Module 7: Plants for Bioretention

Module 7: Plants for Bioretention Melanie Mills, MLA Central Coast LIDI

Technical Assistance Memo (TAM)

Bioretention Area Type and Plant Selection • Surface grade and ponding area • uniform surface grades (Zone A only) • sloped surface area (Zones A and B) • a third planting area

Central Coast Plant List for Bioretention Tolerant of varied moisture conditions (wet and dry) Tolerant of varied soil types and growing conditions pesticides/herbicides Available in Central Coast plant nurseries Low maintenance requirements Not invasive weeds Do not have aggressive/invasive root systems Exhibit an attractive appearance

Plant Selection • Environmental site considerations • high and low temps • coastal influence • winds • fire hazard • Project specific considerations • project type and user expectations • ROW height limits • approved street and parking lot trees • anticipated maintenance level

Native vs. Non-native • List provides primarily native species • wide range of benefits (food and forage for native wildlife, adaptation to local conditions, low/no water use) • do not specify non-native plants in proximity to natural areas • be aware of invasives (California Invasive Plant council, www.cal-ipc.org)

Irrigation • 2-3 years for establishment • Supplemental for periods of extreme drought • Consider accepting a “dry” look • Weather-based controller to avoid watering during wet weather • Proper design of application rates to avoid overwatering

Trees in Bioretention • Provide sufficient landscape width (8’ preferred) • Locate trees on side slopes* • Select trees that tolerate seasonally wet soils • Do not specify trees with invasive roots • Provide extra support on slopes • stake securely (during establishment) • inspect 2x/year and after storm • Locate trees on slopes min. 5’ from inlets to avoid erosion around root ball

Incorporating Existing Trees Location Species Anticipated disturbance

Guidelines for Municipalities • RFPs and/or bid packages for public bioretention projects should clearly define expectations • bioretention soil mix specification • provide guidance for plant species selection • require appropriate plant zone placement • operations and maintenance protocols

Finding the Plants • Some Central Coast nurseries that regularly grow the plants on this list • Central Coast Wilds, Santa Cruz • Last Pilitas, Santa Margarita • Native Sons, Arroyo Grande • Rana Creek, Carmel Valley • San Marcos Growers, Santa Barbara • Santa Barbara Natives, Santa Barbara

www.centralcoastlidi.org

Module 7: Plants for Bioretention