The Importance of Drainage for Indoor Plants

Good drainage is an often overlooked aspect of proper houseplant care

When people ask me for advice on houseplant care, one of the most common questions is, "How much water should I give my plant?" There are plenty of books and online sources eager to answer this question, but I won't. Why? Because it's the wrong question. The real issue isn't the amount of water you provide; it's how much water your plant retains after watering. This is a matter of drainage. Houseplant experts often give this misleading advice: Don't overwater your plants. As a result, plant owners think they should give their plants less water. Then the plants begin to wilt and develop crispy leaves, so they try adding more water, but the leaves continue to droop and fall off. Soon, that beautiful Philodendron or Ficus resembles Charlie Brown's Christmas tree, leaving the frustrated caregiver scratching their head and wondering what went wrong. Often, the answer to that question is: drainage. Drainage went wrong.

What is drainage

Drainage refers to how water moves through the soil to reach your plant's roots and how any excess water drains away. In their natural habitat, plants like calathea or begonia benefit from almost limitless drainage due to the many layers of soil and gravel between the plant and the deep bedrock. However, in a home environment, this isn't the case. You typically have a maximum of 10 or 12 inches of soil, often less. This is why planters have drainage holes; without them, your plant would sit in mud, which most plants dislike. This can lead to root rot, from which many plants cannot recover. Conversely, if the soil doesn't retain enough moisture, your plant will dry out, begin to wilt, and eventually die. The proper moisture retention for your particular plant depends on the preferences of that plant type and environmental factors such as soil type, pot size, and material.

Well-draining soil

We often encounter the term "well-draining soil" when discussing houseplant care. But what does this mean? It refers to the soil's ability to retain the right amount of water while allowing excess water to drain away. How does soil achieve this? By containing various organic and mineral substances with consistent water retention properties, such as peat, coir, sand, perlite, and vermiculite. Peat and coir (coconut fiber) are organic materials that form the base of potting soils. They can retain some moisture while allowing excess water to drain. Additionally, perlite (those small white specks) is a natural volcanic mineral that doesn't break down in the soil, enabling controlled drainage. Vermiculite traps a small amount of water in the soil to help extend moisture retention and is used for plants that prefer moister soil environments, like tropical plants and aroids. Coarse sand is added to potting mixes for cacti and succulents to prevent water retention, as these plants prefer drier soils. You can learn more about soil components here. With some practice and experimentation, you can even create soils that meet the specific drainage needs of your particular plant (here are a few recipes to get you started).

Drainage pots

Pots and planters are crucial for drainage as well. Generally, it's best to avoid pots without drainage holes. For most plants, the ideal container is a grower's pot similar to the one it came in from the greenhouse. These typically have several holes and raised areas at their base to assist with drainage. If you find these pots unattractive and utilitarian, you can place the grower's pot inside a decorative container or "cover pot." If you use this method, ensure that water isn't accumulating in the outer container, as this would negate the drainage pot's purpose. Small plants sold in grower's pots that are placed inside decorative non-draining cover pots are popular in retail shops, but be cautious: a common cause of root rot is water retained by these outer pots. Be sure to lift your plant out of its cover pot and empty any remaining water about 15 minutes after watering, and you should be fine. If you absolutely must repot your plant into a non-draining or slow-draining container, add some drainage pebbles to the bottom of the pot to keep the roots out of any pooling water. These plants must be top-watered because the added drainage material won't wick water into the soil as necessary for bottom watering. So proceed with caution. In addition to my plant obsession, I also collect (or perhaps hoard) vintage mid-century pottery and have occasionally taken risks by placing a plant directly in a small vase or pot that doesn't drain. Choose a plant that isn't particular about watering, such as a pothos or small philodendron, and be sure to add drainage pebbles and add water slowly to the vessel.

Is you planter the right size?

Pot size significantly affects drainage and water retention. If your plant is cramped in its container, there might not be enough soil to retain the necessary moisture for it to thrive, indicating it's time to repot. If you find that a plant can't last a week without watering, this is also a sign that repotting is needed. Conversely, houseplants in oversized pots may not dry out sufficiently to meet the plant's growth needs. Additionally, pots that are too large can cause the plant to focus its resources on root development instead of foliage. This is why you should increase pot size gradually. Novice growers often attempt to repot a 4-inch plant into an 8 or 10-inch container, only to be frustrated when their plant "doesn't grow." Therefore, increase pot size one step at a time to encourage a balance between root and foliage production.

Warning signs of bad drainage

There are two risks associated with poor drainage. The first is "overwatering." When your container doesn't drain properly, your plant's roots remain submerged in water, making them susceptible to root rot. Leaves that change color without becoming crispy and fallen leaves are warning signs of this dreaded condition. On the opposite end of the spectrum is dehydration, indicated by droopy, weak foliage and crispy leaves. In both cases, don't adjust your watering schedule; instead, repot into more suitable soil and a container. Underwatered plants can usually recover (depending on the species and the severity of the drought). Unfortunately, by the time a plant shows signs of overwatering, it may be too late to save. To assess the extent of the damage, remove all the soil from the affected plant down to the bare roots. If the roots are rotten, it is likely best to let that plant go and start anew. If there isn't significant damage, you may have been fortunate enough to catch the problem in time. Let the bare-rooted plants sit in a warm, dry area for a few hours, then replant them in dry, well-draining soil. Wait a few days before watering, and then gently apply moisture a little at a time until you see signs of recovery, such as upright leaves and new growth.

Understanding the relationship between water, soil and drainage is, in my opinion, the most overlooked aspect of houseplant care. Once you learn to get drainage for indoor plants right and you see your formerly struggling fern or dracaena come back to good health, you'll never think about watering the same way again. Drainage is the secret weapon in your plant care arsenal! 🪴