Are Oak Leaves a Good Mulch for Tomatoes?

Improving Soil

• Oak leaves are slightly acidic, and when used continuously, will lower the pH of the soil slightly. Tomatoes thrive in soil with a pH between 6.8 and 7.2. Oak leaf mulch benefits tomatoes grown in alkaline soils, but may lower the pH of acidic soils too much. As the oak leaves break down, they add nitrogen to the soil and improve the soil's texture and drainage.

Moisture Levels

• A 2- to 3-inch layer of oak leaf mulch helps regulate moisture levels, an important consideration for growing tomatoes. When tomatoes receive inconsistent moisture, they may develop cracked skins or blossom end rot. An oak leaf mulch conserves moisture and reduces problems associated with inadequate water supplies.

Application

• Apply oak leaf mulches after the soil has warmed and tomato plants stand at least 6 inches tall. Oak leaf mulch acts as an insulator and may keep soils cold and wet in the spring, delaying tomato growth. Dry leaves work better than fresh leaves, which may mat together and become slimy. Shred dry leaves by running over them with the lawn mower to create a thin, fine mulch. Don't apply more than 3 inches at a time. Apply a second layer of mulch in midsummer if the mulch wears thin.

Considerations

• Although oak leaves eventually add nitrogen to the soil through the decomposition process, they initially take nitrogen. To avoid a nitrogen deficiency, fertilize the tomato plants with a balanced nitrogen fertilizer when the plants begin to produce flowers and fruit. Carefully hoe or pull weeds before applying the mulch. An oak leaf mulch will prevent most future weeds from germinating.