Nov 09, 2017
BY:
THEME: Sustainability

When (Still) in Drought

One year ago, in response to California’s historic drought, Perkins+Will took action. Tearing out half of the lawn in front of the office, we launched an experiment in drought-tolerant plantings, installing five species of grass and groundcover as well as a fescue-blend sod.

Over that time, we learned a lot about each species’ drought tolerance and enjoyed the lawn’s visual interest and seasonal variation. We also kept results showing which were in good health, in marginal health, and dead. Plants were watered daily for three months to establish roots, and then irrigation was turned off for three months during the wet winter of 2016/2017. Irrigation now occurs one day per week.

Native Mow Free sod looking lush in the summer.

The clear winner turned out to be Delta Bluegrass’ Native Mow Free sod. It gained immediate coverage and created a lush green carpet for winter, followed by a tasseled look for spring and early summer. Everyone in the office asked where they could get some for their own yard. The sod did have immediate coverage, which gave it a possibly unfair advantage against weed encroachment compared to the individual grass plantings, which have more space between them. The runners-up were Dymondia, Festuca glauca, and Fescue rubra. The Dymondia is a very different look, with flat creeping coverage, so if you want something more vertical, the fescue is the way to go.

The project required much more ongoing maintenance than some had anticipated. We recommend decreasing plant spacing to reduce opportunities for weeds and adding a thick layer of mulch. Also, different grasses like to be cut back at different times, so make sure to schedule maintenance by season.

For our next step, we will be replacing the lowest performing grasses with a new selection of drought-tolerant grasses and pollinator species. We have already noticed an increase in biodiversity since the planting and hope to encourage further improvements. We will report back to the Port and our community on progress, and would love to understand the neighborhood’s appetite for a more permanent open space in this location. Our detailed results are below.

Native Mow Free Sod taking off in foreground, Nasella pulcha struggling on left.

#1: Fescue Mix (Native Mow Free by Delta Bluegrass):

Results: 100% success

Description: A combination of native (Fescue idahoensis and rubra) and naturalized (Festuca occidentalis) shade tolerant fescues available in sod

Observations: Achieved full coverage quickly, and looks lush even with reduced water. It is summer dormant so be prepared for the “golden” look. If you prefer it stay green, continue to water in late spring. Once it goes dormant, it will stay dormant through the summer. In fall, mow to allow for new growth.

Results: 90% success

Description: Low-growing, silver-leaved evergreen spreading groundcover with yellow flowers. Prefers full sun and well-drained soil. It can be a slow grower in drought conditions but will eventually fill in to provide a low-maintenance, silver-carpet look.

Observations: Individual plants have begun to combine into larger groups. For quicker coverage, space 6”-9” apart on center.

Scrubby bunches of Dymondia starting to spread.

#2: Dymondia margaretae (Silver carpet):

Results: 90% success

Description: Low-growing, silver-leaved evergreen spreading groundcover with yellow flowers. Prefers full sun and well-drained soil. It can be a slow grower in drought conditions but will eventually fill in to provide a low-maintenance, silver-carpet look.

Observations: Individual plants have begun to combine into larger groups. For quicker coverage, space 6”-9” apart on center.

 

Festuca glauca starting to show its summertime gold.

#3: Festuca glauca (Blue Fescue):

Results: 83% success

Description: An evergreen clumping silvery blue grass that prefers full sun on the coast and some protection inland. Trim in the winter for a neat appearance.

Observations: Was not as impressive initially but once the seedheads arrived, it was dramatic even through the dry summer.

#4: Festuca rubra (Red Fescue):

Results: 82% success

Description: Native grass that prefers sun and has an attractive mounding, windblown quality. Is located in part sun/part shade and has expanded moderately.

Observations: Similar to Festuca glauca, but prune in early spring for a more vigorous regrowth.

#5: Nassella pulcha (Purple Needlegrass) Planting Area #2:

Results: 55% success

Description: Summer dormant California native (and official state grass!). Blooms in late winter to early spring, with showy seed heads going from purple to tan, and roots that can go as deep as 20 feet, for extreme drought tolerance.

Observations: It has looked sparse this summer but is starting to green with winter rains. Not recommended in mass. Small groups of specimens would look better mixed with stones and other drought tolerant plantings.

#6: Carex divulsa (Berkeley Sedge):

Results: 54% success

Description: Evergreen arching clumping grass that prefers full sun to shade and tolerant of wet and dry soils.

Observations: Started out strong, but has not continued to grow as fast as other species. Although it is a shade tolerant species, the shade from the nearby Ficus tree could have been too heavy. It also respond poorly to foot traffic at the corner, and to dogs at the sidewalk edge.

#7: Nassella pulcha (Purple Needlegrass) Planting Area #1:

Results: 0% success

Description: Same as Nassella #2

Observations: The entire area was bare by winter but in spring small shoots started appearing—some where they were planted, and others in new locations. Ultimately, the shoots did not result in successful plants. This location gets more shade from the nearby Ficus tree and the winter was very wet. Since the #2 location was more successful, we conclude that Nassella does not prefer the shade or additional water.

  1. Ora Berman
    11:39 am on November 13, 2017 | Reply

    What a great idea. Did you also have any ‘public’ response to this experiment?

    • Jennifer Cooper-Sabo Jennifer Cooper-Sabo
      12:28 pm on November 14, 2017 | Reply

      Ora,great point! We’ve had a lot of casual conversations with neighbors usually while walking their dogs and spoke to the people in the businesses next door. So far the results are positive but I think many people would love to see a more public usable space utilizing both sides of the lawn. But we would love to know more about the reaction to the different plantings before we move to Phase 2. We had an intern do a pedestrian survey on a Giants game day so we can see the difference if it eventually becomes a more diverse public open space. Here is a link to the results. https://www.youtube.com/watch?v=JVNEGqQVxIQ

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