VINEGAR SPRAY TRIALSOhlone Hillside at Lawrence Hall of Science, Berkeley
"xǔčyun" the region that is part of the ancestral and unceded homeland of the East Bay Ohlone (pronounced "HOOCH-
yoon" in Chochenyo language)
By Jen Toy
Test Plot Director
DATE: April 4th, 2024
Last fall, we got a grant from the Xerces Society (more insects!) to plant milkweed and other nectar plants. We quickly mobilized to make a new home for them on a degraded hillside overlooking the SF Bay, just outside the Lawrence Hall of Science, a beloved science museum operated by UC Berkeley. Our partnership includes Vincent and Luis, Ohlone tribal members and the phenoms behind Cafe Ohlone/mak-’amham, Dee their business manager, Jedda from The Lawrence and Story and Sarah from Terremoto SF.
Long term, we have big plans to restore the former grazing land, currently dominated by fireprone annual grasses, into a T
est Plot that establishes native food and medicinal plants across 1.5 acres. In the meantime, we’re getting going, experimenting with a site preparation strategy using vinegar spray. We’re fortunate that we have been learning from the stellar restoration project down the road called Skyline Gardens. As we share a similar geology - the Sibley Volcanic Ridge - we are able to share seeds and continue supporting hyperlocal genetic diversity. Here’s a summary of our process so far:
OCT 24 2024
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Inventory existing species both native and introduced (natives include a couple oak trees, coyote brush, naked buckwheat, horse weed, bracken fern, rooreh, goldenrod and wild cucumber.)
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Rake off dead thatch from annual grasses that browned out and finished their reproductive cycle
OCT 31 / NOV 8 / DEC 8 2024
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Three planting days (thank you volunteers and Xerces Society for the plants!)
JAN 23 2025
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The fall rains got things going and by January the hillside is looking green with non native grasses.
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“Collar” around existing plants by hand pulling immediate weeds and spray new weeds with vinegar spray. The “collar” protects them from inadvertent contact with the vinegar.
- Weeds included: six weeks fescue, plantain, thistle, vetch, oats and bromes
- We attempted to spray, but the fog rolled in as we were finishing and it rained over night so it did not work
MARCH-APRIL 2025
Two rounds of vinegar spray. We selected a small area at the top of the plot to spray. After we “collared” around the existing native plants we wanted to keep, we sprayed using a Solo backpack pressure applicator. The formula is:
- 5-7% vinegar (can use the 5% white vinegar from Costco - 2g pack for $7)
- Mix in a teaspoon of dish soap (to help with adherence to the plant material)
Tip: Spray on a sunny clear day when the plants are photosynthesizing a lot. You want the vinegar to burn the material. The motion should feel like you are “painting the plants.” Keep pumping to maintain a strong steady pressure to shoot the vinegar down into the roots. Go slower than you think. Come back after a day or two to evaluate your work and you’ll see where you missed a spot.
SUMMARY
The spray is effective, particularly on broadleaf dicots. The oat grasses with larger seeds that are below the soil (in the white part of the plant) are harder to kill and it takes multiple rounds of vinegar because they keep growing back. It is not 100% effective by any means, but the vinegar definitely slows things down. The patch that we concentrated on has noticeably less weeds and we are letting the yarrow and wildflowers and purple needlegrass do their thing.
I’m also happy that this year we were able to mow the grasses before they produced viable seed. We waited until they expended energy producing a nice flower stalk, but cut them back before the seeds ripened. We concentrated on doing this within the plot and in a 15’ buffer upwind. It will be interesting to see if there are fewer grasses next year.