The Latest Dirt - July 2024

Worms, Bees, Rainwater: An Update from the Water Conservation Garden

Article & photos by Liz Rottger

I want to update you on the progress we’ve been making at the Water Conservation Garden in El Cerrito. We have regularly scheduled work parties on the second Saturday of the month, but I know many of you can’t make our work parties. But I think all of you are interested in the Water Conservation Garden’s progress.

We are still using the rainwater we collected in the winter of 2023-24 to water our four raised beds. We collected over 2000 gallons of rainwater and could have collected much more if we had had more storage capacity. We’re down now to the last 400 gallons. We used over 1000 gallons to water tomato seedlings. We hope that we can make it through to the autumn rains without re-filling the large water tank at the top of the garden. It will be touch-and-go, but we might just make it.

The raised beds also have subterranean reservoirs filled to capacity (~125 to 200 gallons) with rainwater. The wicking action of the soil and the roots of the plants draw the water up from the reservoirs into the plants on an as-needed basis. The plants in the raised beds are solid and robust, growing like gangbusters! Even shallow-rooted plants like lettuces and cucumbers have developed strong root systems and are thriving in these raised beds after only a few weeks of top-watering to get them started. We have stopped watering all the raised beds.

We’ve been fairly successful in planting native trees and plants to begin to re-create the wooded wildland-urban interface of a habitat garden.

After the demolition of the old school on this site, only three coast live oaks (Quercus agrifolia) were left. Yes, some natives we planted a few weeks ago have died. (It is always better to plant natives in the fall before the rains than in the spring.) For example, of the 14 coastal lupines (Lupinus arboreus) we planted, only seven remain with us. But many of the shrubs we planted last year—ceanothus, currants, cream bush, buttonwillow, sugar bush, fremontias, and several buckeyes—have taken off and established themselves around the garden’s edge.

The Island Oak (Quercus tomentella), the rarest of all California tree oaks, was planted back in the fall as the anchor tree for the garden and is doing very well. We did plant a Styrax snowdrop bush a few weeks ago, which may have been a mistake. It’s struggling now in the heat. But, if it makes it, it will be mesmerizing when it blooms. We are nurturing many coast live oak seedlings and buckeyes that David George brought us from Lafayette, along with some we’ve collected locally. We will wait for the fall rains to plant these trees across the landscape.

We spread a 12” deep layer of mulch across the entire garden two years ago—over twenty truckloads—to rebuild soil structure, increase water retention and provide a durable, protective surface barrier. It was a lot of work! It may have seemed thankless at the time. But, slowly, it has begun to pay off. This past month, we dug several holes down through the (still moist!) mulch to check on the slippery, serpentine clay underneath, and guess what we found? Small worms! They weren’t very deep yet, but the edge of the soil beneath all that mulch is beginning to regenerate with life. The worm eggs came from the mulch itself. It might be interesting to experiment with a smaller section by removing the mulch, spreading a layer of compost, and then re-covering it with mulch.

Would this layer of compost help regenerate the soil more quickly? This garden is all about experimentation, and soil regeneration is crucial to any garden’s success. Just look at Our Garden. One thing we do know for sure: the mulch has cut down enormously on weeds. They haven’t exactly disappeared, but there are certainly fewer of them. And are they easy to pull out? Definitely!

The pollinator garden we started two years ago is glorious. It’s full of all kinds of happy bees, butterflies and other insects. We recently discovered the hornworm of a white-lined sphinx moth (Hyles lineata) feeding on Clarkias, one of its host plants. We’ve planted more sunflowers to keep the bees happy.

Maybe you didn’t realize it, but the Water Conservation Garden is an exciting, growing place. Here are some activities we could use help with:

Propagation of native plants is something all of us can do at home. We welcome new additions to our garden. Please let me know if you want to expand our habitat garden. And more pollinator plants would be great for the bees. The pollinator garden could also use some tending before the clarkias take over. Please let me know if you are interested in soil regeneration or water conservation. Expertise and more research in these areas are always welcome. We welcome your participation and fresh ideas. On July 13th, we will participate in the BioFuel Oasis Garden Tour, which will be open to the public from 11:00 AM to 3:00 PM. Join us at the Water Conservation Garden!