A garden riddle for the asphyxiated

For more articles by Larry Gnome, Please see the Perennial Article Index.

Ready for a riddle?

O.K., What's invisible, feeds your plants, fights off bugs, brushes off disease, helps your crop bring food and water up from the roots, keeps garden temperatures just right, and hauls away excess water? It has no batteries, no mechanical parts, and you'll never run out of it!

Of course we're talking about air! It's the most versatile, yet unappreciated, worker in the garden. When gardeners understand how many chores a little air can do, they can put it to better use to make their gardens healthier and more productive.

Let's start with air "feeding" plants. Everyone knows that plants grow from fertilizers, right? Guess again! Almost HALF the dry weight of plants is carbon, taken from air! Another 42% of your plants is oxygen! All those fertilizers you've been mixing and feeding to your crops? They only make up about 2% of your crop's dry weight! Considering air only has 300-400 parts per million of carbon dioxide (0.03%), we can conclude two things: plants are pretty good at grabbing CO2 from the air, and they can use all the fresh air they can get!

Air is your greatest ally in the war against bugs and disease! Moving air can blow insects off your crops, and interfere with their meal-times. Who can eat in a hurricane? Air movement also plays havoc with egg-laying and the growth of baby bugs in your garden. Bugs want still, moist air - and if they can't get it in your garden, they'll go somewhere else! This is one good reason why we emphasize good spacing between plants.

Air movement through the garden helps keep diseases in check, by keeping humidity levels from climbing to unhealthy levels. Diseases multiply quickly in still, moist air, and use any water on the leaf as an entry point to damage leaves.

Air fights disease in the root zone, too. The worst diseases need waterlogged conditions to multiply and attack roots - air is their poison! (talk about a safe, cheap fungicide!) Want to keep roots - and plants - healthy? Don't overwater, and let air work for you in the root zone.

How can air make crops take up water and food faster and better? In two ways: first, air in the root zone means healthy, growing roots eater to work hard supplying the top growth with food and water. Second, good air movement through plants draws lots of food and water up from the roots. How? To understand this, you'll want to meet the STOMA, a tiny breathing pore on the underside of a leaf. This stoma's a busy place - a sort of grand central station of the plant world. Carbon dioxide and oxygen are coming and going through this tiny opening, and this is where water vapor drifts out of the leaf into the air. Lots of water vapor - if your crops used 100 gallons of water last week, they "transpired" 99 gallons of water out of this breathing pore, keeping only one gallon for actual growth! It sounds wasteful, doesn't it? But plants have a purpose in handling all this water: as a drop of water evaporates and drifts out of the leaf, it yanks another drop of food and water into the roots. In this way, plants suck water and food into the roots and draw them up the stem to the leaves, concentrating the minerals from the fertilizer soil in the leaves for use by the plant. Evaporation of the excess water also cools the leaf, keeping it at an efficient working temperature. Another important use of this water movement: it keeps air spaces in the leaves moist so CO2 can dissolve into the damp air - a necessary first step for uptake and use of CO2 by the plant. When we supply good air movement through the garden, we help to speed everything up - CO2 uptake, food and water movement into the plant, utilization of minerals by the leaves - in other words, we speed up GROWTH!

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