DIY Self Watering Planter

How does a self watering planter work?

A self watering planter uses capillary action — the same process that draws water up a paper towel — to pull moisture from a lower reservoir into the root zone of the plant. Roots stay consistently moist without sitting in standing water.

The design separates the plant’s soil from a water reservoir below it. A wicking column or basket filled with potting mix bridges the two zones. Water moves upward from the reservoir through the soil column into the main growing area. Roots grow downward toward the reservoir, finding water on demand.

This bottom-up watering method has two advantages over overhead watering. First, the soil surface stays drier, which reduces fungal disease and slows weed germination. Second, plants regulate their own water intake — they pull what they need and stop. Overwatering is nearly impossible once the overflow holes are positioned correctly.

Commercial self watering planters sell for $30–$150+. A DIY version built from two 5-gallon buckets delivers equivalent performance for $8–$15.

Materials list

For a 5-gallon bucket self watering planter:

Substitute options: Instead of a second 5-gallon bucket, some builders use a large plastic storage tote as the outer container and a single bucket nested inside. This increases reservoir capacity to 3–4 gallons — useful in hot climates where plants are heavy drinkers.

For guidance on potting mix choices that support wicking, see best potting soil.

Step-by-step build instructions

Step 1: Create the wicking basket

The wicking basket is the key component — it holds soil in contact with the reservoir and acts as the capillary bridge.

Option A (mesh basket method):

1. Place the 6-inch mesh basket in the center of the inner bucket bottom.
2. Trace around it and cut a hole in the bottom of the inner bucket sized to hold the basket with the rim resting on the bucket bottom. The basket hangs down into the reservoir when assembled.
3. Fill the basket with potting mix and pack firmly.

Option B (PVC pipe method — simpler):

1. Cut a 6-inch section of 2-inch PVC pipe.
2. Drill 1/4-inch holes along the entire length of the pipe at 1/2-inch intervals.
3. Push this perforated pipe vertically through a hole in the bottom of the inner bucket so it extends 3–4 inches below the bucket floor and 2–3 inches above.
4. The perforations and the soil column inside the pipe act as the wick.

Step 2: Drill overflow holes

This step is critical. Overflow holes prevent the reservoir from overfilling and drowning roots.

1. Stack the inner bucket inside the outer bucket.
2. The gap between the two bucket bottoms — typically 2–4 inches depending on basket depth — determines reservoir size.
3. Drill two or three 1/2-inch holes in the outer bucket at the level of the inner bucket floor. Water that rises above this level drains out immediately.

Double-check overflow hole placement by filling the reservoir with water and confirming that water drains from the overflow holes before reaching the inner bucket floor.

Step 3: Add the fill tube (optional but recommended)

A fill tube lets you add water without disturbing the plant.

1. Drill a 1-inch hole in the side of the outer bucket near the top of the reservoir.
2. Insert a 12-inch section of 1-inch PVC pipe at a slight angle so the bottom end sits in the deepest part of the reservoir.
3. The pipe sticks up above the container for easy pouring.

Without a fill tube, you add water by pouring directly into the outer bucket gap — workable but messier with established plants.

Step 4: Assemble and fill

1. Place the wicking basket or pipe assembly in the inner bucket.
2. Nest the inner bucket inside the outer bucket.
3. Add a small piece of weed barrier fabric over the bottom of the inner bucket (around the wicking basket) to prevent fine potting mix from falling into the reservoir.
4. Fill the inner bucket with potting mix to within 2 inches of the rim.
5. Plant your vegetables, herbs, or flowers.
6. Fill the reservoir by pouring water into the gap between the two buckets (or through the fill tube). Stop when water exits the overflow holes.

Best plants for 5-gallon self watering buckets

Tomatoes, peppers, herbs, and lettuce produce best in 5-gallon self watering containers. The consistent moisture prevents blossom end rot in tomatoes and keeps lettuce from bolting as quickly.

Avoid plants that need dry conditions — lavender, rosemary, and succulents prefer well-drained soil that dries between watering. A self watering system keeps moisture too consistent for Mediterranean herbs.

For help choosing between container types for small-space growing, see container gardening for small spaces.

How to maintain a self watering planter

Check the reservoir level every 2–3 days during summer heat. In Zone 6b during July, a tomato plant drinks the 1.5-gallon reservoir in 3–4 days. In Zone 8 and south, daily or every-other-day refilling may be needed during peak summer heat.

Signs the reservoir is empty: plant wilts slightly mid-afternoon even in adequate sun, or soil surface in the inner bucket feels bone dry.

At the end of the season:

• Remove the plant and root ball.
• Empty remaining water from the reservoir.
• Wash both buckets with diluted bleach (1 tablespoon bleach per gallon of water) to kill any fungal or bacterial pathogens.
• Inspect the wicking basket or pipe for clogging. Replace potting mix annually — used potting mix loses its wicking structure over time.

Larger-scale version: storage tote planter

A 27-gallon plastic storage tote makes a high-capacity self watering planter suited to larger vegetables like indeterminate tomatoes or cucumbers.

The same principles apply: cut a hole in the tote lid sized to hold a 5-gallon inner bucket (or two). The lid acts as the floor of the growing zone, with the tote body below serving as the reservoir. This version holds 5–8 gallons of water and suits large, thirsty plants in hot climates.

For a full introduction to sub-irrigation gardening at scale, see drip irrigation system for comparison with automated watering alternatives.

Why sub-irrigation outperforms overhead watering for containers

Research from Purdue University’s horticulture department found that sub-irrigated container plants produced 30–40% higher tomato yields compared with overhead-watered controls under identical conditions. The yield advantage came from three factors: consistent root zone moisture, reduced nutrient leaching (water moves up, not through), and lower disease pressure.

Nutrient leaching is a significant issue with overhead container watering. Each watering pushes fertilizer nutrients through and out the drainage holes. Sub-irrigation recirculates water upward and holds nutrients in the root zone longer, reducing fertilizer needs by roughly 25%.

For information on self watering planters already available commercially, see self watering planters for a comparison of commercial models.

Outbound resource: Penn State Extension (extension.psu.edu) publishes research on sub-irrigated container growing systems, including yield comparisons for vegetable production in container gardens.