Rain Gardens & Drought

By Layne Knoche, RORG Landscape Designer

As of July 7, 2022, a portion of east-central Illinois, including where the Red Oak Rain Garden is located, is now listed in severe drought by NOAA and the National Integrated Drought Information System. This is the driest we’ve been here since the dreaded drought of 2012, which is a great reminder that when planning a rain garden, it’s important to remember that it won’t always be rainy!

For the entire month of June, RORG’s CoCoRaHS rain gauge watchers reported .88 inches of rain, which is only 20% of the average 4.34 inches of rain Champaign-Urbana typically sees for the month. To make things even worse, .65 of that came from one fast hit of heavy rain, much of which didn’t have time to soak into the ground. While not as severe as the conditions in Champaign County, much of the rest of Illinois is also experiencing abnormally dry conditions.

U.S. Drought Monitor Conditions for IL as of 7/7/22.

It’s important to note that, according to Trent Ford, Illinois State Climatologist, winter and spring have undoubtedly gotten wetter over the past 50-100 years. Summer has also gotten wetter statewide, although at a slower rate. However, due to hotter temperatures, there are summer drought risks like we’re facing now.

What Drought Means for Rain Garden Plants

When planning a rain garden, plants on the banks, or the “top” of the garden, already need to be tolerant of drier soils. They shouldn’t ever have to deal with standing water. Plants in the basin, or the “bottom” of the garden, have to be able to handle wetter soils and standing water for short periods of time. However, droughts do happen and the basin will not always have wet soils unless you plan to irrigate the garden. This means plants located in the basin may need to be adapted for both drought & deluge.

Luckily, Illinois has native plants adapted to both of these extreme conditions. At the Red Oak Rain Garden specifically, species like Southern Blue Flag Iris, Emory’s Sedge, and Common Rush have been proving themselves worthy this summer. In the below image, note the lush foliage in the center of the garden as compared to the brown, dormant lawn surrounding the garden.

The sea of Southern Blue Flag Iris, Emory’s Sedge, and Common Rush at the center of the Cell 1 basin, shown above, is still lush during a severe drought. Photo by Dennis Bowman.

Some other Illinois native plants that have been noted to withstand these harsh dry and wet conditions include the following:

  • Purple Coneflower Echinacea purpurea
  • Rattlesnake Master Eryngium yuccifolium
  • Early Sunflower Heliopsis helianthoides
  • Blazing Star Liatris spp.
  • Stiff Goldenrod Oligoneuron rigidum
  • Wild Quinine Parthenium integrifolium
  • Jacob’s Ladder Polemonium reptans
  • Mountain Mint Pycnanthemum virginianum
  • Orange Coneflower Rudbeckia fulgida
  • Sweet Black-Eyed Susan Rudbeckia subtomentosa
  • Rosinweed Silphium integrifolium
  • Culver’s Root Veronicastrum virginicum
  • Linked names are plants found at RORG.

When to Water

During the establishment period, especially in the first year after installing your rain garden, irrigation is needed during dry spells. A general guide is to ensure ~1 inch of water is applied once per week. Water heavily with less frequency to encourage deeper root growth. Native plants typically take three years to establish, with plants that are known to be drought-tolerant generally sustaining themselves from that point.

Many native plants have leaves that may yellow and droop during extended droughts. This doesn’t necessarily mean the plant is dying, this is a way of conserving water. If you prefer the lush look, watering at this point may be necessary.

RORG is into its third year of establishment. In the first two years after the 2019 renovation, RORG’s plants were busy putting down deep, extensive root systems. During this period, the garden was watered during dry spells to help the plants get established. RORG is now on the cusp of being solidly drought-tolerant, but to err on the side of caution, our volunteers have begun helping to water the garden during these extreme conditions. If we experience similar conditions in the future, we shouldn’t need to apply any additional water.

Royal Catchfly Silene regia is an example of a drought-tolerant species at RORG.

While it has been a great learning experience to watch RORG handle its first drought, the RORG team is hoping for some rainfall soon!

Learn more about the plants of the Red Oak Rain Garden at our Plant Library.

To learn about volunteering at RORG, visit our volunteer hub.

To explore Illinois drought conditions, visit https://www.drought.gov/states/illinois.

Cover photo by Dennis Bowman, Extension Digital Agriculture Specialist

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