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Arnold Arboretum

M. Victor and Frances Leventritt Garden

Dwarf Conifers of the Leventritt Garden

About
A small collection of dwarf conifers is located on the slope between the Leventritt Shrub and Vine Garden and the Larz Anderson Bonsai Collection. There are also several dwarf and weeping conifers within the Leventritt Shrub and Vine Garden.

Dwarf conifers are variants of conifers; they grow more slowly and remain significantly smaller than normal for the given species. For example, white pine (Pinus strobus) normally grows 80 or more feet tall, but the dwarf white pine cultivar ‘Blue Shag’ reaches only about 3 to 4 feet tall, growing slowly to form a dense, globe-shaped plant. A general rule of thumb is that true dwarf conifers reach 1/20th or less of the normal height for a species, grow less than 6 inches per year, and are still less than 6 feet tall after ten years of growth. Intermediate dwarf conifers are a bit bigger—they may reach 1/10th of the normal height for a species, grow 6 to 12 inches per year, and may be 6 to 15 feet tall after ten years.

Dwarf conifers originate in a number of ways. They may be seedlings with genetic mutations that reduce their growth, or they may arise as branch sports (mutated growth on otherwise normal plants) that are then propagated. A fascinating and fairly common origin of dwarf conifers is from witches’-brooms [pdf] —dense, twiggy eruptions of growth on branches of otherwise normal trees. Witches’-brooms may be caused by mutations, insects, or diseases. New plants propagated from a witches’-broom retain a dwarf growth habit. Most conifers are difficult to propagate from stem cuttings, so grafting is the usual propagation method for dwarf conifer cultivars.

Highlights
New! Link to a dwarf conifer tour on Arboretum Explorer.

  • A number of dwarf conifers are noted for their colorful (non-green) foliage. Plants with yellow or gold foliage can make effective accents in the landscape, since the lighter, brighter color stands out from surrounding green tones. Look for the gold-tipped foliage of Chamaecyparis obtusa ‘Golden Nymph’, a dense, mounded shrub about 5 feet tall and wide. Blue-foliaged dwarf conifers are also eye-catching; an example is the broad, conical specimen of Picea pungens ‘Hunnewelliana’.
  • Some dwarf conifers sport unusual foliar characteristics. One striking example in the collection is the Korean fir cultivar Abies koreana ‘Silberlocke’, an intermediate dwarf conifer that has short, dark green needles that curve upward around the stem, revealing silvery white undersides. Adding to its garden appeal are the purplish upright cones, often frosted with sticky resin.
  • Cryptomeria japonica ‘Rein’s Dense Jade’ is a dense, upright growing cultivar of Japanese cryptomeria. Its closely pressed, awl-shaped needles give the branches a ropelike appearance. Foliage is bright green in summer and develops bronze tints during the winter.
  • Dwarf Alberta spruce (Picea glauca ‘Conica’) is a popular dwarf conifer. It has very short, fine needles that form a dense outer layer on its neatly cone-shaped form. The original plant was found in Alberta, Canada in 1904 by J. G. Jack and Alfred Rehder of the Arnold Arboretum.
  • Several slow-growing weeping conifers are included in the dwarf conifer and shrub collections. In the shrub garden, look for the weeping European larch (Larix decidua ‘Pendula’) gracefully trailing over a stone terrace wall. This deciduous conifer has lovely bright green summer foliage that turns gold in autumn. Even the bare winter branches add interest, especially when outlined with fresh snow. In the upper collection, a weeping Carolina hemlock cultivar (Tsuga caroliniana ‘LaBar Weeping’) is set off by a backdrop of red-fruited winterberry (Ilex verticillata ‘Winter Red’).

Arnoldia

  • Fordham, A. J. 1967. Dwarf Conifers from Witches’-brooms. Arnoldia 27(4-5): 29-50 [pdf]
  • Fordham, A. J. 1963. Tsuga canadensis and Its Multitude of Variants. Arnoldia 23: 100-102. [pdf]
  • Sax, K. 1950. Dwarf Trees. Arnoldia 10(12): 73-78. [pdf]

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