Should You Put Rocks in the Bottom of a Garden Container?

Generally, you do not need to put rocks at the bottom of a garden container. Rocks do not enrich the soil within your container from a nutrient standpoint, and they do not have a significant positive effect on drainage, as many people assume. Instead, the nutrient content of your soil and the container in which it sits determines the quality of your growing medium.

Using Rocks for Drainage in Pots – Necessary or Not?

Despite what many gardeners assume, adding rocks to the bottom of a garden container does not benefit your plants. In fact, in some instances, this practice can have a negative effect. The next three sections will explore the reasons why you don’t need rocks at the bottom of your garden container.

Rocks Don’t Determine Drainage Quality

Common sense suggests that a porous material such as small rocks would improve drainage in a garden container. However, the presence of rocks is not the main determiner of how well your container drains water.

The main influences over how efficiently your garden container drains are the container’s materials and design. Containers that are non-permeable and lack drainage holes will hold water whether you add rocks or not. Conversely, containers with drainage holes or breathable materials will allow for a sufficient flow of water and air through the soil.

Rocks Are Nothing More than Filler

The next main issue with putting rocks in a garden container is that they act as a filler. For some, adding filler appears to be a sensible way to cut down on potting soil costs. However, this can be a short-sighted approach as the rocks will take up space that could have been occupied by more nutrient-rich soil.

Most plants will not spread their roots through rocks as rocks do not hold moisture or valuable nutrients that the roots would benefit from absorbing. Alternatively, replacing your rocks with a high-quality potting soil mix gives your plant’s root system more space into which it can expand while supporting further healthy growth above the soil.

Recommended Repotting Supplies

Are There Any Materials You Should Put in a Garden Container?

Stones are not the only material that gardeners put in the bottom of their containers. Alternatively, some people use plastics, cardboard, and other materials in their garden pots. However, these materials are no more advantageous for this use than rocks are. They don’t make a dramatic improvement to drainage and continue to take up valuable space that could house healthy soil your plants would love.

Occasionally, it is a smart idea to place a single stone at the bottom of a garden container. This tactic is applicable if your container has a single drainage hole. Putting a stone in that hole will help stop soil from flowing out when you water your plants. However, you do not need a full layer of stones. Instead, one well-sized and well-placed pebble will do the job.

Is it Bad to Put Rocks on Top of Soil?

Placing rocks at the bottom of a garden container is not advantageous. However, adding a layer of stones on top of your garden container soil is. The correct type of stone can act as a form of mulch for your plants that will help to regulate soil temperature and moisture.

Mulch acts as a buffer between the soil in your container and the sun and open air. In that role, mulch prevents water from evaporating too quickly before it can seep down to the root level. Mulch also reduces significant temperature changes that can shock your plant’s roots.

Rocks can act as an adequate form of mulch, but it is not always the ideal option. While rocks can moderate soil moisture and temperature, they do not increase soil nutrients as organic mulches do. On the other hand, stone mulch offers you many different color and texture options and will not need to be replaced as often as it does not break down over time.

Final Thoughts on Using Rocks for Drainage in Pots

Although placing rocks at the bottom of a garden container is a popular habit of some gardeners, it is not a wise approach to container gardening. Rocks at the bottom of a container do not deliver on the benefits that most people believe they provide. But as this article shows, stones can play a helpful role in container gardening if you know when and where to use them.