5. DRAINAGE IN POTS—NEW RECOMMENDATIONS

Filling planters and pots with bagged potting mix is not difficult. The tricky part is to ensure proper drainage at the bottom of the container. The standard practice has always been to fill the base of pots with a layer of gravel or stones for drainage. It was time-consuming but we were told it was important. Recently, the recommendations have changed! Life is now simpler for the container gardener.

Scientists have found that water moving down through a pot will not easily go from potting mix into a coarser material like gravel. The water remains in the mix portion and does not seep down. Why? Because water does not pass quickly from one material into another material that has a different pore (opening) size. In other words, gravel and stones actually hinder the movement of water down through the pot. The water tends to stay in the potting mix layer.

The suggestion now is simply to fill the pot with potting mix. For optimal drainage in your planters, make sure there are drainage holes in the base (important!). You may choose to cover the holes with mesh to prevent soil from washing out. You can make your own mesh by using a netted bag that holds fruit. Simply cut a small piece of the plastic mesh and place it at the bottom of the pot before filling with mix.

If you have a large planter, in the bottom-third of the pot place one or two lightweight bulky items that don’t rot, such as clean, empty plastic milk jugs or soda bottles. This saves on potting mix and makes the pot less heavy. If you have a large container in which you intend to plant annual flowers, the bottom of the pot can be filled with chunky bark mulch. This last tip works with annual flowers because they have shorter root systems than perennials or tropical plants.

Once the pot is filled, compact the mix around the inside of the rim. Just use your hand pointing downward. This is the area where the most compaction is needed. Never compact the potting mix too much in the center, because then the water cannot pass through.

Bagged potting soil, begonias, and coleus are all you need for a great-looking planter in the shade. Fill the planter completely with the potting soil—no drainage materials needed at the base! Note that the planter is “footed,” which means it is raised off the ground. This helps with drainage.