How to tell if a plant is overwatered or underwatered

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It’s every gardener's worst nightmare to find their plants yellow, wilting and lifeless.

If you’re wondering ‘what went wrong?’, we’re here to tell you that the key to houseplant success is a good watering schedule. Watering is a delicate balance between understanding your plant’s needs and using visual cues to diagnose issues.

But what if you don’t know the signs? Well, learning how to tell if a plant is overwatered or underwatered is the perfect place to start!

What are the signs of overwatering?

While you might feel like giving your plant that extra bit of water is an act of TLC, it can be detrimental to its health.

Yellowing and wilting leaves: One of the first signs of overwatering is yellowing leaves, often accompanied by wilting. Unlike underwatering, overwatered leaves may feel soft and limp rather than dry and crisp.

Leaf drop: Both old and new leaves may begin to drop off the plant: this can happen simultaneously and is a clear sign that the plant is stressed due to excessive moisture.

Mushy or rotting roots: Overwatered plants often develop root rot, which is characterised by black, mushy roots. Healthy roots should be firm and white, so any deviation from this indicates a problem.

Fungal growth and mould: The presence of mould or fungus on the soil surface is a common sign of overwatering. Fungus gnats, small flies that thrive in damp conditions, may also appear.

Unpleasant odour: Overwatering can lead to a foul, musty smell emanating from the soil: this odour is due to the decay of roots and the build-up of harmful bacteria.

Saturated soil: Continuously wet or waterlogged soil is a clear indicator of overwatering. The soil may take an unusually long time to dry out between watering.

What are the signs of underwatering?

Equally, by allowing your plant too much time to soak up its last feed, you could be depriving it of the essential nutrients it needs to survive.

Drooping and wilting leaves: Underwatered plants exhibit leaves that are dry, brittle, and wilted.

Dry and crumbly soil: If the soil in your plant's pot is pulling away from the edges and feels dry and crumbly, it’s a clear sign of underwatering. A crumbly texture indicates that the soil isn’t retaining enough moisture to support the plant's needs.

Leaf curling/browning: When a plant is underwater, leaves may start to curl at the edges and turn brown. Browning is due to the plant's inability to transport sufficient water to its foliage, which then causes the leaves to dry out.

Slow or stunted growth: Underwatered plants often show signs of slow or stunted growth. Without adequate water, the plant suffers reduced growth rates and smaller leaves.

Lacklustre and dull appearance: A plant that is not getting enough water will lose its vibrant colour and appear dull. The leaves may also lose their turgidity, which gives the plant a lifeless appearance.

Soil pulling away from the pot edges: This occurs when the soil is extremely dry and contracts, pulling away from the sides of the pot. It’s a clear visual cue that the plant is not receiving sufficient water.

How to diagnose the problem

As the signs of over and underwatering are actually quite similar, what’s the best way to diagnose the issue? You can do this with a couple of simple procedures:

Soil moisture check

Finger test: Insert your finger into the soil up to the first knuckle. If the soil feels dry, the plant likely needs water. If it feels moist, it may not require immediate watering.

Moisture Meter: A moisture meter provides a more precise measurement of soil moisture. Insert the probe into the soil to get a reading. As a houseplant tool, it can help prevent overwatering and underwatering by providing accurate moisture levels.

2. Root inspection

Healthy roots: Healthy roots are typically white or light tan and firm to the touch. They should be evenly spread throughout the soil.

Signs of overwatering: Overwatered plants often have dark brown or black roots that are mushy and may emit a foul odour. This condition, known as root rot, is caused by prolonged exposure to excess moisture, which deprives the roots of oxygen.

Signs of underwatering: If a plant is underwatered, its roots may appear dry and brittle. They might also be shrivelled and lack the firm structure of healthy roots.

What are the solutions/preventative measures?

Now you know the signs and what to look for, how can houseplant gardeners prevent the issue?

For overwatered plants

Stop watering immediately: If you notice signs of overwatering, stop watering your plant immediately. Allow the soil to dry out before adding any more water.

Improve drainage: Make sure your pots have adequate drainage holes to allow excess water to escape. Adding a layer of gravel or using a well-draining potting mix can help stop water from accumulating at the bottom of the pot.

Repotting: If the soil remains waterlogged, repot the plant in fresh, dry soil. Doing so can help eliminate excess moisture and provide a better environment for the roots. When repotting, trim any black, mushy roots to prevent further rot.

Aerate the soil: Gently aerate the soil by poking holes with a stick or a pencil; this can help improve air circulation and promote faster drying of the soil.

For underwatered plants

Water thoroughly: When you water an underwatered plant, water it thoroughly until water drains out from the bottom of the pot: this ensures that the entire root system receives moisture.

Soak the plant: For severely underwatered plants, place the pot in a sink or a basin of water and let it soak for about 30 minutes. This process allows the soil to rehydrate evenly from the bottom up.

Establish a regular watering schedule: Set a consistent watering schedule based on the plant's specific needs. Most houseplants prefer to be watered when the top inch or two of soil is dry.

Mulch the soil: Adding a layer of mulch on top of the soil can help retain moisture and reduce the frequency of watering. Mulch acts as a barrier that prevents water from evaporating too quickly.

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