CEU Series: Tree Growth And Deterioration

Trees speak to me. I see how they grip the ground with a strong embrace. They stretch and ache, always upward. They exhale life-giving oxygen. Their leaves or needles fall timely and gracefully to nourish the soil. They travel around the sun with us, in life and death providing shade, protection, and structure. Many take them for granted, but a few of us may choose to study them in appreciation of their service to our human species.

To understand a pesticide or chemical affect on a tree or its wood, it is important to understand the growth and deterioration process. Whether it is a herbicide, insecticide, fungicide or preservative, knowing about the cell structure of trees will help in good decisions making for pest control operations.

Tree growth is what makes wood one of our most valuable natural resources. As a building material, only wood is a sustainable, renewable resource. Using water and nutrients from the air and soil, trees build wood. Photosynthesis is the process. Tree roots move water and nutrients from the soil to the leaves through hollow cells in the xylem or sapwood. Tree leaves absorb carbon dioxide from the air, using chlorophyll and sunlight to make sugary food for the tree. These sugary solutions manufactured by the leaves are moved through phloem in the inner bark to the growth areas of the tree, such as the tips of branches and roots and the trunk. The trunk hosts the cambium, a layer of reproductive cells found between the inner bark and the sapwood.

Water and nutrients up = xylem

Sugary solutions down = phloem

This narrow cambium layer does the work of making wood, creating new sapwood cells toward the inside and new inner bark cells to the outside, responsible for the tree’s growth in diameter. As the tree grows, older phloem cells are pushed out, die, and become part of the outer protective layer of trees called bark. Bark serves as the skin of the tree, protecting tender cells near the cambium from attack by insects, animals, birds, fungi, cold, wind, or fire.

The wood of the tree is the xylem, and includes both the sapwood and heartwood. The heartwood is darker colored dead xylem cells, providing the strength of the tree.

As the circumference of the tree grows, the thin ring of cambium grows equally. Climatic conditions affect the growth of cells; near the tropics, the growth in nearly constant. In temperate areas, the wood cells grow quickly in spring and slow in the fall. This pattern of fast/slow growth of cells gives trees the distinctive annual rings; thin walled cells in spring, thick walled in fall.

The function of these cells is critical to chemical control and preservation. To kill unwanted invasive tree species (preserving space for the desirable trees) a cut-stump or girdle herbicide application works because the phoem cells transport the herbicide down to kill the roots. Herbicides applied just inside the bark provide the best control. An injection of a systemic insecticide, alternatively, needs to reach into the inner living xylem cells to move up throughout the tree. Preservatives for wood will only penetrate effectively if the outer cells are permeable, influenced by the type of cells, pits, ray cells, and presence of extractives.

Comments (3)

Tina Kahn (Tue Apr 16 11:18:18 2013)

Hello - I took Series 43 test on Tree Growth and Deterioration on 2/21/13 - I haven't recieved the Record of Attendance Sheet - would it be possible to email it as an attachment so that I can print it to be sent to FNGLA? This is the last of my required CEU's. Thank you - Tina Kahn 727-439-2697

Marianella Hernandez (Wed Dec 12 19:36:36 2012)

Hi, I have submit a test # 43 the last week, until today I haven't received any electronic certificate . I will appreciate if you send it as soon as possible to my e-mail. My License # PV39137

Joseph Adams (Wed Oct 31 14:38:46 2012)

I have submitted test # 43 quiz for grading. The site would only allow submission with a fax number, however, my fax will not work without a phone call first. Please submit certificate electronically, if possible. Thanks, JNA

Understanding the natural process of a tree's life cycle will help cut wood worries. Earn one Core CEU credit. Take Series 43 test now.

Water and nutrients up = xylem

Sugary solutions down = phloem