Updated: Oct 2, 2021
Juncus patens is a workhorse in a relatively new landscape industry, green stormwater infrastructure, or GSI for short. Sure, it is a native species great for habitat restoration projects, especially along creak corridors, but J. patens is tough and adaptable to wet or dry conditions, perfect for GSI where rain gardens may be dry during the summer and inundated during the winter. Other plants can dry out or rot, respectively. To be clear, they still need summer supplemental water in ornamental landscapes, particularly if green rather than brown is desirable.
We discuss GSI throughout our landscape architecture study at West Valley College because cleaning our storm water has become a critical...I would say dependency, but others may disagree...method to address pollutants in our water ways. For the San Francisco Bay, historically polluted by a lot of nasty things, the development of GSI can move the needle toward cleaner creeks, rivers, bay, and ultimately, the ocean. Ask any knowledgeable fisherman about the significance of clean water for fish we eat, and the priorities become clear.
Landscape architects are jumping on board, too, because GSI has been prioritized in most municipalities charged with cleaning up their waterways. GSI are designed landscapes, and the best ones are multi-purpose including aesthetics and outdoor uses. I will not get too into it here, but Juncus patens, or common rush, is well known within California's GSI industry.
From a distance, J. patens looks like a grass, but closer inspection notes the cylindrical leaves, whereas most grasses essentially have flat blades. Or as every horticulturalist knows:
Sedges have edges, rushes are round.
Common rush flowers, too, but the blooms are not showy...green turning brown and persist on their stems close to the top of the plant. When the plants are green and lush, they are a nice addition to the native garden or other landscapes where texture is key. Allowing them to dry out means they will turn brown, appear dead (they can certainly die if dry for too long), then spring back as rains (or irrigation) provides sufficient moisture. I grow mine in a pot, mostly to keep it contained. When happy, the clump continues to spread, sending out short runners to expand outward. This is helpful in a habitat restoration project but maybe not desirable in small garden spaces.
A note about pruning because most gardeners have the practice wrong. Whereas other perennials and ornamental grasses benefit from a hard pruning each year, rushes do not. When gardeners prune them, either a light toping to make a flat top or cut close to the ground, it kills the leaf. First the tip will tie back, then the rest of the leaf will wither back to the ground. They do not bounce back like grasses. If this should occur during the heat of summer, the exposure can cause serious harm to the overall plant. New growth is slow to recover, so the plant will look unsightly for some time. Instead of pruning, gardeners should use rubber gloves to comb through the plants and collect whatever easily pulls away. This routine practice helps keep the plants looking greener than gray with dead foliage.
West Valley College Campus Location: Juncus patens
Cilker (south facing)
Long: 122° 0'40.71"W
Botanical Name: Juncus patens
Juncus: Latin traditional name for rush. It could be an early derivative of iungere, "to bind," because the leaves were used to produce rope.
Patens: Latin pateo, or lies open, for the growth form of the plant
Common Name: California gray rush; common rush; spreading rush
Family Name: Juncaceae
Origin: Native; California & Oregon
Positioning: Stream embankments, marshes
Garden Themes: Native/habitat, riparian, woodland edge, rock, modern, rain
Uses: Green stormwater infrastructure, mass, container, texture contrast, border
Type: Evergreen perennial; rhizomatous
Form: Spikey, grass-like
Size: 2' tall and spreading
Outstanding Feature(s): Foliage texture, moisture tolerances
Shape: Blade with 14 ridges per side
Color: Dull blue-green
Flower: Spring to Autumn. Several flowers from side stem on leaf. Light green quickly turning brown
Fruit: Summer to Autumn. Brown capsules follow flowers. Small.
cultural requirements, tolerances & problems
Sunset Zones: 4-9, 14-24
USDA Zones: 4-9
Light: Full sun to light shade
WUCOLS SF Bay Area Hydro Zone: Low
Texture: Sand, loam, clay
Moisture Retention: Tolerates periods of dryness and saturation
pH: Slightly acidic to neutral
Tolerances: Drought, heat, inundation, deer
Problems: Slow to respond to pruning or division
Insects: Not identified at time of recording
Disease: Not identified at time of recording
citations & attributions
Calscape. "Common Rush." California Native Plant Society, Sacramento. Accessed on July 25, 2021, from https://calscape.org/Juncus-patens-().
Jepson eFlora: Taxon Page. "Juncus patens." The Jepson Herbarium, Berkley. Accessed on July 25, 2021, from https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=29701.
San Marcos Growers. "Juncus patens." San Marcos Growers, Santa Barbara. Accessed on July 25, 2021 from https://www.smgrowers.com/products/plants/plantdisplay.asp?plant_id=892.
Norris Brenzel, K. (Ed.). (2012). The New Sunset Western Garden Book. New York: Time Home Entertainment, Inc.
Water Use Classification of Landscape Species. "WUCOLS IV Plant List." University of California, Division of Agriculture and Natural Resources, Davis. Accessed on July 12, 2021 from https://ucanr.edu/sites/WUCOLS/Download_WUCOLS_IV_List/.
All photos by TELCS.