Centennial Tree Project
In our area, venerable trees (many more than 100 years old) of native species are among the most recent descendants of a regional forest thousands of years old. Christened “Centennial Trees,” they are known to be adapted to the local soils, sites and climate of the Birmingham, Alabama, region. Their progeny – future Centennial Trees, the focus of this program – have a greater potential to live for multiple human generations than most non-native species on similar sites, and with greater sustainability (with less long-term human intervention).
Ecologically, locally-sourced native trees are synchronized with Birmingham's growing seasons and with the growth, development and movements of associated animal populations, from salamanders to pollinator insects to migratory songbirds. However, numerous factors including habitat loss, an overabundance of seed predators, crowding out by invasive exotic plant species, and human use and maintenance practices inhibit natural seed regeneration throughout much of the urban forest. In addition, a majority of these species are under-represented in or completely absent from the horticultural trade. The need for stewardship activities such as this program is acute if the future urban forest is to be a viable part of our communities and our regional ecology, in synch with the elements of natural forests, such as the timing of spring leaf bud break and flowering.
Aesthetically, Centennial Trees are as iconic to the Birmingham landscape as its historic architecture. Native trees define the character of many neighborhoods and the “feel” of our parks. The Centennial Tree program is broadly applicable to many sites where the native forest has been diminished or lost, including eroding slopes of new housing developments, in tornado-damaged communities, and on the eroding banks of ancient waterways such as Shades Creek, a tributary of the Cahaba River, eroded by years of excessive storm water runoff. The many native tree species available for planting include upland species such as scarlet oak, blackjack oak and southern sugar maple, and river species such as green ash, American hornbeam, and tag alder.
From 2009-2014 approximately 1,500 native tree seedlings were planted on about fifteen sites in the metropolitan area of Birmingham. The typical planting site is about a half-acre, planted with about 100 seedlings. Survival after two years has averaged about 80%, even on sites with very poor soils and after summers with pronounced droughts. This is testimony to both the adaptability of locally-collected seed to the local climate, and timely after-care by trained volunteers. At the first (and flagship) planting site, George Ward Park, designed in 1925 by the Olmstead Brothers, the planting of 1,000 seedlings over five years resulted in matching one-for-one the original trees on the three-acre site. Some so-called slow-growing oaks and hickories grew ten feet in five years, and were the first progeny of the original forest trees to grow in-situ in over 80 years. In addition, native herbaceous plants that colonized the site and the accompanying accumulation of organic matter, such as leaves and branches, in the planting area created new habitat for additional “volunteer” seedlings beneath their parent trees.
Youth Serve of Birmingham Potting Oaks
A planting of ~50 oaks, upland species including northern and southern red oaks, black and blackjack oaks, and white oaks, raised through this program was installed at Red Mountain Park in 2013. Birmingham Mayor William A. Bell declared these to be “Freedom Oaks” to commemorate fifty years of civil rights progress amid the city’s historic year-long celebration. Red Mountain Park is a former mining site, and in 1890 it became the first such operation to pay its African-American workers in currency, as opposed to company scrip. Plantings here will continue.
The Centennial Tree Program has ignited the interest and enthusiasm of a number of organizations (see Partner list). The program is an excellent means of partnership development in which BBG can lead positive community efforts in tree planting, forest rehabilitation, renewed civic pride in under-maintained public property, river enhancement, tornado damage relief, educational opportunities for schools, civic groups, churches and city governments. Many educational topics can be woven into these “teachable moments” including soil science; plant-soil relationships; plant nutrition; seasonal phases of plant growth and development; seed germination; proper planting techniques; proper tree species selection, establishment and care; fall color; winter dormancy; ecology; landscape design and local history. The program is a great means of bringing citizens together with public officials for tree planting events on significant holidays and commemorations. In 2015, the Cahaba River Society will award the Centennial Tree program its “Vision Award” for creative solutions to watershed restoration, an important piece of the society’s mission.
Program activities are largely dictated by the timing of seedling growth and development, weather, and best practices. They occur throughout the year, but peak in the fall with seed collection and out-plantings. Typical activities are as follows: fall seedling planting and simultaneous seed collection for future crops; fall seed preparation and storage; fall transport to BBG for storage and germination; planting the germinating seed in containers through winter and spring; labeling and tracking seed lots through the year; watering, fertilization and weeding during active growth (mostly in summer); covering containerized seedlings growing outdoors to protect against deep freezes in winter; identification of planting sites and seed source trees throughout the year.
Each step of the process provides an opportunity for BBG’s staff to teach volunteers. The educational value of the Centennial Tree program is assumed to be fifty percent of the program; the other fifty percent is “trees in the ground.” Volunteers have included school children and their teachers, college students and their professors, working and retired professionals, members of civic clubs, elected officials, and girl scouts.
Seeds and seedlings are already in the pipeline for the program’s continuation, and partners have been recruited. Friends of Avondale and Red Mountain Parks, for example, have each committed to planting for at least three consecutive years. The Edgewood Garden Club has written in their 2014-15 membership booklet that the Centennial Tree program is a program that they intend to continue to support. The city council of Homewood has voted to continue their participation in the Centennial Tree program for a number of years to come, upon the advice of the citizen’s advisory committee, the Homewood Environmental Commission. The Creative Montessori School in Homewood will replace their heritage trees (slated for removal in 2015 for building expansion) with the progeny from those trees. Seed is being collected by school children under a teacher’s supervision and instruction from BBG staff. The community of North Smithfield-Greenleaf Heights has committed to a third consecutive annual planting of their tornado-damaged main park in 2015.