Southern Live Oak, Quercus virginiana
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. Often described in the literature as evergreen, Live Oaks shed leaves in spring just prior to the emergence of new foliage. Dryer, colder climates may contribute to greater, more seasonal defoliation.
Trees initially grow at a moderate rate that slows as trees begin to mature. Thick, darkly colored, vertically fissured bark is typical of maturing tree trunks. Younger trees have smoother bark. A dense canopy of deep green, leathery leaves, with a shiny surface and gray green undersides, generate shade, 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 in the Southeast 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. In spring small, brown, inconspicuous flowers appear that are wind pollinated. 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 or multi-trunk tree to add to our desert 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 distribution are greater than expected relative to 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 streetscape and parking lot planting, 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 until recently, have not been available. Pruning of maturing trees, to lift the scaffold branches, improves view lines, and pedestrian access without compromising canopy shade.
Southern Live Oak can be propagated from seed and cuttings. There have been many Live Oak hybrid cultivars and patents marketed. Many of these are not currently commercially available or are produced in limited quantities. Seed grown trees exhibit inconsistent horticultural traits, as would be expected from collected, naturally hybridized seed. Such selections can vary from massive spreading canopies to upright traffic/pedestrian friendly specimens. At present, seed propagated trees are the most readily available in Arizona wholesale production. AZT has begun an extensive screening and evaluation program to identify source trees to include in our ‘Variety AZT’ development program. It is our intention to bring a cloned Live Oak to the market within a few years that will have all the uniformity and superior horticultural properties you have come to expect from ‘Variety AZT.’
Interesting Facts
The durability of Live Oak is legendary. The hull of USS Constitution nicknamed “Old Ironsides,” was built of live oak and survived naval battle cannon fire during the War of 1812. The scientific name Quercus virginiana was officially named in 1768 and means “fine tree of Virginia”.
Maintenance Suggestions:
The acorns should be cleaned up from lawn or DG areas or they will sprout making a bed of saplings.
Aphids like Oaks. Their feeding can distort leaves and the sticky honeydew they excrete can lead to unsightly sooty mold on affected leaves. It is recommended to apply a dormant oil to Oaks to suffocate any Aphid eggs on the underside of the leaf. A systemic or contact insecticide can be applied for active infestation of aphids. Follow all label instruction when applying any pesticide.