The lasagna gardening method lends itself quite well to heavy rains and downpours if it is designed correctly. In my garden on the Oregon coast, it rains 65 inches a year, which is three times the national average. By placing large coarse twigs and gravel on the bottom of the structure, I eliminate root rot while maintaining nutrient-rich soil. Weed barriers that do not use plastic are a must in this area.
Drainage Solutions
- Install 4-inch gravel base under cardboard
- Slope top layer 2% away from plants
- Use breathable landscape fabric instead of plastic
- Add sand to clay soils (1:4 ratio)
Material Priorities
- Choose rot-resistant cedar chips over pine
- Layer burlap between greens for airflow
- Avoid mat-forming leaves like maple in wet zones
- Replace newspaper with straw in >50-inch rain areas
Keep track of soil moisture levels at $15 for a tensiometer. Moisture readings should be in the 10-30 kPa range during the rainy season. My clients in Washington combine rice hulls into the layers to help remediate waterlogging.Rice hulls will hold up to 3 times their weight in weight while breaking down. Adjust the thickness of each layer for every 4 inches of rainfall in the month.
Emergency Fixes
- Insert vertical PVC pipes as drainage vents
- Remove top 6 inches during downpours
- Apply gypsum (1 lb/sq ft) to break up clay
Mold Prevention
- Turn layers weekly with broadfork
- Add crushed charcoal (5% volume)
- Plant antifungal marigolds at edges
Long-lasting success has its roots in the natural floor of a forest ecosystem. My rainiest bed combines alder branches, fern fronds, and mushroom compost for a native Pacific Northwest forest edge. After two seasons, earthworm populations tripled, creating self-aerating channels that work more efficiently than a French drain.
Read the full article: Lasagna Gardening Method: 10 Essential Steps for Success
