A weed barrier (such as plastic or fabric) is generally not necessary beneath mulch—and can actually create long-term maintenance issues. These barriers do not effectively prevent weeds from establishing themselves, as weed seeds often germinate in the mulch layer above. Instead, applying a pre-emergent weed control product (like Preen) is a more effective way to reduce weed growth.

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As mulch naturally breaks down and enriches the soil, new mulch can simply be added on top.

However, if a barrier is installed, it prevents this organic material from integrating with the soil, leading to an unnecessary buildup and restricting soil health over time.