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Native Plant Synoptic Garden
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Longhorned Beetle (Anoplophora glabripennis) or Sudden Oak Death (Phytophthora ramorum).
Since the plants, trees, and shrubs in the Native Plant Synoptic Garden are natives of Western
Washington or cultivars of those natives, it is fair to say that regionally or locally observed
disease and pest problems can alert the Washington Park Arboretums Ground’s staff to problems
that could affect this particular collection. Second, when the Native Plant Synoptic Garden Plants
are first introduced, they will very likely undergo stress as they establish root systems and
acclimate to site conditions. This will be an important time to be vigilant about monitoring for
plant stress and taking remedial actions when necessary. Through personnel interview, it has
been confirmed that the Arboretum’s Grounds Staff agrees with this need for monitoring and
already has a plan in place which includes increased monitoring of new plants for the first three
years after introduction. For example, symptoms such as water stress are quickly diagnosed and
measures are taken to alleviate the problem. Finally, through monitoring it may be determined
that a plant, tree, or shrub needs to be removed all-together from the Native Plant Synoptic
Garden because of poor performance, hazardous condition, or a pest or disease that could threaten
other plants in the collection.
Mulching
Mulching around plants, trees, and shrubs provides many benefits. First, by using
mulches it may be possible to eliminate the need for additional fertilizers (Harris et. la., 2004).
As mulch decomposes, it contributes plant desirable nutrients into the soil; since it does
decompose, additional mulch will need to be added to maintain a proper depth for optimal
benefits to the plants (Watson et. la., 1997). Second, organic mulches should be applied to a
depth of three to four inches, “but even a thin layer of these mulches can quite effectively reduce
surface puddling, erosion, and mud splashing from rain” (Harris et. la., 2004). Third, mulch
applied correctly can benefit the soil by “increasing aeration, temperature, and moisture
conditions near the surface which encourage rooting and biological activities that enhance soil
structure” (Harris et. la., 2004).
For the Native Plant Synoptic Garden mulches should be used around plantings of trees,
shrubs, and plant beds. The arboretum already receives a fairly constant supply of wood chips by
allowing commercial landscape and tree care companies to dispose of the chips at the arboretum.
This supply of wood chips should be utilized in order to achieve the benefits previously stated.
Furthermore, as discussed in site preparation, wood chips would be an ideal mulch to be applie d