular varieties include Grand Western Juniper and Accidental Western Juniper.
Growing Conditions for Juniper
Most juniper varieties enjoy full sunlight exposure. However, in warm climate areas, some juniper varieties prefer a bit of afternoon shade during the hottest parts of the day, especially in the summer. They need about six hours of direct sun exposure every day, and too much time in the shade can make juniper plants lose their shape. This is because their density is compromised as their inner branches stretch out for a bit of sunlight.
Juniper prefers a soil with a slightly acidic pH, but will grow in non-acidic soils as well, as long as there is good drainage. Though they are adaptable to many soil types and environmental conditions, they will not tolerate soggy soil for even brief periods, and are quick to develop root rot and other fungal issues when exposed to waterlogged soil. Once a juniper plant has become unhealthy, it becomes much more likely to develop diseases, or become infested by pest insects. Excellent drainage is paramount, but juniper is tolerant of sandy, rocky, and clay soils, as long as they are fast draining.
Juniper plants can also handle temperature shifts within reason and can survive in most climates that are not extremely hot or cold, though some juniper varieties are more cold hardy than others. Juniper plants are generally quite tough in both arid and humid environments, as long as their roots are not sitting in water.
How to Plant Juniper
Part One – Gathering Cones
Before you can plant juniper seeds, you must first extract them from juniper berries, which are the berry-shaped cones that are formed on juniper plants. In late autumn, gather cones (juniper berries are actually cones, not berries, but are called berries because of how they look, which is actually quite similar to blueberries) which are two years-old and dark blue, and sometimes have a waxy, white coating.
Young juniper cones are green, sometimes with light blue highlights. Leave young cones on the plants to mature. Take only the mature cones, which will feel soft when you press them between your fingers. Mature berries are easy to pick off the plants by hand, or if you are harvesting from a large shrub or tree, you can also shake the plant mightily to get the berries to fall, which should loosen mostly mature cones that are ready for harvesting.
Part Two – Seed Extraction
To get the juniper seeds out of the berries, you have to perform an extraction. To do this, first soak the cones for several days in a diluted citrus-based hand soap, such as Gojo, or Fast Orange. Soak them until the stickiness is removed, then take them out of the cleaner water and rinse them off well to remove any soapy residue. Next, spread out your cones on a paper towel to dry.
After they dry, use a colander with a metal screen, or some other piece of screening, to rub the dry cones onto the screen, which will scrape off the skin, revealing the seeds inside. Be careful not to damage the seeds inside when scraping off the outer layer of the cones. Inside the cones is a mass of usable seeds, pulp, and older seeds, which have likely gone bad within the seed.
To separate the usable seeds from the pulp and the unusable seeds, just soak the opened cones in water. The good seeds will float to the top so that you can easily collect them with a spoon, while the heavier pulp and old seeds will sink to the bottom. There is typically between one to four harvestable and plantable seeds in each cone.
Once you have extracted the good seeds, lay them back out on a paper towel until they are dry and put them in an airtight container, such as a jar or good tubberware, and store them in the refrigerator until you are ready to use them.
Part Three – Stratification
Juniper seeds must be stratified before you can have any success growing them, as they must be brought out of their dormancy before planting or the seeds will fail to sprout. Different species of juniper require different stratification techniques. One technique involves placing the seeds in a colander under the faucet in the kitchen sink. Give the seeds a bath with a light stream of water from the faucet and leave them under the water draining through the colander beneath them for 48 continuous hours.
Then put the still wet seeds into a plastic bag in moistened sand or peat moss and seal the bag. Keep the sealed bag of seeds in an area that is kept at room temperature for two months, followed by three months in the refrigerator. After three months in the fridge, your juniper seeds will be ready to plant. This method works for most juniper varieties, as it mimics the weather of the passing seasons that juniper seeds are exposed to in order for their seeds to break dormancy in the wild.
Eastern Red Cedar varieties need to soak for four days in a one percent solution of citric acid before undergoing the stratification process. Alternatively, Eastern Red Cedar seeds can be sown in August without any stratification.
Part Four – Planting Juniper
Once you have your juniper seeds ready to plant, either plant them outdoors in a partially shady location during the spring or summer, or plant them in a planter with a peat-based potting soil mix and excellent drainage. Outdoor juniper plants will grow better in full sun, but seedlings need partial shade to develop. Amend the planting site with sphagnum peat moss to give your juniper a soil with an acidic pH. Indoor juniper should be given a bright but indirect light source and kept between 75 and 80 degrees Fahrenheit. Keep their soil moist at all times, as seeds are prone to going dormant if the soil around them dries out completely. The seeds should germinate in approximately one month.
Care for Juniper
Established juniper plants are very drought tolerant and like drier soil conditions. They still require water, but you can let the soil dry out between waterings once the plants are established. Do not plant junipers near lawn sprinklers, as they will likely cause overwatering. During the first three months, newly planted junipers should be watered two times per week in the absence of rainfall. New juniper plants will need weekly waterings during their first summer in order to grow their intricate and extensive root system. After the first summer goes by, the majority of junipers can thrive with only natural irrigation.
Junipers will grow in infertile soils, but not as vigorously as they should, or are capable of. Junipers benefit from fertilization twice per year, in the early spring and again in late summer. Apply a half pound of general purpose fertilizer for every 100 square feet of space. Slightly nitrogen heavy feeds like 16-4-8 or 12-4-8 will work nicely. Rhododendron fertilizer for evergreen plants will work as well. To feed your junipers, sprinkle fertilizer on the soil around your plants right before it rains or just before you plan to water your soil to get the feed moving through the soil towards the roots.
Unless you are growing your juniper as a bonsai, you won’t need to do any extensive pruning, as junipers don’t respond well to heavy trimming. New green growth does not emerge from mature juniper wood, so never cut back to bare wood. Instead of pruning junipers into the size you wish them to be, select the right juniper for the location and move mature plants where they are desired. The only extensive pruning that junipers should receive is the removal of dead branches. When dead branches are taken, also trim the needles from the underneath part of the plant in order to increase air flow through the branches.
How to Propagate Juniper
Juniper is typically propagated by cuttings or by layering, but can also be grown using the seeds in a juniper berry. For more information on growing juniper from seed, consult the, “How To Plant Juniper,” section above. To propagate juniper from cuttings, use the following steps:
Step One – Fill a six-inch container with one teaspoon of slow-release, all-purpose fertilizer topped with a soil blend of equal parts chopped bark and peat moss.
Step Two – Use a sharp, clean pair of garden pruners to cut about seven, five to six-inch stem cuttings from an established, healthy juniper plant. Ideally, take new stems which are still green and slightly firm. Remove leaves from the bottom third of each cutting by pinching them off. Leave only three to four sets of leaves on the top of each cutting.
Step Three – Roll the base end of the stem in rooting hormone (the hormone gel will likely stick to the surface better, even after irrigation, but any kind of rooting hormone should work). Plant your cuttings around two inches into the substrate with the leaves sitting slightly over the top of the potting soil. Space cuttings out one and a half inches apart. Water gently to help settle the soil around the plant.
Step Four – To provide a greenhouse-like environment for your cuttings, cover the planter with plastic, using a bag and a small rubber band. Poke or cut four to five small holes or slits into the plastic bag to provide some air flow.
Step Five – Keep the planter in a bright but indirect light, checking moisture level weekly and watering lightly when the substrate is dry. Too much water will cause your cuttings to rot, so be sure not to overwater or let soil get soggy. Though you may see your stems start to root by the end of winter, you shouldn’t see any new growth on the plants until early summertime.
Step Six – Now that your cuttings have developed roots, move each one into a three-inch planter lined with a blend of two parts potting soil, one sand, and one peat moss. Keep your pots in a shady location for three to five days to allow time for your roots to relax, then the pots can be moved into a full sun location.
Step Seven – Provide indoor shelter for young juniper plants for one full season before moving the shrub outside. Larger shrubs will have a better chance of surviving outdoors. If your juniper plant begins to outgrow the container it’s in, switch to a bigger container, just remember to use a blend of soil, peat and sand in the bigger container as well.
Garden Pests and Diseases of Juniper
There are four main pests that are known to attack Juniper plants, which are aphids, scale, spider mites, and bagworms. Aphids are tiny but visible flying insects that leave behind a sticky residue and black sooty mold on the branches of infected plants. Scale insects are smaller than aphids and harder to see, but they also leave behind a similar footprint, leaving branches sticky and covered in black mold.
Spider mites are visible, but only if you were to shade a branch while holding up a piece of black or dark colored paper behind the action, could you see the tiny mites, which are about the size of a grain of sand. They leave evidence of their presence in the form of small spider web-like webbing on the branches, which turn a light yellowish-gray, then brown. Bagworms are caterpillars that change into small black moths. They feed on juniper needles and form them into two-inch-long cocoons that hang down off the branches of juniper shrubs and trees.
Aphids and spider mites are both small insects that can be knocked off with a blast of water from the garden hose. If the hose treatment doesn’t work, release ladybugs or spray contact insecticides to treat aphid infestations, and spray systemic insecticides to treat spider mites. Treat scale insects with systemic insecticides or use a dormant oil treatment during the wintertime. Pull the cocoons of bagworms down from the branches and crush them by stepping on them.
Occasionally, juniper plants have issues with nematodes. The microscopic roundworms live in the soil and feed on juniper roots, which can lead to bacterial and fungal infections and secondary diseases. There is no known effective treatment for nematodes other than soil solarization.
There is one other insect pest that is an issue for juniper growing in California called the Juniper Twig Girdler. This moth larva is known for burrowing into branches and killing the branch in the process. If you peel back the bark on a branch where the green changes to brown, and inspect the wood for tunnels, you may find some holes, and maybe even a ¼-inch-long Twig Girdler worm. To treat infested trees, prune out dead or dying branches, and spray a systemic insecticide during the spring or in the first few weeks of summer.
In the Great Lakes area, the Northwest, and the Pacific Coast, there is a small leaf miner that is known for killing the tip ends of juniper branches in these regions. They bore inside the needles from autumn until they hatch into moths in the springtime. Treat these leaf miners by applying a systemic insecticide in both summer and autumn and pruning infected branch tips.
Juniper plants have a handful of diseases that sometimes occur, which include Cedar Rust, Twig and Needle Blight, Root Rot, Botryosphaeria stevensii fungus, and Botryosphaeria cankers. Most disease issues are due to overly wet soils or too much shade. If you have apple trees on your property, avoid planting juniper. The two trees both attract a fungus called cedar apple rust which appears first on junipers, then spreads to any apple, crabapple, hawthorn, or quince tree in the area. Eastern Red Cedar Junipers are especially susceptible to cedar apple rust infections.
Three environmental issues that can cause damage to juniper plants include salt injury, dog urine disease, and drought. Juniper trees growing in areas near oceans and roadsides, and in high-alkaline soils in dry regions are all susceptible to salt injury. In areas where juniper trees get salt mist on their bark and branches, occasionally wash off the salt by spraying down the juniper shrubs or trees. Keeping your junipers well watered will also help reduce salt injury damage.
Dog urine on a juniper can hurt the plant severely, and can turn whole branches brown. Keep the plants washed off by spraying them down with a garden hose and consider spraying a dog-repellant if dog urine damage is a persistent problem in your area.
Junipers may be drought-tolerant, but that doesn’t mean they can do without water. Junipers need water just like every other plant, especially when they are young. Evergreen junipers dry out in the winter when the ground freezes, but they can dry out in the summer as well, due to drought and hot weather. Young juniper plants cannot survive extended dry periods. If you notice your juniper plants turning pale and appearing dry while turning brown, it is most likely due to lack of water.
Many parts of Juniper plants, shrubs, and trees are toxic. Juniper berries, needles, and stems, can all be slightly toxic to dogs and cats if ingested. Most pests won’t eat parts of a juniper plant, due to its bitterness, so they usually do not ingest enough to cause a problem, and ingestion is rarely fatal. However, eating parts of the juniper plant can cause stomach aches, vomiting, diarrhea, and, in rare and extreme cases, kidney issues. Eating large amounts of juniper berries could cause aborted pregnancies in dogs. Contact poison control or your veterinarian if your pet shows symptoms of juniper berry poisoning.
Also, the resinous sap that juniper plants produce is combustible. So, if you live in an area with high fire danger and especially dry conditions, juniper might be a bad choice for your landscape.