Chinese elm (Ulmus parvifolia Jacq.) is an attractive, medium-sized ornamental tree with excellent urban-hardiness and pest resistance. Introduced into cultivation in the late 1700s, this species is commonly grown in parks, lawns, and streetside locations in the southern United States and California. There have been only three Chinese elm cultivars selected in this country (1, 2). Nurserymen have expressed their desire to find a Chinese elm with an increased level of cold hardiness so that the species could be used in cities in the northern United States. The ‘Aross Central Park’ Chinese elm is cold hardy to zone 6 (Arnold Arboretum hardiness zones) and will grow in protected areas in zone 5. Thus, it is the most cold hardy Chinese elm available.
Amur maackia (Maackia amurensis Rupr. & Maxim.) has potential for use in small, urban, or cold landscapes. Although Amur maackia is becoming increasingly popular, plants are currently grown from open-pollinated seed populations, and there has been no selection of cultivars. We have addressed the effects of climate on growth and have begun field trials for selection of horticulturally superior genotypes. In May 1995, a field trial near Ames was begun with 337 plants. These were selected from more than 2000 greenhouse-grown seedlings to represent 32 half-sibling seed groups from 16 arboreta across North America. After two growing seasons, the increase in stem length among seed groups ranged from 3% to 75%. Survival rate did not vary with seed group. In a related study, 30 plants from six half-sibling groups have been established at each of 10 sites in the U.S. and four in Canada to assess effects of location on survival and growth. The influence of seed group on survival after 1 year varied with the trial site location. Survival among combinations of half-sibling group and trial location ranged from 0% to 100% (mean = 54%). Half-sibling group and trial location affected growth without interaction. The greatest growth across locations, an 83% increase in stem length, was shown by seeds that originated from a tree at the Arnold Arboretum. At the 14 locations, changes in stem length over half-sibling groups varied from <0% in Ithaca, N.Y., to 179% in Puyallup, Wash.
and tight branch angles typical of C. canadensis .
Dissemination of Cultivars
Grafted stock plants and scions were provided to Arnold Arboretum nursery partners through the “ArnoldSelects” PI program ( https://arboretum.harvard.edu/plants/plant-introductions/arnold-selects
It has been estimated that as many as 100 species of palms will tolerate temperatures as low as 20 °F ( Frankco, 2003 ). Selected palm species grown in warm to cool temperate regions and their reported cold hardiness are provided in Table 2 ( Arnold
selected for trialing or designated for promotion based upon trial site performance are made by the Texas Superstar ® Executive Board. Members are: B. Pemberton (Chair), Texas AgriLife Research, Overton; M. Arnold, Texas A&M University, College Station; T
nice form ( Arnold, 2002 ; Cox and Leslie, 1988 ). Two varieties, T. distichum var. distichum (baldcypress) and T. distichum var. imbricarium (Nutt.) Croom (pondcypress), have good fall color in some areas, whereas T. distichum var. mexicana
Fraser fir established in 1983 found significant differences among sources and among families within seed sources for all traits measured ( Arnold and Jett, 1995 ; Arnold et al., 1994b ; Jett et al., 1993 ). Heritabilities for most traits important in
demographics but also on policy issues. Specific information ( Arnold et al., 2006 ) on the programmatic processes, admissions criteria, demographics, finances and metrics of evaluation of horticulture graduate programs is limited. Previous work ( Arnold et al
Landscape Plants for the South-Central United States. Michael A. Arnold. 2022. Stipes Publishing, Champaign, Illinois. 1686 pp. $144.95. Hardcover. ISBN: 978-1-64617-289-4.
The author of this book is Michael A. Arnold, who is a professor of
extended length of color show ( Arnold, 2002 ; Liberty Hyde Bailey Hortorium, 1976 ). This striking wildflower has a colorful ethnobotanical history related to its use by various Native American tribes. It is reported the Acoma and Laguna Indians drank an