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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Feb 16

‘Tis the Season

Posted on February 16, 2018 at 10:01 AM by Ann Vallee

by Charlene Burgi

As I drove up the ranch road yesterday upon returning from my vacation in St. Lucia, I noted a hint of green poking up in the pastures. As I understand it, in my absence the temperatures warmed up, which along with damp soil made for the perfect recipe for weed growth. It is the season to nip these little invaders in the bud (no pun intended) before they take serious root. 

The question is how to proceed? Actually, there are five methods to mitigate weed growth: preventative, mechanical, biological, cultural and chemical. Different situations call for different techniques. And in some cases, you might need to combine a few of these five methods to successfully manage this ongoing chore. 
The easiest method to start eliminating weeds is prevention. Using clean topsoil, weed-free seeds and well-processed compost are great ways to prevent accidentally sowing weeds in your garden. If you use garden tools in a weedy area, clean them before moving on other parts of the garden. Adding a thick layer of mulch can also deprive weed seeds of the sunlight they need to germinate.

Mechanical methods include mowing, weed-eating or rototilling the existing weeds. Even the use of my new hori-hori tool would qualify as a mechanical/manual method of disturbing weed growth, as would hand-weeding. 

 Goat grazing on weeds in St. Lucia
Biological methods include an interesting range of approaches. While I was in St. Lucia, it was common to see goats, horses and cattle tied securely along roadsides as they grazed on the weeds. While this might be a bit extreme in Marin, we can utilize chickens that scratch the new sprouts to unearth them, or peck at the lush greenery springing up. Certain insects, pathogens, nematodes, fungi and bacteria can also be used to target weed problems. (The goat/horse/cow methods, while helpful, might require additional work as I am sure the manure from these animals carries weed seeds that, in time, will germinate!)

Cultural controls include garden management practices such as crop rotation, cover crops and the use of slow-growing vegetables such as cabbage that shade the soil and prevent weed growth. Adding lime to alter the pH of the soil to discourage weeds is another avenue employed. However, this gardener would require far more knowledge about the specific weed seeds present and the pH levels needed to offset their germination.

Lastly are the chemical means of eradicating weeds. These methods need not be harmful to the environment. For example, spraying white vinegar and dish soap will burn back the top growth of weeds before they take root. Plant oils such as orange oils can be used. Other organic methods employ boiling water or even salt. Still, be careful even with these organic methods as they are all non-selective killers. This means they may impact the root systems of nearby plants, thereby damaging wanted plants in the garden. 

Non-organic chemicals (herbicides) are also commonly used. However, these chemicals can leave residues or toxins in the soil that can be harmful, so it is important to do your research. Check to make certain the product is effective against the weeds you are targeting. For example, some herbicides only kill grasses, while others target broad-leaf plants. All chemicals carry MSDS labels providing important information. Before purchasing, read the labels. Look for the signal word indicating relative toxicity—that is, does it say “caution,” “warning” or “danger”? Are there crossbones or does it say “poison”? All herbicides are required to go through toxicity tests that determine their handling and usage.

As for this gardener—weeding has its rewards. As one website suggested, you can even eliminate weeds by eating them. Dandelion greens are supposed to be a delicacy. Bon appetit!


Anonymous User
February 17, 2018 at 12:36 PM
.A very helpful article. Thank you! Should the vinegar be diluted before spraying?
Anonymous User
February 23, 2018 at 3:29 PM
Thanks for asking! Use the vinegar full strength on unwanted vegetation. Just remember it will not kill the roots of plants - only the top growth which is perfect for annual weeds! Always, Charlene

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