Is One Drainage Hole Good Enough for Plants?

Shopping for planters should not be about appearance and adding character indoors or outdoors. There’s an essential function your plants’ pots should include, and that’s proper drainage. Planters come in all shapes, sizes, and designs, but always check for drainage holes on the bottom. 

One drainage hole centered on the bottom is typically good enough for efficient drainage. However, the soil mixture can affect proper drainage. For water to drain easily, ensure the correct soil medium is used for plants and add more holes around the center hole if needed. 

Plants are a wonderful addition to our homes, and it would be sad to lose a plant just due to a drainage issue. This article will explain why your planters need at least one drainage hole, what can affect drainage, and how to add more holes.

Key Takeaways

  • Essential Drainage: The most crucial feature of any planter is proper drainage, which is vital for the health of your plants. Ensure that every planter has at least one drainage hole at the bottom.
  • Preventing Root Rot and Oversaturation: Adequate drainage prevents root rot and oversaturation by allowing excess water to flow out, ensuring that your plants are not sitting in waterlogged soil.
  • Soil and Additional Holes: The soil mix affects drainage efficiency. If necessary, add more holes around the central drainage hole to improve drainage, especially if the soil retains too much moisture.
  • Signs of Poor Drainage: Look out for symptoms like droopy leaves, yellowing, or a white powdery residue on the soil, indicating overwatering and poor drainage.
  • Choosing the Right Planter: Beyond aesthetics, choose planters that fulfill the functional requirement of drainage. If a decorative planter lacks holes, consider drilling some or use a double potting method.

Importance of Drainage Holes in Planters

Plants are pretty vulnerable in their potted environment compared to if they were growing in their natural habitat. The pots you house your plants force them to rely on you for water, sunlight, and nutrients. They also depend on you to ensure they have adequate drainage to prevent them from developing root rot from waterlogged soil. 

Having at least one drainage hole for the excess water to flow out will keep your plants happy and prevent health issues that saturated soil causes. 

Preventing Root Rot

As your plants receive water, the soil will retain what plants need for photosynthesis, respiration, and transpiration. Even though plants release about 97% of the water they uptake, they will not be able to absorb an overload of water in their soil before the root system suffers from suffocation, causing damage and rot. 

This sensitivity to excess moisture is why it’s imperative to have an exit for the excess water to drain out of the soil.

Therefore, any planter you pot your plants in should have at least one decent-sized drainage hole for water to flow through unless you have an earthen planter (more on that later).

There’s less ground to absorb the excess water when your plants are potted. So, there’s no escaping root decay when the soil is over-saturated, as they would in their natural habitat.

Facilitating Removal of Mineral Concentration

As you water your plants from the top, gravity causes the water to trickle through the soil, breaking up the mineral concentration and flushing the excess minerals out of the drainage holes. 

When minerals build up, the soil becomes hazardous and burns the roots. Root hairs take in nutrients through diffusion or active transport and absorb water through osmosis. The high concentration of nutrients in the roots pulls the water into them.

However, if the soil has a high mineral concentration, water will naturally be drawn out of the roots in an attempt to balance the concentration. As a result, the roots dry up.

Breaking up mineral concentration is especially important with salt build-up from using tap, hard water, or softened water for watering your plants. Too much salt will cause dehydration, and you’ll see signs of a miserable plant.

Signs your plants may be suffering from dehydration and mineral build-up are the following:

  • The plant leaves appear droopy.
  • Leaves are wilting or falling off.
  • There is browning or yellowing of the leaves.
  • The tips of the leaves appear ‘burnt.’
  • There is a white powdery residue on the top of the soil.
  • You will notice stunted growth and blooming.

Ensuring Adequate Airflow

When water fills the air pockets in the soil, it becomes anaerobic, and plants cannot breathe or carry out other essential functions. As a result, they will become damaged and begin to rot from being suffocated. Drainage holes and the correct soil mix allow water and oxygen to flow to the roots, keeping your plants healthy, hydrated, and happy. 

Preventing Oversaturation

Without drainage holes, there’s no exit for the extra water when watering your plants. The water will collect and saturate the soil, creating a wet environment that is hazardous to your plants’ health. The end game for this situation is the previously mentioned root rot. 

If the soil in any planter has become soggy from overwatering, it is crucial not to allow your plant to sit in the soil. If needed, repot your plant with a new soil mix to prevent decay from forming in the root system. 

Even with earthen planters, the amount of water causing soggy soil will not be able to evaporate quickly enough through the porous material.

When to Add More Holes

When one drainage hole isn’t cutting it, and your soil mixture isn’t contributing to insufficient drainage, you can make more holes in the bottom of your pots.

When making the holes, they should be about:

  •  ¼ inch (6 mm) for pots less than 12 inches (30 cm)
  •  ½ inch (12 mm) for pots 12 inches (30 cm) or larger 

When the holes are too large, too much soil will escape while water drains.

Adding more holes can be done using a drill or other methods.

To use a drill on plastic pots, follow these six easy steps: 

  1. Depending on the pot size, you’ll need tape and a drill with a bit size of ¼ (6 mm) or ½ inch (12 mm).
  2. Place tape on the outside and inside of the pot over areas you want to add an extra hole. You need at least three extra holes around an existing center hole or four, including a center hole. The tape will help keep the plastic stable and reduce the chance of cracking when drilled.  
  3. Using the drill with the bit attached, hold it straight over the taped spot and slightly pull the trigger to begin drilling. While drilling, don’t apply too much pressure, or you’ll crack the plastic. You’ll see the bit work through the layer of plastic until finally punching through the bottom. 
  4. Once the bit has drilled through the plastic, keep the trigger pulled back and pull the bit back through the hole. 
  5. Repeat for the remaining marked holes.
  6. Once you have your holes, remove any plastic debris and tape from the inside and outside of the pot.

Factors That Affect Drainage in Pots

Your planters, soil, and materials used play a huge role in the effectiveness of water draining correctly from the soil, not just drainage holes. 

If your pot has no holes, it’ll eventually give you trouble because all the water will sit in the bottom of the planter with nowhere to go. There is an overwhelming choice of pots on the market, but there are only two main functions your pot should include: drainage and big enough housing for your plants to grow healthily. 

Design

When you choose a planter solely on appearance, even when it lacks drainage ability, it’s not achieving its purpose for your plants. While many flashy planters may be lovely to look at, your plants will suffer when the soil stays saturated without drainage holes. The accumulated water will ultimately drown your plant. 

Therefore, you’ll end up with a beautifully decorated pot showcasing a dead plant. 

A couple of suggestions for those appealing pots with no holes include:

  • If possible, add holes by drilling or another method.
  • Double-pot your plants by placing your already potted plant inside the decorative planter with no holes. And by double potting your plants, you can also use the bottom watering method by pouring water into the pot without holes. However, don’t leave the main pot in water for more than 10-30 minutes, as it will saturate the soil and damage your plant. 

Material

Most earthen pots, or planters made of earth materials, come with only one hole. Some don’t come with holes, but these are porous and allow air and moisture exchange through the pot structure. Excess water evaporates through the walls and bottom of the porous planter unless there’s an outside coating of non-porous material, such as glaze. 

You’ll even notice after several waterings, the salts and other minerals will seep through the pores of the pot with moisture, creating a white residue on the outside of the pot. 

Soil and Amendments

Check your soil mixture if you notice little drainage from the one drainage hole. Some soil and materials can retain too much water, not allowing much drainage. And the added amendments, such as wood chips, can clog the bottom holes, preventing drainage from occurring. 

The sole purpose of your plants’ mixture is to provide nutrients, aeration, and allow drainage. 

If it’s not achieving its purpose, you should repot your plant in a suitable soil medium with materials that aid in natural drainage to keep your plants happy and thriving. 

Rocks at the Bottom: Debunking a Gardening Myth

Some suggest adding materials like rocks to the bottom of the planter to assist with drainage, especially if you have no drainage holes. 

However, studies have shown this theory does not work because the water will not drain from the soil with rocks lining the bottom of your planter. Water will accumulate in a layer at the bottom of the soil, and that layer is known as the saturated zone (or phreatic zone).

The best example to better understand the saturated zone is by thinking of a sponge soaked with water (soil absorbs water like a sponge). When you turn the soaked sponge on any side, the water collects at the bottom of the lowest level side, and very little water will escape the sponge. The water in the saturated zone will stay wet for longer, unlike the rest of the sponge. 

These results are the same with your soil, and since the saturated zone remains the same no matter the level it’s at, the rocks lessen the amount of dirt, and the zone will be close to or within the root system.

Final Thoughts

One drainage hole is usually enough for the excess water to drain from the soil. However, the soil and materials used can also contribute to one drainage hole not being enough to allow the water to drain correctly. 

Ensure you have a suitable soil mixture for your potted plants to prevent the roots from sitting in saturated soil and allow the water to flow through the materials to the drainage hole. 

If you find one drainage hole isn’t cutting it, you can make three or four more holes surrounding the center hole on the bottom of your planter.

Dr. Moritz Picot

Dr. Moritz Picot is a horticulture enthusiast and the founder of TheGrowingLeaf.com, where he serves as the lead content writer. He established the website in 2022 as a valuable resource for both gardening aficionados and beginners, compiling all the gardening tips he has accumulated over the past 25 years. Alex has a passion for nurturing plants, transforming backyards into inviting spaces, and sharing his knowledge with the world.

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