Arid Zone Tree-Mail
Southern Live Oak (Quercus virginiana)
from AZT
After nearly 30 years screening, appraising, and propagating desert-adapted trees to add to our select line ‘Variety AZT,’ we know quality when we see it. Several years ago, AZT began collecting acorns from Southern Live Oak (Quercus virginiana) to germinate and plant in our demonstration garden. The garden planted trees let us assess the Oaks field growth and development. Acorns were processed through our propagation system to see how they would integrate into AZT Root Management and Quality Control programs. Eight years later, AZT can offer market sizes Southern Live Oak, Quercus virginiana specimens in #25 and #45 containers for installation in your next project.
Southern Live Oak, Quercus virginiana, has been part of the southwestern landscape palette for decades. While native to the southeastern US, it can be found growing wild along the coastal plains of the Gulf of Mexico and into Texas. Described in the literature as evergreen, Live Oaks shed leaves in spring just prior to the emergence of new leaves. Dryer, colder climates may contribute to greater, more seasonal defoliation.
Trees initially grow at a rapid rate that slows as trees mature. Thick, dark colored, vertically fissured bark is typical on maturing trees. Younger trees have relatively smooth bark. A dense canopy of dark green, leathery leaves, with a shiny surface with gray green undersides, generate abundant shade, nearly year-round. Live Oaks are incredibly long lived with some of the oldest specimens in the US estimated to be several hundred years old. Given this long life, mature height and spread are a function of age. On average trees can reach 50’ tall with 80’ wide canopies. No specimens this large have been yet found in the southwest. Estimates suggest that trees reach maturity in about 75 years. Small, brown flowers are inconspicuous, and wind pollinated in spring. Acorns fall in autumn and serve as a food source for many animals. Studies suggest that trees are cold hardy to 5 - 10 F.
Southern Live Oaks offer a durable, shade generating, single trunked tree to add to our desert landscape palette. Trees respond well to drip irrigation in desert settings and have proven to be well adapted to desert soils and climate. In well drained soils, and with proper irrigation, root systems are well distributed and shallow. For young trees, root growth and size are not necessarily reflected in canopy mass. In the wild, these oaks display a variety of forms from single trunked to massive, spreading low breaking specimens that can reach 80’ wide. Nursery grown specimens, for landscape plantings, tend to be single trunked. This form is ideal for streetscapes and parking lot plantings, as theme or perimeter plantings and screens, at entry monuments or pedestrian areas. They have also been used in golf courses, public parks, and open spaces within residential communities. There is a clear need and place, within the designed landscape, for multiple and low break specimens that, up till recently, have not been available. Oaks respond well to pruning, to lift scaffold branches, improves view lines, and accommodate pedestrian access without compromising canopy shade.
Southern Live Oak can be propagated from seed and cuttings. There have been many Live Oak hybrid cultivars patents and trademarks. Many of these are not currently commercially available or produced in limited quantities. Careful collection of select acorns can produce trees that are highly consistent in appearance and horticultural traits. As Oaks readily hybridize, poor acorn screening can lead to trees that vary in stature from spreading canopies to upright traffic/pedestrian friendly specimens Leave characteristics can vary from narrow and pale green to more lush, compact, and dark green in color.
We have identified an acorn source that allows us to grow Oaks with highly uniform structure, dense, dark green leaf canopies and, excellent root growth. AZT continues to screen and evaluation Live Oak selections to ultimately incorporate into our ‘Variety AZT’ development program. Within the next few years, we plan to bring a cloned Live Oak to the market that will have all the uniformity and superior horticultural properties you have come to expect from ‘Variety AZT’.