Your Guide to Vibrant Indoor Plants!

learn how to make indoor plants thrive.

Dracaena: an easy indoor plant.
Mikael Quick – CC BY-SA 2.0

For me, there is something special about a home or apartment full of thriving indoor plants. The color, texture and the life they bring to any living space is something that simply can’t be duplicated by inanimate artwork, much less fake plants.

Add to that the oxygen they produce and the air cleaning service they bring, and you really have no reason for not having at least a few plants in the home.

I understand that everyone has different experiences when it comes to growing plants, and I am sure some may consider themselves cursed with a “black thumb.” However, the truth is that whether or not you’ve had a long track record of failures, you can grow beautiful plants indoors that will beautify and enrich your home. I promise!

You just need to steer clear of some rookie mistakes and adopt some healthy plant care habits.

Here are the 10 most important rules to live by for growing spectacular and awe-inspiring houseplants.

CLICKABLE TABLE OF CONTENTS:
1)          Don’t Underestimate The Light Indoor Plants Require
2)          Don’t Rush to Re-pot a New Indoor Plant
3)          Water Houseplants Only When They Need It
4)          Ensure Proper Drainage When Watering
5)          Fertilize Your Houseplant, But Be Conservative
6)          Avoid Extreme Temperatures & Drafts
7)          Maintain Sufficient Humidity
8)          Avoid Light Shock & Allow Your Houseplant to Acclimatize
9)          Select Only Healthy, Vigorous Indoor Plants
10)        Watch for & Deal With Pests Proactively

1) Don’t Underestimate The Light Indoor Plants Require

Houseplants vary widely in terms of their light requirements, but most common indoor plants tend to be moderate to low-light types, which in the wild manage to eek out a living in the dappled light that penetrates the forest canopy in tropical/subtropical climes. But don’t confuse their tolerance for shade outdoors with the comparatively weak light that they receive through windows in a home.

The staghorn ferm make a great indoor plant if provided with enough light.

Staghorn fern enjoying direct sunlight.
photo by Ben Husmann under CC BY 2.0

Understanding and accommodating an indoor plant’s particular lighting needs is the single most important factor controlling its long-term survival and health.

While light is not exactly food for plants (plants actually use it to make their own food via photosynthesis), you can think of it as such, because if all other conditions are optimal it is generally the only limiting factor for their growth.

Thus, without sufficient light, all of the fertilizer, doting, and TLC in the world can’t help a plant.

Gauging Light Levels Indoors

Light can be quantified by talking in terms of “foot-candles” (or “ft-c” for short). Outdoor on a sunny summer day, a plant placed in direct sunlight at around noon may receive around 8,000-10,000 ft-c of light. Compare this to the mere 200 ft-c that a plant sitting on a north-facing windowsill may receive. Even direct light passing through a window may not be as strong as you think. For example, an east-facing exposure might only register measure around 5,000 ft-c when receiving direct light.

indoor plants need sufficient light to thrive

Seedlings will elongate in inadequate light.
rudy.kleysteuber – CC BY 2.0

Also, keep in mind that light levels plummet quickly as you move away from the windowsill. While the spot below your large skylight may look “bright” to your eyes, depending on the plant, it may be too dark to survive, much less grow.  Particularly when making use of indirect light, always keep your plants as close to a window as possible to promote the most vigorous growth!

Further, each home, window and room is different, and two southern exposures on the same street can differ wildly depending up the extent of nearby vegetation, the presence of overhangs, the type, color and thickness of the glass, and the size of the window through which the light is passing.

Although it’s not necessary, it may be helpful to obtain some light measurements in your home for yourself with a 35 millimeter camera, so you can see just how “bright” the light is in your home really is.

Season affects the amount of light indoor plants receive.

Indoor plants receive varying light during the year
Solar altitude”by Hartz under CC BY-SA 3.0

Whether you calculate luminosity or merely eyeball it, bear in mind that light intensity is always changing throughout the day and season of the year, so don’t hang your hat on a midday measurement in winter!  Winter sun always penetrates a home far better because the sun hangs lower in the sky, thus allowing it to hit a window more perpendicularly.

In summer, the suns shines more down on, rather than into, a house. Thus, its rays may get fully or partially clipped by roof overhangs, and/or infiltrate the home just a few feet from the window even if it isn’t obstructed. Consequently, your indoor plant may get twice the amount of light energy in the winter as it does in the summer.

Having said all that, rest assured that you don’t need to invest in expensive light meters or map the light energy all over your house if you follow some general rules of thumb and use the right plant for the right space.

The best way to do this is to understand and apply the following light level categories, which we will use to characterize all of the indoor plant species discussed on this site.

Very low light indoor plants

The heart-leaved philodendron is one of the hardiest very low light houseplants.

Heart-leaved philodendron need little light to thrive.
photo by Katie Brady under CC BY 2.0

These are houseplants that can survive and grow in locations that are several meters from any window, even a relatively dim north-facing window.They may even be able to survive and flourish in windowless areas, so long as the space is illuminated by typical florescent overhead office lighting.

These are among the hardiest and most “bulletproof” of indoor plants. They also allow the greatest freedom in terms of interior design since they do not need to be closely associated with windows.

Although there are exceptions, these plants usually do not like direct light, but enjoy bright indirect light and may even benefit from a brief exposure to early morning direct sun from an east-facing window.

Common plants that fit in this category are Chinese evergreen (Aglaonema commutatum), peace lily (Spathyphilium sp.), some dark-leaved members of the genus Dracaena, and heart-leaved philodendron (Philodendron sp.)

Low light indoor plants

Spider plants do will indoors, wherever good indirect light exists.

Spider plants can tolerate low light, but don’t push it!
photo by Sharon under CC BY 2.0

This refers to species that can generally do will in locations that are dim, but not quite as dark as those above.

For example, the darkest locations in which you should try to grow these plants are those two to three meters away from a north-facing window.  In rooms with unobstructed east, west or south-facing exposures, they can be placed 4-6 meters away from a window depending on how well the light penetrates the particular room.

These plants generally will not grow well in windowless spaces, unless subjected to sustained and strong overhead florescent lighting. And even then, growth will likely be slow and the plant may appear weak.

Once again, while they may survive in dim conditions, most of these plants will look much better and grow more vigorously in very bright indirect light and many can benefit from brief exposure to direct sunlight. Just make sure that it is early morning light or filtered (through blinds, other plants, heavy screening, etc.) if coming form a southern exposure.

Representative low light species include Golden pothos vine (Epipremnum pinnatum), spider plant (Chlorophytum comosum), most Dracaena (e.g., Dracaena deremensis), parlor palm (Chamaedorea elegans) and snake plant (Sansevieria sp.).

Moderate light indoor plants

The Boston fern requires moderate light levels to look its best.

A moderate light indoor plant: the Boston fern.
photo by lyd_f under CC BY-ND 2.0

These houseplants need substantially more illumination, and generally can only grow near a north-facing window if they are right up against the window.

If you move even a few feet away or off to the side of a north-facing window, they will often stop growing and begin to deteriorate. Still, it is advisable not to situate these plants along norther exposures at all, if other brighter locations are available.

Plants in this category differ considerably as to how much direct light they can stomach, but as a general matter they are best located along east facing windows (ideal), or west/south-facing windows so they can get at least some direct sunlight. Most species will need some protection from too much direct light, either by filtering the light or moving the plant further away from the window.

The varieties of houseplants to chose from really opens up if you can provide sustained bright indirect light. In fact, you will almost certainly run out of room in your house before you exhaust your options. Just a some of the plants in this category include gardenia (Gardenia jasminoides), dumb cane (Dieffenbachia bowmannii), certain bromeliads (e.g., Vriesea and Guzmania sp.), large philodendron species (e.g., Philodendron sp. “Rojo Congo”), elephant ear (Colocasia sp.), African violet (Saintpaulia ionantha), Kentia palm (Howea forsteriana), Boston fern (Nephrolepis exaltata), lipstick plant (Aeschynanthus speciosus) and certain orchids (e.g., Phalaenopsis and Ludisia sp.) – to name a few!

High light indoor plants

Croton are a striking indoor plant if you can provide strong direct light.

Croton need high light for vivid color.
photo by daryl_mitchell under CC BY-SA 2.0

High light plants are those generally requiring placement near a south-facing window so they can receive sustained direct light and/or the very brightest indirect light – i.e., the type of indirect light you get outdoors in a shady spot surrounded by direct sunshine.This type of indirect light can usually only be duplicated indoors by subjecting a plant to filtered direct light.

Do you want an indoor herb garden? Most windowsill herbs like basil will need at least 5 hours of direct (unfiltered) sunlight each day. Anything less will usually result in long, spindly and slow growth. Most orchid and bromeliad species also require high light in order to bloom and grow properly.  Some species like croton, for example, can tolerate more shade but only show their true kaleidoscopic colors when grown in direct sun.

In many cases, high light plants can be placed outdoors for the summer, or year round if you live in warmer zones. Keep in mind that while these plants need intense light, they don’t like to be shocked by it. So if you buy a high light plant that’s been sitting indoors for a while, it’s best to increase light intensity gradually over a one-week period to avoid leaf scorch.

Some common examples of indoor plants that need high light to thrive include most vegetables and herbs, most orchids (e.g., Cymbidium) and bromeliads (e.g., Neoregalia), Venus fly trap (Dionaea muscipula), croton (Codiaeum sp.), jasmine (Jasminum sp.), most cacti, angel’s trumpet (Brugmansia sp.), indoor citrus trees, most palms (e.g., Dypsis lutescens), bird of paradise (Strelitzia reginae), and dwarf banana (Musa sp.).

2) Don’t Rush to Re-pot a New Indoor Plant

I see this time and time again. Someone goes to a nursery and gets a beautiful houseplant, then goes home and immediately transplants it into a pot two or three times the size of the original so the plant “has more room to grow.” Big mistake, and one I’ve made myself!

Resist the temptation to repot a new houseplant immediately after purchasing.

Don’t repot new indoor plants too quickly.
photo by Tara Severns under CC BY 2.0

Most of the time, a plant that you buy is actually quite comfortable in the pot it arrived in, despite how it may look.

It’s natural to want to free them from their small growing containers, and it’s true that many tropical plants are so large for nursery pots they can easily tip over. However, considering that you are moving the plant to a totally new location, it’s often wiser to leave the pot alone, at least for a month (or longer if the plant is not actually in danger of becoming root-bound) so the plant can otherwise ease into its new surroundings. You can always place it in a larger decorative pot in the meantime if the nursery container is unattractive.

And when you do repot, be conservative; only use a new pot that is at most 1/3 percent larger than the old. For example, if transplanting something that came in a typical 4-inch nursery pot, the new pot should provide room for anywhere between 1-2 inches of fresh soil all around the root ball. There’s no need for any precision here, but you don’t want to surround the roots in too much new soil for a couple reasons.

First, it greatly magnifies the threat of over-watering. New potting soil is very dense and holds much more water than old soil, which is lighter and more well-draining as it is somewhat displaced by a developed root mass. This makes new transplants with a relatively high percent of newly added soil slower draining and much wetter. Continual moisture is a problem (especially in most commercial mixes) because it reduces the amount of oxygen that can enter soil and therefore easily starve a plant’s roots of oxygen, which in turn can promote rapid root rot. Once the roots begin to rot, the problem becomes even more grave, as the process of decomposition consumes even more oxygen and kills even more roots, with a snowballing effect. The end result could be a big beautiful pot with a dead plant, which succumbed to it’s owners good intentions!

Secondly, aside from the threat of root rot, over-potting can foster conditions favoring deleterious pests. For example, soil gnats are usually benign in low numbers, but give them an over-sized pot with continually moist soil and their population can quickly swell to a size that could impact your plant’s health, as well as drive you crazy when they buzz about your face and TV screen.

If you’ve got a pot plagued with a burgeoning population of gnats (not the occasional gnat here or there which is normal) your best bet is to pull out the plant, knock off the loose soil down to the original root ball and pot again – this time in a smaller pot.

3) Water Houseplants Only When They Need It

It’s a common question most nurserymen receive: how often should I water my plant? However, it’s also flawed because it presupposes that an abstract schedule can be imposed in the first place. Yes, I know, you’ve got a plant and you water it every 10 days and it’s happy – but you have arrived at that schedule based on the circumstances of your plant and home, which is precisely the point.

Developing good watering habits is a skill that will develop with time.

Water well, but careful not to overdo it.
photo by chichcacha under CC BY 2.0

So many things influence how often a plant needs water. For example, high light, high temperatures and low humidity all contribute to rapid water loss, as does a very loose, airy soil and being in a relatively small pot or one where the plant has filled it with roots. Conversely, a plant in a comfortably large pot in a cool dim corner in a home with high humidity will need to be watered much less.

Unless otherwise stated for the particular indoor plant discussed, you should assume that most houseplants will benefit from drying out slightly between waterings. Don’t wait for them to wilt or become stressed, but you can wait for at least the superficial layers of the soil in the pot to dry. This helps bring more oxygen into the roots and helps discourage outbreaks of soil gnats and other moisture-loving roo-tball pests.

But don’t just the look at the soil surface; this could be misleading. I encourage you to use the “finger-stick method”: stick your fingers into the soil like a probe; send a finger one to two inches in the pot (go deeper for large pots) and feel your fingertip for any hint of moisture below. A very slight moist feel, enough to have the soil barely stick to your fingertip; that is what you want. This is the ideal. Any dryer than this and you want to water; any wetter and you should hold off and recheck the next day.

Do this as often as needed at first to get a feel for how often you should water, then use that as your baseline watering schedule. Continue to use the finger-stick method occasionally and when things conditions – like season, temperature, humidity and the size/maturity of the plant.

4) Ensure Proper Drainage When Watering

Most houseplants do not appreciate standing in a tray of water. Make sure your pot has one or more drainage holes and that the water passing through can actually leave the pot for good, rather than being pooled against the holes up so it can wick back upwards into the plant. You can do this a couple of ways: 1) by setting the pot on a flat stone or other object to elevate the drainage holes above the tray slightly; or 2) water the plant outside, in a sink or in a basin and immediately discard all drainage water.

Good drainage is essential for any indoor plant.

A layer of rock over pot holes can improve drainage.
photo by Francis Chung under CC BY 2.0

Good drainage does a two very important things. First, it allows the soil to de-saturate quickly, thereby preventing root infections and maintaining healthy soil oxygen levels. And two, it flushes the salts and minerals that have accumulated due to hard water, fertilizers and other additives.

Flushing is vitally important to your plant’s health, in ways that may not be obvious.

In addition to the salts added by plant fertilizers, most municipal water itself contains considerable amounts of dissolved minerals and other chemicals, like chlorine, sodium chloride, flourine, calcium carbonate and magnesium. And while both calcium and magnesium is beneficial to plant growth in moderate amounts, without flushing, these salts and minerals can gradually increase over time and become harmful if not flushed. The way these minerals accumulate is simple; while water evaporates, dissolved solids do not. Imagine filling a glass and replacing water as it evaporates, time and time again without washing. If you let the class dry completely, you will see it coated with a crusty white substance; this “crud” is typically composed of hardwater minerals.

You can easily witness the effect of “salt” burn in plant leaves themselves. The tips of the leaves (where transpiration rates are highest) is where the salts accumulate the fastest and where the plant tissue dies first. Have you ever seen houseplants with blackened leaf tips? This is often the result of salts or other chemical in tap water. Dead leaf tips due to mild salt burn are actually quite common and will not kill the plant (they can be cut off usually without damage to the rest of the leaf), but in time the effects of salt build up in the soil can and will kill a plant, especially in areas where the water is particularly hard (like in most of the arid southwest).

So, to come back to the point here, water your plant so the water flows out of the bottom and dump what drains out or otherwise ensure that it does not wick it’s way back up! You may still get slightly salt-burned leaves depending on the nature of your tap water (or presence of flourine for some sensitive plants like Dracaena), but you will avoid more serious consequences of root necrosis due to chronic soil salt accumulation.

5) Fertilize Your Houseplant, But Be Conservative

Osmocote is a great time-release fertilizer that I use on all my houseplants.

Fertilizer is vital for indoor plants.

Any houseplant that is in good condition will need to be fertilized to sustain growth and vigor; however, they don’t need as much as you may think. First off, if you’ve just transplanted it, check to see whether the potting soil contains some fertilizer (they often do). If so, do not fertilize for at least a month after re-potting.

Also, keep in mind the time of year and match your fertilization rate to the plant’s growth rate. For example, most houseplants tend to grow very slowly in winter and/or in dim light – so in either case be very sparing with fertilizer. If in doubt, cut the manufacturer’s dose by half. Conversely, if its summertime and your plant is throwing new shoots, you can step things up and maintain a more regular feeding schedule, and following full recommended fertilizer dosage and frequency.

Nevertheless, to minimize fertilizer burn I encourage you to use a high-quality time-release fertilizer, such as Osmocote. Keep in mind that you can still burn a plant with this (and I’ve done it unfortunately), so be judicious with your application and watch for any early signs of serious fertilizer burn, which can resemble ordinary wilting from lack of water. A well-watered plant that wilts soon after the application of fertilizer should be flushed thoroughly and pit in a protected location until the plant recovers turgidity.

6) Avoid Extreme Temperatures & Drafts

Since most houseplants are native to warm climates, they generally do fine and thrive around the same temperatures that humans enjoy. Temperatures of around 80oF during the day and 70oF at night are ideal, but anything between 60oF and 90oF is acceptable for most species.

Just be careful of extremes and avoid cold drafts in winter.  For large floor pots, it’s a good idea to place them on a small stand – or anything that gets them even a couple inches off of a cold floor. This will help keep the root mass from getting too cold, which could stress the plant or halt growth.

7) Maintain Sufficient Humidity

Most indoor plants enjoy as much humidity as we can tolerate.

Shoot for at least 35% humidity in the home.
photo by Claudio Matsuoka under CC BY 2.0

Again, given the balmy tropical places where most indoor plants originate, they’ve become quite fond of humidity and many will do poorly if deprived of it. This is especially true of fine-leaved ferns and delicate mosses. For these plants, and virtually all houseplants (except those with hairy leaves), it’s a good idea to keep a small hand sprayer and mist them often. You can also use a room humidifier or set them on a tray of pebbles and water.

Depending on the plant, a relative humidity of 50% (around the plant itself) is usually ideal.

Humidity can be particularly challenging to control in very arid regions, or in any home where air conditioning and/or forced air heat bring humidity levels down too low.

Humidity levels much below 25% can start posing problems for many plants, such as making them susceptible to certain dry-air-loving pests, like spider mites.  You will also need to pay close attention to your watering in such conditions, as water loss will be rapid.

Although plants normally like high humidity, a comfortable minimum humidity level for most indoor plants and people is around 35-40%; any more than this in a home and it could increase the risk of promoting harmful or unsightly molds.

8) Avoid Light Shock & Allow Your Houseplant to Acclimatize

Plants will try to adapt to ambient light levels if they can, but rapid changes can be very stressful. In particular, taking a plant that has been grown in indirect light and thrusting it into direct light can give it sunburn, which may not kill the plant entirely, but could cause most of the exposed leaves to die. Even a long ride home in a car where a houseplant is left in the sun can cause significant damage that may not be visible until days later.

Sun scorch is a consequence of failing to gardually acclimatize your houseplant.

Avoid sun scorch by gradual light acclimatization.
photo by Daniel R. Blume under CC BY-SA 2.0

On the other hand, the effects of taking a plant from high light to low light are no less significant but aren’t as rapid.

For example, I recently bought a gorgeous golden pothos that had been growing in a hanging basket in a greenhouse. It was spoiled by the high light and humidity it was receiving; the plant was so dense with foliage I could barely find the soil to water it! Although I admired the plant for this vigor, I was saddened by the awareness that it would not remain quite so leafy after adjusting to its new home.

Sure enough, as I anticipated, the plant dropped about 20% of it’s leaves and took on a deeper green in the medium-low light location in my home just weeks later.  The reduction in leaves was an inevitable consequence due to the reduced availability of light and the economy afforded by losing  unnecessary leaf mass. And the darker green resulted from the increased production of chlorophyll in the remaining leaves, which made them more efficient at capturing light energy. Nature is truly amazing.

Leaf drop/thinning can occur for any plant that goes from high to low light, but some react more dramatically than others. For example, weeping fig (Ficus benjamina) are well-known for shedding lots of leaves in even mild instances of light level change. There’s usually no need to panic, as long as minimum acceptable light levels exist. Try not to over-water during this period of acclimation as well, since the plant’s rate of transpiration will slow due to the sudden decrease in the rate of photosynthesis.

9) Select Only Healthy, Vigorous Indoor Plants

These snake plants exhibit strong growth and bright colors.

Select indoor plants with good color.
photo by Greenery Nursery under CC BY 2.0

When shopping, take care to examine any prospective purchase. Avoid plants that look wilted or have discolored or damaged leaves. Also do a quick check for parasites – look under the leaves, around the leaf axils (where they connect to the stem) and around the growing tips. Do you see any white, fluffy material, fine webbing or any visible pests near the shoots?

Check the base around the soil, and if possible lift the plant out of the pot to look at the roots; most healthy plant roots are white or light colored and should look crisp. If you see dark brown black roots at the bottom of the root ball this could suggest root rot or infection.

Finally, set the plant on the floor and spin it around – does it look healthy and strong? In most cases a weakened plant will just look tired. If there are several specimens of the same species, look at more than one to see if you can observe differences between them; pick the one that has most strong, fresh growth.

10) Watch for & Deal With Pests Proactively

When properly maintained, most indoor plants are usually trouble-free, but if you have any size collection, a pest problem is an inevitable fact of life. But don’t fear, the good news is that most parasites can be dealt with fairly easily; however, like most things in life, early detection and prompt action is key.

Here are some usual suspects to be on the lookout for.

Aphids

These are small sap sucking insects and the most common of plant pests. The can come in various colors but are typically bright green, yellow or black. They tend to aggregate around the tops of a plant, on the new shoots, and particularly along fine stems and under young leaves; this is precisely where a plant’s sap is flowing strongly. While adults are easily visible with the naked eye, they are still quite small.

Aphids are a common, but usually easy-to-rid indoor plant pest.

Pea aphids extracting sap from garden peas.
photo by Shipher Wu under CC BY 2.5

Aphids can and will infest an indoor plant, but are often more problematic for patio plants. As they draw plant fluid, they produce a honeydew substance that seems to ingratiate them with some species ants, which will feed on this substance in exchange for protection. Interestingly, there are certain plants that seem immune to aphids, like various low light plants including as golden pothos and peace lilly. On the other hand, most high-light species, especially vegetable and food crops, seem to be constantly plagued by them.

These sap suckers, if not protected by ants, are easy targets for a variety of natural predators, including ladybug larvae, lacewings, and some species of flies and wasps. Unfortunately, these usually do not help indoor plants, and are usually too few in number to put a dent in a large infestation outdoors.

The good news is that they are pretty easy to deal with simple DIY methods. Perhaps the easiest way of combating aphids is to spray the plant forcefully with a soapy water solution (1 tsp. of plain, fragrance-free dish washing soap to gallon of warm water), which will kill any adult aphid on contact through suffocation. In my experience, soapy water applications, when applied thoroughly and periodically at the first sign of infestation, are enough to control aphids. Another good option for more difficult infestations is neem oil, which may offer some residual protection as well; but take care because neem oil can be a bit harsh on some delicate plants.

Spider Mites

Spider mites, a distant relative of spiders, are the bane of many houseplant owners, and can be particularly nasty on some plants like gardenia and roses.

There are many different kinds of spider mite, but the most relevant for houseplants around the globe is the is the two-spotted spider mite (Tetranychus urticae). These are super tiny (less than a millimeter) sap suckers that favor growing shoots but can be found just about anywhere, especially on the undersides of leaves.

The two telltale signs of spider mites is 1) a dusting of super-tiny pale spots on the surface of leaves (each tiny dot is where the mite pierced the leaf with its mouthparts) and the fine webbing that they produce around more heavily infested parts of the plant. The webbing is much more delicate than a spider’s, and if you look carefully you can probably see small specs moving along some of the threads. These are the mites.

Spider mites can be very hard to eradicate and kill a houseplant rather quickly.

Lemon tree with bad spider mite infestation.
photo by Paramecium under CC BY-SA 3.0

Spider mites are real trouble for any houseplant they infest, and are much more problematic than aphids.

Mites prefer hot, dry conditions, where they their population can explode. Indeed, the speed of an infestation is due to the short reproductive cycle and fertility of the female, which can lay 20 eggs each day (with or without a male around), each of which can give rise to a reproductively mature mite in as few as five days from laying! Under warm conditions, it is estimated that a single female mite can lead to a colony of a million mites within a month.  This quick generation time also allows mites to develop pesticide resistance fairly quickly.

When spider mites are detected, action must be swift. The first step is to begin killing the adults mites, typically with a commercial miticide of some type. Neem oil is a good first-line approach, which should be applied thoroughly (especially on the undersides of leaves) and repeatedly, I would suggest a minimum of two treatments about 7 days apart unless specified otherwise by the manufacturer.

The next step is to create conditions unfavorable for mites, such as increasing humidity around the plant with frequent misting or a humidifier, and ensuring that the plant remains properly hydrated. Dropping the temperatures down into the low 70s may also help. For example, if the plant has been growing in direct light but can tolerate some shade, cut down direct light exposure to provide additional cooling. After mites are successfully controlled, take care not to allow the plant to come into contact with other plants that may facilitate a re-infestation.

Mealybugs

Another very bad actor, the mealybug, which is a type of unarmored scale insect, can cause great damage to a variety of indoor plants.

They are usually first noticed by the white, cottony fluff that the female secrets around herself while happlily sucking away at your plant’s sap. The male is not actually not parasitic and is winged at adulthood. Depending on the species, the female is happy to lodge herself in the rootball (i.e., root mealybugs) or more commonly along the fresh stems of the plant, especially at leaf axils (where the leaf connects to the plant stem) where clumps of various sized individuals will often congregate. Like aphids, some will excrete a sugary substance while they feed to buy the protection of certain ants.

Mealybugs are a very damaging indoor plant pest that can infest many different species.

Mealybugs feeding on hibiscus plant.
photo by Alexlutor under CC BY-SA 3.0

As with spider mites, the fecundity of mealybugs commands an immediate response. An untreated infestation above the soil will normally result in limb and/or leaf drop (abscission); whereas below the soil extensive root death can occur. In either case, this pest can kill an indoor plant in short order. Further, unlike aphids, which tend to prefer high-light indoor plants and cash crops, mealybugs can put a blight almost any indoor/outdoor plant species.

I’ve found insecticidal and other soaps largely ineffective for mealybugs. A good first-line treatment for small above-ground infestations is to swab the mealybugs and their cottony secretions with a q-tip soaked with rubbing alcohol. Do this diligently and it may be all that’s necessary. For more extensive infestations, neem oil is the next best choice, with synthetic pyrethroid-based sprays being available for even more aggressive treatment.

Root-based mealybugs (detected by pulling the plant from the pot and looking for the white secretions on roots) are typically treated with insecticidal dips or systemic pesticides. However, it has been reported that a dip in 120oF water can be effective at eliminating root mealybugs on Rhapis palms without adversely affecting the plant.

Whiteflies

Whiteflies are, as they sound, a very small white fly in the order hemiptera.

Whitefiles are very serious commercial and agriculatural pests, but can usually be handled simply indoors.

Close up of adult whiteflies on leaf.
Wikimedia Commons under CC BY-SA 3.0

Like the other pests above, whitefiles are sap-feeders and can cause direct damage to an indoor plant’s health by diverting nutrients and sugars intended for plant growth. However, their broader and more global threat is related to their tendency to spread serious plant viruses among subtropical agricultural crops as they feed.  The winged, white adults and their bright green (wingless) nymphs are typically found on the underside of fresh young leaves.

Although they are one of the most serious agricultural pests, I find them to be relatively easy to eradicate on indoor plants. However, given their mobility, they should not be underestimated, especially in large collections where they can spread easily.

The impact of whiteflies is quite similar to a aphid infestation, and I find them similarly vulnerable to a simple soapy water solution. Infected plants should be sprayed several times no more than 7 days apart or as needed until controlled. For more serious infestations, neem oil or other commercially-available pyrethrin-based sprays can be used.

Scale Insects

Like mealybugs (which are an unarmored scale), scale insects are odd in that the female does all of the plant sucking. They are somewhat less common than mealybug infestations in my experience, but can be equally deleterious and hard to eradicate.

Although they feed and behave like above-ground mealbugs, the female scale insect is completely sessile (immobile) and will normally secret a waxy shell to serve as armor; this covering can be fuzzy or, in many cases, look reptilian upon close inspection, hence the name “scale” insect. They come in many colors and varieties, and some are parasites only on certain plant species.

Scale insects are often difficult to detect until the plant shows signs of poor health or starts dripping sap.

Scale insects on the stem of Cornus sanguinea.
photo by Gilles San Martin under CC BY-SA 2.0

It’s very easy not to notice a light scale infestation, since the adult females can be very small and their armored bodies can appear like plant markings or harmless abrasions.

Scale can attach to virtually any part of the plant. Again, they too excrete a sugary sap that some ants find irresistible. In fact, it is often the presence of large amounts of this sap excrement on the ground around the plant that gives the first indication of a serious scale infestation.

While they can parasitize many indoor plant species, they are often found plaguing palms and orchids. Treatment is similar to that recommended for mealybugs, with a preference for manual removal (scraping) if very few in number. For more information about scale and how to deal with them on outdoor and indoor plants, go here.

 

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