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Leaf-Out Update: March 20, 1998

Today's Report Includes

Leaf-Out News
According to reports from our southern observers, spring hasn't progressed far over the past 2 weeks.

"As of today, the redbuds have not leafed-out. The buds are really getting big, but no leaves have appeared," reported David Palmer yesterday from the northern Texas town of McKinney (33.19 N, -96.68W). Watch for spring to move at faster pace as last week's cool temperatures are replaced by more spring-like conditions. leafout-redbud_map032098.gif

Click to see the current redbud leaf-out map Click to see the current dogwood leaf-out map

Help Track Spring
We hope you'll help us measure spring's northward journey by reporting when leaves emerge on your trees. When the leaves on your adopted tree are the size of a quarter (our definition of "leaf-out"), report to Journey North. Simply press the Owl Button and a Field Data Form will appear.
Discussion of Challenge Question #2
"Are dogwood flowers actually leaves or flowers?"

"Neither, they're actually bracts," replied Laura Staley of Kennewick, WA.

"The flowers on a dogwood are small and green," say students at St. John the Baptist Schools in Milwaukee, OR. "On the outside of the flowers are white bracts that many people think are flowers. We found this information in our enclyclopedia and in our dictionary. (ekennedy@teleport.com)

If your adopted tree is a dogwood, be sure to report leaves of the green kind!

Click to see full Maple Sugaring map
Maple Sugaring Update
From Maine to Minnesota, 30 sites now report to have tapped their sugar maples trees. How long after the sap begins to flow do you suppose leaf-out will occur?

Here are the locations of the most recent trees tapped:

How Old is Your Tree?
Knowing the age of a tree can help us all appreciate trees. Normally a forester will take a core-boring into a tree and count the annual rings if he or she would like to know the age of a tree. Unfortunately, this method can be very harmful to a tree, since the boring will leave a hole in the tree which insects may enter. The method for aging trees described below was developed by the International Society of Arboriculture. This method will give a good estimate of a tree's age. After you've determined the age of your tree,

Try This!

  • Draw an Age ring diagram of your tree.
  • Mark the rings of your tree by writing in the year on various lines (i.e.mark the lines corresponding to the decades...1990, 1980, 1970, etc.)
  • Find years of historic importance--both nationally and locally in your own city--and mark it on your diagram next to the year it occurred.
  • Students could ask their parents for the year of a significant event in their past, or for a significant event that occurred in a specific year plotted on your tree line.
  • Next, students could ask their grandparents for the year of a significant event in their past, or for a significant event that occurred in a specific year plotted on your tree line.
  • How does your rate of growth (human growth) compare to the rate and direction of tree growth? What factors can influence both of these rates?

How to Estimate Age:

1. Students should work in groups of 3 or 4.

2. Determine the species of your tree. Make sure it is on the list below.

3. With a tape measure, find the circumference of the tree (in inches) 4 1/2 feet above the ground.

4. Determine the diameter of your tree.

Diameter = Circumference divided by 3.14 (pi)

5. Calculate the age of the tree.

Formula: Diameter X Growth Factor

Tree Species

Growth Factor

Tree Species

Growth Factor

Red Maple


White Oak


Silver Maple


Red Oak


Sugar Maple


Pin Oak


River Birch


Linden or Basswood


White Birch


American Elm


Shagbark Hickory




Green Ash




Black Walnut




Black Cherry






Lesson provided by Jim Gilbert & Cathie Plaehn
Drawn from the
International Society of Arboriculture

Jim Skiera of the International Society of Arboriculture provided these important notes about the accuracy of this method:

"The figures provided for in your chart are taken for forest grown trees. In a landacape setting, where trees are being provided additional care, these figures probably would need to be adjusted to get an accurate estimate. Growth has to do with the location of the tree and the type of care it has received. Trees in the landacpe tend to grow faster and develop wider growth rings more quickly because the competition from other trees is usually less and the additional water and fertilizer that is provided by the home owner will also increase growth.

"If you are working on school projects you may also want to visit the treetures website at www.treetures.org or the ISA website at www.ag.uiuc.edu/~isa and look in the publications area under consumer tree care information."

How Tall is Your Tree?
As you continue to look up at your tree and wait for its leaves to appear, think about this question:

Challenge Question #4
"Without climbing to the top with a measuring tape, how could you estimate the height of your tree?"

In our April 2nd update we'll share a fun method used by Jim Gilbert and Cathie Plaehn.

How to Respond to Today's Challenge Questions
1. Address an e-mail message to: jn-challenge-leaf@learner.org
2. In the Subject Line of your message write: Challenge Question # 2 (or #3)
3. In the body of the message, give your answer to ONE of the questions above.

The Next Leaf-Out Update will Be Posted March 20, 1998.

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