SPRUCE FOR THE ROCK GARDEN
There are as many different rock garden designs as there are people, but the one unifying theme is the use of rocks in developing this type of garden.
The primary goal in the creation of a rock garden is to bring an alpine setting into the gardener’s landscape. Although some planning is needed, unless a specific type of rock garden is being constructed (scree, crevase, etc.), the gardener’s main concern should be, “What do I like?”
That being said, a garden with a natural appearance will be more appealing to most people than a pile of rocks mixed with some dirt and a few plants. Likewise, a garden smothered in perennials with a few rocks hardly fits anybody’s definition of a rock garden.
Finding pictures of alpine scenery and areas just above the tree line in mountainous regions is a good way to start planning and designing a rock garden. Focus on the rock outcrops and notice how the rocks sit relative to each other. There are many ways rocks express themselves in a natural setting. Select scenes that appeal to you and work to duplicate aspects of those scenes in your own garden, working within affordable parameters. Keep in the back of your mind that you are building this garden for yourself, not for anyone else.
Once the rocks are in place and the hardscape is done, plants must be selected and planted. Many professional landscape firms use fast growing plants for higher profits, ease of availability, and instant gratification. Too many perennials and herbaceous shrubs will soon hide many of the rocks, and the alpine setting quickly becomes a perennial garden. Many times a whole rock garden has to be rejuvenated by ripping out overgrown plant material and replacing it with new plants- a rather costly venture.
Plant material for a rock garden is often difficult to locate, even by landscape professionals and is usually purchased from specialty nurseries. Landscape professionals cannot make a profit with this select material since little is available at a wholesale price. Using a professional to do a rock garden’s hardscape can save a gardener's back, and having them do about 20% of the plants can provide a basic framework that the gardener can build upon and enhance over a period of several years. Then if any of the original plants prove to be unsuitable, they can be removed with minimal labor and/or expense.
Of course there are advantages to doing your own planting. First, there is the exercise. Second is the increased satisfaction. Third, the education gained in selecting and planting appropriate material is priceless. Fourth, the material used can be high quality and very special which means it can give many years of pleasure and enjoyment to the gardener at a reasonable cost.
A young garden needs a mixture of plant material. Faster growing plants scattered throughout the garden will provide instant gratification and should be considered temporary. The slow-growing, more expensive material has a long life expectancy and should be planted in the prime locations throughout the garden. As they develop and begin to take on a presence in the garden, the larger, cheaper material can gradually be removed.
Following are some spruce cultivars that I consider suitable choices for a rock garden.
Picea abies ‘Brno’
A dense, miniature globe with a flattened top, it grows about 1.5cm (3/4") per year and may be 40cm (15") wide by 25cm (10") high in twenty years. Its tiny brown buds are especially apparent during the winter, and the needles are exceptionally tiny. This little prize will never outgrow its location in the smallest garden. As with all of the miniature Picea abies, give it some protection from the hot summer afternoon sun.
PICEA abies 'DUMPY'
This dense, little ball grows considerably faster as a grafted plant, eventually slowing to its expected growth rate of less than 1 cm (1/2") per year. In the garden it will look like an alpine plant that has been grazed by mountain goats. I first saw this cultivar in England around 1982. It was growing in a clay pot, and after twenty years was only the size of a soccer ball.
PICEA abies 'EVA'
Plant this selection where a conical little spruce with small, thin needles is wanted. In fifteen years it may be almost 1 m (3') tall by 1/3 as wide.
PICEA abies 'FORMANEK'
A slow growing, prostrate selection that grows about 15 cm (6") per year, its foliage is dark green and the original plant may still be seen at Pruhonice in the Czech Republic (upper right picture). Use this plant to create a slow growing mat over or around rocks where the rock garden has a slope.
Picea abies `Frohburg’
This prostrate plant will grow up to 25 cm (10") per year and rapidly create a cascade of foliage down a slope in any rock garden. Use it to flow over or around rocks or to cascade next to a water feature. I first saw a mature specimen of this cultivar at the Hillier Arboretum in England. It had been staked to a height of about 3 m (10') and then allowed to cascade down and surround itself with a wide-spreading, ground-hugging mat of its own foliage.
PICEA abies 'HASIN'
A dwarf, dense, globular selection, it grows about 2cm (1") per year with green foliage and short needles. The branchlets have small, brown buds that are highly visible in the winter. This selection can be used much like 'Brno' in the rock garden since it is very similar as a young plant.
PICEA abies ‘Hildeburghausen’
This dense, perfectly shaped globe grows up to 6 cm (2"-3") per year with light green foliage and has needles that stick straight out from the stems. Every terminal shoot grows the same length each year and produces five lateral buds. Use it where a larger globe of evergreen foliage is wanted in the rock garden.
Picea abies ‘Pusch’
The first time I saw this plant I was visiting Jan zu Jeddeloh in Germany and he had hundreds of them in a small greenhouse. He explained to me that it was discovered as a witches' broom on Picea abies 'Acrocona'. In effect, it is a miniature 'Acrocona', making it very suitable for the smaller garden. In the spring it develops red cones on most of its branch tips, making a colorful statement in the spring garden and showing that not only herbaceous plants produce colorful flowers. It develops into an irregular mound when left to its own devices and will take over twenty years to become 1 meter (3') high by wide.
Picea abies `Little Gem’
Discovered before 1960, this very dwarf form, originated as a witches' broom on Picea abies `Nidiformis’. It has a flat-globose habit, with a nest-like depression in the middle. Twigs are very thin, tightly crowded with the needles very densely arranged and totally covering the shoots. It may also be kept pruned in a manner to have it appear as a small, open tree for an alpine setting.
Picea abies 'Malena'
My oldest stock plants of this cultivar are about twenty years old. They are dense little cushions, which are so tight it is extremely difficult to push a finger through the branches to the inside of the plant. It is a dark green selection that has never burned in the hot summer sun and has performed admirably. Anyone who wants a tight green cushion for the rock garden definitely needs to have one of these.
Picea abies 'Nidiformis Kalous'
Similar to Picea abies 'Brno' and 'Hasin' in growth rate, maturing to about 25 cm (10") in height and width after about fifteen years, it has more of a conical shape as compared with the flattened, globose shape of the other two. It also has tiny, but conspicuous winter buds that add much interest to this plant in the winter.
Picea abies 'Saint James'
A low mound with all of its branches standing at about a 60o angle, it grows about 2 cm (1") per year. The foliage is short and dark green. When allowed to develop naturally, its outline is irregular, making it look like a naturally created alpine cushion.
PICEA abies 'TOMPA'
A slow growing, dense, conical selection, it is a great alternative to Picea glauca 'Conica'. Its squatness helps it fit into any rock garden where something dwarf yet contrasting to the rounded shape of many types of rocks is desired.
PICEA abies 'TUFTY'
This slow growing, irregularly shaped bush has branches shooting off in all directions. The foliage is light green with thin needles that are often found along short sections of the thin branches. It has all the appearance of a shrubby little tree above the tree line in an alpine area.
Picea abies 'Wichtel'
At a glance, an old specimen of this cultivar may be mistaken for a moss covered rock. The annual growth rate is so slow that scion wood can only be obtained from young specimens growing in 50% shade conditions. I cannot think of a slower growing conifer. My two oldest plants are twenty years old and are about 15 cm (6") wide and less than that high. This is an excellent choice for any size rock garden or even a trough garden. But give it some afternoon shade or the August sun may burn the center of the plant.
Picea abies 'Witches' Brood'
When first propagated, this selection is globose and very dense with thin, short, light green needles. As it matures, the plant becomes conical and the foliage on the upper part of the plant becomes more species normal. It grows about 3 cm (1-2") per year when young and 10 cm (4") per year when older, attaining a height of about 1 meter (3') at twenty years. Many rock gardeners might like to have this plant due to its history. It was discovered as a witches' broom seedling about 1970 by H. Lincoln Foster, who wrote a classic book about rock gardening.
Picea abies ‘Zajecice’
A dense, globose selection with thin branchlets comprising the spring flush of new growth, it grows less than 2cm (1") per year; The foliage is light green and adds a nice touch to the smaller rock garden. The name means “place with rabbits”.
Picea glauca 'Burning Well'
This gray-blue cushion spreads much wider than high with round winter buds that are shiny, cinnamon brown, contrasting nicely with the blue foliage. It grows about 2 cm (1") per year and works well in any size rock garden.
Picea glauca 'Cecilia'
Discovered near the Skippack Highway near Philadelphia by Greg Williams, it was renamed by Humphrey Welch. This miniature bun with short needles arranged radially around each branchlet grows about 1 cm (1/2") per year in the northeastern United States. Its foliage is silvery-grey to blue with globular, dark brown buds. A reverted form that grows at about four times the true rate of this cultivar is also being marketed under this name .
Picea glauca 'Goldilocks'
This plant will be difficult to locate, but it is well worth the search. It is bright yellow throughout the year and is free from sun burn in most areas. It grows about 3 cm (1"+) per year and naturally becomes a dense, yellow ball in the garden. Use for a color accent that will not outgrow its space for many years.
Picea glauca 'Pixie'
A miniature pillar that is possibly the most dwarf selection of 'Albertiana Conica' yet found, it is extremely dense and when grown in the full sun may sun scald on its south side. It grows about 3 cm (1"+) per year. The foliage is light green with prominent round buds. It can be used to provide a vertical aspect to the smaller rock gardens.
Picea glauca 'Pixie Dust'
Picea glauca 'Pixie Dust' is a tight little spire with green foliage. This sport develops bright yellow new growth in the summer, contrasting nicely with its basal green color. Warmer summer nights will enhance the bright yellow foliage. Use this plant for a colorful vertical accent in a smaller rock garden.
PICEA OMORIKA `Pimoko’
Discovered about 1980, it is a dwarf form with a dense, irregular growth habit. The annual growth is up to 7 cm (almost 3") with the twigs conspicuously covered with numerous dark red-brown buds and the terminal buds nearly totally hidden by needles. The foliage is emerald-green with white stomatal bands. Not for the tiny rock garden, it, nevetheless, has a place in rock gardens of a moderate size.
PICEA OMORIKA 'TREBLITSCH'
A compact, cushion shaped selection, its foliage is coarser than that of 'Pimoko'. It has a more open growth habit but is still very dwarf, growing about 5 cm (2") per year. It is globose when young, become squatly conical as it ages.
Picea orientalis 'Mount Vernon'
A miniature selection with a globular shape and very high density of foliage which does not suffer in the full sun like some of the other ultradense spruces, it grows 3 cm (1"+) per year in the northwestern United States but less than 1 cm (1/2") per year in the northeastern United States. The tiny needles are dark green and create a different color and texture for the rock garden.
PICEA ORIENTALIS 'PROFESSOR LANGNER'
I used to think that 'Professor Langner' was one of those miniature spruces that looked great for a few years and then burned out and died. However, after seeing some fine specimens in Europe, I changed my mind. I have discovered that it likes a bit of afternoon shade to prevent burning on an exceptionally hot summer afternoon. This is also true of the miniature selections of Picea abies. 'Professor Langner' is a miniature, globose selection that is exceptionally dense and grows about 2 cm per year (1"). Its foliage is dark, shiny green with very short needles. I like to think of it as a green form of 'Tom Thumb Gold'. Use it on the east or north side of a larger rock of in an area of the rock garden with some filtered sunlight in the afternoon.
Picea orientalis 'Tom Thumb Gold'
A truly miniature bun, this plant grows about 1 cm (1/2") per year. Its foliage is bright gold with a tendency to burn in the full sun, which is not surprising since it was discovered as a witches' broom on 'Skylands' and has its color. Give it about 3/4 shade and it will still be gold without burning.
I remembering visiting with Jean Iseli one summer and he was all excited about a new discovery. A Picea orientalis 'Skylands' that had a witches' broom had been seen by one of his salesmen in a front yard somewhere in New Jersey . Jean was beside himself with eager anticipation, just waiting to hear from the salesman about getting scion wood that winter. He was so upset when he discovered that John Verkade had already tied up the rights to it, and wasn't ready to share it yet, that I thought Jean was going to fly to New Jersey and browbeat John into sharing it. An hour later he calmed down and told me "I'll have it in two years. I have lots of things John would like from me." Two years later, he had several pieces of scion wood from John. I didn't have the heart to tell Jean that Verkade had sent me two young plants a year earlier. I really miss Jean.
Picea pungens 'Blaukissen'
The Colorado spruce (Picea pungens) has produced a nice selection of cultivars. Some are exceptional while some are rather blah. This cultivar is one of the best of the cushion forms. The color is very good and the growth habit is consistent. It doesn't have the occasional dead buds that cause it to be slightly irregular in outline and the foliage is larger than others. It makes a good complement to 'St. Mary' and 'Blue Pearl' in moderately sized rock gardens.
Picea pungens 'Blue Pearl'
Picea pungens 'Fat Albert' develops into a symmetrical tree with little effort on the part of the grower. Jean Iseli recognized what a valuable trait that was in a blue Picea pungens and worked very hard at popularizing it. Some years after Jean's death, a 'Fat Albert' was found with a witches' broom. The broom was propagated and named by the nursery. It has even better color than 'Fat Albert' and develops into a dense cushion with short needles. Use 'Blue Pearl' in the rock garden where a blue, symmetrical cushion is desired.
Picea pungens 'Donna's Rainbow'
A dwarf, dense, conical plant with all of the new shoots angled sharply upward, giving it a very distinctive appearance, it grows about 7 cm (3") per year. Its foliage is light blue with the needles slightly angled toward the tip of the branch, similar to the foxtail spruces. It can be used for some height in the medium sized rock garden or as part of the border of a smaller rock garden.
Picea pungens 'Early Cones'
This selection develops into a flat topped bush twice as wide as high with cones forming at the ends of the branches making it an 'Acrocona' variety of Picea pungens. The cones are purplish when they first appear in the spring, drying to paper-bag brown and hanging on the branches until the following year. It grows about 5 cm (2") per year with gray-blue foliage. I first saw this plant when I was visiting Australia in 1992. It is very slow to develop and needs about five years before it starts to assume a nice shape. Use it in any size rock garden where a small blue cushion is wanted and the cones are a bonus.
Picea pungens 'Fat Mac'
This selection develops into a compact, rounded bun, 25 cm high by 40 cm wide at ten years. Its foliage is gray green with normal length needles making a very dense dwarf.
Picea pungens 'Hermann Naue'
A dwarf, shrubby Picea pungens has many uses in the rock garden. This one has good color and develops mid-sized cones at the branch ends. It is similar to 'Early Cones' but develops into a nice, bushy plant in half the time. The growth rate is faster and more even with larger cones.
Picea pungens 'Jean Iseli'
Edsal Wood was the owner of a conifer seedling nursery and devoted part of his business to working with bonsai and prebonsai material. He would set the dwarf and variegated seedlings aside from his production area and watch them develop. He found a number of very choice plants. One of the nicest was a miniature nest form of Picea pungens that he named for his very good friend, Jean Iseli. When grown from a cutting, this selection is a low spreading bush with a depressed center, but as a graft its appearance is coarser developing into a dwarf, irregular mound. It grows about 3 cm (1"+) per year from cuttings with very fine textured, gray-blue foliage. Use it among rocks, where it will mimic some of their shapes, but with a blue color.
Picea pungens `Moll’
I have seldom seen this selection in any gardens I have visited over the past twenty or more years. I am not certain why it is so rare because it is a rather nice, irregularly conical dwarf selection of Picea pungens. Its color is blue and the growth rate is very slow. Its irregular outline and squat growth habit make it a natural for any rock garden except the smallest.
Picea pungens 'Porcupine'
A dwarf bun of exceptionally high density, it grows about 3 cm (1"+) per year. Its foliage is blue with short, stiff and sharp needles. The needles are longer than the annual growth and the winter buds are so small as to be easily overlooked. It will never be easy to find simply because a nursery has to grow it for a long time before it reaches a saleable size. The original plant was first exhibited at The Farwest Trade Show in Portland, Oregon in the early 1980's. Jean Iseli tried to purchase it, but the owner refused to part with it. Then when Dick Bush asked for it, he just gave it to him. Dick was a close friend of Jean's. He would land his airplane on any open spots at Iseli Nursery whenever he wanted to visit Jean. He seldom ever got "one up" on Jean, but this time he did. Jean was disappointed but happy that a close friend got 'Porcupine'. Dick propagated it and shared it with Jean and with me. Eventually the original plant was stepped on by a horse and lost.
The only plant that compares to it is Picea pungens 'Yvette', named for Jean's younger daughter. It is very similar and may be used in the same way in a rock garden. Put it wherever a tiny blue mound with dense, coarse foliage is desired.
Picea pungens 'St. Mary'
A dwarf, dense mound with conspicuous buds that grows about 3 cm per year, this bright blue plant was found as a witches' broom at Saint Mary's Convent in New Jersey. It is often called 'St. Marys Broom'. It is not uncommon for specimens of this cultivar to have many buds that never push, leading to slower growing regions on the plant. Use it in the rock garden near larger rocks for the best effect.
Picea pungens 'Waldbrunn'
I first saw this plant in Holland in the late 1980's. At that time I was told it was a blue Picea abies. It almost looks like a cross between pungens and abies when grown from a rooted cutting. When grafted, it is more upright and coarse, showing its Picea pungens heritage. On its own roots it makes an exceptional nest-shaped shrub the grows about 4 cm (1.5") per year.
PICEA SMITHIANA 'BALLARAT'
Picea smithiana is a striking species with drooping branchlets that make the tree seem to be wilting from lack of water. Peter Nitschke, Hahndorf, Australia discovered a witches' broom in a Picea smithiana that develops into a diminutive, dark green mound with drooping branchlets. It is very dense and may grow up to 4 cm (1.5") per year. The foliage is dark green with short needles. It is a natural for the smaller rock garden with its unique appearance of drooping branchlets. Nitschke was a very enthusiastic "broomer" from 'down under' who was responsible for many introductions during his all too short life. I only met him once when he came to America, but his enthusiasm and knowledge made a lasting impression.
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