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Conifer Size Categories

To assist in garden design, the ACS has been instrumental in refining the definition of conifers in ornamental horticulture by creating four categories of sizes based on average growth characteristics over a 10-year period.

Landscape designers have only recently discovered dwarf conifers as housing prices climbed and lot sizes shrank. Virtually every major conifer species has a number of cultivars that defy their species by growing only a few inches (or less) per year, giving a small garden a palette of evergreen colors, textures and shapes that will hold together for many years, perhaps decades.

Some cultivars grow less than 1 inch (2.5 cm) per year thereby ensuring a design scheme that can be effective in a container, on an outdoor patio, or in a trough situated on a hardscape feature. Though not widely available in mass market garden centers, collectors and enthusiasts can find these “true dwarf” conifers in specialty nurseries, some of which ship mail order. ACS publications and meetings are a great way to tap into this network of growers.

ACS has established four size categories for conifers — Miniature, Dwarf, Intermediate and Large, to aid in landscape design. Once established, these plants’ growth may vary some due to cultural, climatic and geographical conditions but these registered cultivars have, through trials and succeeding generations, maintained their described size. The individual plant records in the ConiferBase contain this information.

Unfortunately, not all nurseries and growers provide this data about annual growth and anticipated size at ten years on their plant tags – yet. Spread the word.

Category Abbreviation Growth per year1
Approximate 10-year size2
Miniature M less than 1 inch (2.5 cm) less than 1 foot (30 cm)
Dwarf D 1 to 6 inches (2.5 – 15 cm) 1 to 5 feet (0.3 – 1.5 m)
Intermediate I 6 to 12 inches (15 – 30 cm) 5 to 10 feet (1.5 m to 3 m)
Large L more than 12 inches (30 cm) 10 feet (3 m) or more

1: Size may vary due to cultural, climatic and geographical region
2: Refers to growth in any direction

It must be greatly emphasized that, as in all woody plants, conifers will continue to grow at their stated rate for the life of the plant. Many gardeners and home owners have the (false) opinion that a dwarf conifer will grow to ten-year dimensions, then abruptly stop growing. That is not the case.

 

Editor’s Note:  Want to learn more about Conifers?  Become a member of the American Conifer Society and receive our renowned ConiferQuarterly, with articles written by some of the most respected plantsmen and women in the country.  You will also be eligible for discounts from many nurseries and help to promote the development, propagation and conservation of conifers around the world.  JOIN HERE!

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