John Young, Owings, Allen D.
Sustainable Landscape News Distributed 11/21/08
By LSU AgCenter Horticulturists
Southern live oaks, known by the scientific name Quercus virginiana, are one of the most popular trees found in Louisiana landscapes. They certainly are considered to be a signature tree in many public places across the state and are widely used in home landscapes.
We also regularly hear news stories about old live oaks when development threatens individual trees. You can register and name live oaks that fit the size requirement with the Live Oak Society operated by the Louisiana Garden Club Federation. Live oaks definitely are one of Louisiana’s most sustainable trees.
Fall and winter are a great times to care and maintain your live oak trees. From selecting trees at the garden center, to planting, pruning and fertilizing, November through February is the time for live oak maintenance
All trees do great when planted in the fall and winter months, and live oaks are no exception. Live oaks are grown at many wholesale nurseries in Louisiana and are one of the most sold trees at garden centers.
Select trees with a well-developed central leader system. Be sure the trees were properly pruned at the nursery. Proper pruning at a young age is important for long-term tree health and shape.
Most home gardeners should select trees to plant growing in 3- to15-gallon containers, although you can purchase live oaks that are much larger. It is hard, however, for an average homeowner to handle planting trees larger than those growing in a 15-gallon container.
When planting, be sure to follow LSU AgCenter tree planting recommendations. Dig the planting hole the same depth as the root ball and two to three times as wide as the container in which the tree has been growing. Make the sides of the planting hole rough, not smooth. After removing the tree from the container and placing it in the hole, fill in around the roots with the same soil that was removed to create the hole. Do not amend this backfill soil with compost, pine bark, or similar materials. Trees establish best when amendments are not added to the backfill soil.
After the hole is filled in, water thoroughly to eliminate any air pockets and mulch around trees. The mulch should extend out at least as far as the edge of the hole, be no deeper than 2 inches and pulled back slightly from the base of the trunk.
Live oaks are an outstanding native tree, but they are very large, with a wide spread and low branches. Be sure to give your new live oak tree adequate room to grow. Most of the time, live oaks are now planted on 30- by 30-foot spacings. These intervals, however, are way too close. You also see live oaks planted on 60- by 60-foot spacings. These are better, but, ideally, live oaks need to be planted on 90-foot centers.
Unfortunately, live oaks are commonly planted in average urban lots that have no room for a tree this large. Also, live oaks are routinely planted between streets and sidewalks. Once again, this is the wrong tree in the wrong place. Be sure to plant live oaks where they have room to grow and do what they want to do.
Fertilizing live oaks is not recommended the first year after planting. You can start a fertilization program thereafter. The first year, the emphasis on the tree should be directed to the root system. Nitrogen fertilizer applications during this time favors shoot growth at the expense of root growth. Mature live oaks generally do not need fertilization. However, you can examine the new growth to see if it might be beneficial.
If new growth in spring is significant, fertilization is not needed. If not much new growth or no new growth is obvious, fertilization or other cultural practices may need to be implemented. In that case, a licensed tree care professional should examine your mature live oak trees to determine a course of action.
Live oak trees originating from seed sources in Louisiana will grow best in Louisiana. In other words, do not expect acorns obtained from a tree in Texas to produce trees that grow as well Louisiana. An excellent seed grown variety of live oak, called Orange Island, is produced from locally gathered acorns by Live Oak Gardens in New Iberia. It grows vigorously and is generally superior to other seed-grown live oaks.
Wholesale growers also now have access to the Cathedral and Highrise varieties. These varieties are asexually propagated from stem cuttings. As a result, the trees within each variety are similar in growth habit and size providing a very uniform look in a landscape planting. These are not being grown in large numbers in Louisiana, and at this time are limited in availability to home gardeners.
Southern live oak trees are planted as a perimeter in the landscape at LaHouse. Come to LaHouse in Baton Rouge to see sustainable landscape practices in action. The home and landscape resource center is located near the intersection of Burbank Drive and Nicholson Drive (La. Highway 30) in Baton Rouge across the street from the new LSU baseball stadium. For more information, go to www.louisianahouse.org and www.lsuagcenter.com/lyn.
Dan Gill at (225) 578-2222 or firstname.lastname@example.org
Allen D. Owings at (985) 543-4125 or email@example.com
John Young at (225) 578-2415 or (225) 578-2222 or JoYoung@agcenter.lsu.edu
Editor: Mark Claesgens at (225) 578-2939 or firstname.lastname@example.org