Mulching with woodchips is a great way to control weeds, retain soil moisture, keep plant roots cool, and add slow-release organic nutrients to the soil. To be effective for several years (in a low-maintenance garden), the mulch should be at least 4″ deep. If you have paths at the same level as the beds, the thick mulching can make each bed look higher than the path. At the edge of each mulched bed, gravity and ground feeding birds (scratchers) will conspire to cause the chips to slowly bleed into the paths as well. How can you keep the woodchips in the beds where they belong and yet not fall on to the paths in the garden?
It is really simple, say landscape professionals who do this for a living. Say your path is made of hard material like flagstone or concrete. Before applying mulch, first dig a shallow trench all around the bed; the trench should be as deep as the thickness of mulch you want to apply. The cross-section of the trench should be an inverted saw-tooth: nearly vertical near the path, and sloping up gently on the other side to the level of the bed.
Now apply mulch all over the bed, including the trench. The mulch will give the appearance of raising the bed by the depth of the mulch, and gently slope towards the level of the path. Walk on the chips near the edge to make sure it is packed well.
Today we got to practice edge mulching in the bed with the “NATIVE GARDEN” sign. This bed is adjacent to Park Road, and a 6″ tall concrete curb separates the bed from the asphalt. The bed is at the height of the top of the curb. So when we lay a thick layer of woodchips on the bed, it has a tendency to spill over the curb and onto the asphalt.
To solve this problem, we began by digging a 6″ deep trench all along the curb. We saw-toothed the trench, so it was sharp at the curb, and sloped upward to bed level.
We then filled the trench with woodchips, packing them tightly by walking on them, and grading it gradually towards the bed.
If our efforts are successful, the road should remain free of woodchips, and the edge of the bed should be free of weeds for many years.
This weekend brought the first major storm of the season to the Bay Area. It rained off and on all day Saturday and Sunday. Despite the drizzle and the rain, volunteers from Foothill College, West Valley College, and Milpitas High showed up on Sunday to help out. Job one was loading and spreading a thick mulch layer in the bed facing Park Road and rearranging the logs to make them more visible. It was quite a workout. After a short rehydration break, we switched gears to remove invasive grasses at the base of a young coast live oak and several coyote bushes; below them we spread a thinner mulch layer to keep the weeds out and let the water through. We pruned up the coyote bushes to improve visibility and make it easier to work near them. The rain didn’t discourage the wildlife: we spotted a fence lizard, many Anna’s hummingbirds near the California fuchsia, and a scrub jay on the blue elderberry.
Although summer has yielded to fall, the Loma Prieta fire still raging in the Santa Cruz Mountains is a reminder that fire season is not yet over. Fire, an integral part of California’s ecology, can still wreak havoc after decades of fire suppression and periods of prolonged drought. Once upon a time, native Californians routinely set small fires to clear out low growing vegetation without harming larger shrubs and trees. They knew that without periodic small fires, they would eventually be faced with a catastrophic crown fire that would consume everything, small and large. Their land management practices thus created the magnificent estate-like landscapes the Spanish encountered when they first came upon this land: vast meadows of bunchgrasses, annuals, and perennials interspersed with giant valley oaks that resembled the finest country gardens of Europe’s upper classes.
Within the comparatively short span of 250 years, California’s open spaces have now been overrun by invasive non-native annual grasses from Europe. These invaders live fast and die young; by early summer they have scattered a prolific amount of seed. Their dry stalks persist, however, and act as kindling for today’s fires, usually the first to ignite. Reducing and removing these invasive non-native grasses can diminish the fire risk.
In Lake Cunningham Park, the fire risk is low — Fire Station #21 is just one block from the White Road entrance — but we remove these invasive plants for another reason: they out-compete young native plants. We spread arbor mulch (woodchips) thickly over open areas to control weeds, to retain soil moisture, and to slowly enrich the clay soil with organic material.
An enthusiastic and effective crew from Silicon Valley Volunteers joined us today to mulch a large area between Park Road, the accessible path, and the parking lot. Volunteers worked efficiently to load the chips into wheelbarrows and bring them to the beds where they were spread evenly around the native plants. We weeded around each existing native plant so it was prepped for the rains with maximum exposure to sunlight.
The California fuchsia was in full bloom, and two resident Anna’s hummingbirds were squabbling over it. The toyon berries were reddening but not fully ripe. A Monarch butterfly wafted by while two dragonflies flew in formation. The day was mild and sunny, making it a joy to be out in the open, to exert ourselves without overheating.
Thanks to the El Nino rains this winter, the native plants are doing well in the Native Garden. So are the invasive annuals. Open areas in garden beds are overrun with invasive annuals like slender oat (Avena barbata), ripgut brome (Bromus diandrus), and red brome (Bromus madritensis). This is because those open areas were mulched five years ago and have not been mulched since; the original mulch has decomposed to a fine compost, creating a fertile medium for annuals to thrive in. So the main focus in the garden now is to weed the invasive annual before they drop seed.
On Saturday, May 14, 2016, Clinton Nguyen of Independence High School Red Cross Club helped us remove invasive annuals from several beds. We started by weeding around the Native Garden sign off Park Road. This bed features a baby Califonia buckeye tree which has flowered for the first time.
We then worked on the beds around the western sycamore trees by the lake. Here are pictures of the bed before and after the weeding:
We finished the session by weeding around the large stand of California buckwheat off the accessible path. In a month or so, the buckwheat will be blooming its head off, and pollinators in the area will take notice.
The following day, Sunday, May 15, 2016, we were joined by Silicon Valley Volunteers. The group of seven volunteers worked on removing the invasive annuals from the bed adjoining the parking lot. Oat and brome grasses were removed without harming existing native plants. When we finished, the parking lot looked neat and well-maintained.
The weather was cool but not cold and mostly sunny. Some 30 people showed up, including members of CNPS, SCV Audubon, Open Space Authority, Silicon Valley Volunteers, Latino Outdoors, and the general public.
Vicki started the walk in the Marina parking lot, where we saw great-tailed grackle up close, and an American white pelican in the distance. On the way to the native garden, we encountered many more birds, including Anna’s hummingbird, black phoebe, bufflehead, California towhee, Canada goose, killdeer, mallard, ruddy duck, song sparrow, tree swallow, and yellow-rumped warbler.
Arvind pointed out common non-native plants like blue gum eucalyptus and London plane, as well as many native plants in the native garden, including Bee’s Bliss sage, black sage, blue elderberry, California sagebrush, chaparral clematis, Fremont cottonwood, hummingbird sage, purple needlegrass, valley oak, western sycamore, woodmint, and Yankee Point ceanothus. Members of Silicon Valley Volunteers have been working in the garden since fall 2015 on tasks like weeding, mulching, and planting.
The walk was cosponsored by the California Native Plant Society, Santa Clara Valley Audubon Society, and Open Space Authority in cooperation with Lake Cunningham Park staff and San Jose Parks & Recreation staff.
Many thanks to Vicki, Ashok, and Steve Rosenthal for organizing/leading/supporting the walk. Special thanks to Susan Sundberg whose untiring efforts in the native garden have produced superb habitat that is also beautiful and charming.
Stay tuned for the 1st Day of Summer bird+plant ID walk in June.
This Saturday, January 16, Piedmont Hills High School Red Cross Club returned to the Native Garden on a visit scheduled by Albert Duong. The team of seven volunteers, along with Xin and Arvind, mulched large beds overgrown with invasive annual grasses. Take a look.
Now these newly mulched beds will remain free of invasive grasses for up to 5 years — a worthwhile investment in controlling invasives.
The skies were overcast, but it was dry until noon when it drizzled just a bit. It was not cold — a great day to be outdoors. The garden was full of bird chatter.