Garden Near a Downspout: Using Roof Runoff Without Flooding
A garden near a downspout gets a burst of roof runoff with every storm. University of Florida IFAS notes 1 inch of rain on 1,000 square feet of roof gives about 600 gallons, so beds near a downspout need a plan to spread that water out.
The short answer
You can plant near a downspout if the water spreads out plus drains away from the house. UF IFAS notes barrel overflow can damage a foundation, so direct it away. A rain garden is a shallow planted dip with mulch. Wet tolerant natives such as swamp milkweed or cardinal flower suit it.
Can you plant near a downspout?
Yes, carefully. UF IFAS notes overflow from a barrel can damage the foundation, so runoff should flow away from the house. The UConn NEMO program describes rain gardens as shallow planted depressions with mulch that collect runoff.
How do you stop downspout water from flooding beds?
Catch some runoff in a rain barrel. UF IFAS notes barrels hold 50 to 80 gallons. Send overflow to a shallow rain garden clear of the house. UConn notes home rain gardens are typically 50 to 100 square feet.
Which plants handle wet plus dry spells?
Iowa State University Extension lists native perennials for moist to wet soils.
| Plant | Light | Note | Source |
|---|---|---|---|
| Swamp milkweed | Full sun | Tolerates short dry periods | Iowa State |
| Turtlehead | Part sun to part shade | Moist soil | Iowa State |
| Joe Pye weed | Full sun | Moist soil | Iowa State |
| Cardinal flower | Sun to part shade | Moist soil | Iowa State |
How to: step by step
- Trace where the downspout water flows.
- Add a rain barrel with a screen plus a tight lid.
- Route overflow away from the foundation.
- Dig a shallow rain garden of about 50 to 100 square feet.
- Plant wet tolerant natives such as swamp milkweed.
- Mulch bare soil.
Troubleshooting
Water pools by the house: route overflow farther out, since UF IFAS notes it can harm the foundation.
Mosquitoes in the barrel: UF IFAS advises a screen plus a tight lid.
Plants rot in the low spot: pick plants from the Iowa State list for moist to wet soils.
For more on site planning see garden microclimates for cannabis, planning an outdoor cannabis garden layout plus the guide to overwatering and cannabis growth. Kind Seed Co also stocks cannabis seeds.
Sources
- Rain gardens, UConn CT NEMO Program
- Rain barrels, UF IFAS Gardening Solutions
- Native perennials for moist to wet soils, Iowa State University Extension, Yard and Garden
FAQ
Can a rain barrel go on the downspout?
Yes. UF IFAS notes rain barrels sit under a downspout plus hold about 50 to 80 gallons. It advises a screen plus a tight lid to stop mosquitoes. Overflow should be routed away from the house, since it can damage the foundation, plus the barrel should be disconnected when you are away.
Which plants suit roof water?
UF IFAS suggests using rain barrel water on ornamental plants such as flower beds, shrubs or lawns. That makes a downspout bed a good place for perennials.
How much water comes off a roof?
UF IFAS notes 1 inch of rain falling on 1,000 square feet of roof yields about 600 gallons of water. That is far more than one barrel can hold, so most of the runoff from a single storm needs a place to soak in, such as a rain garden or a wide planted bed.
How big should a rain garden be?
The UConn NEMO program notes rain gardens are shallow planted depressions covered with mulch. It notes home rain gardens are typically 50 to 100 square feet.
How do you stop mosquitoes in a rain barrel?
UF IFAS advises fitting a rain barrel with a screen plus a tight lid so mosquitoes cannot lay eggs in the water. Using the stored water regularly on ornamental plants also helps. Check the screen after storms, since leaves from the gutter can clog it plus cause the barrel to overflow.
