How to Make a Garden Trough Planter? | Step-by-Step Build

A garden trough planter is a repurposed galvanized stock trough or a wooden planter box with drainage holes, a gravel layer, and soil, ready for planting in about an hour.

For the full breakdown, see our best Garden Trough Planters guide.

Turning a galvanized water trough into a planter gives you a durable, weatherproof garden bed without the cost of a raised bed kit. The process is direct: drill holes, add drainage layers, fill with soil, and plant. Below are the verified steps and the common mistakes that ruin a build.

What You Need for a Galvanized Trough Planter

A metal stock or feeding trough from a farm-supply store is the most common base. The materials that follow are confirmed across major how-to guides.

• Galvanized trough — any size, but smaller troughs (under 3 feet) are easier to move and fill.
• Cordless drill and 1/8-inch cobalt drill bit — standard bits dull quickly on galvanized steel; cobalt bits cut cleanly.
• Large gravel or drain rock for the bottom drainage layer.
• Landscape fabric or window screen — placed over the gravel to keep soil from washing into the holes.
• Quality topsoil or potting mix, plus optional slow-release fertilizer mixed into the upper third of the soil.
• Rot-resistant wood strips (cedar planks) to elevate the trough off the ground for airflow and drainage.

How to Drill Drainage Holes and Build the Base

Drainage is the single most critical step. The This Old House guide recommends holes spaced about 6 inches apart — roughly 10 holes around the perimeter near the bottom and 10 more across the base. Use the 1/8-inch cobalt bit and drill slowly to avoid tearing the metal. The burrs left on the inside are sharp; tap them flat with a hammer or cover them with a strip of tape before adding the gravel.

Place the trough in its final location before adding any gravel or soil. A filled trough is too heavy to move safely, and an unleveled base causes the metal to deform over time or the planter to tip. Set the trough on a flat surface and shim it with cedar planks if needed.

Drainage Layers and Soil Fill

Add 2–4 inches of large gravel to the bottom of the trough. Some sources recommend filling the bottom third with non-biodegradable packing peanuts and covering them with landscape fabric — this reduces weight in large troughs while still providing drainage. Cover the gravel (or packing peanuts) with a layer of landscape fabric or window screen to prevent soil from settling into the drainage zone and clogging the holes over months of watering.

Fill the trough with topsoil or a nutrient-rich garden soil mix appropriate for your plants. If you choose to amend, mix a slow-release fertilizer into the upper third as you fill — this puts nutrients near the root zone without washing out through the drainage layer. Leave about an inch of space below the rim for watering.

Common Mistakes That Kill a Trough Planter

Most failures happen before the first plant goes in. Here are the errors that multiple guides warn about.

• Skipping drainage holes — waterlogged soil causes root rot in a matter of weeks. At least 20 small holes are non-negotiable.
• Filling the trough in place after moving it — once filled with wet soil and gravel, a 4-foot trough can weigh 200+ pounds. Position it first, then fill it.
• Using the wrong drill bit — a standard high-speed bit blunts on galvanized steel after 4–5 holes. A cobalt bit lasts for the whole job.
• Filling directly with soil over the drainage layer — without landscape fabric or screen, soil fines wash into the gravel and holes, eventually sealing them. The clog can take one season to become visible.
• Leaving a wood trough’s paint or stain uncured before planting — volatile compounds in uncured finishes leach into the soil and can damage sensitive root systems. Allow at least 72 hours of dry time for any coating.