Growing Food in Planting Strips

Street planting strip garden

Seattle’s rules for gardening in the planting strip next to streets are described in the Seattle Department of Transportation’s (SDOT) page, Gardening in the Planting Strip.

This page provides more information for residents who want to grow food in their planting strip. It is also available as a printable PDF: Growing Food in Planting Strips (pdf).

Is the planting strip my best place to grow food?

Many Seattle residents are beautifying their streets by planting flowers, shrubs, and trees in the planting (or “parking”) strip in front of their property, between the sidewalk and street. The Seattle Department of Transportation (SDOT) encourages this, but requires a free permit for raised beds (or any structure) and tree planting, to insure that sightlines and public safety are considered.

Growing food is another option in the planting strip: vegetables or berries – SDOT prohibits fruit trees because of the slipping hazard for pedestrians from fallen fruit. For some residents, it’s their only sunny area to grow vegetables. But the planting strip is a public space, part of the public right-of-way, so it’s hard to control what pets or people do there. It can be harder to reach with water, and there may be concerns with the soil. So think about other sunny places in your yard first for food gardening, or consider gardening with a neighbor, signing up for a P-Patch garden plot, container gardening on a sunny porch, or call the Garden Hotline to learn about options for sharing gardening spaces.

How can I make it safe and friendly for my neighbors who share the street?

Besides the plant and bed height, walking area, and sightline restrictions described in SDOT’s guide above, think about making sure that people parking can pass through to the sidewalk, consider not planting thorny berries or shrubs, keep trees and shrubs pruned so they’re not a hazard, and be sure never to leave hoses lying across the sidewalk to trip your neighbors. Walk around your neighborhood to see what others have done in the planting strip, and how adults, children and pets interact with it. That’s a good way to get ideas and start planning your planting strip garden. Consider your family’s safety when gardening, too. Gardening next to a busy arterial street may not be a good idea, both because of faster, higher traffic, and because of possible soil contamination.

How do I know if my soil is safe for food growing?

Contaminants like lead, arsenic, and oil are found at potentially unsafe levels in many urban soils. Soil close to houses built before 1978 (when lead in paint was banned) may have high lead from paint flakes. Former orchard sites (pre-1947) may have been treated with lead and arsenic. Some areas are contaminated with arsenic from metal smelters. And soil near high-traffic streets such as arterials or highways may have accumulated lead from leaded gas, and oil too if street runoff flows into the soil.

So if you’re not certain your soil is safe, get a soil test. Tests are easy, inexpensive, and a good idea for almost any urban gardener, especially if you want to garden next to the street – call the Garden Hotline for soil testing information. An excellent publication to learn more is WSU Cooperative Extension’s EB1884 Gardening on Lead-and-Arsenic Contaminated Soils.

What if my soil tests as contaminated?

• Grow food in another location where your soil tests safer – call the Hotline for more information.
• Compost enriches the soil for plant growth, and it also binds metals like lead and helps soil organisms break down oil or pesticide residues. Compost, like lime, also raises the pH of acidic soils, making lead and arsenic less available for plants to absorb. See the Soil and Composting guides to learn more, or contact the Garden Hotline for information on making, buying, or using compost.
• Avoid growing root crops or greens in contaminated soil (because they take up more lead) – instead grow fruiting crops like tomatoes, squash, or berries. Wash any harvest thoroughly.
• Build raised beds and import clean soil - see more information below.

What materials are best for building raised beds?

Treated lumber or creosoted timbers are not recommended for food-growing gardens, because they may leach toxins into the soil. Regular un-treated lumber will rot out in a few years. Some better options include:

• Naturally rot-resistant woods like cedar or juniper (though these will still rot eventually).
• Plastic lumber, made from recycled plastic (doesn’t rot, but a more expensive option).
• Masonry: bricks, broken concrete, landscape blocks, stone. These don’t rot, and they’re even better (and cheaper!) if they’re reused – call the Hotline for a list of sources for recycled an reused masonry. A single row of reused 8x16-inch concrete blocks makes enough height for a bed, is stable but easy to modify, and the holes in the blocks can be filled with soil to make a flower or herb border around your new bed.
• No walls, just amend soil with compost and pile up a raised bed to plant. Many gardeners find this easier.

What soil mix should I use for my beds?

A mix of about 1/4 to 1/3 compost with your native soil makes the best and cheapest gardening soil. But if you have concerns about soil contamination, you may want to buy a compost/soil mix to fill a raised bed. Be aware that some suppliers don’t tell you where their soil came from or what it contains. Call the Garden Hotline at (206) 633-0224 for information on local soil and compost suppliers, and how to shop for a clean garden soil mix.

When filling a raised bed, start with a layer of newspaper or cardboard over the existing lawn (or remove lawn) to limit weed growth. Plastic sheet or landscape fabric are not recommended under soil or mulch because they can limit water movement, and become a half-rotted mess later when you want to modify your bed. Mound the soil up in the bed, and water it well to help it settle and moisten the soil before planting.

How can I turn a lawn area into a garden bed?

The easiest method is called “sheet mulching”. You cover the grass with newspaper or cardboard, and then 6 to12 inches of shredded fall leaves, grass clippings, or compost. Wet that “mulch” well. You can then mulch the surface with wood chips to limit weed growth. Keep it all moist, and let the area sit through the winter to kill the grass and compost the mulch. Then plant perennials and trees through the mulch, or till it up for vegetables (remove wood chip mulch before tilling). Call the Hotline for more ideas on turning lawn into beds.

What are the best food plants to grow in the planting strip?

As noted above, if soil contamination is a concern avoid root crops and greens, and instead grow fruiting crops like tomatoes, eggplant, squash, and artichokes. Perennial fruits like blueberries and strawberries are another good bet, but thorny cane fruits like raspberries are only good if you’re willing to regularly prune or contain them. Grapes or other fruiting vines are another option, but be aware of SDOT’s plant height restrictions: 24 inches high, including the raised bed height, within 30 feet of intersections, and maximum 32 inches high elsewhere. For trees or vines, the area between 32 and 82 inches above the ground must be pruned to allow an open sightline for driver and pedestrian safety.

What about watering my planting strip garden?

Watering is challenging, because you’re far from the house faucet, and for safety you don’t want to leave a hose connected across the sidewalk (trip hazard!). Choosing lower water use plants like herbs and perennials helps, along with building the soil with compost and maintaining a mulch layer to conserve water. Soaker hoses or drip lines under mulch are the most water conserving method, but only if you can route the water supply under the sidewalk. Mulching, and using a watering wand to water individual plants may be easiest.

Do I need to care for my planting strip garden in the winter?

Yes! SDOT requires adjacent property owners to maintain their planting strip vegetation year-round. That means clearing out vegetable beds and planting a winter cover crop, pruning berries and trees, and maintaining walking areas around and through beds from parking areas to the sidewalk.

Where can I learn more?

For information on gardening classes, printed copies of Growing Food in the City (pdf), soil testing, raised bed materials, best plants for your site, least-toxic solutions to pest problems, and other questions, call the Garden Hotline at (206) 633-0224 (language interpretation available) or email questions from www.GardenHotline.org or see more My Lawn and Garden topics.

This information was developed in collaboration with the Tilth Alliance, Seattle Department of Neighborhoods P-Patch Program, and the Seattle Department of Transportation.