The best of the organic options involves the spreading of a very thick (4”) layer of wood chips over the garden site. It not only supports the microbiology below by feeding worms, fungi, and micro organisms with its decaying matter, but it also robs the top surface layer of nitrogen which further aids in its plant suppressing abilities.
The option can take up to at least 1 growing season, possibly 2 depending on the vegetation present and its persistence (deep strong rooted plants need more time under the mulch). This approach is recommended for transitioning lawn spaces into a lawn alternative where the remaining chips can be used again in other parts of the landscape.
Besides the time it takes to work, its other biggest drawbacks are its the most expensive option (material and labor to apply and remove). Often wood chips make sense when the chips are available from a local tree company or if the homeowner is willing to do some of this work herself.
Is another effective herbicide free option for transitioning a garden space. The benefits that black plastic has over wood chips is its lower costs for materials and installation. It can still get cost prohibitive over larger sites and is best utilized for smaller garden spaces (~5,000 sq ft or less).
Like wood chips it will still need at least 1-2 growing seasons for an effective kill of the vegetation underneath.
The draw back to this herbicide free option is the environmental cost of its eventual place in a land fill. While it removes herbicides from being used in your landscape, it puts the toxicity of plastic elsewhere in the environment. To help maximize its use, the plastic may be reused for another season for another section of the landscape. Its lifespan is effective for about 2 seasons.
While the use of these products has become something of a four letter word as of late, they are commonly used in native plant restoration projects to control invasive plants and prepare sites for native seeding.
The main benefits to using systemic herbicides (i.e. Glyphosate) is:
1. Short preparation time scale. A garden site needs about 4-8 weeks of prep before planting, with 1-2 herbicide applications about 4 weeks apart.
2. Kills existing plants at roots, providing a very effective clean seed bed for planting in.
3. Low cost (material and labor) and scalable for larger garden sites.
4. Timescale for toxicity/impact on environment is much less than plastic (months as opposed to decades/centuries).