10 Facts on Leaves

A gardener has to spend a lot of time in their gardens looking over the health of their plants. Much of this observation is done by closely examining the plant's leaves, also known as the foliage. Leaves can be wilted, scorched, burned, eaten, moldy, and much more. Most of these symptoms are caused by various diseases and pests. Here are some fun facts about leaves.

Many Types of Leaves

With the exception of flowers, leaves are the most morphologically diverse plant structures. We’d need a lot more than 10 facts to do them justice.

Many Names for Leaves

There are more than 60 botanical terms used to describe the structures and forms of leaves.

Not Too Many Parts, Though

Leaves are plant organs, usually having two basic parts: the blade (lamina) and the petiole, which is the short “stem” that attaches a leaf to the rest of the plant.

It's All About Photosynthesis

Most photosynthesis takes place in the leaves, although some does occur in green stems.

It Starts on the Surface

The principle site of photosynthesis in leaves is inside the mesophyll, a layer of spongy tissue located just below the epidermis on the upper leaf surface.

Some Plants Don't Have Leaves

Mosses and liverworts look like they have leaves, but they don’t. A true leaf is composed of more than one layer of cells, including a cuticle (waxy outer covering), stomata (for gas exchange), xylem (water-conducting tissue), phloem (sap-conducting tissue) and internal air spaces.

True Leaves Don't Appear Right Away

The first leaves that appear on a plant after germination are called cotyledons. They all look about the same and do not look like the true leaves of a plant that develop later.

Narrow and Broad Distinctions

Monocots, which are plants with narrow, sword-like leaves such as grasses, grains, onions, tulips and bananas, produce one cotyledon. Dicots, which are broad-leafed plants like tomatoes, beans, lettuce and oak trees, produce two cotyledons upon germination.

Pine Needles are Leaves, Too!

Do conifers have leaves? Yes, needles are leaves that are specialized to resist desiccation.

A Cactus Could be Covered in Leaves

Yes, a cactus can have leaves too, but they are either microscopic or soon fall off after a short growth spurt in the spring.