The Garden Guru: Ode to the oak

Posted Monday, Sep. 30, 2013  comments  Print Reprints
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Live oaks are the oldest trees in Texas. Estimates have them at 1,000 years and older. Their trunks are the largest of any tree in our state. The circumference of the Goose Island Oak’s trunk is more than 35 feet, for a diameter sprawling beyond 11 feet. Its canopy spreads to almost 90 feet, yet the tree is only 44 feet tall. To locals around Rockport, it’s known simply as “The Big Tree,” and with merit. That baby is huge, and it has seen its share of hurricanes, droughts, pirates and wars. Whooping cranes overwinter nearby. Lotsa history in that tree!

Arguably the most famous tree in Texas is also a live oak, known to Texas history as the Treaty Oak in Austin. It, too, is many hundreds of years old, and it is credited with being the site of the signing of the first treaty between American Indians and settlers led by Stephen F. Austin. According to TexasEscapes.com, the tree was recognized as being “the most perfect specimen of a North American tree” in 1927, yet there it was, growing just feet south of Sixth Street near downtown Austin — not the place you’d expect to find such a tree.

That was where a horrible vandal found his way to the base of the tree, armed with a barrel of powerful herbicide in the late 1980s. He poured the poison out in the dark of night, and the tree showed its toxic effects almost immediately. The Treaty Oak appeared to be doomed, but legions of arborists worked mightily to save it. Part of it was lost in spite of their efforts, but the rest still stands and continues to grow and reign over its domain.

If you think about iconic tree species of the Lone Star State, you might think first of pecans. The pecan is, after all, our official state tree. But let your mind drift to the hundreds of paintings of bluebonnets you’ve seen over the years, and they’re almost always amid Texas Hill Country live oaks. (Curious, isn’t it, that this glorious species of Texas carries the name of another state far away? Live oaks are botanically identified as Quercus virginiana. I guess Gov. Hogg and his cronies felt the pecan to be a more loyal candidate. But it is Carya illinoinensis!)

In fact, if you think about where live oaks are native, it will validate their significance to Texas. You’ll find them in the salty marshes along the Gulf Coast, up through the Hill Country and all the way into Tarrant County.

That’s part of the reason most of our state’s most prestigious landscapes feature live oaks. The campuses of TCU, SMU and Baylor; the Battle Oaks of the University of Texas at Austin; the Century Tree of Texas A&M; that majestic live oak on the northwest corner of the Alamo, transplanted there almost 100 years ago — the list goes on and on and on.

Still, there are those who shy away from live oaks because they think they’re slow-growing. “I want a shade tree in my lifetime,” they say. “I don’t have enough years to wait on an oak.” Well, gardener, that’s very short-sighted. Given the same normal care you would be giving to some hurtling racehorse of a fast tree, a live oak will grow two-thirds as quickly, yet will live 30 or 40 times longer, and with dignity and elegance and far fewer problems.

Live oaks are an investment you’ll get to watch and enjoy, taking pride that you’ve planted something that will be appreciated for generations. If you want shade several years quicker, just start with a larger tree at the outset. Nurseries offer them in all sizes, from 5-gallon pots up to plants with soil balls 6 or 8 feet in diameter.

How best can you use a live oak in your landscape? First, be sure you have enough room. Give it at least 30 or 35 feet from the house and from all other trees. Know that the tree will eventually cast shade over much of your yard, and that you’ll be forced to change over from turfgrass to groundcover as its spreading branches turn down toward the soil. Know that it’s going to produce large buttressing surface roots that almost mirror the size of those spreading branches. That’s part of the grace of this glorious evergreen, but those powerful roots can also work against you if you plant a live oak too near a walk or driveway.

As good as they are, there are a few downsides to live oaks in landscapes. Since they’re evergreens, they can be hurt by wintery blasts. Their wood is unusually strong, but hundred-year ice storms can coat the branches with hundreds of pounds of ice, and that can cause them to snap. If you have a big live oak, you might want to discuss this concern with a certified arborist, to see if there are precautions you could be taking.

Live oaks also have a few minor insect issues known collectively as “galls.” The adult female of a species lays her eggs in the leaf or twig tissues, and the plant responds by forming woody oak galls or wooly oak galls around them. There is basically no harm, and no call to action.

Oak wilt is a different story. It’s a fungal disease that has killed many live oaks in the Hill Country and even into DFW. However, arborists can help you keep your tree healthy, and since every tree species has one or more problems of equal concern, there’s no reason to be leery of live oaks.

Fall is a great time to plant any new tree, and nurseries are well-stocked with live oaks. Growers even offer special selections of improved types. This would be a good weekend to go shopping.

Neil Sperry publishes “Gardens” magazine and hosts “Texas Gardening” from 8 to 10 a.m. Sunday on WBAP AM/FM. Reach him during those hours at 800-288-9227.

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