The world is full of flowers. They grow on every continent. They grow in the hottest, driest deserts and in the frozen Arctic . People grow them year-round. No matter where you live, you can usually see a flower somewhere.
What exactly is a flower? What’s it for?
Plants make flowers because flowers make seeds. Seeds are a way many plants reproduce, or make new plants. So, flowers help plants reproduce themselves. Flowers also make fruit as part of the reproduction process. Once the seeds start to ripen, a part of the flower grows around them. This is what fruit is. Fruit feeds, protects, and helps to spread a plant’s seeds. So, the next time you eat an apple or pear or peach, think about this: what you’re eating came from a flower. In fact, without flowers, there would be no fruit at all!
ALL SHAPES AND SIZES
Flowers come in all shapes and sizes. Some are so small you can barely see them. A type of duckweed called Wolffia makes a flower so small that a dozen blooms could fit on the head of a pin. Other flowers are enormous. A flower in Southeast Asia called Rafflesia can grow to 3 feet (about 1 meter) wide.
WHEN DO PLANTS MAKE FLOWERS?
Some plants make flowers year after year. Others only bloom every two years. And some flowering plants live only one season. New ones must grow from seeds every year. Most flowers wait for a certain time of year or certain conditions to bloom. The morning glory opens with the sunrise. Yucca flowers open at sunset. The night-blooming cereus opens only at night. Sometimes a bare desert can burst suddenly into colorful flowers after a single big rain. The flowers wait for just the right conditions and then bloom quickly.
HOW DO FLOWERS MAKE SEEDS?
Seeds only develop after they are fertilized by pollen. So to make seeds, flowers must first make a powdery substance called pollen. The pollen then has to be carried from one flower to another flower of the same type, or sometimes to a different part of the same flower. Once this happens, the seeds are fertilized. They can then begin to mature.
For flowers to move the pollen, they need help. In many plants, wind or water spreads the pollen. But most of the help comes from insects such as bees and butterflies, or other animals such as bats. These creatures all feed on flowers. When they do, they move the pollen.
Maybe you’ve seen a honey bee working in a flower? The bee is collecting pollen or maybe the flower’s sweet nectar. Bees use pollen to feed young bees. They use nectar to make honey. While the bee works, pollen sticks to its body. When the bee moves to a new flower, some of the pollen falls off on the new flower.
HOW PEOPLE USE FLOWERS
People prize flowers for their beauty. We paint pictures of them and use them for decorations. We give them as signs of friendship, love, or remembrance. Some flowers are important in religious ceremonies. Others are considered sacred by some groups. Flowers have many practical uses. Lavender is a flower used to make perfume. Witch hazel is used in cosmetics. A flower called the rosy periwinkle is used to make medicine to fight leukemia, a blood disease.
Like other animals, people even eat some kinds of flowers! You probably have. Broccoli and cauliflower are flowers that haven’t quite opened yet. Some people add flower petals to salads. Roses are used to make tea or jelly. Dandelions can be used to make wine. But you don’t have to use flowers to enjoy them. Flowers are sometimes nice just for their shape and color or for their sweet smell.
Can you imagine growing taller than a ten-story building? How about living to be 4,000 years old? Ever grow 2 inches (5 centimeters) in one day? Such things are not likely to happen in your life. But life would be very different if you were a tree!
WHAT IS A TREE?
Trees are plants. They are usually tall and have a main stem called a trunk. They come in many colors and sizes. The tallest trees are the tallest plants on Earth. Some trees can grow as tall as a soccer field is long. Trees grow everywhere on Earth, except for deserts at the equator and the North and South poles.
WHY ARE TREES SO IMPORTANT?
Trees provide protection from the wind. Tree roots spread through the ground and keep wind and rain from washing soil away. Trees and forests store water during times of drought and suck up extra water when it rains a lot. Without forests, areas would flood more often. Trees provide places for animals and other plants to live. Trees help keep Earth the right temperature for life. Trees help create the air we breathe by turning the gas carbon dioxide into oxygen.
Aside from all that, many people rely on trees to earn their livings. Wood from trees builds houses. We eat fruits and nuts that grow on trees. Olive oil and coconut oil come from trees. Corks, spices, and maple syrup are tree products. Trees are even used to make some medicines that fight cancer and other diseases.
PARTS OF A TREE
The five major parts of a tree are roots, trunk, leaves, flowers, and seeds. All these parts work together to help a tree live, grow, and produce new trees.
ROOTS
What do all those roots do underground? Roots hold the tree in place. They also have tiny, little hairs that absorb water and minerals from the soil. The tree needs water and minerals to live and grow. Roots are always growing. In some trees, roots spread farther underground than the tree spreads up in the air!
TRUNK
How does the trunk help the tree? A tree’s trunk is covered by bark, which protects the tree. Openings in the bark let air get in and out of the trunk. Bark is made of mostly dead cells. Bark can be a different color and thickness on different trees. Scientists often use bark to help tell types of trees apart. Under the bark, a tree’s trunk moves water and minerals around to parts of the tree that need them. As the tree grows, cells inside the trunk are continually dying and being replaced. The cells closer to the center of the trunk die. New cells grow around them and make the trunk thicker. This growth leaves behind rings in the tree trunk. You can tell how long a tree lived by cutting through the trunk and counting these rings!
LEAVES
Why are leaves green? Leaves contain a chemical called chlorophyll. Chlorophyll is green. Chlorophyll combines with carbon dioxide from the air, water in the leaf, and light from the Sun to make food for the tree. This food provides energy for the tree to grow. Water constantly leaks out of a tree into the air through its leaves. This evaporating water keeps the tree cool on hot days just like evaporating sweat keeps you cool. The tree’s roots draw water from the ground to replace what is lost. The trunk carries the water to the leaves. It’s important that water keep moving through a tree to prevent it from overheating.
