Tiny gnats in your coffee, yellowing or dropping leaves, crispy or distorted growth… these may all be symptoms of common houseplant problems that are easily addressed if caught early. Read on to learn what to watch for and how to diagnose, treat, and prevent common indoor plant issues. Gain some knowledge, up your skills, and protect your collection!
Regardless of the season, here are a few of the most common houseplant symptoms and their possible causes and treatments:
- Yellowing leaves
- Dropping leaves
- Discolored leaf tips or edges
- Distorted or misshapen growth
- Dull leaf color or fading to green
- Weak, spindly growth and tiny flying bugs
- Sticky or shiny residue on foliage and nearby surfaces
1. Yellowing Leaves
Watering issues: may be caused by overwatering or lack of water depending on the leaf location; yellow leaves towards the lower or inner part of the plant often indicates overwatering (check to see if soil is wet/heavy/dark colored) but yellow new growth may indicate that the plant is too dry (again check soil moisture). Occasionally a very dry plant may need to be submerged in a saucer of water to allow it to slowly soak up water to rehydrate. Allow overwatered plants to mostly dry out before watering again; if roots have not begun to rot (plant wilting although fully watered), it should be able to recover with time.
Sunlight: leaves may yellow (or fade to a dull color) if exposed to too much direct sunlight, usually outer foliage, or newer growth; leaves may yellow if in too low of light (usually lower, older growth towards inside or bottom of plant). Move further away from window or add sheer curtains if too bright; provide supplemental light or relocate if too dark.
Pests: early signs of thrips, spider mites and other pests may show up as yellowing leaves; carefully inspect entire plant under strong, bright light for signs of insects. Clean/wipe leaf surfaces (tops and bottoms) with water, insecticidal soap or neem oil; spray plant or treat individual pests as needed.
Life doesn’t last forever: Sometimes a leaf is just “old” and is no longer useful to the plant. Nutrients are often reallocated further up the plant and absorbed by newer foliage as the old leaf turns yellow and eventually drops off. This is usually one of the lower leaves or towards the inside of the plant and often not more than one leaf at a time.
2. Dropping Leaves
Shock/stress: Some plants (especially Ficus) don’t react well to sudden changes in their environment and drop leaves when they experience changes in light exposure, cold drafts, or swings in temperature. Avoid making too many changes at once; most plants should recover from shock within a few weeks.
Overwatering: Often, a plant that is kept constantly wet will begin dropping green, healthy-looking leaves as an early sign of root-rot. Allow the plant to dry out before watering again, possibly repot into better draining soil, and make sure container has drainage. Root rot is often fatal—once it has been diagnosed, it may be too late to save the plant. Conversely, a very dry plant may also drop leaves to conserve water.
Pests: Carefully inspect entire plant under strong, bright light for signs of insects.
3. Discolored Leaf Tips or Edges & Curling Leaves
Black, brown, or yellow leaf tips may be caused by lack of humidity (dry air) or by accumulation of salts/minerals from water or fertilizer. Increase humidity by misting, providing a humidifier or pebble tray, or grouping plants together. Avoid fertilizing during dormant growth season (October through February) and allow tap water to “rest” for at least 24 hours before giving to plants. Make sure plant is not close to fireplace and heat or A/C vents, and keep clear of cold drafts.
Inconsistent watering can also be the cause. It is best to have a regular, consistent watering routine that is seasonally adjusted to reflect the active or dormant growth periods.
Some fungal diseases cause tip damage or curling. Allow foliage to dry out during the day (mist in morning), treat with neem oil as fungicide, or bring a leaf sample into the nursery for diagnosis and treatment.
If your potting soil is old and “tired” or has become compacted, it may be time to repot the plant and refresh the soil so it can hold more moisture (good to do at least every 2 to 3 years, even on very old, mature plants).
4. Distorted or Misshapen Growth
Pests can cause distorted leaves, especially on new growth. Thrips, aphids, and other pests may be small and difficult to notice until they cause unusual growth patterns; closely inspect plant for signs of pests, and use sticky pest traps to help identify insect. Treat with insecticidal soap, neem oil, or in some severe cases, systemic houseplant insecticide.
Disease: Curled leaf edges or new growth that fails to fully unfurl may be caused by a fungal disease. Allow foliage to dry out during the day (mist in morning) and treat with neem oil as fungicide, or bring a leaf sample into the nursery for diagnosis and treatment.
Compacted soil or a plant consistently kept too dry may cause leaves to grow smaller then normal or to curl up like a taco. Refresh soil if old, submerge in a tray of water to rehydrate if soil is hard and dry, use a chopstick or pencil to poke some holes into soil for aeration, and/or water more frequently.
Stretching for more light is a frequent cause of a plant changing its growth shape. Sometimes plants become lopsided (towards the source of light) or grow tall and “leggy” with long spaces between leaves. Occasionally rotate plant to expose all sides equally to light, relocate, or provide supplemental, artificial lighting, if possible.
5. Dull Leaf Color or Bright Colors Fading to Green
Pests such as spider mites can often cause a leaf surface to appear dull or dusty. A fine webbing may be visible under bright light and with close inspection. Isolate plant and treat with insecticidal soap or neem oil.
Light exposure, especially too bright or direct sunlight, may cause a leaf to burn or become dull or faded. Most tropical/indoor plants prefer indirect or filtered light over direct sun. If a brightly colored plant like a purple succulent or one with variegated foliage slowly loses color and fades to green, it may be due to light conditions being too low. Relocate plant to brighter light or add artificial light and the plant should return to its former colors.
6. Weak, Spindly Growth & Tiny Flying Bugs
Low light: Stretching for more light is a frequent cause of a plant changing its growth shape; sometimes becoming lopsided (towards the source of light) or growing tall and “leggy” with long spaces between leaves. Occasionally rotate plant to expose all sides equally to light, relocate, or provide supplemental, artificial lighting, if possible.
Fungus gnats (tiny, black flying bugs) brought on by overwatering can be a nuisance in the house, but larvae living in wet potting soil can do damage to plant roots as they feed. Isolate plant and allow it to dry out as much as possible, then repot into a container with drainage if not currently in one. Use products like Mosquito Bits to sprinkle on top of the soil to kill the gnat larvae. Sticky traps can also help control flying adults.
7. Sticky or Shiny Residue on Foliage & Nearby Surfaces
This is almost always a sign of pests—usually mealy bugs, scale, or aphids. Carefully inspect plant in bright light and wipe all leaves (tops and bottoms) with insecticidal soap or neem oil. Spray plant or treat individual pests as needed. You may need to isolate the plant until the pest is under control to avoid it spreading to others nearby.