Safe Weed Management Without Dangerous Chemicals

Photo courtesy of Suzanne Bontempo

"Dandelions: Enemy to most, but friend to a few."

Beautiful gardens and lawns are possible without putting hazardous chemicals into our streams and bodies of water, say local experts in integrated pest management.

The Alameda Countywide Clean Water Program paired with the Our Water Our World nonprofit in a February 16 online webinar on controlling weeds in environmentally friendly ways. Some of these involve no chemicals, said co-hosts Suzanne Bontempo and Charlotte Canner. 

Anything applied to lawns that are not absorbed eventually flows into storm sewers, which then deliver their contents unfiltered into streams and creeks, which flow into bodies of water such as the San Francisco Bay, said Bontempo.  

Children and pets are better off not ingesting chemical lawn-care products by walking or playing on the lawn, either, she added. Information on alternatives is on the Our Water Our World website https://ourwaterourworld.org/. Bontempo is a certified Integrated Pest Management (IPM) Advocate who works with the group and others.

Meanwhile, there are ways to prevent those weeds in the first place, rather than using chemicals to get them out once they've established themselves, said Canner, a certified Gardening & Composting Educator who works with Earth Ally and Our Water Our World. 

You probably want to start by finding out what kind of weed you're fighting, as weeds vary in what makes them flourish — or wither, Canner said. That's most easily done by looking it up on the University of California's Weed Photo Gallery at ipm.ucanr.edu/PMG/weeds, she said.

Then consider various barriers to keep the weeks out in the first place. Canner suggests using layers of cardboard with mulch to kill off weed roots before planting or replanting what you want to grow.

Some weeds like acidic soil, while others thrive in alkaline soil, so changing your garden's pH might prevent some weeds from ever visiting, she said. That's assuming the new pH is OK with the plants you're trying to grow, however. The same goes for dry soil versus wet, although few plants other than weeds like wet, slow-draining soil. 

On lawns, many people water shallowly rather than deeply, which helps weeds with their typically shallow roots more than grass. The advantage nature gives grass over most weeds is potentially deep roots, so encourage your lawn to send its roots deeper, Bontempo said. 

One way to do this is to water less frequently but for longer. Lawns should be aerated once or twice a year also, she said. Overseed with grass relative to what you might think is needed, and then mulch to keep weeds down. 

Unfortunately, if they do pop up, the best way to remove them is by pulling them out. But there are specialized tools to remove almost any specific weed, including dandelions, Canner said. You can get them in better hardware stores, garden shops, and farm supply stores that still dot the Bay Area. 

Do take heart if you try but fail to get the whole weed out, she said. Every part you remove weakens the weed; repeating this will eventually kill the plant.

Vinegar will also kill weeds, she said, but you need to use horticultural vinegar, which is much stronger than the household variety. It can burn you badly if you spill it on yourself.

There are do-it-yourself remedies that can kill weeds but do your homework first. Salt indeed kills weeds, but also most other plants. Dishwashing "soap" is a detergent, Bontempo cautioned, and not good for the environment.

Information on natural products is available from the Organic Materials Review Institute at www.omri.org and the Alameda Countywide Clean Water Program: https://cleanwaterprogram.org/yards-and-gardens/

The February 16 seminar, for those who missed it, is available on the Clean Water program YouTube channel at https://www.youtube.com/@cleanwaterprogramalamedaco3232/videos