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What's Blooming: Children's Garden Water Feature


By Chelsea McLean, Horticulturist

One of the best parts of working at a cultural institution like The Gardens on Spring Creek is working with volunteers, students, and civic groups who step up to join our Centre Ave adventure. When local Eagle Scout Walker Armstrong came to us last year with a proposal to build a water feature for the Children’s Garden, it was a no-brainer.

Walker Armstrong

Walker grew up visiting The Gardens with his family and felt compelled to give back after years of enjoyment. During his visits he noticed that the existing pond and waterfall operate in a closed loop, the result being dark, cloudy water with low oxygen levels as vegetative matter decomposes and the sediment cycles through the system. I can attest to the work that goes into keeping the system functioning soundly.

He found a solution in biomimicry, the concept of taking design cues from the natural world. “I am hoping to achieve a healthy ecosystem, along with revitalized aesthetics,” Walker explains. “The up-flow wetland filter allows for additional biological filtration, creating a more stable, healthy ecosystem.” In a natural wetland environment, murky water enters, the particulate matter is taken up by plant roots in a process known as rhizofiltration, and out flows clear water. Cattails (Typha spp.) are a well-known example of plants found in marshes, riparian zones, and swamps that are hard at work keeping the ecosystem functioning properly.

Strolling through the Children’s Garden you’ll notice a raised gravel basin overlooking the pond. Three seasons a year you’ll find water-loving plants like cannas (Canna x generalis), rush (Juncus effusus), creeping jenny (Lysmachia nummularia) and papyrus (Cyperus prolifer) planted within the gravel. Inside a skimmer box to the east side of the pond, a pump moves water from the main body through a system of tubing where it then percolates up through the gravel and fills the basin. The filtration mechanism is a two-step process: the bacteria that naturally colonize the basin break down the silty particulate matter that has breached the two filters safeguarding the pump. Then, the roots of the plants absorb the particles and the now thrice-filtered water cascades down a waterfall back into the main body of the pond.

Summer: in full operation, cannas blooming

Regular maintenance of the up-flow filtration pond is crucial to prevent the system from becoming overwhelmed. Each week I flush out the tubing to prevent silt from clogging the outlets. I also clean the filters in the skimmer box to ensure large debris doesn’t prevent water from reaching the pump. If the pump is not able to draw in water at a precise rate, it will burn out.

Winterizing a feature like this is important. Wind and ice make for harsh winter conditions that will damage various elements of the feature. The pump gets disconnected and stored indoors in water to prevent the gaskets and seals from freezing and drying out. The cannas and papyrus are dug up for the winter and sleep soundly in our on-site nursery where they will be re-installed during the warming temperatures of the spring.

This year I left the rush and creeping jenny planted as an experiment to test hardiness in less-than-ideal conditions. Rush is semi-evergreen in warmer climates, and being rhizomatous, has established itself nicely in the basin. As of this writing, they have not had any regular or supplemental water save for a few rain and snow events. So far I’ve been pleasantly surprised but the true test will be how they fare in the depths of our Colorado winters.

Winter: winterized basin with rush and creeping jenny

As is often the case, the system is theoretically simple, but in practice can be complicated. It takes someone with a passion and practiced experience to design and install a feature of this scale. In working with Walker over the course of a season, I was curious how a high school student arrived at a project like this. “I have been interested in water features for my entire life, and I began installing water features around my house as a child,” he says. “I continued to improve upon my skill set as I installed reiterations on my previous features.”

The filtration pond is not just functional, but also adds beautiful color, texture, sound, and dimension to the space. Thanks to Walker’s contribution, visitors can witness ecological design in action and simultaneously snag a zen-like moment in their day. Be sure to check it out next time you’re on the grounds. It just might inspire you to dig into some biodesign for your own residential landscape challenges.

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