Friday, January 13, 2012

When Good Plants Grow Bad

Most indoor plants are quite resilient but no matter how tough their constitution is they will eventually succumb to the blunders that we carry out and impose upon them. We drown or dehydrate our houseplants by carrying out improper watering techniques, neglect to provide them with sufficient humidity, place them in locations where the lighting is inappropriate, expose them to cold temperatures, drafts, heaters and air conditioners, plant them in poor quality soil mixtures, make a multitude of repotting mistakes and quite often feed them too much, too little or not at all. Trapped in containers, indoor plants rely on us to provide all their needs; their well-being and survival is entirely in our hands. We decide whether they thrive or weaken. We decide whether they grow vigorously or sluggishly. And we decide whether they live or die.

No plant is brought home in poor shape from a reputable garden center or florist. It begins its journey in top form – without unhealthy leaves, poor growth and aesthetical imperfections. Its decline is caused by well-meaning humans who neglect to provide the appropriate care –mostly unknowingly. So when good plants start to grow bad, it’s usually because of something that we did - or did not do. And sure, the invasion of pests can cause damage, but since we’re responsible for checking for (and exterminating) those harmful critters, if a plant deteriorates or dies because of unwanted guests, it’s still due to our negligence.

Since most of the problems associated with houseplants are the consequence of poor growing conditions and inattentive care that we impose on them, I’d like to write about symptoms that appear on your indoor plants and what typically causes them. Once you recognize what faulty conditions are stressing and weakening your plant, you can take the appropriate steps needed to correct them.

What Causes Good Plants To Grow Bad?

Symptom(s): Plant will not bloom (has reached maturity & blooming period)

Cause(s): Insufficient light, excess nitrogen feeding, wrong day length (short day plants need less hours of light), dry air, under watering, repotting to larger containers (some plants need to be slightly pot bound to bloom), improper temperature (too warm/too cold)


Symptom(s): Buds fall off or fail to open, premature flower loss

Cause(s): Excessive heat, plant relocation (especially when buds form), fluctuating temperatures, cold drafts, under or over watering, improper lighting, low humidity, pests


Symptom(s): Yellowing leaves

Cause(s): Improper watering (most often over watering), cold drafts, temperature extremes, too much or too little light, too much or too little fertilizer, poor drainage, plant needs repotting, pests

Note: It’s normal for an occasional lower leaf on mature plants to yellow and drop as time progresses.


Symptom(s): Wilting, drooping of foliage

Cause(s): Under watering (immerse in water for quicker recovery), over watering (roots may be rotting and incapable of absorbing water), too much light, high temperatures (especially if plant wilts daily in midday sun), cold temperatures, low humidity, excess fertilizer, compacted soil, root, stem or crown rot, plant needs repotting

Note: Severe over watering (soil is soggy) and under watering (soil is bone-dry) can both cause wilting; make sure you determine which one is troubling your plant before taking appropriate action. A chronically over watered plant should be repotted in fresh soil.


Symptom(s): Tall, leggy, spindly growth

Cause(s): Generally this is a result of insufficient light. Other causes may include underfeeding.


Symptom(s): Little or no growth

Cause(s): Insufficient light, underfeeding, pot bound plant, dormancy


Symptom(s): Curling Leaves

Cause(s): Over watering, humidity too low, too much light, cold drafts, temperature too low or too high


Symptom(s): Small, pale leaves

Cause(s): Not enough light, underfeeding


Symptom(s): Brown leaf tips, brown leaf margins

Cause(s): Air too dry, under watering, over watering, overfeeding (fertilizer burn), temperature too high, drafts, chemicals in the water (especially fluoride), root rot

Note: Brown tips can also be caused by leaves touching cold or hot surfaces such as window panes and radiators.


Symptom(s): Lower leaves dry up and fall

Cause(s): Under watering, too hot, not enough light


Symptom(s): Abrupt defoliation of healthy leaves

Cause(s): Transplant shock, not enough light (leaves will fall from the bottom), under watering (leaves will fall randomly from the plant), over watering (root rot), changes in environment that drastically affect previously enjoyed levels of light, humidity or temperature

Note: It is normal for newly-purchased plants to drop a few leaves as they try to acclimatize to their new environment.


Symptom(s): Yellow leaves, veins still green

Cause(s): Iron deficiency (most often), hard water


Symptom(s): Gradual (but continuous) defoliation

Cause(s): Under watering (plants drop leaves if there isn’t enough water available to support them), over watering (roots have been damaged), insufficient light, plant needs to be fed


Symptom(s): Brown, yellow or black spots and patches on leaves

Cause(s): Too much sun, cold water (make sure water is room temperature), over watering (spots will be brown and soft), under watering (spots will be brown and crispy), pests


Symptom(s): Variegated leaves revert to all-green shades

Cause(s): Not enough light


Symptom(s): Foliage pale and lifeless

Cause(s): Not enough light, not enough fertilizer, soil too dry, pests (mainly spider mite)


Symptom(s): Black leaves

Cause(s): Cold damage, consistent over watering


Symptom(s): Crown, stem, roots and leaves are soft, rotting

Cause(s): Over watering (especially in winter)

Note: If a plant has been frequently over watered in the winter, especially if it’s situated in a cooler location, this can cause the crown, stems, leaves and roots to rot. Move it to a warmer spot immediately, allow it to dry, repot if necessary to improve drainage and hope that it’s not too late.


Symptom(s): Complete plant collapse

Cause(s): Most houseplants are killed by kindness than neglect and the kindness in question usually involves water – mainly over watering. Other common causes of plant death include chronic under watering, severely insufficient light, very cold temperatures (transporting from garden center to home in the midst of winter can cause the death of a plant), cold drafts, strong sun, pests (if infestations are left untreated they can become severe enough to kill the plant)


Symptom(s): Cottony masses on stems, yellowing leaves, distorted foliage, presence of honeydew or mold, sticky patches on leaves, stems or axils

Cause(s): Mealy bug


Symptom(s): Discoloured, distorted foliage, speckled, scorched or bronzed leaves, fine silk webbing, leaves may appear dusty and dull

Cause(s): Spider mites


Symptom(s): Small, dark bumps on stems and foliage, sticky spots on leaves or on the floor near the plant

Cause(s): Scale insects

Note: Damage caused by these parasites includes delayed, poor, stunted or curling new growth, discoloration, yellowing foliage, premature dropping of leaves and noticeable wilting.


Symptom(s): Severely distorted leaves and stems, damaged flowers, sticky spots on leaves or on the floor around the plant, wilting, curling, yellowing and eventual leaf loss

Cause(s): Aphids

It’s not always easy to diagnose the root of your plant’s troubles, especially when many of the likely causes share the same symptoms. In those cases you will have to eliminate one possible cause at a time or check for other symptoms to help zoom in on the right problem. For example: over and under watering may cause the same symptoms but the soil will be soggy in over-watered plants and bone-dry in plants that are parched.

In addition, in order to limit the need to diagnose and treat unwanted problems, dedicate some time in practicing preventive measures. Open windows daily if possible, run floor and ceiling fans to circulate the air, isolate newly-purchased plants to rule out pest infestations that can sweep through your entire collection of houseplants, clean, wash or shower your plants regularly and make sure humidity levels are at optimal levels (especially during the winter). Learn about your plant’s needs in order to be able to supply it with the appropriate amount of light, water and warmth. The reward from these small added efforts, particularly when carried out routinely, is healthy plants and no major problems to contend with. “An ounce of prevention is worth a pound of cure”


  1. What about a plant that has all of the above symptoms?!! Hahaha.
    I actually purchased a poinsetta this year - a lovely cream one - and it's still alive! I sit it in the sink every 8-10 days with water and plant food and it's in a bright location. In the past I've tended to abuse my poinsettas - ie ignore them :)

  2. I'd add to "Variegated leaves revert to all-green shades" that some plants' variegation is just not that stable, and those plants will try to revert sooner or later even when light intensity is correct. Supposedly Schefflera actinophylla is one such plant (I've never grown a variegated one); variegated Ficus pumila tends that way as well. Some of the Syngonium podophyllum, Hedera helix, and Philodendron hederaceum varieties do this too (though they all revert to other kinds of variegation about as often as they revert to solid green). The point being that it's possible to get the light intensity right and still have this happen.

  3. @Jane: Poinsettias can live for a long time if properly cared for. The cream-coloured ones are lovely. I almost picked one up this year but got a red one instead - again!

    @Mr. Subjunctive: Very true. Some of my own plants have done the same no matter how hard I try with them and no matter how much light I provide. This is good advice, so people don't get frustrated and think they're doing something wrong. Sometimes it is what it is with no fault of any kind.