Thursday, March 6, 2014
WHAT SHOULD I PLANT
Jens Jensen, an early practitioner of the use of native plants and prairie restoration was influential at the turn of the 19th century –his perspective promoted reconnecting people to their landscape in the face of rapid modernization and homogenization.
As early as 1924 The Garden Club of America published a booklet by Edith Roberts and Margaret Shaw on the Ecology of Plants Native to Duchess County, which led to the publishing of their book American Plants for American Gardens. This was one of the first books to promote the use of plant ecology and native plants in gardening and landscaping. According to Darrel Morrison, (former Dean + Professor emeritus at the University of Georgia) who wrote the introduction to the reprinted copy in 1996, “utilizing patterns and processes that are intrinsic to naturally evolved landscapes, we can create designed and managed landscape that are clearly “of the place” and approach the ideal of sustainability.” We can also “protect biological diversity in the human developed landscape”.
Equally influential in this discussion was Ian McHarg’s, Design with Nature, the seminal text written in 1969 and consistently reprinted every decade since. It stressed the importance of considering ecological and environmental factors. According to Time Magazine, which labeled him “ an apostle of using ecology for planning”, he “cries that man is poisoning the very biosphere that sustains him and calls for a new ecological religion based on living in harmony with nature rather than on conquering it.
Janet Marinelli of NYBG writes that “biologists consider invasive species to be one of the two greatest threats to native plants and animals, second only to the outright loss of habitat to suburban sprawl, agriculture and industrial development.”
Within the last ten years the argument for planting natives over exotics has become heated. Virtually every garden magazine writes on natives, garden shows promote it and design competitions award methods of sustainability, inclusive of which is planting natives.
Currently, academics such as Doug Tallamy (Professor and Chair, Department of Entomology and Ecology, University of Delaware) write and lecture about the link between insects and native plants. In his most recent book “Bringing Nature Home” he exclaims that as biodiversity depends upon native plants, invasive turfgrass lawns limit the “carrying capacity” – that is the amount of species and foods available in a healthy ecosystem. The challenge is to recreate foodwebs in our gardens as some plants (natives) are significantly more effective that non-natives.
For millions of years these native plants have co-evolved with the native insects, and most insects can only reproduce and feed on the plants that they share an evolutionary history with. Wildlife is threatened when suburban development encroaches on once wild lands. As these beneficial insects are deprived of essential food resources when suburban gardeners exclusively utilize nonnative plant material. This leads to a weakened food chain that will no longer be able to support birds and other animal life. As we’ve lost 40% of all bird life in the Northeast over the last fifty years, this presents a compelling argument.
** It is important to note that native is not necessarily of the same country or continent, rather part of the same plant community or the same evolutionary background. Interestingly, a plant that is moved outside of its “native range” can still perform similar functions within this new ecosystem if it is linked genetically to a relative that typically exists within that new ecosystem. “Animals adapted to using/eating one member of a genus are often able to use a ‘congener’, (a member of the same genus) even if they have never interacted with that particular plant species in their evolutionary past. Traits such as leaf chemistry, shape, toughness can be so similar among cogeners that adaptations enabling an insect to grow and reproduce on one member of the genus predispose that insect to using other members of the genus.” 1
An example below...
Rhododendron periclymenoides (Pink Azalea)
photo: ctbotanicalsociety.org
Rhododendron viscosum (Swamp Azalea)
photo: plantsmen.com
Tallamy urges readers to do what they can to eliminate invasive alien species, to use native plants, to replace sterile lawns, which consist of two or three alien grass species that support little more than Japanese beetle grubs, with sustaining native plant refuges.
“There is no redundancy in plant species here, and consequently no redundancy in the community of natural enemies that can survive in lawn based habitats. There is no hope of controlling the millions of Japanese beetles being produced in our neighborhood lawns each year. The balance to control Japanese beetles can be achieved through well designed landscapes founded on a diverse array of native plants.” “Planting one type of crop typically favors only a few types of insect herbivores – not enough to support a diverse, redundant community of predators and parasites. Under these oversimplified conditions, herbivorous insect populations typically escape the control of their natural enemies and explode. This is good for the pesticide industry but little else.” 2
1 Doug Tallamy, Bringing Nature Home
2. Ibid, D. Tallamy
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