Is the following fact or fiction?
“Using gravel or coarse material in the bottom of containers improves drainage for your plants or flowers”
It’s actually fiction. It’s one of those myths that, in the words of leading expert Dr. Chalker-Scott from Washington State University, ‘refuses to die’. Some gardeners advise adding coarse materials to planters, but they are doing more damage than good, and experts in the horticultural field agree that it’s a myth.
Dr Chalker-Scott explains the reason why gravel or coarse material is a problem:
Soil scientists demonstrated that water does not move easily from layers of finer textured materials to layers of more coarse textured. One study found that more moisture was retained in the soil underlain by gravel than that underlain by sand. Therefore, the coarser the underlying material, the more difficult it is for water to move across the interface. Imagine what happens in a container lined with pot shards!
An additional explanation is provided by The University of Illinois:
It is a myth that a layer of gravel beneath the soil improves container drainage. Instead of extra water draining immediately into the gravel, the water “perches” or gathers in the soil just above the gravel. The water gathers until no air space is left. Once all the available soil air space fills up, then excess water drains into the gravel below. So gravel in the bottom does little to keep dirt above it from being saturated by overwatering.
To avoid unhappy plants that may be suffering from root-rot due to water-logged dirt, follow these four simple rules to optimize drainage in your container or planter:
One: The Hole – ensure that your planter has a hole. If there isn’t one already, improvise by drilling through the bottom of the pot.
Two: Quality soil – choose high quality potting soil that is well draining.
Three: Minimize over-watering – Be aware of the watering requirements for your plants by following the instructions on the label, or do research. To check if your plant needs watering, put your finger into the soil up to your second knuckle. If the soil at your fingertip feels dry, water your plant.
Four: Container-drainer aid – Using a product such as Drain Smart will help to promote better drainage. The discs go in the bottom of the pot and are designed, using proprietary technology, to encourage the water to drain directly into the mesh and then out of the planter. They also stop dirt leaking out of the drain hole on patios and surfaces.
If you feel that your plants or flowers are over-watered, let the soil dry out by moving the container to somewhere dry. You could also re-pot your container following the rules above. And don’t forget that under-watering is as bad for your plants as over-watering – especially when the sun is out! Your containers will need to be watered daily during warm weather.