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University
of Rhode Island GreenShare Factsheets
Sustainable
Trees & Shrubs
Plant lists are invaluable resources for garden enthusiasts,
designers, nursery trades people and landscape architects. We
constantly consult books and nursery catalogs which list landscape
plants, especially those that organize plants by their characteristics
and landscape uses. As times and fashions change, new plants
emerge, old plants are rediscovered, and others lose favor and
disappear from these lists. But one point remains clear: listing
plants encourages their widespread distribution and use. The
purpose of this publication is to encourage the production and
use of landscape plants that are more sustainable: those which
are not invasive and require reduced inputs of pesticides, water
and maintenance.
Not long ago, plants from around the world could be introduced
into the landscape and provided with the care needed to ensure
their long-term beauty and success. Pesticide use was widespread
and its effectiveness unquestioned, labor for intensive care
was available and affordable, and the supply of natural resources
was considered limitless. Much has changed in recent decades;
we have become painfully aware of the limits of our natural resources
and the precarious balance of nature in which we play a pivotal
role. Many in our society are looking for ways to reduce human
impacts on the environment. Others lack the time or resources
to manage pests or maintain shrubs that require frequent pruning
or irrigation. These people should find the sustainable plant
list an invaluable resource.
Careful plant selection is the key first step in developing
a balanced and self-perpetuating landscape. However, plant survival
with minimal maintenance is not the only issue in sustainability.
We are having more difficulty with invasive exotic plants which
have escaped from managed land-scapes, displacing native plants
and disrupting natural ecosystems. The use of these potential
invasives cannot be seen as sustainable except in very controlled
situations.
This list of sustainable plants is not offered as the entire
answer. Proper siting, planting and maintenance are necessary
for a plant to prosper in the landscape. Therefore, climatic
conditions, exposure to sun and wind, subsurface soil and moisture
conditions, etc. must be considered when selecting plants for
a particular location. Sustainable or not, if one ignores the
site and a plant's cultural requirements, that plant will suffer.
In preparing this list and the accompanying plant descriptions,
we have targeted a professional audience, with an expectation
that through time, as these plants become more available, this
information will filter down to the consumers. Plants on this
list are proven performers in Southern New England (USDA Hardiness
Zones 7a - 5b), and many of them can be grown both north and
south of here (although the pest complexes might change). This
list is dynamic and will continue to change as new plants and
pests are introduced and as we learn more about existing ones.
The list is only a guide. Plants are included which have
qualities appealing to designers and plant lovers alike. Plant
descriptions include color, form, texture and growth habits as
well as maintenance requirements and hardiness. Many of the plants
on the list are well known and currently in production, while
others need to be grown and distributed more. We are well aware
that it will take a decade or more before some of the newer plants
are readily available in the trade.
Many of our favorite plants are not on the list, because
serious pests threaten their existence or their maintenance requirements
are too high for them to be considered sustainable. That doesn't
mean that we won't include a few of them in our landscapes. Life
would be indeed dull without a rose, but most of us would not
want to maintain a half-acre of them. Plants with occasional
pest problems or those with relatively minor problems are included
on the list with cautionary notes. It is only those plants with
life-threatening or chronic pest problems that are omitted from
the list, along with seriously invasive species. The list is
not intended to eliminate the production of high maintenance
plants with desirable traits. Instead, it is intended to encourage
the broader distribution of plants which seem to be better suited
to satisfying not only our horticultural requirements, but also
our environmental concerns.
There is renewed interest in native plants (those found
growing outside of cultivation in this region during pre-Colonial
times) which often are better acclimated, less pest prone and
more favorable for native wildlife than exotic plants. Native
plants are identified in Appendix 2. However, it should be noted
that many exotic insect and disease pests have been introduced
in the past 300 years. They have virtually eliminated some of
our native plants and become serious pests of others. In these
cases, it is useful to look to other parts of the world where
plants have evolved resistance to these pests. Even without introduced
pests, some native plants have problems in our landscapes where
they are far removed from their natural environments. A fabulous
forest shrub can have serious difficulties when sited between
a driveway and a sidewalk. It is likely that a sustainable landscape
will feature many native plants, but we think there are many
non-natives which should be considered as well.
Pesticides
are poisonous! Read and follow all safety precautions on labels.
Handle carefully and store in original containers out of reach
of children, pets or livestock. Dispose of empty containers
immediately, in a safe manner and place. Pesticides should never
be stored with foods or in areas where people eat.
When trade names are used for identification, no product endorsement
is implied, nor is discrimination intended against similar materials.
Be sure that the pesticide you intend to use is registered for
the state of use.
The user of this information assumes all risk for personal injury
or property damage.
For more
information, call the URI CE Gardening and Food Safety Hotline
at 1-800-448-1011 or (401)874-2929 from outside Rhode Island;
Monday-Thursday between 9 am and 2 pm.
University
of Rhode Island Cooperative Extension provides equal program
opportunities.
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