Guide to different mulch materials, their benefits, and proper application techniques. Includes locally available options and special considerations for tropical climates.
Mulching is the practice of covering soil with a layer of material to conserve moisture, suppress weeds, regulate soil temperature, and improve soil health. In African climates, where heat, drought, and heavy rains can challenge gardeners, mulching is an essential practice for sustainable gardening success. This fact sheet explores different mulch options, their benefits, and how to apply them effectively in your garden.
These break down over time, adding nutrients to the soil.
| Mulch Type | Benefits | Considerations | Best Uses |
|---|---|---|---|
| Grass Clippings | Readily available, high in nitrogen, decomposes quickly | Apply in thin layers to prevent matting; avoid clippings from herbicide-treated lawns | Vegetable gardens, annual flower beds |
| Leaves | Free, abundant in many areas, good for soil structure | Shred before applying to prevent matting; may blow away if not wetted | Around trees, shrubs, perennial beds |
| Straw | Excellent insulation, good weed suppression, stays in place | May contain weed seeds; can attract termites if placed against wooden structures | Vegetable gardens, strawberry patches, pathways |
| Coconut Husks | Long-lasting, excellent moisture retention, attractive appearance | May need to be chopped; can be expensive if not locally available | Ornamental gardens, container plants, around trees |
| Banana Leaves | Readily available in many regions, breaks down to add potassium | Decomposes relatively quickly; may need frequent replenishment | Vegetable gardens, around fruit trees |
| Rice Hulls | Good drainage, slow to decompose, lightweight | Can blow away in windy conditions; best mixed with heavier materials | Container plants, nursery beds, seed starting |
| Compost | Nutrient-rich, improves soil structure, contains beneficial microbes | May contain weed seeds if not fully composted; relatively expensive | Vegetable gardens, flower beds, new plantings |
| Wood Chips | Long-lasting, excellent weed suppression, attractive appearance | Depletes nitrogen as it decomposes; avoid fresh chips around young plants | Pathways, around trees and shrubs, perennial beds |
These don't break down and don't add nutrients but are long-lasting.
| Mulch Type | Benefits | Considerations | Best Uses |
|---|---|---|---|
| Gravel/Stone | Permanent, excellent drainage, reflects light to plants | Can heat up soil; difficult to remove if needed; expensive initially | Drought-tolerant plants, rock gardens, pathways |
| Plastic Sheeting | Excellent weed suppression, warms soil, conserves moisture | Not biodegradable; can overheat soil; requires irrigation system underneath | Commercial vegetable production, weed control in rows |
| Landscape Fabric | Allows water penetration, good weed control, long-lasting | Expensive; degrades with sun exposure; weeds can eventually grow through | Under stone mulches, permanent plantings, slopes |
| Recycled Materials | Environmentally friendly, often free, good use of waste | Variable quality; check for harmful chemicals; appearance may not be ideal | Utility areas, production gardens, temporary solutions |
Many effective mulch materials can be sourced locally at little or no cost:
Remove weeds and water the soil thoroughly before applying mulch. This gives your plants a head start against weeds and ensures moisture is sealed in.
For coarse materials like straw or wood chips, apply 7-10cm deep. For fine materials like grass clippings or leaves, apply 5-7cm deep. Too thin won't be effective; too thick can prevent water from reaching the soil.
Leave a 5-10cm gap between mulch and plant stems or tree trunks. Mulch piled against stems can cause rot and create habitat for pests.
For trees and shrubs, extend mulch to the drip line (outer edge of canopy) where possible. This protects the entire root zone.
Replenish organic mulches as they decompose. In tropical climates, this may be needed 2-3 times per year. Fluff up mulch if it becomes compacted.
Piling mulch against tree trunks in a volcano shape. This causes bark rot, creates habitat for pests, and can kill trees. Instead, create a flat or slightly bowl-shaped layer with a gap around the trunk.
Using fresh grass clippings, manure, or wood chips can rob soil of nitrogen as they decompose and may burn plants. Compost these materials first or use only in thin layers mixed with aged materials.
Mulching over already dry soil locks in the dryness. Always water thoroughly before applying mulch.
Mulching with diseased plant material can spread problems throughout your garden. Compost these materials at high temperatures first or dispose of them elsewhere.
Excessively thick mulch can prevent water from reaching the soil and create anaerobic conditions that harm plant roots.
While both are beneficial, mulch and compost serve different primary purposes:
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