Terrific Trees

Trees are all around us. These complex plants have adapted to stand tall and strong, and they are essential to the world around them. There are over 70,000 species of trees on Earth; each species has amazing adaptations and unique stories hidden within.  

Parts of Trees

A tree is a tall plant with a single trunk and branches that support its leaves. Trees are easily recognized by their height, as they are usually the tallest plants. Like all plants, they have roots which anchor them in the ground and absorb water, a stem which is called the trunk, leaves which absorb sunlight and exchange air, and seeds which help to produce new trees. Some of them even have flowers and fruits.

Trees are different from other plants because of their hard stems and branches. Rather than the fleshy green stems of many flowering plants, tree trunks are armored with bark to help strengthen and protect the tree. As the tree ages, the trunk and branches thicken. This is called secondary growth and the reason why trees can grow so tall and stretch their branches so wide.

Level up! As you can see on the tree cookie diagram below, the trunk consists of six main parts. All plants have a phloem and xylem within their stem to move water and sugar up and down the plant. The xylem moves water from the roots to the leaves, and phloem moves sugar from the leaves to the roots to be stored. The core of the trunk is called the pith. It is the oldest part of the trunk and stores lots of nutrients for the tree. Heartwood is the hard, dead tissue surrounding the pith. Its role is to provide structural support. The lighter wood after heartwood is called sapwood; this is where the xylem is located. Next is the layer on the outside rim of the xylem called the cambium. The cambium is a layer of tissue that creates the xylem and phloem. It is located right in between them and adds new growth to each of these layers over time. The last two layers are the phloem and then the outer bark which protects the trees from the environment.