Pines for the Rock Garden
The planting feature known as a ‘rock garden’ takes on many different forms. But the true rock garden is a representation of a alpine area that has been reduced in scale and brought into a home landscape. It consists of rocks (of course), well drained soils, and an assortment of alpine plants suited for the gardener’s part of the country. These alpine plants are mostly herbaceous plants that stay small and/or low and generally produce flowers sometime during the spring or summer.
These alpine plants often include a smattering of conifers. Since conifers are present in most parts of the world up to and even beyond the tree line, examples do belong in every rock garden. In my case, I have a rock garden with 90% conifers, but then I am prejudiced in their favor and make extensive use of them.
Pines are synonymous with great age. The Methuselah Tree is a pine, and the bristlecone pines (Pinus aristata) of the Sierra Nevada Mountains are works of art. Japanese gardens and bonsai make extensive use of pines. They are revered for the feeling of age that they give a garden.
Knowing that pines work well in an alpine rock garden, the gardener then has to find the answers to two very important questions: First, what pine selections do I make for my garden? Second, where can I purchase these selections?
Both of these are difficult questions to answer. This article will help you with the first question. Finding these dwarf pines will not be as easily accomplished.
Alpine conifers take on two basic forms, both of which result from their environment, not their genetic makeup. They are either sparsely branched, contorted, and wind swept, or they are cropped into cushions by grazing animals. Both growth habits are also possible in the rock garden and may be attained through the careful selection of the pine cultivars to be planted or by persistent, careful pruning or by a combination of the two.
Cultivars that have been grown twenty or more years, will have a reliable history regarding growth habits and variations. These selections will perform in a predictable manner. Cultivars that have been selected within the past twenty years may not be reliable and show some variation from their expected growth habits, especially those that are described based upon the performance of the mother plant or witches’ broom that provided the selection. Many times a less knowledgeable nurseryman will give a description based upon either a mislabeled plant or a plant that was grown under stressful conditions.
Many of the newer selections are exciting, and a number of these will probably perform nicely in the rock garden. Others will disappear due to changeable growth habits or a lack of distinguishing characteristics.
Keeping these facts in mind, I will describe some of the pine cultivars that I think will be suitable for the rock garden. giving the reader a mix of new and old selections.
The cushion-shaped cultivars can be planted almost anywhere in the rock garden. One can be tucked up against a rock or out in an open area between rocks. They will give an appearance similar to an herbaceous alpine but with a different texture and color that may be seen throughout the year.
Pinus banksiana ‘Chippewa’ is the most dwarf of the Fordham banksiana selections, ‘Chippewa’ develops into a miniature, irregular, flat-topped mound. It grows less than 1 inch (2 cm) per year, and the foliage is light green with tiny needles mostly held parallel to the branchlets. The buds are elongated, gray-white, and slightly resinous. ‘Chippewa’ was seedling grown from a witches’ broom about 1970 by Alfred Fordham, Arnold Arboretum, Jamaica Plain, Massachusetts. Fordham was one of the first to experiment with this type of seedling. A.G. Johnson of Minneapolis, Minnesota, a close friend of Fordham’s who sent him the seed for a number of named seedlings, was possibly the first. Fordham’s other witches’ broom seedlings in this species include ‘Manomet’ and ‘Neponset’. Neither of these is a diminutive as a ‘Chippewa’, but both are excellent, compact selections.
Pinus densiflora x mugo ‘Edsal Wood’ becomes a miniature green globe with relatively large, brown winter buds. It grows less than 1inch (2.5 cm) per year. It was found as a seedling by the late Edsal Wood of Bonsai Village, Aurora, Oregon in a batch of Pinus mugo seedlings. Ed grew thousands of seedlings of various conifers every year and always selected anything unusual from each crop. This plant had been set aside and was picked out as having merit by Don Howse soon after Ed’s death. It has characteristics of both Pinus mugo and Pinus densiflora, thus the hybrid designation.
Pinus flexilis ‘Witches’ Broom’ is a miniature bun that grows horizontally rather than conically, at less than 1 inch (2 cm) per year. The foliage is green with a bluish tinge. The origin of this selection is uncertain. It had been given to the Arnold Arboretum by Layne Ziegenfuss in the 1960’s. I obtained my start from this same plant and, to the best of my knowledge, all of the plants in circulation came from this source. Layne never shared the name of the discoverer nor the name of the plant so it has always been offered under the illegitimate name of ‘Witches’ Broom’. There are many other flexilis witches’ brooms that have recently been appearing in gardens and plant lists through the efforts of Jerry Morris. Many of them are also very nice but need more years of evaluation for dependability. I have not seen any that are superior to this selection, but quite a few have stayed small for over ten years in garden settings.
Pinus leucodermis 'Smidt', another small, congested plant, has thick, dark‑green needles and becomes almost conical as it grows. Its maximum growth is less than 1inch (2.5cm) per year. This plant was found in the Czech Republic before WWII and the parent plant is still growing in the Pruhonice Arboretum near Prague. Two other forms of its name are ‘Schmidtii’ and ‘Smidti’, both of which are incorrect.
Pinus mugo 'Corley's Mat' is a prostrate mugo pine that grows less than 2inches (5cm) per year. The needles are thin and twisted, adding a distinctive quality to the plant. This selection would make a very interesting, slightly rounded cushion in the smaller rock garden.
Pinus mugo 'Mitsch Mini' is possibly the dwarfest of the mugo pines to be found in the better garden centers. It is flat‑growing but does mound up slightly as it ages. Rooted plants develop much slower than grafted plants, but both are very dwarf. It lends itself very well to pruning and shaping into a miniature tree. It grows about 1 inch (2.5cm) per year.
Pinus mugo 'Mops' becomes slightly broader than high. It is a good selection for someone wanting a moderately dense selection than can be pruned into the shape of a small tree. Unpruned, it develops into a dense globe 3 feet (1 meter) wide in 15 years.
Pinus peuce ‘Arnold Dwarf' is a dwarf selection that develops into a dense, narrow, little mound. It grows about1 inch ( 2 cm) per year. The foliage is dark green, and the needles are actually longer than its annual growth, giving it the appearance of a conical mound of needles. It was discovered as a seedling at the Arnold Arboretum, Jamaica Plain, Massachusetts, about 1965. It is also found under the incorrect name of 'Nana'.
Pinus mugo ‘Bozidar’ is a dwarf, globular selection that originated as a witches’ broom discovered about 1986 by Karel Kalous at Erzgebirge near Bozi Dar, Czech Republic. The name means “God send”. It grows 1 inch (2-3cm) per year. In poorer soils it is exceptionally small and dense.
Pinus mugo ‘Little Delight’ is a miniature cushion that grows less than 1 inch (2 cm) per year. The tiny needles and miniature buds make it exceptionally attractive. It is an ideal choice for a small pine to grow in a crevasse between two rocks. I discovered it as a witches’ broom on a specimen of Pinus mugo ‘Mops’ in 1990.
Pinus mugo ‘Carsten Wintergold’ develops into a compact, broadly globose plant. It grows about 2 inches ( 5 cm) per year. The foliage is a rich, bright yellow during the winter. It originated with Erwin Carsten, Varel, Germany before 1988. There are a number of mugo pines that turn gold in the winter with this selection being the brightest and most compact. It is an exceptional plant for brightening the winter garden with a splash of yellow gold.
Pinus mugo ‘Sherwood Compact’ develops a globular shape at a young age. It is quite slow and dense, making a distinctive plant for the rock garden. Growing just over 1inch (2.5cm) per year, it is a reliable selection.
Pinus nigra ‘Oriesok’ is a dense, little globe that grows about 1 inch (2 cm) per year, ‘Oriesok’ originated from a witches’ broom discovered in 1981 by Jaroslav Kazbal at Rodopy, Bulgaria. The name means “little nut”.
Pinus strobus ‘Greg’ is a dense, miniature bun that grows much like 'Horsford' and 'Sea Urchin' but with some differences. ‘Greg’ grows about 2 inches (5 cm) per year with light green foliage and needles half the length of 'Horsford', and was selected from a batch of witches' broom seedlings sent to an unknown person on Long Island, New York, by Greg Williams, Vermont, about 1970.
Pinus strobus ‘Horsford’ is a cushion-shaped, dense little bun that grows about 1 inch (3 cm) per year. Its foliage is light green, and its relatively long, thin needles and short annual growth give it the appearance of a shaggy little cushion. This selection originated as a seedling discovered by William Horsford, Vermont, about 1960. As with most of the miniature Pinus strobus it must be cleaned of dead needles each winter or sudden death may occur in the spring.
Pinus strobus ‘Sea Urchin’ is a very dwarf shrub that develops into a low mound. It grows about 2 inches (5 cm) per year. Its foliage is bluish-green with short needles. It originated as a witches' broom seedling selected in 1978 by Dr. Sidney Waxman, University of Connecticut, Storrs, Connecticut. This selection has proven to be the most popular of all the Waxman seedlings. Of the four dwarf forms of Pinus strobus discussed here, it is possibly the most popular due to its soft texture and bluish foliage.
Pinus strobus ‘Uncatena’ is another green dwarf selection that develops into a low, dense cushion-shaped plant. It grows about 2 inches (5 cm) per year with short needles. This witches'-broom seedling, grown about 1970 by Alfred Fordham, Arnold Arboretum, Jamaica Plain, Massachusetts, was from seed he collected.
Pinus sylvestris ‘Jeremy’ originated from a witches' broom found at Wellingborough, Northants, England by B. Reynolds in 1973. It is a compact, broadly globular selection; growing up to 3 inches (7 cm) per year. Its foliage is dark green with short, straight needles and prominent, bright brown, pointed winter buds.
Pinus sylvestris ‘Little Ann’ grows about 2 inches (4 cm) per year. This dwarf, dense, little globe with a flattened top has dark green foliage with short needles. It originated from a group of witches' broom seedlings grown by J. D. Hoste, Manchester, England about 1970.
Pinus sylvestris ‘Pixie’ was introduced in 1983 by Don Hatch, Chantry Nursery, Honiton, Devon, England. This dense, globular selection; grows about 2 inches (4 cm) per year; and has green foliage with short leaves.
Pinus sylvestris ‘Repens’ is a prostrate scots pine that grows about 2 inches (5 cm) per year. The winter buds are extremely resinous. As the plant ages, it mounds up slightly in the center. It looks especially nice growing among several large rocks on a slope.
Pinus thunbergiana ‘’Ogi Matsu’ is unique because it has a tendency for the stems to develop as cockscombs with scattered normal shoots. It is a very dense, dwarf selection, growing up to 2 inches (5 cm) per year, although most years it grows less than 2 cm. Its foliage is dark green with relatively long needles. It was introduced into America during the 1970's.
Pinus uncinata ‘Paradekissen’ was found growing in the wild by the late Gunter Horstmann, Schneverdingen, Germany before 1980. A dense, miniature, low-growing cushion, it grows about ½ inch (1 cm) per year as a young plant. The original plant is 15cm high with a diameter of 70cm and was estimated by him to be 400-500 years old when found.
Pinus uncinata ‘Offenpass’ is a dense, conical, dark green, dwarf selection; growing about 1 inch (2.5 cm) per year. It originated from a witches'-broom found before 1983 by the late Gunter Horstmann, Schneverdingen, Germany.
Pinus virginiana ‘Driscoll’ is possibly the smallest Virginia pine available anywhere. It is an emerald green cushion that grows just over ½ inch (1 cm) per year.
deformed little tree
The other growth habit that works nicely in the rock garden is that of a twisted, sparsely branched, deformed little tree much like those observed at the snowline in alpine settings. These trees are indicative of cold, windy areas with thin, nutrient poor soils. They add a sense of authenticity to any rock garden.
Several cultivars with these attributes are placed in this descriptive category.
Pinus albicaulis #1 dwarf has never been given a valid name. It is a dwarf, densely branched little tree. It may be as tall as 3 feet (1 meter) in 15 years. With some selective pruning (or abuse), it can easily be shaped into a wind-blown appearance.
Pinus aristata ‘Silver Alibi’ is mentioned here because a slower growing bristlecone pine is perfect for the alpine rock garden. This one is not quite as dwarf as some, but it does grow very slowly and the needles are literally infested with white resin ducts. This characteristic provides an interesting color accent for the garden.
Pinus mugo ‘Jakobsen’ is a slow-growing, bun-shaped selection with areas of exceptionally dense foliage. It grows about 1 ½ inches (4 cm) per year. Its foliage is dark green with curved needles held tightly together against the thick branchlets and their dark green color contrasts nicely with the bright white winter buds. Its dense, irregular (bumpy) outline makes it a perfect choice for the alpine garden. It originated with Arne Vagn Jakobsen, Denmark before 1990.
Pinus mugo 'Mr. Wood' was a seedling selection from Pinus mugo made by the late Edsal Wood and named by Talon Buchholz. It is a diminutive little mugo that at first glance can be mistaken for Pinus parviflora. It is difficult to establish but well worth the effort. Many of the needles are fishook shaped.
Pinus parviflora 'Al Fordham' is a miniature open tree that is quite narrow for its height and has some areas of congested growth. It grows about 2 inches (6 cm) per year. The foliage is light green with short, twisted needles. Summer bud elongation is common and quite pronounced. The late Al Fordham, Head Propagator at the Arnold Arboretum, Jamaica Plain, Massachusetts, collected three seeds off of a Pinus parviflora 'Glauca Nana'. The most dwarf of the three plants grown was named in his honor by the people at the Arnold Arboretum in 1986.
Pinus parviflora ‘Glauca Nana’ ia a narrow, open, irregular little tree growing about 4-5 inches (15 cm) per year. The foliage is bluish green with short, straight needles, and it was introduced about 1965.
Pinus parviflora ‘Hagaromo’ is a very dense mound, as a young plant. It becomes more conical as it ages and develops a single trunk while growing about 2 inches (5 cm) per year. The foliage is glaucous with short, twisted needles. Introduced about 1970 by Tage Lundell, Helsingborg, Sweden, it has also been sold in America under the name 'Hagoromo'.
Pinus parviflora ‘Pygmy Yatsubusa’ is a dwarf selection that becomes a dense, miniature tree with no effort on the part of its owner. Single trunked with a central leader and dense branching; it grows about 2 inches (5 cm) per year. Its foliage is light green with short, twisted needles and pronounced winter buds.
Pinus strobus ‘Hillside Gem’ was found as a seedling about 1964 by Layne Ziegenfuss, Hillside Nursery, Lehighton, Pennsylvania. It is a dwarf, open tree with sparse, thin branches and areas of congested growth. It grows about 2 inches (6 cm) per year with light green foliage and thin, short needles.
Pinus strobus ‘Tiny Kurls’ is an exceptional dwarf shrub for any rock garden. It has the characteristics of Pinus strobus ‘Torulosa’ (thin, twisted needles and crooked branches) but becomes a small shrub rather than a tall tree. It was grown from seed collected from a Pinus strobus ‘Horsham’ growing under a Pinus strobus ‘Torulosa’ by Greg Williams in Vermont.
Pinus sylvestris ‘Bennett Compact’ was discovered in the 1960's by William Bennett, Virginia, who was adept at discovering unusual plants growing along the highway as he traveled. This miniature selection becomes a dense, irregular little mound. It grows about 1 inch (2 cm) per year with an occasional shoot of up to 5 cm. Its foliage is blue-green with relatively long, stiff, thick, sharp needles. Occasionally a plant will send up strong growing shoots, most commonly in colder climates.
Pinus sylvestris ‘Little Brolly’ is a dwarf, flat-topped globe with curved and twisting branches. Its foliage is dark green with short leaves. The small winter buds are prominent and sharply pointed. It originated as a witches' broom seedling at Almondell Nursery, Methven, Scotland before 1989.
There are many new pines that are suitable for the rock garden, but until they have been properly evaluated, the gardener has to be prepared for a number of possibilities, some of which may be quite good. Meanwhile, the average gardener can work with the cultivars I have described to develop the backbone of an alpine rock garden that will be authentic and provide many years of pleasure.
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