Going away on vacation or tired of watering thirsty balcony plants twice a day during peak summer heat? A Sub-Irrigated Planter (SIP) delivers water directly to plant roots from an underground reservoir via capillary wicking action. Your plants drink exactly what they need, saving up to 70% of water.
How Sub-Irrigation Works
A false bottom separates the soil chamber from a 2-gallon water reservoir at the bottom. A central wicking basket filled with soil pulls water upward into the root zone automatically through capillary action, keeping soil evenly moist 24/7 without surface evaporation.
Materials Required (Cost: Under $10)
- Two 5-Gallon Food-Grade Plastic Buckets (nested together).
- One 1-inch PVC pipe (cut to 18 inches long) for the water fill tube.
- One small plastic net pot or perforated yogurt cup (for the wicking chamber).
- Cordless drill with 1/4-inch and 1-inch spade drill bits.
- Lightweight potting mix (do not use heavy garden soil).
Step-by-Step Construction
Step 1: Drill the Wicking & Drainage Holes
Take Bucket #1 (the inner bucket). Drill a 3-inch hole in the center of the bottom for your net cup. Drill twenty 1/4-inch aeration holes across the bottom floor.
Step 2: Drill the Overflow Hole
On Bucket #2 (the outer bucket), drill a single 1/4-inch overflow drain hole 4 inches up from the base. This prevents the water level from ever flooding the roots.
Step 3: Assemble and Install Fill Tube
Place Bucket #1 inside Bucket #2. Insert the net cup into the center hole so it dips into the bottom reservoir. Insert your PVC fill tube down into the corner of the bottom bucket.
Step 4: Pack Soil and Plant
Pack the wicking cup tightly with moist potting soil to initiate the wick. Fill the rest of the bucket, plant your tomatoes or peppers, and fill the reservoir through the PVC pipe until water trickles out the overflow hole.
