V4 12 Stormwater Maintenance Manual

GREEN ROOF MAINTENANCE GUIDE Performing routine, preventative maintenance is essential to keeping your green roof healthy. All maintenance should be performed by trained and qualified personnel and using horticultural and safety best practices. Working on elevated structures may require safety training and specialized, protective equipment. Please consult applicable safety regulations and building codes. This installation guide outlines the basic tasks associated with ongoing green roof plant care and maintenance. Seasonal plant care and green roof maintenance is outlined below for traditional ‘extensive’ (nominal 4” depth) green roofs. Green roofs involving ‘semi-intensive’ (6”) and ‘intensive’ (8”) modules (aka “roof gardens”), typically incorporate larger and more diverse plantings like ornamental grasses and herbaceous perennials. The associated care and maintenance for these applications is generally more frequent and similar to ground-level landscaping. MAINTENANCE ACTIVITIES AND SCHEDULE The type of maintenance activities required for a green roof will depend on the plantings and regional climate. The seasonal guidelines noted below are typical for ‘extensive’ green roofs planted with low-growing, drought-tolerant sedum and succulents in most moderate climates (Zones 3-7) with 30-50 inches per year of precipitation. Basic green roof maintenance involves watering, weeding, and plant care. Proactive maintenance will always be best. Watering Green roof systems are typically designed using hardy, drought-resistant varieties that can thrive in a harsh roof top environment. Extensive green roofs typically don’t require built-in irrigation systems in most regions. However, during periods of prolonged drought, the extensive green roof should be watered to sustain plant health. As a general rule, if natural precipitation is < 0.5-inch in a 10-15 day period during the growing season, watering may be needed or plants may become dormant or fail. Prolonged temperatures above 85 degrees F and/or very windy locations may need to be watered sooner. Supplemental irrigation should include the application of approximately 1 inch of water once per week until more moderate precipitation patterns resume. In

ooner. Supplemental irrigation should include the application of approximately 1 inch of water once per week until more moderate precipitation patterns resume. In arid climates (including Southern CA, Southwest U.S., High Plains and Mountain states and central TX) as well as the Southeast U.S. and Gulf Coast regions, permanent irrigation systems are recommended for all green roof systems. Weeding The green roof should be visually inspected and spot-weeded every 2-4 weeks during the growing season. It is important to remove weeds before they flower and set seed to minimize future efforts. Like any garden, preventative, regular weeding has the best results with the least total effort. In most climates, for green roofs < 5,000 sf, weeding will require about 10 to 20 man-hours per year. While weeding, it is a good idea to inspect the roof drains and insure that water not utilized by the green roof can drain freely off the roof. Plant Care Green roof plant care has two primary components – fertilizing and trimming. Fertilizing should be conducted at least annually in spring for the first 3-5 years after installation, and then on a reduced schedule if soil testing and plant performance suggest it is advisable. Late summer or early fall fertilizing may also be suggested depending on the plant mix and region, but is (888) 404-4743