Gully-washing rain off metal roofs erodes landscape beds and floods sump pumps. A rain garden intercepts the torrent, soaks it into deep-rooted plants, and adds color to the yard. May’s moderate temperatures jump-start native plugs before summer stress. Designing the basin size, soil mix, and plant palette now turns stormwater from foe to friend.
Size Basin, Prep Soil
Capture the first inch of runoff: roof area in square feet divided by 6 equals cubic feet to store. Dig basin one foot deep, twice long as wide, sloping sides at 3:1. Mix 40 percent sand, 40 percent loam, and 20 percent compost for infiltration.
Planting Ideas
- Blue flag iris in bottom zone.
- Swamp milkweed mid-slope.
- Little bluestem top edge.
- Mulch with shredded hardwood to hold moisture.
Connect Downspout and Mulch
Run 4-inch solid pipe to garden inlet. Incorporate rock splash pad to slow flow. Mulch, then water deeply first two weeks.
Maintenance Tips
- Weed lightly the first season.
- Cut stalks each March and leave stems over winter for habitat.
- Divide crowded clumps every three years.
- Monitor ponding; adjust mix if water stands > 48 hours.
Final Thoughts
A rain garden transforms roof runoff into a living sponge, watering itself while brightening the landscape. Plant this May and enjoy blooms, birds, and a drier basement for years.