What should you put in container bottoms?
Written by
Paul Reynolds
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Water drainage preparation. Coffee grounds are great, but soil isn't ideal for covering the holes in your planting container. Ideally, it's better to fill the bottom of the containers with material that allows drainage but won't let your soil slough through. Coffee filters or landscape fabric work well to cover the holes. Rocks at the bottom trap moisture, leaving your roots with nowhere to go.
Recommended Materials
- Coffee filters allow water flow while blocking soil
- Landscape fabric lasts multiple seasons
- Biodegradable coconut coir mats
Materials to Avoid
- Rocks reduce soil volume and trap water
- Gravel creates perched water tables
- Packing peanuts decompose unevenly
"Install drainage layers" before soil is added. Cut such materials to cover all the hole clusters completely; it may be easier to use different materials for different holes (such as single coffee filters for the small holes and layered landscape fabric for the larger openings). The goal is to ensure that there are no holes left where water-soaked soil might wash out of the pot during heavy watering. Make sure the edges are pressed firmly against the wall of the container as well.
Quality potting mix fills the container to the top of the drainage layers below. Never use garden soil that will compact. Potting blends also contain perlite or vermiculite for aeration. Those materials support root growth and water movement. Fill the containers to within 2 inches of the rim.
Dispel Myths Like Gravel Improves Drainage. Studies have shown that gravel layering actually retains more water. This leads to saturation of the underlying soil, which can cause root death due to drowning. Good drainage occurs when there is uniform soil texture and good drainage holes. Test for drainage by watering the entire pot thoroughly till it runs from the bottom.
Read the full article: 10 Essential Container Gardening Tips for Beginners
