Policy Statement on Tree Planting
Adopted September 1991; Revised September 1993 (PDF Version)
The California Native Plant Society (CNPS) is dedicated to
the preservation of native flora, and to the restoration of that
flora where it has been damaged or destroyed. Thus CNPS will
encourage the planting of trees where appropriate. Tree planting
projects have been frequently damaging to local ecosystems, due
primarily to poor planning. The intent of this policy statement
is to encourage appropriate tree planting programs and
discourage those which are inappropriate. The cumulative impact
of development in California has removed so much native
vegetation that appropriate native species should be planted
wherever possible, even in the context of the urban garden. CNPS
encourages persons planning a tree planting program to evaluate
their program relative to this policy.
Why should native trees be used in urban settings?
- Many California native trees are attractive in urban
settings by conventional landscape criteria. Enjoyment of
these trees by urban residents can broaden public awareness
of what is truly beautiful in natural environments.
- The planting of native trees in urban settings may enhance
gene flow between native stands separated by urban
development and habitat fragmentation.
- The planting of native trees in urban settings can result
in increased numbers of native birds in the area; many birds
and other fauna are adapted to using native trees and prefer
to feed and rest in these plants.
- The presence of native trees in an urban environment
provides an educational benefit. They serve as a living
illustration for discussions about the biology,
identification, and uses of native species.
- Many native trees (in particular, many oaks) are adapted
to low summer water demands; indeed, mature trees of these
species need no summer water, and are particularly
appropriate for areas with low water availability.
When should native trees be planted in natural settings?
California Native Plant Society supports tree planting when the
following criteria are met.
1) The tree species exists, or existed, in the area chosen
Tree planting is not appropriate where trees have
not been a historic component of the plant community. Planting
should enhance an altered or destroyed part of a plant
Tree planting is encouraged by CNPS when the
planting contributes to the attributes of the local ecosystem.
Species selection should be of species found, or once found,
naturally in the area considered for planting.
Since a CNPS goal is to enhance natural, native
plant communities, a planting should be representative of that
plant community. The definition of natural and native should be
rigorous and highly localized. This, however, is a very common
misunderstanding in tree planting, where 'any' California native
tree has been considered appropriate. Tree planters should
consider and evaluate variations in slope aspect, soil type,
degree of soil saturation, amount of shading, and several other
factors when selecting particular species to be planted.
2) The seeds or planting stock were gathered from local
sources, or can be shown to be genetically identical to local
Genetic contamination may result from the
importation of seed or cutting stock from a different area. For
example, different foreign stocks are currently contaminating
local stands of Monterey Pine in the Monterey area. It should be
recognized that local populations may have subtle genetic
adaptation to the area that may not be present in other
In some cases plantings have used species that are
closely related to the endemic species. These might result in
unforeseen effects to dependent ecosystems, and possible
undesirable genetic contamination, but may in some cases be
harmless and would restore such things as a vertical layered
structure or animal habitat that could not otherwise be
3) The planted species should represent a full range of
species that are found naturally in the area.
The plantings should represent an appropriate range
of species, in order to recreate as natural an ecosystem as
possible, and to avoid the replacement of a heterogeneous,
multispecies community with a monotonous single species
Tree replanting after fire or harvest has
frequently been from a single species, usually with the goal of
enhancing some commercially exploitable species. This leads to a
loss of diversity, and the possible risk of extinction of
non-target species. It is therefore CNPS policy that the natural
state of tree species diversity be a primary goal of any tree
planting, and that the species selection represent all
successional stages in the development of the ecosystem,
especially where the establishment of such communities is vital
to species preservation.
4) The planted species should be appropriate to the stage of
plant community development at the site.
It is important for tree planters to understand the
level of development in the plant community. Certain trees occur
early in the development of the community, to be replaced by
different species as the community changes with time. The stage
of plant community development into which a planting would be
placed should be understood, so that planting be appropriate to
the stage that is desired. In addition, there could be poor
survivability of a species not suited to the stage currently
represented at the site. Plantings should not be designed to
eliminate successional communities that are vital parts of the
regional ecosystem, and plantings should be appropriate to the
successional community at the planting site.
5) The planting will not have an adverse effect on rare,
threatened, or endangered animal or plant species.
The likely impact on surrounding rare, endangered,
or threatened species of plants and animals should be strongly
considered. Evaluate what changes in shading, water
distribution, litter buildup, habitat provision, secondary
support for competitive species, etc., would be induced by the
planting. This may invalidate the selection of otherwise
appropriate species in the area occupied by rare, endangered, or
threatened species. CNPS realizes that, due to loss of community
diversity and the loss of availability of sites for plant
reintroduction, it is necessary to inhibit the natural community
progression and development in order to protect certain species.
Thus tree planting should be considered relative to these goals.
6) If the first five conditions cannot be met, but a
significant advantage can be claimed through the planting of a
non-native species, then only non-invasive species should be
Invasive non-native taxa have excluded native
species from millions of acres in California. Examples include
highly invasive trees such as Tree of Heaven (Ailanthus
Exceptions to policy may be made where range
extension or community alteration is being attempted in order to
preserve a rare and endangered species that cannot be protected
by other means