V4 12 Stormwater Maintenance Manual

generally not necessary. Avoid feeding during the hottest/driest parts of the year or late in the season when plants should be entering a dormant or less active phase. Nutrients should be added with granular, slow-release fertilizer (minimum 3 months) with a target N-P-K ratio of 18-6-12. Alternatively, a generic 10-10-10 slow-release general landscaping fertilizer can be used and is often available at garden and home centers. We recommend Harrells, Osmocote®, and Nutricote® products. Where an organic fertilizer is preferred, Plant Tone (Espoma), or Earthworks Replenish are also effective. Apply fertilizers in accordance with the manufacturer’s recommendations and instructions on the container. Soil tests are recommended every year or every other year, with target values the same as for general landscaping. Every two to three years, trim the green roof to encourage additional leaf development at the plant crown and to spread regenerative cuttings across the system during the spring season. A string trimmer or even a lawn mower set at the maximum height with a mulching blade can be used. Everybody likes a haircut, and so do your plants! During each green roof maintenance event (or monthly) it is advisable to monitor plant health. These observations may adjust the timing or needs for other maintenance tasks. An overview about green roof maintenance in each season and general sequencing about plant care seasonal is illustrated below. SEASONAL GREEN ROOF MAINTENANCE – MOST U.S. REGIONS Plant Type Spring Summer Fall Sedums Fertilize (April) Weed (every 2-4 weeks) Weed (October) Weed (May) Watering (during Trim* (optional – May) droughts) Perennials Trim* (March-Apr) Weed (every 2 weeks) Weed (October) Fertilizer (April) Activate irrigation system Replant* (if necessary) Replant* (if necessary)

Fertilizer (April) Activate irrigation system Replant* (if necessary) Replant* (if necessary) Winterize irrigation Ornamental Grasses Trim* (March-April) Weed (every 2 weeks) Weed (October) Fertilizer (April) Set Watering Schedule (or Replant* (if necessary) Replant* (if necessary) use irrigation system) Winterize irrigation *Trimming of grasses and perennials should be conducted early spring before new growth appears, or late fall, depending on the specific plant variety. Sedum trimming should be conducted during active growth in spring. Replanting in spring or fall will also be determined by the specific plant variety. SPRING SEASON  Conduct routine inspections and spot weeding (2-3 week intervals) to prevent flowering and reseed.  If soil testing suggests it is required, or in the absence of a soil test, apply slow release fertilizer.  Monitor plant health and replace any plants, as necessary, taking note of any areas impacted by rooftop microclimates (shady spots, exhaust vents, drip edges, intense reflected light, etc.) where replanting may not be successful, and alternate plantings or an alternate approach (i.e., decorative stone) may be necessary.  Do not apply herbicides or pre-emergent weed control without first consulting a horticulturalist or your GreenGrid representative. (888) 404-4743