How to Prepare a Trough for Planting | Ready in 10 Steps

To prepare a trough for planting, start by adding or confirming drainage holes, cover them with mesh or stones to prevent soil loss, and fill with a free-draining mix like equal parts John Innes No. 2 and coarse grit.

Whether you are repurposing a stock tank or using a glazed planter, the prep work between a failed waterlogged mess and a thriving container garden comes down to drainage. The steps here follow official guidance from the RHS, Pacific Horticulture, and This Old House — no guesswork.

Step 1: Drill Drainage Holes

Flip the trough upside down and drill holes across the bottom. This Old House recommends spacing them about 6 inches apart. If the trough is metal, use a bit designed for metal; for hypertufa or ceramic, use a masonry bit. Waterlogged soil kills roots in days, and any trough without drainage will fail.

For large feeding troughs, consider drilling a few extra holes along the lowest edge of the sides — this helps if the bottom sits flush on a surface.

Step 2: Elevate for Airflow and Drainage

Set the trough on a level, supportive base. Cedar planks, bricks, or cinder blocks lift the bottom off the ground so water can escape freely and the surface underneath stays protected. An unlevel trough will drain toward the low side and can warp or crack over time.

Step 3: Cover the Holes

Before adding anything else, cover every drainage hole so the growing mix stays inside. The RHS recommends squares cut from shade netting, terracotta pot pieces, or stones. Pacific Horticulture suggests a full screen lining across the base. Skip this step and your soil will wash out with every heavy rain.

Step 4: Add a Drainage Layer (Optional)

If your trough is deep enough to spare 1–2 inches of height, add a drainage layer. Pacific Horticulture recommends coarse gravel topped with a layer of rough material like coarse peat or partially decomposed compost. For shallower troughs, skip this layer — it steals root space without helping much if holes are well-covered and the mix drains well.

Step 5: Fill With the Right Mix

Heavy garden soil has no place here. The RHS specifies equal parts John Innes No. 2 and coarse grit for most trough plants. For acid-loving plants, use John Innes ericaceous instead of No. 2. This Old House recommends a high-quality, nutrient-rich garden soil mix. Whichever you choose, leave about an inch of headroom at the top so water does not run straight off.

Water the filled mix gently so it settles, then top up if the level drops. After that, plant according to mature size — larger specimens toward the back for mixed plantings.

If you are still deciding which container to buy, our roundup of the best feed trough planters covers the most durable options for this exact project.

Common Mistakes People Make

• No drainage holes: This is the single fastest way to kill plants. The trough becomes a bathtub and roots rot within weeks.
• Unlevel placement: Water will pool at the low end, saturating half the root zone while the other half stays dry.
• Garden soil alone: It compacts in a container and holds too much water. Use a gritty potting mix designed for containers.
• Skipping hole coverage: Soil clogs the holes within two waterings and then the drainage stops.
• Filling to the rim: Leave headroom or water splashes out, taking soil and nutrients with it.