Potted plants and planters are a great way to improve the green space in your home. Finding the best potting mix for each comes with its own challenges, and it’s usually a good idea to build your own using a combination of materials that, when combined, create the optimal conditions for watering, moving, and decorating your plants.
Rocks and gravel are one of the most versatile in this regard and can provide a solution to many of these issues when used correctly. Here, we’re going to look at when and how to put rocks in potted plants and how to bulk up your substrate to promote drainage and save on soil in your planters.
The Role of Drainage Plants
We all know that plants love water, but having too much of it pooling around their roots can interfere with a number of biological and chemical processes within the plant, and even cause it to suffocate and die if it isn’t corrected soon enough.
While plants create oxygen by photosynthesizing carbon dioxide in the air, they also need oxygen to respire and grow. Too much water in the soil displaces air pockets and restricts the roots’ access to these necessary gaseous exchange points.
Further, water in soil dissolves a number of compounds from the substrate and can concentrate them around the root surface, essentially poisoning the root mass, if the soil is too waterlogged. It will also alter the natural biodiversity of microbes and fungal mycelia in the soil that would otherwise work in symbiosis with the plant to create optimal chemical processes for its health.
So, it’s important to keep your pots and planters well-drained, and for this, it’s possible to strategically use different types of rocks and gravel.
But there are more applications for rocks in pots than simply improving drainage, all of which we’ll go into very shortly. First, let’s look at the types of rock available for use in planters and pots.
Types of Rocks in Planters and Pots
The first type of rock commonly used for drainage is simple gravel. Gravel is cheap, weighty, and small enough to mix into the soil uniformly, in most cases. It’s good as a stabilizer for top-heavy plants and can come in handy for filling gaps in large pots. Its downside is its weight, making transporting it expensive and difficult and making planters and pots cumbersome.
Another common rock is expanded clay. These are balls of clay that have been treated at high temperatures to make a low-density rock that is lighter than gravel and more porous. The porosity of these makes them better as a hydroponics substrate but they also weigh quite a lot and can be expensive to transport and unsustainable to manufacture.
Arqlite Smart Gravel is made from 100% recycled food packaging and fills a very similar role to expanded clay. It’s inert, much lighter than clay, and actually reduces waste in its production, rather than adding to it. Smart Gravel can be used to create the perfect drainage layer at the bottom of your plant pots or as a substrate on its own in hydroponics.
Its light weight makes it a great filler for pots and planters. It’s also a much more eco-friendly alternative to many types of commonly-used rocks.
Here are some of the major reasons why to put rocks in potted plants.
Why Put Rocks in Potted Plants
- Drainage
Your choice of potting media, the temperature and humidity of your environment, your watering schedule, and the plant’s needs will all affect the moisture content in the soil. Most plant pots have holes in the bottom for drainage, but if the potting medium is too dense, water will still be held around the roots, potentially leading to root rot.
To give your roots more space to breathe, place a 2-inch layer of gravel at the bottom of your pot or planter and drain the excess water away.
- Weight
While standard rocks and gravel are great for adding weight to a pot or planter for outdoors, Arqlite’s Smart Gravel can create a large amount of lightweight space inside pots, which allows you to keep those decorative large pots and planters while still being able to move them around as necessary without breaking your back.
This is especially good for large, decorative planters or pots that carry a lot of weight of their own, but can be useful in numerous small pots too.
- Humidity
It’s thought that keeping a tray under your pot plants filled with rocks helps increase the surface area for evaporation of excess water, this, in turn, improves the humidity of indoor plants as the water vapor rises up around the plant itself.
- Hydroponics
Rocks and gravel are great as a substrate for certain types of hydroponics systems.
They provide a lot of binding surface area for roots, maintain access to air, and can give stability to the plants.
Gravels are particularly useful for DWC(Deep Water Culture) systems, which are a very popular form of hydroponics system involving a continuous supply of nutrient-rich water being pumped over the roots and substrate of the plants.
- Decoration
Soil isn’t the most aesthetically appealing surface to have indoors; covering it with a tidy layer of gravel not only makes it look better, but helps prevent clumps of earth from spilling onto your clean floor when you move it around.
- Water Retention
Rocks and gravel scattered in a thin layer on top will also help keep water inside the soil by reducing evaporation from the surface. This can reduce the need to water so often and reduce the humidity in the room the pots and planters are in as a result.
Since water moves readily from coarse grains to a finer-grained substrate, watering the plants and adding liquid fertilizer is not affected by a layer of gravel on top of the soil.
- Saving Soil
In many planters or pots, the plant itself has a smaller root bed than the vessel provides space for. In this case, you can either fill the entire pot or planter with soil, or you can fill up space with rocks.
Using rocks in the bottom of pots and planters allows you to fill up the unused space with an inert medium, keeping the optimal amount of soil for your plants while saving soil for the rest of your plants.
Conclusion
So, why put rocks in potted plants? There are a number of reasons!
For drainage in potted plants, a small layer of gravel beneath the soil can keep excess water away from roots, helping to avoid root rot. Rocks are a great choice as an inert substrate in hydroponics, too, and when placed in a tray under the pot, can catch the excess water and redistribute it as humidity around the leaves of the plant above.
In large pots with smaller plants, gravel is an invaluable way to save on soil, and, when using lightweight Smart Gravel, it improves the portability of the planter itself.
Finally, covering the outer layer of soil keeps your pots and planters looking tidy in your home and reduces the chances of a muddy spill.
