Horticultural Consultant Tim Thornhill dispelled a number of myths regarding tree care and preservation at a recent education session at the annual Green Industry Expo.		Two huge live oaks (Quercus virginiana) being moved for Walt Disney World , Orlando, FL.

Watering a tree three times a day with the same amount of water as when watered once a day has resulted in as much as 50% more growth in some studies . This was one of a multitude of inside tips on saving, moving, and caring for trees that expert Tim Thornhill gave at a Sunday session sponsored by the Professional Grounds Management Society and held at this year's Green Industry Expo in Baltimore, Maryland.

"Imagine yourself in a concrete vault for a week," he illustrated. "and you had enough water to last the week. Would you drink it all at once, or a little each day? Well likewise for a tree."

Thornhill, respected as a champion of trees in the industry and known for his work at DisneyWorld transplanting and caring for trees, shared a number of other anecdotes and challenged many myths prevalent in the tree industry.

Mulching can damage a tree's root system
One such myth was the wisdom of mulching trees. "Too much mulch has killed many trees," he said. "Mulch turns to soil and eventually the roots begin to grow upward into the soil and they soon lose their initial direction." Roots grow naturally in directions away from the tree. But with soil gradually piled on top, the roots twist, become deformed and confused. "Trees suffer immensely," he said, when this occurs. Moisture and air are both restricted. Most specifications call for 4-6 inches, he recommends 1-2". If re-mulching annually is required for aesthetics, remove old mulch before adding more.

The best "mulch" Thornhill recommends is pine straw, which will keep the sun off the soil, maintain a slow temperature change, and help retain moisture. Small stones or gravel also works . "And it takes a long, long time to turn to soil," he added.

It is often best to move trees in the summer, while in full leaf
Another popular notion Thornhill dispelled was when to move trees. Many believed trees were moved best when dormant. But Thornhill said, "The best months are July and August when the tree is fully leafed and growing tips have hardened-off." he said. "You'll get the most immediate root regeneration this way." He explained that after a tree is completely leafed out, it will be able to put more of its energy into root regeneration into late autumn. However, trees moved in this way will require intensive irrigation monitoring and aftercare until established. If an intensive after-care program is not part of the plan stick to dormant transplanting.

Trees should be planted three to four inches above grade
Often, planting specifications call for newly installed trees to be planted at finished grade. Thornhill aggressively refutes this practice and says that three to four inches above grade is best. "A tree will almost always settle once it has been planted and even at three or four inches above grade initially, the tree will eventually settle to grade," he explained, "while I've never seen one planted too deeply rise later on." He also pointed out how common it is to find newly installed plants that had settled below grade, only to have the resulting trough filled up with a suffocating mulch.

Fertilizer best applied on top of ground
On the topic of fertilizer, he said injection fertilization is good, if for no other reason, because the tree is getting some moisture. Generally, a probe is inserted into the soil about 6-10 inches and then a fertilizer solution is pumped in. "Roots are found in the top few inches of soil," he explained. "Such a probe often misses most of the root system."Top-drenching is therefore my preference," he said.

Gravel doesn't help if drainage isn't already good
Another misconception about putting gravel in the bottom of a tree hole. Putting gravel in to help drainage is futile if there isn't already good drainage, according to Thornhill. "The gravel is really for horizontal draining," he said. "If there is no place for the water to go, don't bother." He suggested putting in a drain or even a vertical shaft through which water can be pumped out if need be.

A good, easy way to tell if the soil is going to drain properly, he noted is to simply to dig a hole and fill it with water. "If the water is still there the next day," he said, "the drainage is not good."

Earthworms in the hole is a good trick to remember Another trick Thornhill shared with the audience is to toss a few earthworms into the hole before planting the tree. "The earthworms are amazing," he said. Or make several vertical holes around the tree and put earthworms in those, he said. They will aerate the soil naturally like no machine yet invented.

Thornhill also stressed the importance of watering. He showed graphic proof in a slide of a row of shrubs. One end had shrubs twice as large as the rest of the row. It was located where a man often washed his boat and, thus, the large end of the shrub was getting this extra runoff water.

Tensiometer is best method of knowing when to apply water
He also noted it was important to know exactly when a tree needs watering. And, he said, the best way he knows to accurately tell is with a tensiometer. "You just insert the probe into the soil and it will tell you exactly how much energy the plant must expend to obtain it's needed moisture," he said.

Fences work well in protecting trees during construction
Protection of trees during construction is more important today than ever. "There are a number of ways to protect the trees," he said. "Fencing, plywood, or moving the tree out of the way." Another very effective measure is to include in a contractor's contract a clause that there is a penalty of $10,000 if anyone crosses over a fence erected to protect the trees. "Someone just has to do it once," he said, "and everyone on the crew will be watching everyone else."

These fences, anything from a snow fence to plywood walls will work, will reduce the problem of soil compaction around a tree's roots. One of the most damaging practices is merely walking on the soil. Also, a frequent problem is construction workers parking their cars under trees to keep them in the shade. "This compaction can easily damage a tree since the most sensitive roots are right on the surface," he said.

Backfilling only couple inches can kill tree by blocking air and moisture
The fences also prevent another practice that is deadly to a tree-that of backfilling. Raising the level of grade around a tree just a few inches can kill it. Building a well around a tree works only to the extent that the tree is properly watered. Rarely is a well large enough to accommodate the entire root spread so that it wouldn't need the additional watering.

Sometimes, however, fences aren't enough and trees have to be moved in order to save them. This is what Thornhill is most famous for. Developers around the country call on him to move trees that most would think impossible. He made it sound easy as long as certain procedures were followed. "A tree is often better off after it is moved," he said. "In the wild it may be barely surviving. We move them to better locations, water them and care for them. They grow even better, possibly due to the rejuvenation effect of the root-pruning."

Follow certain precautions to successfully move a tree
When moving a tree, whatever size, he recommended:

• If you don't have the budget to do it right, don't do it.
• Hire an experienced big-tree-moving contractor.
• Constantly monitor soil moisture, and water tree as necessary.
• Contain the root ball in a number of materials including "saran wrap," fabric, or wood crating.
• Try to replicate the tree's microclimate during the move and in its new location.
• Do not fertilize with nitrogen before the move or within a year after the move.

Thornhill wrapped up the session by urging the attendees not to be afraid to move trees. It's easy if a few precautions are followed. The public relations value of saving trees by moving them is great. "You go from being a jerk for leveling everything to being a hero for saving it," he said.

For more information, Thornhill may be contacted by calling 888-257-1113.

Spring 2001

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