MILWAUKEE - If you're heading to a Christmas tree farm - a traditional holiday outing for many families - heed the research of tree scientist Les Werner and his students: Keep that fresh-cut fir or pine watered once you get it home, and you'll be rewarded with fewer needles to sweep off the floor.

Werner for years thought that keeping water in the Christmas tree stand was pointless.

The associate professor of forestry never watered his own family's Christmas trees because, he reasoned, trees stop photosynthesizing when they're cut from their root systems. Unconvinced, his wife would water the tree anyway when Werner wasn't looking.

Universities debate, research, and answer real-world questions. So, who better to explore the physiology of the common Christmas tree than a scientist at the Stevens Point, Wis., university, which has the nation's largest undergraduate program in natural resources?

"For years, I asked plant physiologists around the country: 'Do you water your Christmas tree?' " Werner said. "Most of them, like me, said they didn't. But their wives would water the tree behind their back."

Werner and two students decided to document moisture loss in cut Christmas trees that were watered vs. those that were not watered. A tree farm donated 54 fresh-cut trees of four different species for a four-week study.

They set out to study whether loss of a root system, combined with an unnatural indoor environment, would severely limit a cut Christmas tree's biological functions, including water uptake, photosynthesis, and transpiration.

Would water taken up through a cut-conifer's conductive tissues be sufficient to replace water lost by the foliage? Would watering the tree affect needle moisture and needle-retention rates?

The research proved a direct correlation between needle retention and moisture content, Werner said. Needle moisture in unwatered trees diminished significantly over time, while watered trees maintained needle moisture.

Based on the research, Werner advises consumers to buy as fresh a tree as they can, or to cut their own tree, if they don't enjoy sweeping needles.

"Then make sure you give it plenty of water for at least the first week and a half, when it takes up the most water," he said.

After about a week, the tree will respond to the cut on its trunk by excreting resin, which naturally seals the "wound." Then it no longer takes up as much water.

Cutting a few inches off the trunk before putting it in the stand opens the capillaries to allow the tree to draw moisture up the trunk and into the needles, said Werner. The water level should be two to three inches above the cut.

The study also determined which tree variety best retained needles.

The researchers determined that Fraser firs are best for water uptake, sap flow, and needle retention, followed by Balsam fir, Scotch pine, and Black Hills spruce (a white spruce variant).

The research has since been incorporated into two forestry classes at the university.

Next, Werner wants to research whether the length of time in storage affects a Christmas tree's moisture content, and at what point loss of moisture significantly increases the risk of combustion.

First, he needs someone to donate $20,000 to buy a flammability chamber to answer the question: Under what conditions would a tree ignite?

Christmas trees are blamed for house fires every year, caused by faulty or exposed wiring on lights and by sparks from fireplaces.

The question of moisture loss over an extended time in storage would apply to the thousands of Christmas trees that are cut as early as the end of October to be trucked to commercial tree lots in time for Thanksgiving weekend shopping, Werner said.

Here's a little-known fact:

Many Christmas tree growers apply a "needle lock" compound to trees after they are cut to keep the needles from falling, Werner said. It's Elmer's Glue dissolved in water, often applied to longer needle trees such as Scotch pines.

"It dries clean and hard," he said, "and keeps the needles on the tree."

Buyers tend to be strongly attached to specific tree species, based on family tradition, said John DuPlissis, a state forestry specialist at the University of Wisconsin-Stevens Point.

DuPlissis writes a blog, "Stump the Forester," at fyi.uwex.edu/forestry/, in addition to teaching classes in the College of Natural Resources.

You can take perfect care of a tree once it's cut, and the needles still may dry out quickly if the tree was harvested during a dry fall, said DuPlissis. Fortunately, this fall was wet, so trees on the lots should be in good shape unless they were cut from an area with drought conditions, or the trees aren't properly stored to protect their moisture, he said.

For those who believe in adding sugar, aspirin, or vodka to the tree water, none of those so-called additives will help, Werner said.

"I would love to come up with an additive that works," he said. "Clean water still works the best."

Tannenbaum Tips

If you cut a tree at a farm, keep it fresh when you get it home by laying it on the ground out of the sun and wind until you are ready to put it in your house. Cover it to keep it cool and moist.

When you're ready to place it in a stand, cut one inch or more off the trunk. This will open the capillaries, allowing the tree to draw moisture up the trunk and into the needles.

Check your stand twice daily - especially in the first week - and add water as necessary.

An eight-foot tree can often "drink" a gallon

of water per day.

Choose the location of your tree carefully. Do not place it near a heat source such as a heat register, fireplace, or window where direct sunlight hits it.

Often, a tree obtained soon after its arrival on the retail lot will be very fresh because it was cut recently. Consumers should ask the retailer when he/she gets the trees: Are they delivered once at the beginning

of the season, or does he/she obtain several shipments during the season?

Do a freshness test on the trees. Green needles on fresh trees break crisply when bent sharply with the fingers - much like a fresh carrot. Pines have different indicators because of the fibrous nature of their needles compared to firs. The needles on fresh pines do not break, unless they are very dry.

Look for other indicators of dryness or deterioration: excessive needle loss, discolored foliage, musty odor, needle pliability, and wrinkled bark. A

good rule of thumb is,

when in doubt about

the freshness of a tree, select another one.

If none of the trees

on the lot looks fresh,

go to another lot.

SOURCE: Wisconsin Christmas Tree Producers Association

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