Treecology: 30 Activities and Observations for Exploring the World of Trees and Forests
Is It a Tree or a Shrub Trees and shrubs are large plants with hard woody trunks or stems Most have leafy branches or groups of leaves Size is generally the best way to tell the differ ence Shrubs usually grow less than 15 or 20 feet tall and often spread out close to the ground A mature fully grown tree can grow tall and straight to a height well over 20 feet Most trees have a single main trunk that branches out into many smaller branches and twigs But most shrubs have several woody stems rising right from the ground and then dividing into thinner branches Your school house apartment or nearby grocery store parking lot prob ably has several shrubs planted around it Here are some examples of shrubs e flowering lilac e blueberry bushes e azaleas e honeysuckle bushes e flowering forsythia e others hawthorn trees witch hazels and sumacs can often grow more than 15 feet tall so they are described in field guides as small trees or large shrubs A single plant family can include both trees and shrubs and even small woodland wildflowers It can be confusing to tell a tree from a shrub Some trees don’t grow tall because they are stunted by insect damage or poor growing conditions such as drought And many trees are pruned and trimmed so that they remain small Even though they could left This large sil ver maple planted as a shade tree is about 40 feet tall right Hawthorns are often described as shrubs or small trees because they usually grow less than 20 feet tall This downy haw thorn is in full bloom and about 12 feet tall 22
become much taller they are kept to the size of a shrub less than 20 feet tall Here are a few examples e Apple trees can grow more than 20 feet tall but in orchards they are usu ally pruned and trimmed to keep them smaller to make it easy to harvest ripe apples from them e Rhododendrons can grow well over 20 feet high in the wild but when planted in front of houses or public buildings they are kept trimmed to stay small e Hemlock trees growing naturally in the wild can grow 60 to 70 feet tall with some huge specimens reaching more than 100 feet But they are sometimes planted in rows near a building and trimmed and pruned to form a low hedge e A balsam fir can grow to be a large tree usually 50 to 60 feet tall But on a tree farm where Christmas trees are raised and grown they are trimmed so they can fit inside a house for the holidays Balsam firs in poor growing conditions may only grow a few feet tall On the coast of Newfoundland Canada balsam firs are stunted and windblown Even though they are mature trees they can’t grow very tall Groups of these stunted low trees are called tuckamore The tuckamore firs shown here are only about four feet tall Rhododendrons are often used for landscaping in front of homes and public build ings This rhody is kept pruned to maintain its shape and size Several different species and cultivated varieties are grown and used for planting 33
Parts of a Tree On the ground at the base of a tree you can often see the top surface of large roots spreading away from the trunk If you could dig up a large tree you would find that the big roots divide into smaller roots then into tiny rootlets and finally into tinier roots called root hairs You can sometimes see the entire root system of a tree when it has been blown down by a severe storm and the roots have been ripped out from the ground The trunk of most trees rises upward to spread out into large branches then smaller branches and then smaller and shorter twigs The twigs support buds and leaves The leafy top of a mature fully grown tree is called the crown The tops of many trees including maples birches oaks and ash trees are rounded An American elm has branches and a crown that grow in a fan or fountain shape A blue spruce often planted near homes and buildings has a American elms are found in most of the eastern and central United States and in parts of southern Canada This huge specimen is almost 100 feet tall The crown of this sugar maple is a beautiful sight in the fall when the leaves turn bright orange 44
triangular shape with a pointy top Balsam fir trees have a triangular shape too also called a pyramid shape Parts of a Leaf The flat part of a leaf is called the blade Some leaves have a very wide blade like those of the American sycamore which can be eight inches across Other leaves are quite narrow The leaf of a black willow tree is only about one-half inch wide Pine The parts of a leaf This is the leaf from a white birch also called a paper birch White birch is the state tree of New Hampshire and the official tree of the province of Saskatchewan Canada leaves are called needles because they are long and very thin Leaves are attached to twigs by a stem called a petiole PET-ee-ole The petiole on the leaves of elms chest nuts birches and oaks is fairly short But the petiole on the leaf of a bigtooth aspen or on most maples is long Look at the petiole on the leaf of any tree or shrub and observe how long it is Is the petiole shorter than the length of the leaf blade or is it longer than the leaf Bigtooth aspen cottonwoods and trembling aspen all have long flat petioles which cause the leaves to wiggle in a breeze Leaf Shapes and Designs Leaves have many different shapes Each species type of tree has its own leaf shape There are many different species of maples and birch trees and the leaves of each species have a distinct shape and size Leaves can be long and narrow like those of willows They can be oval like those of cherry and plum trees Some trees have leaves that come to a long point The leaves of a white oak have rounded finger like lobes The leaves of sassafras trees can Some different shapes of leaves Compound leaves Each is a single leaf divided into several leaflets Each leaflet is attached to the main petiole by a tiny stem The leaf on the left is from a white ash The leaf on the right is from a shagbark hickory Walnut trees and locust trees also have compound leaves 55
