Sunday, October 28, 2012

A Tree Grows in Texas

Last week I had an opportunity to visit the Lady Bird Johnson Wildflower Center in Austin, Texas, and got to see how folks garden in a very different climate.

Water collection and retention are big deals in drought-prone Texas: a striking feature of the Wildflower Center is the huge stone cistern that looms over the entrance. In the three days I spent in Texas with the Garden Club of America, much of what I know about sustainable landscaping was confirmed in a site where gardeners have to work much harder than we do to keep things green.

Bill Neiman of Native American Seed gave a talk on his efforts to hoard water, and showed spectacular slides of his half-acre lawn re-engineered with rain gardens and native grasses and plants. Austin may have three totally dry months, followed by a massive gully-washer of a storm – a scenario not entirely unknown these days in our area.

The Wildflower Center, having mastered the art of wildflower preservation and now a research arm of the University of Texas, is branching out – literally – by adding an arboretum to its newly expanded campus.

Philip Shulze, an arborist on staff, talked to my group about the challenges of planting trees in the rocky, alkaline soil of central Texas. He also planted a young maple tree to show us best practices, all of which are applicable in Connecticut.

In contrast to what many people think they know about tree planting, Philip and his assistant had selected a small maple tree in a five-gallon pot as the likeliest to survive in harsh conditions. Further surprising the group, he had dug a hole just as deep as the potted root ball, and twice as wide.

After watering the tree well, he removed it from its pot to show us how compacted the roots of the tree had become. One of the big advantages of selecting a potted tree, rather than a larger one that has been balled and burlapped is that you can examine the tree’s root ball and loosen its roots before planting. In the case of this small maple, the potting soil was mostly knocked loose before planting, as he spread the roots out and revealed exactly where the trunk flared out into the upper roots.

This is important, because the tree should be planted with those roots just barely covered by soil. Planting it lower makes the tree roots work hard to get the water and air that they need, and the tree often grows new “adventitious” roots which frequently wrap around the trunk, eventually girdling the young tree.

Before planting the tree, Philip took up a pickaxe and loosened the soil around the edge of the planting hole. Particularly apt for clay soils, this practice allows the young roots a better chance to grow from the loose soil it’s planted in, out into the surrounding, undisturbed soil.

Settling the young tree in the center of the hole, Philip explained that he does not use soil amendments when he plants trees: if the soil added to the hole is much looser and more nutrient-rich than the surrounding soil, the tree may never send its roots out where it should, again encouraging root growth that wraps around inside the hole.

Once the soil was replaced around the tree and firmed slightly, he poured about five gallons of water onto the tree’s roots. Gently, so as not to crush the young roots, he tamped down the soil so that no air pockets remained, then very lightly covered the area with a loose mulch. The mulch was mounded a little around the edge of the hole, creating a berm to hold moisture over the newly-planted roots.

And that was it – no pruning, no volcano of mulch, no stakes and no ropes. Just a happy-looking little tree, waiting for its next watering. And that’s the most important piece: for the next two growing seasons, the tree needs to receive about ten gallons of water a week. After that, the tree should be watered any time there is a prolonged dry spell.

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