September Garden Update: I Want A Sidewalk Garden Part 2: Design features

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The city is heating up. Green blocks like the 20th Street garden are the antidote – less heat-reflecting concrete and more cool greenery. Inspired? Now is a great time to plan your sidewalk garden for a fall or winter installation. In the last blog post, we discussed the permit process for getting a sidewalk garden in San Francisco. Now we’ll talk about the more interesting part – design.

 

Sidewalks are public spaces. They need to be accessible to pedestrians of all ages and abilities as well as drivers getting in and out of parked cars. A successful sidewalk garden design must take into account the following features:

 

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(In this design elsewhere in the city, the sidewalk is less than 6 feet wide, making it hard to pass other pedestrians.)

    • Minimum sidewalk width. Pedestrians should be able to pass each other safely on the sidewalk without stepping into the garden or the street. The City requires the sidewalk to be at least 6 feet wide after landscaping. This is possible if your unlandscaped sidewalk is 11 feet wide or wider. (The 20th Street sidewalk was originally 15 feet wide). If your sidewalk is 9 feet wide before landscaping, you may be able to get away with leaving a 4-foot-wide sidewalk, but that is an absolute minimum and not preferred. Contact the Department of Public Works (DPW) about your specific situation. (http://www.sfdpw.org/index.aspx?page=1532)

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(The “courtesy strip” between the garden and the curb on 20th)

  • Courtesy strip. People getting in and out of parked cars don’t need a face full of plants or a twisted ankle. For this reason we don’t plant all the way up to the curb, and provide a stable area known as the “courtesy strip” between the garden and the curb. The courtesy strip is 18 inches wide plus the 6-inch curb, creating a 2-foot space to step out of the car. (Note: if there is no street parking allowed, a courtesy strip is not required.)The courtesy strip doesn’t have to be made of concrete, but it should be solid enough to provide stability to people using walkers, canes or wheelchairs. On 20th Street, which was installed in 2012, some of the courtesy strip area is earth, and some is covered with permeable pavers. Now, the City prefers concrete or pavers on a firm base instead of soil in the courtesy strip. Visit the DPW website for suggested materials to use in the courtesy strip.  (http://sfdpw.org/Modules/ShowDocument.aspx?documentid=869)

 

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(On 20th Street, the accessible path and the courtesy strip are paved with permeable pavers, allowing rainwater to enter the soil.)

  • Accessible path. Where there is parallel parking, there must be a minimum 4-foot-wide path connecting the curb to the sidewalk every 15 to 20 feet to allow people safe access through the garden. Where parking is perpendicular (as on Florida Street at 20th), the paths must be located every 12 feet. Again, these paths must be solid and level for people with varying mobility. On 20th Street and Alabama Street, the accessible paths are made of permeable pavers, but on Florida, the concrete has been left between the green spaces.
  • Planting at intersections. People need to be able to see stop signs and traffic at intersections. If your property frontage extends to the corner, choose plants that will grow to less than 3 feet in height within 25 feet of an intersection approach (with or without stop signs), and within 5 feet of the exit from an intersection. This means no trees within those areas.

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(The raised edging around the planted areas on the corner of 20th and Alabama protect the plants from pedestrians using the crosswalks. )

  • To edge or not to edge? The 20th Street garden has no raised edging borders, except at the corner of 20th and Alabama. Raised edging is optional, unless your slope is greater than 10% (which some San Francisco hills are). If you are on a hill, the edging on the downhill side will be useful to catch soil and mulch that may slide downhill over time. Edging can also be a guide for blind pedestrians so they don’t step into the garden and lose their footing. However, edging can also be a trip hazard, especially if not maintained properly. Edging may be stone, brick, concrete or other sturdy material and must be 4 to 6 inches in height. Visit the DPW website for edging ideas – some are quite attractive. (http://sfdpw.org/Modules/ShowDocument.aspx?documentid=869)
    • Raised beds or planters? Since one of the benefits of sidewalk landscaping is its ability to capture stormwater runoff, raised beds or planters are not recommended. Water would just flow around these items. Instead, be sure the soil in a sidewalk garden is one inch lower than the sidewalk itself so water will flow into it. You can put an inch of mulch on top of the soil to bring it back to sidewalk level. Mulch can be bark, stone or decomposed granite.

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(Sea lavender and California fuschia still looking good after 3 years on 20th)

  • Plants! Finally, we get to the good stuff…
    • Don’t plant anything with thorns, spines or irritants.
    • Choose plants that will not grow wider than the sidewalk garden to minimize maintenance. Otherwise you will have to prune frequently to keep plant material from blocking the sidewalk.
    • Select drought tolerant plants. Succulents establish quickly and use little water but can be easily broken or stolen when small, so choose common varieties rather than expensive rarities. Many non-succulents are also good choices. Some are native to California and some are not. Visit the DPW website for plant ideas tailored to the area of the city you live in and your sun exposure.

The time is now! If you want a sidewalk garden, start your research, design and permit application in September. It’s best to plant at the beginning of the rainy season – to be safe, let’s say between Halloween and Thanksgiving, but even up to New Year’s Day. (The 20th Street Garden was planted in October 2012). Get started now and you should have a few flowers by Valentine’s Day, Easter at the latest!

Ellyn Shea is a gardener and consultant in San Francisco. Visit her at http://www.garden-guidance.com

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