If you’ve recently strolled around Nature Boardwalk at Lincoln Park Zoo, you may have noticed its icy disposition. Specifically, oddly configured, jagged chunks of ice positioned near plantings surrounding the South Pond. What’s up with that?

The chunks—repurposed leftovers from the nightly ice-carving demonstrations during ZooLights Presented by ComEd and Charter One—provide a clever method for watering plants as the mercury plunges.

"It’s a little-known gardener’s trick," says Director of Horticulture Brian Houck. "We use the ice to help keep new transplants and potted plants appropriately watered through the winter."

Knowing how to water plants during winter is difficult for gardeners. "You don’t always want to be taking off your gloves to touch the soil to feel if it’s wet or not," says Houck. "And it’s hard to tell even when you do, just because everything is so cold."

Using ice removes the guesswork that can lead to plants drying out or becoming waterlogged and then rotting if you water them too little or not enough.

The trick, says Houck, is to put ice on top of the soil so that, when the weather is warm, the ice slowly melts into the ground (or pot) adding moisture. When the temperature dips below freezing, the ice stops melting. The only work the gardener needs to do in this scenario is to monitor the chucks of ice and refresh when they are nearly gone.

Icy refreshments for the zoo’s plants will be readily available during ZooLights, which shines each Friday–Sunday through December 26 and then nightly until January 6. The zoo's horticulturists have chainsaw-wielding sculptors to thank for that.

Learn more tips from the zoo’s horticulture experts by registering for upcoming garden classes!