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Ten Neat Things About Leaves
by Shauna Dobbie
by Dorothy Dobbie



The Local Gardener magazines, Ontario Gardener, Manitoba Gardener and Alberta Gardener, are published by Pegasus Publications Inc.

Drawing on her 30 years' experience as a senior executive in the magazine publishing industry, Dorothy launched Manitoba Gardener in 1998, initially running the business out of her home. Two years later, Dorothy's daughter Shauna, living in Ontario, jumped into the fray with Ontario Gardener. And two years after that, they started Alberta Gardener. Visit us at www.localgardener.net and register for our "Ten Neat things" newsletter. Watch Shaw TV for garden tips and Listen to CJOB for the Gardener Sundays at 9:08

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June 26, 2011

1. Leaves are lungs. Tiny openings on leaves, usually the underside, called "stomata" act as the "lungs" of plants. Here, through these pore-like openings, leaves take in carbon dioxide and exude oxygen, in the form of water vapour. The leaves of large plants such as trees produce some carbon dioxide and many tons of oxygen, cleaning the air and cooling it at the same time. An average large tree will produce as much oxygen in a season as 10 people inhale in a year. (Six molecules of water plus six molecules of carbon dioxide produce one molecule of sugar plus six molecules of oxygen.)

2. Knowing how to let go. Ever wonder why leaves fall in autumn? It's because they know how to let go. Triggered by light and temperature, plants manufacture a hormone that starts the process. Parenchyma cells, bounded by cork on both sides, form a layer known as the abscission layer, between leaf stem and twig. When conditions are right, this layer disconnects and the leaf drops. Why bother? Because it is "cheaper" in terms of energy, to slough off the old leaf than to try to protect it throughout cold weather.

3. Do plants sleep? Some plants do, or at least they go through a very similar process, dropping their leaves to a drooping position at night and raising them back to a horizontal position at dawn. This circadian pattern in plants is just one of many called, if you're curious, "nyctinasty". Other circadian rhythmic movements (nastic movements) include the closing of petals at darkness.

4. Hairy leaves. All leaves have hairs, as do most stems and flowers. The hairs are called trichomes and they are there for a purpose. On leaves, one of these is to act as an air conditioning unit for the plant - the hairier the plant, the more likely it can withstand great variances in temperature. The temperature at the surface of a hairy leaf can easily be 10 degrees warmer or cooler than the surrounding air.

5. The manufactory. Leaves are food factories for plants and are also home to many interesting little industries where a number of critical chemicals such as scents and volatile oils are manufactured. Leaves also produce toxins to deter insect and other herbivores.

6. Life begins here. Leaves on plants convert solar energy into chemical energy. Photosynthesis takes place when sunlight, water and carbon dioxide react to make glucose (sugar), oxygen and water. Without this, could any life exist?

7. Should you rake the leaves? No. Falling leaves return nutrition to the earth for the tree to recycle. When we neat-freak humans remove the leaves from under the tree, we are not only disturbing this natural cycle, we are depriving the tree of moisture-preserving mulch under its branches. Our tidiness efforts mean we have to expend more energy fertilizing and watering. Aren't we clever?

8. Some leaves are sharper than others. As in when leaves are needles. These leaves have found a different way to cope with drastic temperature change. They coat themselves with a waxy material to preserve moisture because the tree expires minute quantities of moisture all through the cold months and will even photosynthesize on warmer winter days. This is why it is so important to water your evergreens in fall. More urban evergreens die of drought than anything else, although we call it winter burn. Water your evergreens in fall!

9. Everyone loves salad. Well, at least, many do and not just humans. Small and large animals, insects and a host of fungus, bacteria and viruses do too. All that chlorophyll and the many chemicals manufactured in leaves are just too good to pass up. Think of the vitamins and minerals to be found in lettuces and spinach and other "leafy" green vegetables.

10. Speaking of salad . . . Dandelion leaves make the perfect salad addition because of their nutritional value. They are low in calories (24 .7 calories per cup); high in vitamin A (one cup gives you 112% of your daily needs), vitamin K (535% of daily needs) and vitamin C (32%), among a host of other wonderful properties. Try and pay a little respect to the humble dandelion and its leaves this spring when it visits your garden. And if you are tired of pulling dandelions (or dam-delions if you prefer), take the young leaves, butter some bread and make a delicious sandwich. That'll teach 'em!

-Shauna Dobbie

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