It’s not an easy life for municipal street trees, according to the Hailey Tree Committee, but that may no longer be the case if a new ordinance goes into effect this spring.
The proposed city code change—formulated by the Tree Committee—lays out guidelines to both extend the lifespan of trees within Hailey’s rights of way and promote a diversity of species. Under the ordinance, city arborists would classify existing trees based on species, diameter and heritage, preventing those with historical value from being removed during new projects.
Also governed by the ordinance is proper tree spacing, tree well construction and soil composition. Tree Committee Chairwoman and arborist Linda Reis said limiting salts, herbicides, petroleum-based products and heavy metals in topsoil is one means to increase tree longevity. Another is spacing trees at reasonable distances.
“Tree spacing in large-soil areas, like parks, can use group plantings, but it’s more difficult for trees [near] sidewalks when soil space, air space and water are limited,” she said in an interview. “Single-tree plantings work better than groups for sidewalks and limited-soil volumes.”
According to the ordinance, planting material would need to be high-drainage “suitable san-dy loam soil” consisting of 50 to 80 percent medium and coarse sand, up to 35 percent silt and up to 20 percent clay. Sandy loam soil ensures that water can freely move to a tree’s roots without oversaturating the plant, Reis said, and decreases the likelihood of defoliation and fungal infections.
“Sandy loam is an excellent soil type because it has excellent drainage, can retain some nutrients and doesn’t compact as much as clay soils,” she said. “It also provides more air space than heavy-clay soils—oxygen is critical to root health.”
The proposed code change, which cleared its first City Council reading Monday, also mandates that trees be planted during spring or fall and be protected from snow removal equipment and traffic.
“Snow removal can damage and has damaged street trees. When they’re small, their thin bark is easily damaged when the cambium is exposed,” Reis said. “If half the [tree’s] circumference is damaged, it will likely die.”
The Tree Committee ordinance previously earned unanimous Planning and Zoning approval last month.