Rocky juniper is similar to Virginian juniper, they are often confused, there are many similar varieties. The species interbreed easily at the border of populations in the Missouri Basin, forming natural hybrids. Rocky juniper grows in the mountains in western North America. Usually the culture lives at an altitude of 500-2700 m above sea level, but along the shores of the Puget Sound complex and on Vancouver Island (British Columbia) it is found at zero.
Description of rocky juniper
The species Rocky Juniper (Juniperus Scopulorum) is a dioecious coniferous tree, often multi-stemmed, from the genus Juniper of the Cypress family. In culture since 1839, often under incorrect names. The first description of the rocky juniper was given in 1897 by Charles Sprague Sargent.
The crown is pyramidal at a young age, in old plants it becomes unevenly rounded. The shoots are clearly tetrahedral, due to which the Rocky Juniper can be easily distinguished from the Virginian Juniper. In addition, in the first species, they are thicker.
The branches rise at a slight angle, begin to grow from the ground itself, the trunk is not exposed. The bark on young shoots is smooth, reddish-brown. With age, it begins to peel off and flake off.
The needles are most often grayish, but can be dark green; varieties with a gray-blue or silvery crown are especially appreciated in culture. The needles on young specimens are hard and sharp; they can remain so at the beginning of the season at the top of the main shoot in adult plants. Then the needles become scaly, with a blunt tip, located opposite, pressed against the shoot. At the same time, it is quite tough.
The length of spiny needles and scaly needles is different. Sharp longer - up to 12 mm with a width of 2 mm, scaly - 1-3 and 0.5-1 mm, respectively.
The needles of an adult rocky juniper in the photo
How fast the rocky juniper grows
Rocky juniper is classified as a species with an average vigor, its shoots increase by 15-30 cm per season. In culture, the pace slows down somewhat. By the age of 10, the height reaches an average of 2.2 m.An adult tree does not grow so quickly, at the age of 30 it stretches by 4.5, sometimes 6 m.The diameter of the crown of a rocky juniper can reach 2 m.
Species plants live in nature for a very long time. In the state of New Mexico, a dead tree was found, the trunk cut of which showed 1,888 rings. Botanists believe that in that area, individual specimens have reached an age of 2 thousand years or more.
All this time the rocky juniper continues to grow. Its maximum recorded height is considered to be 13 m, the crown can extend to 6 m.The diameter of the trunk up to 30 years of age almost never exceeds 30 cm, in old specimens - from 80 cm to 1 m, and according to some sources, 2 m.
The disadvantages of the species include low resistance to urban conditions and severe rust damage. This makes it impossible to plant rocky juniper near fruit trees.
When buying a culture, you should pay attention to the following fact. Not only junipers, but all North American conifers in Russia grow much more slowly, due to the different climate. In the USA and Canada, there are no such fluctuations in temperature as in the countries of the former Soviet Union, soils and annual precipitation are different.
Frost resistance of rocky juniper
The species plant hibernates without shelter in zone 3. For the Moscow region, rocky juniper is considered a quite suitable crop, as it can withstand temperatures down to -40 ° C.
Blooming rocky juniper
It is a dioecious plant, that is, male and female flowers are formed on different specimens. Males have a diameter of 2-4 mm, open and release pollen in May. The females form fleshy cones that ripen for about 18 months.
Unripe juniper fruits are green, may be tanned. Ripe - dark blue, covered with a gray waxy bloom, with a diameter of about 6 mm (up to 9 mm), rounded. They contain 2 seeds, rarely 1 or 3.
Seeds germinate after prolonged stratification.
Rocky juniper varieties
Interestingly, most varieties are created from populations growing in the Rocky Mountains, stretching from British Columbia in Canada to the state of New Mexico (USA). Of particular interest are cultivars with bluish and steel-gray colored needles.
Rocky juniper Blue Haven
The Blue Heaven variety was created before 1963 by the Plumfield nursery (Fremont, Nebraska), its name translates as Blue Sky. In landscape design, Blue Haven juniper has gained immense popularity due to its bright blue needles that do not change color all year round. Its color is more intense than that of other varieties.
Forms a uniform squat top-shaped crown. It grows quickly, adding more than 20 cm annually. By the age of 10, it stretches by 2-2.5 m with a width of about 80 cm. The maximum size is 4-5 m, the crown diameter is 1.5 m.
To the characteristics of the rocky Blue Haven juniper, it should be added that an adult tree bears fruit annually.
Frost resistance - zone 4. Sufficiently tolerates urban conditions.
Rocky juniper Moffat Blue
The Moffat Blue variety has a second name - Moffettii, which is more often used in special sources and on English-language sites. Differs in high decorativeness, satisfactory resistance to air pollution.
Some domestic nurseries are trying to present the variety as a novelty, but in America it has been grown for a long time. The cultivar appeared in 1937 thanks to the selection work carried out by the Plumfield nursery. The seedling that "began" the cultivar was found in the Rocky Mountains by LA Moffett.
The crown of Moffat Blue is wide, pin-shaped; in an adult plant, it gradually acquires a rounded shape. The branches are dense, numerous. The variety belongs to growing at an average rate, adding 20-30 cm per season. By the age of 10, in conditions that approximate natural conditions, a tree can reach 2.5-3 m.
In Russia, the size of the rocky juniper Moffat Blue is more modest - 1.5-2 m, with a crown width of 80 cm.It will never give an increase of 30 cm, and it is unlikely to be 20. A mature Moffat Blue tree is believed to be the same size as the species tree. But the observation of the culture has been conducted not so long ago to assert this with full confidence.
The cones of the rocky juniper Moffat Blue are dark blue with a bluish bloom, with a diameter of 4-6 mm.
The main charm of the variety is given by the color of the needles - green, with a silver or blue tint. Young growth (which can reach 30 cm) is intensely colored.
Frost resistance - zone 4.
Rocky juniper Wichita Blue
The variety was created in 1979. Rock juniper Wichita Blue is a male clone that reproduces only vegetatively. Forms a tree that reaches a maximum height of 6.5 m with a diameter of no more than 2.7 m, with a wide-shaped loose crown of thin tetrahedral shoots raised upwards. Bluish-green needles do not change color throughout the year.
Wintering without shelter - up to 4 zones inclusive.
Rocky Juniper Springbank
An interesting, rather rare variety Springbank was created in the second half of the 20th century. He annually adds 15-20 cm, which is considered a low growth rate. By the age of 10, it stretches up to 2 m, a mature plant reaches 4 m with a width of 80 cm.
The crown is conical, narrow, but due to the hanging tips of the shoots, it seems much wider and somewhat untidy. The upper branches are spaced from the trunk, young shoots are very thin, almost filiform. Sproingbank rock juniper looks good in free style gardens, but is not suitable for formal gardens.
Scaly needles, silvery blue. Requires a sunny position, since in partial shade the color intensity decreases. Frost resistance is the fourth zone. Propagated without loss of varietal traits by cuttings.
Munglow rock juniper
The variety was created from a seedling selected in the 70s of the last century in the Hillside nursery, and is currently one of the most popular varieties. Its name translates as Moonlight.
Juniperus scopulorum Moonglow forms a tree with a pyramidal crown. It belongs to fast-growing varieties, the annual growth is more than 30 cm. By the age of 10, it reaches a height of more than 3 m and a crown diameter of about 1 m, at 30 it stretches 6 m with a width of 2.5 m.
The characteristics of the rocky Munglow juniper include silvery-blue needles and beautiful outlines of a dense crown. A light shaping haircut may be required to maintain it.
Frost resistance - zones from 4 to 9.
Rocky Juniper Skyrocket
The name of the rocky juniper variety is correctly spelled Sky Rocket, in contrast to the Virginian Skyrocket. But this is of little importance. The variety originated in 1949 in the Shuel nursery (Indiana, USA). He quickly became one of the most popular, which remains to this day, despite severe rust damage.
Forms a crown in the form of a narrow cone, with a sharp top and tightly pressed branches. This makes the tree seem to be directed towards the sky. In addition to the exceptionally beautiful crown, this rocky juniper with blue needles attracts attention. The needles are sharp at a young age, over time they become scaly. But on the top of the tree and at the ends of adult branches, the needles can remain prickly.
Skyrocket is a variety that reaches a height of 3 m by the age of 10 with a crown diameter of only 60 cm. Perhaps this does not make it the narrowest of all junipers, but among the rocky ones, for sure.
At a young age, the tree holds its shape well and does not need pruning. Over time, especially with irregular care, that is, if years of careful care give way to seasons when the plant is "forgotten", the crown may become less symmetrical. The situation is easy to fix with a haircut that the culture handles well.
Without shelter, skayrocket rock juniper wintering in zone 4 is possible.
Rocky juniper Blue Arrow
The Blue Arrow cultivar name is translated as Blue Arrow. It originated in 1949 in the Pin Grove nursery (Pennsylvania). Some consider him to be an improved copy of Skyrocket. Indeed, both varieties are megapopular, similar to each other, and often the owners think for a long time which one to plant on the site.
At the age of 10, Blue Errue reaches a height of 2 m and a width of 60 cm. The crown is conical, the branches are directed upwards and are spaced from the trunk at an acute angle.
The needles are tough, needle-like on young plants, with age they change to scaly. If in the rocky juniper Skyrocket it has a bluish color, then the shade of Blue Arrow is rather blue.
Great for formal (regular) landings. It hibernates without protection in zone 4. In adulthood, it keeps better shape than Skyrocket.
Rocky juniper in landscape design
Rock junipers willingly use landscape designs when decorating the territory. They would recommend a crop for planting much more often, but it does not tolerate urban conditions and is often affected by rust, which can destroy the crop of fruit trees.
Interesting! Many varieties of rock juniper have analogues among Juniperus virginiana cultivars, which are much more resistant to diseases, but they are not so beautiful.
The use in landscaping depends on the shape of the crown of the tree. Rocky juniper varieties with branches pressed against the trunk, such as Skyrocket or Blue Arrow, are planted in alleys and are often placed in formal gardens. In landscape groups, rockeries, rock gardens and flower beds, they can serve as a vertical accent. With proper garden planning, they are never used as a tapeworm.
On the other hand, rocky junipers with a broad-shaped crown, for example, Munglow and Wichita Blue, will look good as single focal plants. Most of them are planted in romantic and natural gardens. You can form a hedge from them.
When planting, do not forget that the culture does not tolerate gas pollution. Therefore, even in the country, rocky juniper is recommended to be placed inside the territory, and not above the road.
Planting and caring for rocky juniper
The culture is drought tolerant and quite healthy, as is clear from the description of the rock juniper, and it needs minimal maintenance. The tree can be planted in infrequently visited areas or where abundant watering is not possible. The main thing is that the place is open to the sun, and the soil is not too fertile.
It is necessary to plant rocky juniper in autumn in regions with warm and temperate climates. It can last all winter if the hole is dug in advance. Planting rocky juniper in spring makes sense only in the north, where the culture should have time to take root before the onset of real cold weather. Summer there is rarely so hot that significant damage to the young plant is caused.
Seedling and planting plot preparation
Rocky juniper will have a positive attitude to stony inclusions in the soil, but will not tolerate compaction, close standing groundwater or abundant irrigation. It needs to be placed on the terrace, a thick drainage layer, or an embankment. On heavily blocking areas, it will be necessary to carry out water diversion measures or plant another culture.
A sunny place is suitable for a rocky juniper, in the shade the needles will become faded, its beauty will not be able to fully unfold. The tree must be protected from the wind for the first two years after planting. When the powerful root grows, it will prevent damage to the juniper, even during a squall.
The soil for planting a tree is made looser and more permeable with the help of sod land and sand; if necessary, it can be deoxidized with lime. Fertile soils will not benefit the rocky juniper, a large amount of sand is added to them, and if possible, small stones, gravel or screenings are mixed into the substrate.
The planting hole is dug so deep that the root and drainage layer are placed there. The width should be 1.5-2 times the diameter of the earthen coma.
A minimum of 20 cm of drainage is poured into the pit for planting a rocky juniper, 2/3 is filled with earth, water is poured until it stops absorbing. Allow to settle for at least 2 weeks.
Saplings are best bought from local nurseries. They should be grown in a container or dug out together with an earthen clod, the diameter of which is not less than the projection of the crown, and sheathed with burlap.
Important! You cannot buy open-root seedlings.
The substrate in the container or earthen lump should be moist, the twigs bend well, the needles, when rubbed, emit a characteristic odor. If planting is not done immediately after purchase, you will have to make sure that the root and needles do not dry out on your own.
How to plant rocky juniper
Planting rocky juniper is not difficult. It is carried out in the following sequence:
- Part of the soil is removed from the planting pit.
- A seedling is placed in the center.
- The root collar should be flush with the edge of the pit.
- When planting a juniper, the soil must be compacted so that voids do not form.
- The tree is watered, and the trunk circle is mulched.
Watering and feeding
Rock juniper needs frequent watering only for the first time after planting. When it takes root, the soil is moistened several times per season, and then in the absence of rain for a long time, and in dry autumn.
The rocky juniper reacts favorably to the sprinkling of the crown, moreover, it prevents the appearance of spider mites. In the summer, the operation is performed at least once a week, preferably in the early evening.
Root feeding of young plants is carried out twice a season:
- in spring, complex fertilizer with a high nitrogen content;
- at the end of summer, and in the south - in the fall with phosphorus and potassium.
Foliar dressings, which are carried out no more than 1 time in 2 weeks, will be useful. It is recommended to add an ampoule of epin or zircon to the balloon.
Mulching and loosening
The seedlings are loosened in the year of planting to break up the crust formed after watering or rain. It blocks access to the roots of moisture and air. Subsequently, the soil is mulched, better - pine bark treated from diseases and pests, which can be bought in garden centers. You can replace it with peat, rotted sawdust or wood chips. Fresh ones give off heat when rotted and can damage or even destroy the plant.
How to properly prune rocky juniper
Juniper pruning can be carried out throughout the spring, and in regions with cool and cold climates - until mid-June. First, remove all dry and broken shoots. Particular attention is paid to the middle of the bush.
In a rocky juniper, with its dense crown and branches pressed against each other, without access to light, some of the shoots die off annually. If they are not removed, spider mites and other pests will settle there, spores of fungal diseases will appear and multiply.
Cleaning the crown of the Rocky Juniper is not a vital procedure, as for the Canadian one, but it cannot be called simply cosmetic. Without this operation, the tree will constantly hurt, and it is impossible to remove the pests.
A shaping haircut is optional. Most varieties have a beautiful crown, but often some kind of twig "breaks out" and sticks out. Here it is what you need to cut off so as not to spoil the view.
With age, in some pyramidal varieties, the crown begins to creep. It is also easy to tidy up with a haircut. Only you need to work not with pruning shears, but with special garden shears or an electric brush cutter.
Bonsai are often made from rocky juniper in the United States. In our country, they usually use Virginian for this, but the cultures are so similar that they are, rather, traditions.
Preparing for winter rocky juniper
In winter, rocky juniper should be covered only in the first year after planting and in frost-resistant zones below the fourth. Its crown is wrapped in white spandbond or agrofibre, secured with twine. The soil is mulched with a thick layer of peat.
But even in those warm regions where it can snow in winter, the crown of a rocky juniper needs to be tied. They do this carefully and not tightly so that the branches remain intact. If the crown is not secured, the snow may simply break it.
How to propagate rocky juniper
Rock juniper is propagated by seeds or cuttings. Especially rare and valuable varieties can be grafted, but this is a difficult operation, and amateur gardeners cannot do it.
Reproduction of rocky juniper by seeds does not always lead to success. Some seedlings do not inherit maternal traits, and they are discarded in nurseries. At an early stage of plant development, it is difficult for amateurs to figure out whether it corresponds to the variety, especially since small junipers are completely unlike adults.
In addition, long-term stratification is needed for seed reproduction, and it is not as easy to carry out it correctly, and not to spoil the planting material, as it might seem.
It is much easier, safer and faster to propagate rocky juniper by cuttings. You can take them all season. But for those who do not have a special room, equipment and skills, amateurs to carry out the operation is better in spring.
Cuttings are taken with a "heel", the lower part is freed from needles, treated with a stimulant, and planted in sand, perlite or a mixture of peat and sand. Keep in a cool place with high humidity. After 30-45 days, roots appear, and the plants are transplanted into a light soil mixture.
Important! Rooting 50% of cuttings is an excellent result for rocky juniper.
Pests and diseases of rock juniper
In general, rocky juniper is a healthy crop. But he may also have problems:
- Rock juniper is more affected by rust than other species. It harms the culture itself much less than the fruit trees growing nearby.
- If the air is dry and the crown is not sprinkled, a spider mite will appear. He is unlikely to destroy the tree, but decorativeness can be greatly reduced.
- In warm climates with frequent rains, and especially when sprinkling the crown late in the evening, when the needles do not have time to dry before nightfall, a mealybug may appear. It is very difficult to remove it from a juniper.
- Lack of sanitary pruning and crown cleaning can turn the inside of the crown into a breeding ground for pests and diseases.
To prevent trouble, the tree must be regularly inspected and preventive treatments carried out. Insecticides and acaricides against pests, fungicides - to prevent diseases.
Rocky juniper is a beautiful, not demanding culture. Its main advantage is the crown of an attractive shape, silver or blue needles, the disadvantage is low resistance to air pollution.