If you think of carbon at all, it's probably only as that pile of dead leaves waiting to be added to your compost bin. But everything has carbon in it: the air, plants, the soil, and you. (Remember your TV sci-fi trivia: Humans are "carbon-based life forms.") Plants don't exist without carbon, and obviously neither do gardeners. If you understand why plants need carbon and how easy it is to make it available to them, your entire garden—flowers, vegetables, trees, shrubs, and lawn—will burst with health and vigor.
Soil organic matter, a.k.a. carbon, is black gold—it makes the garden grow and thrive. Soil with a high percentage of organic matter has a loose, crumbly texture and a dark brown color. When your soil has sufficient organic matter, the plants growing in it:
Tolerate drought better.
Organic matter acts like a sponge, soaking up extra water and releasing it when needed.
Grow larger and more vigorously.
Plants grown in soil with abundant organic matter receive a slow release of nutrients all season.
Resist pests and disease.
Healthy plants are naturally resistant to pests and disease. Research has shown that compost has disease-suppressive qualities. For many areas of the country, the peak breakdown of carbon is May through July. Soils are relatively warm and hold plenty of moisture. This coincides with the time our garden plants need lots of nutrients—when they are growing and setting fruit.