Lake Whatcom-friendly Lawns and Gardens

Lake Whatcom Guidelines

Since Lake Whatcom serves as our drinking water source, the City has adopted specific regulations and guidelines for materials and practices that protect the lake from excess nutrient runoff, especially phosphorus. Too much phosphorus causes oxygen depletion in the lake, which degrades water quality and harms fish and wildlife. In the Lake Whatcom watershed, it’s the law to use zero-phosphorus fertilizers, mulches, and soil amendments (BMC 15.42.050 Section D).

Not sure if you live in the Lake Whatcom watershed? Use this map to help you find out. If you live outside Bellingham City limits but in the Lake Whatcom watershed, requirements may differ. Learn more about Whatcom County’s Lake Whatcom watershed regulations. Live outside the watershed? Washington State has restrictions on phosphorus use that apply to all properties.

Best Practices for Lake Whatcom Lawns and Gardens

Additionally, we tested various landscaping products from multiple vendors to learn about phosphorus and fecal coliform bacteria content. Through this testing and partnership with landscaping professionals, we developed these guidelines to help you pick the best products for your lawn and the health of Lake Whatcom. Some best practices for lawn and garden maintenance in the Lake Whatcom watershed are also provided below.

Avoid fertilizers, pesticides, and herbicides. If you are considering additional nutrients to help your yard, test your soil first to better understand the soils needs. You can buy a soil testing kit at your local garden store.

If you must use these products, remember that fertilizers, mulches, and soil amendments containing phosphorus are against the law in the Lake Whatcom watershed. When shopping for fertilizers, mulch or similar soil amendments, be sure to look for the “0” in the middle of the bag, which indicates a zero-phosphorus product. 

Mulch recommendations vary slightly in the watershed to protect the lake from nutrient (phosphorus) runoff:

  • For landscape beds and gardens, use hog fuel mulch. This material supports helpful soil microbes and is lower in soluble reactive phosphorus.
  • For building healthy soil, use only mulch, topsoil and compost products approved for watershed use by the City. These low-phosphorus products are the best option for protection of lake water quality.
  • For managing weeds, use mulch to naturally suppress them. Learn how to manage weeds naturally.

  • If possible, replace lawn area with native landscaping to reduce nutrient pollution and yard maintenance.
  • For remaining lawns, mow periodically with the mower set to 2” or higher for most turf types. Higher grass absorbs more water and improves capture of grass clippings.
    • Collect grass clippings and dispose them in a curbside yard waste bin or offsite using services listed below.
    • If disposal is not an option, use a mulching mower, being careful to mow at a high setting and during dry periods. Excess phosphorus from mulched clippings can end up in the lake where it feeds algae blooms, harming water quality and fish.
    • After mowing, sweep lawn trimmings away from the street and sidewalk. Lawn trimmings left on pavement can wash into storm drains, clogging the stormwater system and adding excess nutrients to our waterways.

Yard waste such as leaves and grass clippings can cause pollution and you are required to manage it properly. Placing yard waste near ditches, roads, and water bodies is illegal.

Yard waste piled near ditches, roads, or water can:

  • Cause flooding and cost money by plugging storm drains and culverts.
  • Degrade water quality and harm fish and wildlife because pollution from excess nutrients causes oxygen depletion in the lake.
  • Harm native habitat and vegetation by spreading invasive species.

Best choices for yard waste disposal:

Composting at home:

Lake Whatcom is sensitive to nutrients from compost piles and compost use. If you live in the Lake Whatcom watershed, the best option for water quality protection is to dispose of yard waste in a curbside bin or offsite using one of the options listed above. If you do practice home composting, please follow best practices for water quality protection.

Place hardwood chips, arborist chips, or hog-fuel mulch over soil to reduce erosion. Use a barrier such as bricks or wood to contain soil in the garden.

  • Let your grass go dormant during the summer.
  • Plant native plants to reduce the need for water.
  • Avoid over-watering your lawn and garden.
  • Explore more water conservation methods.

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