Dr. Dirr

Fastigiate/Columnar Trees - Stairways to the Heavens

This HMI article/blog is based on a February 2014 consulting visit to the University of Massachusetts (UMass), Amherst. I graduated from UMass in 1972 and continue to support the University. The education was superlative and my wife, Bonnie, and I are forever thankful for the many friendships that continue to the present. Todd Cournoyer, campus […]

Nyssa Sylvatica - The Search for the Perfect Tree Continues

In the previous editions, I presented the case for utilizing Nyssa sylvatica, black tupelo, and cultivars in urban and suburban landscapes. With the demise/ruination of Fraxinus, ash, via Emerald Ash Borer, the invasive nature of Acer platanoides, Norway maple, and necessity for genetic diversity, alternatives are needed. Although not a panacea, Nyssa sylvatica offers aesthetics, […]

Acer truncatum - Shantung, Shandong or Purpleblow Maple & Hybrids

Acer truncatum is certainly not a household word or common in the arboricultural, nursery and landscape industries, but it deserves greater use. Interest in this species is picking up as weather patterns are affecting tree performance. To date, this species has been adaptable to weather's curve balls. Small trees, 20' to 30’ high and […]

Nyssa sylvatica the lovely black tupelo, black gum

Fifteen years ago, I penned a brief article on Nyssa for HMI's TreeTalk™ publication. The present discussion expands significantly on that information and discusses the advances in Nyssa selection, evaluation, and production techniques. Recently, I was asked what I thought of Nyssa sylvatica as a replacement for Acer rubrum by Nate Nix, sales arborist, Monster […]

Appreciating the showy Aesculus x carnea

Commonly called Red Horse Chestnut, Aesculus × carnea was discovered in Europe in 1812 and is best adapted to the temperate Northern Hemisphere. A beautiful tree for parks and large lawns, opportunities abound to study this fascinating Aesculus.

Carya: Hickory species native to much of the U.S.

Carya species, hickory, native throughout the eastern, midwestern and southeastern United States, are seldom available in retail commerce. Primarily relegated to the deciduous forests, commingled with oak, beech, maple, tupelo and birch, few trees are more beautiful in autumn when aglow with the late developing, long persistent, rich yellow-gold foliage. Foliage shows significant frost/freeze tolerance […]

Cornus florida - flowering dogwood and its relatives

Cornus is a fascinating genus with species ranging from groundcover habits (Cornus canadensis) to large trees (Cornus controversa). I relate to students and garden visitors that if one dogwood is recognizable, then all can be. The leaves (primarily deciduous, several evergreen) are linear-ovate to ovate to broad ovate, margins entire (no teeth) with veins originating […]

Dr. Dirr Discusses Quercus virginiana- Live Oak

Bonnie and I spent a few days at Hilton Head during the week between Christmas and New Year’s. At our fourth-floor condominium, the view from the balcony/porch was part beach but primarily treetop green, the latter Quercus virginiana. The species is the dominant noble tree on the island and efforts to preserve it in the […]

Salt Tolerance in Woody Plants

Michael A. Dirr HMI requested a brief discussion on salt tolerance in woody plants. I started my career at the University of Illinois, Urbana, in 1972 after graduation from the University of Massachusetts. While a student at UMass, I was introduced to Acer saccharum, sugar maple, decline, at least partially attributable to deicing salts. The […]

Cornus officinalis-Japanese Cornel Dogwood

The Japanese cornel dogwood is a beautiful small tree, the yellow flowers borne on spur-like naked stems months ahead of the foliage, harbingers of Spring’s awakening. I suspect after the 2020 pandemic, people are looking for signs of hope in the New Year. Gardening provided that to a large segment of U.S. society in 2020 […]

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