Joyce Hostyn

Ditchscaping for watershed health

“We should stop thinking in terms of drought tolerance. Reframing our focus to drought dynamic will give gardens the opportunity to implore their adaptability—to respond to the site conditions and evolve into a stable ecosystem. Drought tolerance is dead. The future is drought dynamic.”

Kevin Williams

ditch planting with cardinal flower

Benefits of ditchscaping

Benefits of ditchscaping include healthy watersheds, habitat corridors, beauty, biodiversity and climate resilience. Every ditch eventually empties into fish habitat—a stream, river or lake. Ditches planted with a diversity of plants act as a soil sponge, either absorbing water on site or filtering and cleaning out contaminants before any water flowing through reaches fish habitat.

image of a diverse selection of native prairie plants and the depth of their underground root systems in contrast to the very shallow root system of kentucky bluegrass
Nature Education-1995 Conservation Research Institute, Heidi Natura

Benefits of replacing turfgrass in ditches with deep-rooted native plants and their associated microorganisms includes:

  • Absorbing and filter contaminants, road runoff, oil, garden chemicals, soap from washing cars, garbage, excess nutrients, pesticides and dog waste
  • Slowing down runoff, reducing downstream erosion and flood risk, increasing the rate and quantity of water infiltration and recharging ground water
  • Stabilizing ditch banks, reducing erosion
  • Providing habitat for birds, butterflies and pollinators
  • Acting as habitat corridors

Guiding principles for ditchscaping

picture of bumblebee landing on nodding beggartick flower with switchgrass in the background

Flourishing ditches have dense vegetation that doesn’t interfere with the ditch’s ability to prevent flooding.

  • Never obstruct the flow of water, seek only to slow it down in order to absorb as much as possible on site
  • Don’t use fertilizers, herbicides, pesticides or gas-powered equipment as every ditch eventually empties into fish habitat
  • Chlorine is highly toxic to fish and amphibians, so when establishing plants use water from rain barrels or allow tap water to sit until the chlorine evaporates
  • Prioritize stabilizing the sides and bottom of the ditch to prevent erosion and avoid downstream silting
  • Avoid compacting the soil by walking on it when wet, which reduces the ability of the soil to act as a sponge
  • Keep in mind that municipal work crews may need to dig up or disrupt your planting, sometimes without warning, if there’s a burst pipe or roadwork

Understanding planting zones

illustration showing low, middle and high planting zones fora ditch
Credit Valley Conservation

Ditches have three planting zones, each one representing a different level of soil moisture that require different plant choices. For inspiration on plant choices for each of these zones, check out Little Forest Kingston’s spreadsheet with seven different Pocket Meadow plant communities.

  • Low zone: Bottom of the ditch. Select plants who who don’t mind being partially submerged in spring or during heavy rain events, but who can also handle drying out. For native plants in our area that might be suitable, check out the wet spots tab.
  • Middle zone: Sides of the ditch. Select plants that stabilize the slopes and that can tolerate both wet and dry conditions.
  • High zone: Top edges of the ditch. Select plants that tolerate drought. If you want to maximize privacy and biodiversity, select taller plants for the edge closer to your house. Consider plants in the keystone bird buffet tab.To avoid obstructing sightlines, using lower growing plants that can handle salt, dog waste and snowplows on the edge adjacent to the road. Consider plants in the sunny boulevard tab.

Designing the plant community

illustration of four planting design layers: 1) groundcover layer with low growing grasses and shallow roots 2) seasonal theme layer which provide visual interest, pollen and nectar through the season 3) filler layer of self-seeding plants which move around and fill gaps 4) structural layer of long-lived forbs and grasses which offer multi-season interest
Kendra Scanlon, Exploring regenerative planting strategies for green rainwater infrastructure

Choose plants that fill different functional roles, filling niches in space and time. Together these plants weave together into a layered, drought dynamic plant community. Each of the plants in the pocket meadow spreadsheet is labelled with functional layer and seasonal bloom time:

  • Cover and protect the soil with a living green mulch of low growing sedges, grasses and ground hugging plants
  • Design for staggered bloom throughout the seasons to ensure a continuous supply of nectar and pollen and increase visual interest
  • Include plants that fill in gaps by seeding or spreading between other plants
  • Use structural plants with strong architecture and four season interest as focal points and to provide seeds for birds in fall and winter
mood board for a ditch planting palette

Plant densely (30 cm on centre) to quickly establish the plant community, stabilize the slope and reduce the ability for unwanted plants to establish. Izel Native Plants suggests the following criteria for choosing plants to help stabilize slopes and increase infiltration:

  • Root structure: fibrous, branching roots or deep tap roots hold soil in place, create passages for water infiltration and aeration, sequester carbon and diversify microorganisms
  • Stem/crown structure: strong, upright stems or dense crowns help intercept and slow down runoff, giving it more time to soak into the ground
  • Leaf structure: broad spreading foliage, with leaves oriented horizontally or with large total surface areas intercept and slow rain before it reaches the ground
  • Colonizers: spread quickly, filling gaps and helping stabilize soil
  • Outside season: plants such as sedges with persistent evergreen basal foliage are effective even during when most perennials are dormant and many native grasses keep their structure in winter, continuing to buffer rainfall and intercept runoff
  • Quickly establish: The force of water can wash away plants that aren’t yet anchored by their root systems.

Increasing biodiversity

  • Maximize support for birds, bees, pollinators and insects by choosing keystone plants and plants which support specialist bees
  • Strategically place stumps or logs to support insects, woodpeckers and specialist plants
  • If your ditch is deep enough, experiment with pool and drop structures that force flowing water to slow down, pool and then overflow and drop to the next level
  • Strategically pile rocks to to support insects, amphibians and specialist plants

Maintaining your ditchscape

“Treat plants as dynamic systems.” Plant Diversity is functional. It arms G.I. facilities with a range of benefits that ensure the vitality of the system, Thomas Rainer

Ensure that your ditch continues to do its job of preventing flooding during a heavy rain. If you impede the flow, while you might not see the impact on your own property, it could impact neighbours further down the street and you may be charged if the city needs to root out debris from a blocked culvert. To prevent debris from entering the culvert, you could cover the opening with chicken wire and periodically clear debris that collects against the wire.

  • Avoid light mulches as mulch can get washed downstream (living green mulches of ground hugging plants are ideal)
  • Remove volunteer trees or shrubs
  • Remove debris blocking culverts
  • Check for signs of erosion, either replanting those areas or increasing planting density or strategically place stones or stumps
  • Check flow during a storm, ensuring vegetation isn’t impeding drainage
  • Increase vegetation density and root diversity to increase infiltration

References