What to Use for Drainage in Pots (Improve drainage in potted plants)

Not sure about what to use for drainage in pots? In this article, you’ll find out the things you can use for drainage in pots, the ones you should avoid, and why some popular pot drainage methods are really bad for plants.

Drainage is very critical to the health of plants grown in pots. For instance, Root rot, a common but deadly disease in potted plants linked to over-watering or waterlogged soil, can easily be prevented when the right drainage techniques are implemented.

There are several proven ways to increase soil drainage in potted plants. Fortunately, implementing these techniques doesn’t require a college diploma in horticulture.

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What to Use for Drainage in Pots

Before we go into what to use in a pot to facilitate drainage, it is only apt to address the ‘myth’ of using pebbles, gravel, stones, pot shards, or sand in pots. In reality, the widespread practice of putting them under the potting soil is bad for proper drainage.

Various research from several universities show that these so-called drainage materials for pots actually inhibit the movement of water out of the potting soil through the drainage holes. Even the purported collateral benefit of stopping creatures from getting into the pot through the drain holes is at best marginal.

The science supporting this assertion has been around for almost a century now. But somehow, gardeners have ignored it and have persisted with the practice of using these drainage materials in pots.

The bottom line is, these drainage materials in pots promote waterlogging of the potting mix! This is ironic since the whole point of lining planter pots with rocks, pebbles, gravel, sand, etc., is to prevent the potting soil from getting waterlogged.

Here is the link to one such study from Washington State University referencing a previous study. The University of Illinois Extension website also has a report throwing this practice under a bus.

If it is not ideal to use all the popular potting soil drainage materials, what should gardeners use for their pots?

What Can You use for Drainage in Pots?

When it comes to deciding what to use for drainage in pots, it’s more about optimizing drainage in the potting mix or potting soil. That said, having good drainage holes at the bottom of the pot is at the center of effective pot drainage.

Below are some materials you can add to your potting soil so you don’t end up with soggy soil in your pots. The first three are all about soil amendment. That essentially means they are added or mixed to the potting soil to improve drainage.

All soil amendment techniques involve repotting the soil. Typically, that means emptying the potting soil into a large container, adding the soil amendment, mixing them very well, and finally replacing the amended or upgraded potting soil into the pot.

Perlite

Perlite is an important ingredient used in making potting mix for growing plants indoors. It is a lightweight, extremely porous material made by applying heat to volcanic silicate rocks at temperatures north of 1500°F.

This thermal treatment converts the water inside the rock to gas. The end-product is a light, soft, whitish material that is also popular in hydroponic farming.

Adding Perlite to the potting mix would create tiny pockets of air in the soil. This lets the soil remain loose inevitably promoting efficient water drainage.

A potting mix or potting soil should already contain perlite. But if you an unsatisfied with the drainage, you can simply purchase some and use it to amend the soil to rectify the situation.

Vermiculite

Vermiculite, like perlite, is a critical ingredient in good potting soil. They are sold commercially as lightweight, glossy flakes with colors that can be anywhere between sandy brown and dark gray.

The highly porous nature of vermiculite makes it a very good drainage material for pots. In potting soil, though, its primary function is to improve the retention of moisture and nutrients. And it’s also used to stabilize the soil pH due to its pH buffering ability.

Coarse Sand

Horticultural grade or washed sand has wide applications in nursery mixes and greenhouses. When used to amend potting soil, as well as improving drainage, it helps to stabilize the pot with the increased weight. This is important for outdoor plants as the increased weight prevents high winds from blowing them away.

Considered the ideal soil drainage amendment material for succulent plants and cacti, the recommended size to use is between 0.25 — 2 mm. Also, the absence of contaminants like silt and clay is an added advantage of coarse sand for amending potting mixes.

However, not all coarse sands are ideal for this purpose. The best and purest source of coarse sand is deeply mined mountain sand. You need to avoid using sands derived from shell fragments, the skeleton of marine organisms, and coral due to their high pH value. You also want to steer clear of sands sourced from the ocean because of the presence of sea salt which is harmful to crops.

Use smaller pot

This ‘pot-in-a-pot’ potting soil drainage technique is usually recommended if you intend to grow plants in a decorative ceramic or terra cotta pot where drilling drainage holes is impractical.

With this technique, the smaller planter pot with drainage holes is placed inside the bigger decorative pot. For this to be effective, the bigger pot should be so big that the water pooling inside it doesn’t make contact with the plants in the small planter pot.

A plastic container can also be used as the planter. The only requirement is that it must have drainage holes and must be completely covered by the decorative pot to maintain the integrity of the larger pot as a decorative piece.

To make it work on a long term basis, you’d have to check the level of water inside the large pot regularly; simply pour the water out when the water level is more than a few inches above the bottom of the pot

Coffee filters

One major problem of growing plants inside a pot is how to mitigate or even completely stop the soil from washing out with water via the drainage holes.

You can stop the soil from draining out by placing coffee filters over the drainage holes ensuring only the water filters out. The coffee filters aren’t so much enablers of drainage in pots as a medium to ensure you don’t gradually deplete your precious potting soil when watering.

If coffee filters are unavailable, a great substitute is a sheet of cheesecloth placed over the drainage holes.

How to Ensure Proper Drainage in Pots

While amending the potting soil is a great way of ensuring great drainage in pots, there are several things you can do to ensure adequate drainage. Implementing the recommendations below might just make it unnecessary to either amend the soil or worry about what to use for drainage in your pots.

All your pots, except the decorative pots, must have holes at the bottom to prevent excess water from remaining inside the pot.
Always check to see if the drainage holes are blocked. Sometimes, blocked holes are the reason the soil is not draining properly.

So before doing something as extreme as repotting and amending the soil, clean the holes first. That could be the solution to your drainage problem.

Drainage holes sometimes get blocked by the ground underneath. This problem occurs more often when the pot is placed on a non-concrete ground.

The solution is to place the pots on a raised platform so the holes are not obstructed. If that is not possible, drilling holes on the sides near the bottom of the pot is another option.

Remove all drainage materials at the bottom of the pot if you have already placed some there. As we stated earlier, drainage materials actually hinder the downward movement of water.

Be sure to properly clean out the pot after removing the drainage material before putting back your potting soil.