California Native Plant Society

Watershed Gardening

Partnerships for a greater good

By Susan Krzywicki

Runoff at Sunset Cliffs Natural Park.
click to view larger

Urban runoff from gardens and hard surfaces is the #1 source of ocean pollution. If you analyzed what was in that runoff, you would find pollutants such as:

  • Pesticides, herbicides, synthetic fertilizers and sediment (soil)
  • Oil, engine exhaust and brake pad dust
  • Dog poo... etc.

But where is the runoff coming from? Much of it is from our gardens - both public and private. Homeowners, condominium associations, business parks - we all garden and water.

We know that native plant gardens almost always are much thriftier on water use, so you may not think this is an issue for native plant gardeners. But even if you garden exclusively with low water use native plants, you may still be causing runoff. This can occur during rainstorms as well as during dry periods, called "wet-season runoff" and "dry-season runoff," respectively.

Wet-season runoff happens when rain lands on permeable and impermeable surfaces at a rate faster than soil can absorb it. Dry-season runoff is similar but is usually caused by irrigation systems that overspray onto impermeable surfaces.

A dry stream helps alleviate runoff.
click to view larger

Dry-season runoff is not as common with native gardens because we have adjusted our watering schedules to reflect the needs of our plants. There still may be adjustments, though, where outdated sprinkler layouts water cement sidewalks, asphalt driveways and impermeable patio areas.

The pollutants in runoff are very concentrated, and move rapidly through our storm drain systems. Very little of this runoff is treated, so it carries the chemicals used in gardening along with street pollution, right through the gutters, down the drains and into the ocean. This large, concentrated volume is dumped in small areas on our beaches. Bacteria counts skyrocket over the healthy limits and beaches are closed. That hurts the quality of our everyday lives and hurts our economy: the tourist and hospitality-related industries rely on our maintaining pristine beaches. And in turn, this affects us all.

We need to think about the entire process and garden in ways that recognize the cycle of connections: plants, soil, water, air.


Watershed Gardening

Extending the concept of native plant gardening by combining watershed concepts starts to improve the sustainable nature of our efforts. We like to think that each garden becomes a watershed unto itself. This means we look to our own property limits: all the rain that lands on that piece of land soaks into that land itself. No runoff.

This is a challenge in much of California, where large roof footprints and small lots are the norm for suburban gardens. Urban density along our popular coastline magnifies this issue: multiple-unit condos, apartment buildings and high-rises increase the amount of hardscaping while also increasing the pressures on water use.

There are organizations and programs that are now addressing these issues and they offer significant synergy for CNPS. The first benefit is that these programs recognize the value of native plants and can help us to spread our message. The second synergy is that programs that focus on watershed help gardeners get back to a more natural gardening style: habitat almost inevitably is created in the process.

So, what is watershed gardening? Let’s look at an important offering from the Surfrider Foundation. Their Ocean Friendly Gardens program was developed about five years ago, with the help of the Green Gardens Group.

The Surfrider Foundation’s vision: garden to protect the ocean.

The Ocean Friendly Gardens ("OFG") program uses three key principles to teach urban and suburban gardeners: Apply CPR to your garden - Conservation, Permeability and Retention - to revive our watersheds and oceans:

  • Conservation of water, energy and habitat through native plants that are climate adapted and spaced for mature growth. Native plants must make up a minimum of 10% of the landscape.
  • Permeability through healthy, biologically active soil, and utilizing materials for - or making a cut in - driveways, walkways and patios that allow water to percolate into the soil. Decomposed granite walkways, well-mulched soil are key components.
  • Retention devices like rain chains, rain barrels and rain gardens to retain water in the soil and restore the water table; preventing it from running off of the property.

CNPS is a perfect partner for Surfrider because the OFG program calls for native plants in the gardens. In San Diego and Ventura Counties, there are very active cross-pollinations (excuse the pun) between CNPS and OFG.


Ocean Friendly Gardens

Ocean-Friendly Garden installation.
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OFG Gardening on a commercial site (Scripps Institution of Oceanography).
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How to find out more:

The OFG blog has posts about OFG programs around the country as well as how-to tips for the do-it-yourselfers, or those who want to be better able to communicate with a professional. There are posts about how to:

  1. kill your lawn naturally by sheet mulching
  2. determine your soil type (helps with choosing the right plant) and see if the soil is compacted
  3. calculate rainwater harvesting potential and area needed to absorb it
  4. how to properly install a plant

The Resources section directs you to the:

  1. OFG Sign Criteria
  2. OFG Online Map
  3. OFG Activist Toolkit 
  4. Program components - walks, workshops and workdays.
  5. OFG videos and articles

How CNPS Members can find out more:
If you live near a Surfrider chapter, get in touch. Here is a link to the local chapters. Connect with the national program manager, Paul Herzog at . If you’d like to connect with me, I’d be happy to point you in the right direction. I have been actively working on connecting CNPS with the OFG program.


About the Author
Susan Krzywicki, CNPS Horticulture Program Director, envisions a California where native plants are widely available and routinely incorporated into public and private landscapes to conserve resources, extend habitat, and create a sense of place. Susan started as chair of the San Diego Chapter Gardening Committee which inaugurated the popular San Diego Native Garden Tour and the Native Garden Symposium, encouraging homeowners to experience the strategic benefits of low water use, habitat creation, and our unique ecological heritage. In addition to her work with CNPS, Susan chaired Surfrider Foundation's Ocean Friendly Gardens Programs Committee, taught the San Diego County Water Authority's California Friendly Landscape Training, and serves on the Port of San Diego Chula Vista Bayfront Cultural and Design Committee where she advocates for strong environmental partnerships with new development.


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