Animal Tales

Mulch

Noah Huber parks next to the leaf pile to show the size. This pile will soon be shredded into mulch. This pile includes evergreen trees used during December and will be made into a bark mulch.

Nature Full Circle

Recycling comes in many different forms and isn’t just about plastic or cardboard.

The Milwaukee County Zoo has found a way to recycle and reuse trees and leaves collected within the Zoo. The Grounds Department makes two different kinds of mulch out of the natural materials – a bark mulch and a leaf mulch – that will end up back in the Zoo giving plants nutrients, preventing weed growth and controlling water.

In late summer, the Grounds crew will collect brush from around the Zoo and pile it in the far back corner of the parking lot. The brush includes tree damage or trees taken down from reforesting work. A big addition to the pile at the start of the year is the 60 plus evergreen trees that were decorated in the U.S. Bank Gathering Place for the Fantastic Forest during the holidays. When spring arrives, a massive shredder comes in and breaks the trees, logs and sticks down into a shredded bark mulch that is most commonly used in the picnic areas around the Zoo. The process is very labor-intensive and time-consuming, says Dave Engelmann, Grounds maintenance manager. “We usually run the wood chips through twice because the second time it shreds them up to a finer quality mulch and it looks nicer.” Going through a shredder twice means doing the lifting and work twice.

The second pile in the parking lot is all the leaves collected from inside the Zoo. “In the fall when the leaves start falling, the crew will go out every morning with a leaf blower and make big piles,” says Engelmann. Once the piles are formed, a big vacuum truck sucks up the leaves and takes them to the parking lot. The leaf collection is usually complete once winter hits, but the pile stays and starts to decompose on its own. The pile has the earth bacteria and microorganisms it needs to break down naturally. The pile is shredded in spring, and then the team waits a few weeks before spreading it to allow it to decompose more. Zoo horticulturist Noah Huber says during the natural process the material heats up and breaks down or sterilizes any seeds that might be in the pile. If the mulch is used too soon, the seeds will sprout and you’ll encounter numerous weeds.

The leaf mulch helps the flowers and plants around the Zoo. “Leaf mulch is basically a fertilizer product. It slowly releases the nutrients as leaf particles break down and the nutrients go back into the earth,” explains Huber. When used correctly it is effective in keeping weeds out. Using the Zoo’s own leaves is also a way to keep unwanted things away from the Zoo, says Huber. “We’re putting down the leaves that came from that area back in that area. Even though all sources carry some risk of invasive organisms and plant pests, we lower our exposure and keep the grounds healthy by knowing and choosing where our mulch comes from.”

This article appeared in the May-June 2020 issue of Wild Things.