Saving the dam, controlling pests, planned for Rhody Garden
A spring meeting of the Portland Chapter of the American Rhododendron Society featured two speakers from Portland Parks & Recreation who discussed upcoming projects addressing the health of the Crystal Springs Rhododendron Garden just west of Reed College off S.E. 28th Avenue.
Betsy Redfearn, PP&R Parks Maintenance Supervisor for South and Southeast, talked about maintaining the lake and dam (which, as THE BEE reported in a previous article, is leaking), and working to discourage nutria rodents, and invasive yellow iris.
PP&R horticulturist Bill Alley described a comprehensive multi-faceted plan to help control insect pests, and then monitor the effectiveness of the program.
Several local, state, and federal organizations are involved in planning the future of the artificial lake at the Crystal Springs Rhododendron Garden. Decisions hinge on establishing compliance with the federally-mandated Endangered Species Act to protect salmon runs.
Redfearn advised, We need to make our choices clear about the dam there. We need to maintain the lake, not have a mudflat.
Were expanding spraying to remove the yellow iris that are spreading and choking the lake, and we need the dam to keep chemicals from spreading downstream. Were also planning to remove the creosoted timbers in the duck feeding area, and replace them with pavers. Redfearn proposed changing the angle of the current dam – but reminded that its removal would adversely affect both salmon runs and the health of the Garden.
We need to get the next generation interested in continuing our work to preserve this unique collection garden, she remarked. Bill Alleys son, Leo, a Lewis School fifth grader, reported that his class had made visits to the Garden part of their science studies.We check the water pH in relation to what is best for salmon habitat, he said. Weve determined that if the dam goes, it will wreck the salmon habitat there.
Bill Alley revealed a new and improved approach to controlling infestations of white flies, aphids, and other destructive insect pests in the Garden, based on a weekly combination of innovative pest controls. We also need to digitally monitor the plants resistance, as we experiment with the plans effectiveness, he said. We began about mid-April, spraying the plants with horticultural oils to inhibit hatching insect eggs. This was followed shortly after by aggressive foliage watering to remove pests and residual oils. The third part of the plan is the weekly release of predatory lacewing insects to eat target pests.
We have limited options for chemical applications, since this is a salmon-safe zone, but horticultural oils will cause no adverse effects. In addition, Alley continued, We need to improve Garden soil conditions to give maximum opportunities for the plants to thrive.
Well have a professional soil analysis to determine pH levels, and change some pruning methods. Spreading a good organic mushroom compost should give a microbial boost to soil ecology. This will be a 26-week commitment.
We also plan to establish patches of nectar-producing plants around the perimeter of the Garden to help feed adult lacewing predators.
We should also establish a control system to add new species to the Garden that are more resistant to insect damage. New equipment for more thorough mixing and spreading of horticultural oils will also be an integral part of the plan.
The Rhododendron Garden is a Portland Parks and Recreation facility – as is the adjacent public Eastmoreland Golf Course.
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