An Arid Zone Trees Publication 2020 Volume 26 Issue 1
Ulmus parvifolia, 'Variety AZT'
Evergreen Elm, 'Variety AZT'
While not strictly speaking a desert native, Evergreen (or Chinese) Elm, Ulmus parvifolia, has been a part of western and southwestern landscape since the great American western migrations of the 19th century. Its classic, upright form, ample shade and deciduous growth reminded early settlers of “home” while offering respite from the desert dry heat and wind. From these beginnings Elms have become a landscape staple as streetscape, monument, screening and theme elements in commercial, municipal and residential landscapes. They are recognized on an array of approved plant list, widely used and generally available in an array of sizes.
In 1928, Dutch Elm Disease was introduced into the United States in a shipment of logs from The Netherlands. Over the next 50 years the disease made a slow march across North America, finally arriving in California in the mid 1970’s, decimating American Elms Ulmus americana. The introduction and spread of this disease lead to ambitious, aggressive research to find selections, varieties and species of Ulmus that exhibited disease resistant or, at the least, tolerance. This research effort not only identified disease resistant species, like U. parvifolia, but encouraged breeding and selection programs that have brought to the landscape a wide assortment of Elm varieties.
Throughout the southwest, Elms are used in streetscapes, parking lot, parks, golf courses, in grouping (as a screen) and as individual, focal point, specimens. They are durable in all landscape applications and respond well to a wide assortment of soil type and conditions. Like many of the mesquite species and varieties, the extent of leaf shed correlates with the severity of winter low temperatures. Ultimately, remaining previous season leave are shed in spring and immature new leaf growth is a striking, bright chartreuse. Elms are essentially pest and disease free in the southwest except for occasional aphid infestations and Texas Root Rot. Summer irrigation schedules need to be sensitive to soil type (with trees in sandier soil requiring additional water) and the source(s) of reflected heat (hardscape, asphalt and other paving) as these landscape will contribute to higher evapotranspiration by Elms. When pruning Elms apply the same methods and practices used on other landscape trees in desert setting. For a review of tree pruning practices visit.
AZT began production of Evergreen Elms in 2015, initially in #25 containers using commercially available varieties from seed and clonal sources. Our current inventory consists of #25, #45 containers, and 48-inch boxes. In parallel with purchased propagation stock, AZT initiated a research program leading to the production of a ‘Variety AZT' Evergreen Elm. Evergreen Elm, ‘Variety AZT’ has been released in limited quantities for the last two years. We will plant an additional 800 Evergreen Elm, ‘Variety AZT’in #25 containers in the spring of 2020. Our production across all container sizes will expand from there. The standards of quality, uniformity, durability and beauty that have been the basis for all our ‘Variety AZT’ trees has been incorporated into this new variety. We anticipate bringing these new Elms to market, in all sizes, in the next few growing seasons. We are confident that Evergreen Elm ‘Variety AZT’ is a worthy addition to our brand.