Why Are My Houseplant Leaf Tips Turning Brown?

The five main reasons leaf tips and edges of houseplants turn brown are:

• Improper watering
• Low humidity levels
• Inappropriate light and temperature conditions
• Buildup of salts or fertiliser
• Plant fluoride sensitivity

When indoor plants display such symptoms, it’s their way of showing us that something may not be right, and they need attention.

1. Improper Watering

When houseplants are overwatered, underwatered, or watered inconsistently, this can cause browning of the leaf tips, and it’s also a major contributing factor to the decline of the plants in general.

It’s safe to say that watering problems are the main reason why beginners accidentally kill their beloved indoor plants! Thankfully, this problem is totally avoidable.

Understanding the Function of Plant Roots

The purpose of plant roots is to take up soil nutrients, and also to take up water to replace what the plant loses from the pores on the undersides of the leaves that need to be opened for the plant to breathe.

The process by which water moves through a plant, and the evaporation of moisture from the leaves, stems and flowers, is known as transpiration.

It’s important to understand that the size of a plant’s root system matches the size of the canopy, in other words, the number of leaves that the roots have to supply water to. If the roots are damaged in any way, they can no longer supply enough water to support all the leaves on the plant, so some of the leaves may wilt, yellow, brown, and drop, resembling the symptoms of a lack of water.

When plants don’t have enough roots to take up sufficient water to replace what is being lost through the leaves into the air, the plant will actually be short of water, even if the potting mix is soaking wet.

What Happens When Plants Are Overwatered

Overwatering of potted plants causes waterlogging of their root systems by pushing out all the air in the spaces between the particles of the potting mix (growing medium) and filling it with water.

All terrestrial (land-growing) plants require oxygen from the air to reach their roots, which is why good potting mixes are formulated to have a porosity of around 25%, providing the right balance between adequate drainage and sufficient moisture holding capacity. When water moves down through the soil or growing medium, it creates a vacuum behind it which pulls down air through the soil towards the roots.

When potting mixes becomes saturated with water, the amount of oxygen available for root growth is decreased, creating an anaerobic environment (lacking oxygen) which favours root diseases and root rot. If the potting mix stays too wet for too long, the roots don’t get any air and they drown, die off, turn black and eventually rot away.

When roots die off due to rot, a plant won’t have enough roots to supply water to all its leaves, so the parts of the leaves furthest from the roots, the leaf tips, run short of water first and dry out, resulting in brown leaf tips.

What Happens When Plants Are Underwatered

Underwatering causes roots to die off due to lack of water. Since the roots are the part of a plant that take up water, if the potting mix is completely dry, the roots will dry out and disintegrate.

In the same way as overwatering, when a plant doesn’t have enough roots to supply water to all of its leaves, the parts of the leaves furthest from the roots, the leaf tips, run short of water first and dry out. If the water shortage persists, the leaves will gradually curl, dry out and fall off.

Inconsistent watering, alternating between too much and too little water can also cause browning of leaf tips through root loss.

How to Diagnose Houseplant Watering Issues

If there’s a watering issue, the potting mix may be either too wet or too dry.

Overwatered potting mix appears darker in colour, may be damp to the touch (though it may be dry on the surface) and the pot will feel quite heavy when lifted.

The potting mix may also rot from the excessive moisture and begin breaking down due to the action of fungi, causing a collapse in volume, indicated by the potting mix level dropping down in height from the top of the pot. Decomposing potting mix will also attract fungus gnats, the annoying little flies that hover around your houseplants.

It may help to read the article How to Control Fungus Gnats in Indoor Plants if you would like to learn how to control this pest!

If houseplant pots are left sitting in trays or saucers of water for extended periods of time, or if self-watering pots are constantly topped up and are never allowed to go through a wet-dry cycle, overwatering and waterlogging will result.

Overwatered plants may have a stem that appears soggy, drooping or rotting, and in severe cases, a gentle pull on the plant may easily lift it out of the potting mix because there will be very little roots left to anchor the plant down have as most will have rotted away. The leaves will begin to brown off at the tips and may show a tea-stained look where the yellow or brown colour appears to be spreading into the leaf and growing fainter as it moves outwards.

Underwatered potting mix is lighter in colour, and in severe cases when it is extremely dry, will crack and pull away from the sides of the pot. The level won’t drop in the pot like it does with overwatering, but the pot will feel extremely light when lifted, and feel much heavier after a good watering.

Underwatered plants may wilt and droop, their leaves may become yellow, dry, curled and crispy. The leaves of an underwatered plant look exactly the same way as leaves that are pruned off and left outside in the sun to dry, which is different in appearance to the leaves of overwatered plants.

No houseplant shows the effects of underwatering as strikingly as a Peace Lily (Spathiphyllum), which droops quite dramatically when it’s short of water, making it a great beginner’s houseplant that can teach good watering practices, and can grow in fairly low light too.

The simplest ways to test if a plant needs watering is to:

• Lift the pot up, if it feels really light it needs watering, if it feels heavy, it’s well-watered.
• Stick your finger into the soil about 5cm (2″) deep, which is about the depth of your second finger joint. If the potting mix feels dry, the plant needs watering.

Some gardeners like to use a moisture meter to determine whether their plants need watering, but this is not really necessary. Having bought one when I first started growing indoor plants, it’s just been sitting on a shelf, and hasn’t been used for years.

How to Fix Houseplant Watering Problems

Water a plant until it just begins to trickle from the drainage holes at the bottom of the pot to ensure that the potting mix is evenly damp all the way through.

All plants need a wet-dry cycle as they experience in nature, so it’s important to allow the first few centimetres (inch) of potting mix to become dry before watering again.

Drainage – Don’t let a plant sit too long in a saucer or drip tray full of water, no longer than an hour or so. Also make sure the drainage holes at the bottom of the pot are not clogged up or blocked, so excess water can drain away.

Make sure all pots used for growing houseplants have drainage holes! It’s surprising how many people unknowingly use planters (decorative holders for pots without any holes) as containers to plant directly into! When using planters, first place a few small stones in the bottom of the planter to elevate the bottom of the pot and provide some space for excess water to drain into.

Dry Potting Mix – For severely underwatered plants where the potting mix has become dry and pulled away from the sides of the pot, regular watering won’t work to rewet then potting mix. Since water follows the path of least resistance, it will just run down the gaps at the sides of the pot and straight out the bottom, none of it will soak into the potting mix to reach the roots. Most potting mixes will also become waxy and water-repellent if they get too dry.

To rewet extremely dry potting mix, sit the pot in a bucket, and fill with water to a level just below the top of the potting mix. Don’t overfill the bucket with water otherwise all the potting mix will float to the top and come out of the pot!

How Often Should Houseplants be Watered?

One mistake beginners make is to water all their indoor plants on a set schedule, such as once a week. Typically, most houseplants will need to be watered once a week or once every two weeks, depending on the season of the year, the indoor temperature and humidity, air flow through the room, the size of the plant and type of plant in question.

When houseplants lose more moisture to the air, such as when indoor temperatures are high, or air conditioning is operating (which reduces air humidity), they may require watering more often.

Large plants in relatively small pots will also need more frequent watering, as they will use up their limited water supply rather quickly and should really be transplanted into larger pots in the spring season.

When indoor temperatures are low, plants transpire less in cold conditions, and won’t need to be watered as often. Aim to keep the potting mix damp, not constantly soaking wet in winter, as most houseplants are tropical or subtropical plants, which grow where summers are hot and wet, with less water in the drier winter season.

Some houseplants don’t require much water at all, need to be watered less often, and are very sensitive to overwatering. These include:

• Mother-in-Law’s Tongue or Snake Plant (Sansevieria trifasciata)
• Cast Iron Plant (Aspidistra elatior)
• Zanzibar Gem or ZZ plant (Zamioculcas zamiifolia)
• Fiddle Leaf Fig (Ficus lyrata)

Check the moisture level of each plant before watering it. With a bit of trial and error, it’s easy to work out the watering requirements of your houseplant.

For example, in a temperate climate with 40-50% indoor humidity on average, with ducted heating running in winter I’m watering approximately once every two weeks, and in summer, with higher temperatures and air conditioning running indoors, my houseplants need watering one a week.

2. Low Humidity Levels

Most houseplants are from subtropical or tropical climates in origin and naturally prefer to grow outdoors in warm, humid environments as understory plants under the cover and dappled shade of tall forest canopies.

A relative humidity between 40 to 60 percent is ideal for most indoor plants. However, in winter, humidity in homes can fall to 10 percent, so increasing humidity may become necessary.

The Effect of Low Humidity on Houseplants

When humidity levels are low, plants lose more moisture through their leaves. If they lose too much moisture, the leaves may yellow, curling downwards, dry out and drop off. Brown tips are often an indicator of low humidity, while browning along the leaf edges indicate underwatering.

To raise the humidity around plants:

• Mist them periodically using a spray bottle set to produce a fine mist.
• Group plants together, place them on a humidity tray, which is just a shallow tray or plastic pot saucer filled with pebbles with some water at the bottom. The water evaporates to increase humidity, the pebbles keep the bottoms of the pots above the water to prevent them getting waterlogged.
• Place a humidifier in the room where the houseplants are located.
• Add a fountain or aquarium to the space to increase the room humidity.

Keeping small plants in a terrarium or under a cloche (glass or plastic dome) is another way of creating a high humidity environment.

Also keep in mind that plants placed close to windows where they receive bright sunlight may lose moisture faster and dry out more quickly, and therefore require more water and higher humidity. 

3. Inappropriate Light and Temperature Conditions

Indoor plants require the correct amount of light and suitable temperatures to grow and thrive, and that will vary depending on the type of plant.

Light Requirements for Houseplants

In rooms where there is low light, such as near an east facing window that receives morning sun, in rooms with no direct sunlight (with a window facing north in the northern hemisphere, or south in the southern hemisphere) or where sunlight is diffused through a lightweight curtains, select plants that can grow well under low light conditions, such as:

• Chinese Evergreen (Aglaonema)
• Cast-Iron Plant (Aspidistra elatior)
• Parlor Palm (Chamaedorea elegans)
• Spider Plant (Chlorophytum comosum)
• Dumbcane (Dieffenbachia)
• Fishtail Palm (Caryota mitis)
• Grape Ivy (Cissus rhombifolia)
• False Aralia (Dizygotheca elegantissima)

Other indoor plants that require more sunlight can be placed near a bright, sunny window that receives midday or afternoon sun. Keep the pots at least 30cm (12″) from the glass, don’t ever put them right against the windowpane, as plants will get burnt. There is lots of heat build-up and a lack of air circulation near the glass surface when the sun is shining.

Temperature Requirements for Houseplants

Most houseplants prefer temperatures in the range of 31°C (55°F) to 21°C (70°F). In winter, the temperature near windows may be cooler than elsewhere in the house and this can damage the plants leaves. An overly hot, dry atmosphere from direct sunlight shortens the life of plants and may lead to brown leaf tips.

The Effects of Improper Light and Temperature on Houseplants

By observing an indoor plant’s condition, we can fairly easily diagnose issues related to excessive or insufficient light or temperature.

If plants are receiving insufficient light:

• The stems may bend or elongate, appearing to be reaching towards the light source.
• The leaves may appear discoloured, but only on the side opposite to the light source.

To provide more light, move the plant to a brighter location near a window, add LED grow lights or position a mirror (or any other reflective material) in a sunny spot in the room to reflect light towards the plant. 

To reduce the intensity of the light when it’s too strong, move plants to a location with less light, or place a sheer curtain over a window to filter the light. Keep in mind that light coloured walls and glossy surfaces reflect more light, so dark walls and matte finishes can be used to help absorb excess light and reduce brightness.

If plants are getting too much heat:

• The plant develop symptoms similar to those of underwatering as described earlier, where wilting and drooping occurs, and the leaves may become yellow, dry, curled and crispy.
• Discoloration may occur on the side closest to the light source, due to leaves getting scorched, especially when they’re located too close to the window pane.

If the temperature is too hot:

• Move plants further away from bright windows, always keep them at least 30cm (12″) away from the glass.
• Relocate plants from windows that receive direct harsh afternoon sun to ones receiving milder morning and early afternoon sun, or to a cooler area.
• Remember not place plants near heating duct outlets or above radiator heaters.

Having a plant up close against the window glass in winter may cause brown leaf tips, as the glass can get very cold at night. Place your hand against the glass at night, and if it feels way too cold, move the plant to a warmer location, or further away from the glass, even if it’s just for the night.

4. Buildup of Salts or Fertilizer

Brown leaf tips and margins (edges) can also be caused by salt accumulation or build-up, which appears as white-to-yellow-coloured, hard, crusty mineral deposits along the edges of the growing medium.

Water naturally contains dissolved mineral salts, and when the water evaporates away, the minerals are left behind and increase in concentration. Each time houseplants in pots are watered, we add more minerals to the growing medium (potting mix) that accumulate within the growing medium. Adding fertilizer that is required to provide nutrients for plants to grow is an additional source of soluble salts that also builds up in the potting mix over time.

High accumulated salt levels in the growing medium make it harder for plants to take up water, and extremely high salt levels pull water out from the roots through the process of osmosis, which results in water loss from the roots, causing them to dry out and die off, and rot away, leading to root rot.

When root tips die, a plant loses its ability to take up water, leading to water shortage, regardless of how wet the growing medium is. Plants suffering root loss due to excessive salts will show the same symptoms as an underwatered plant, with dry, brown leaf tips and edges

If too much fertiliser is applied to a plant, whether in a single application or many smaller applications, this can cause root burn in the manner described above, which will cause houseplants to develop brown leaf tips.

Preventing Salt Build-Up in Pots

The best way to prevent soluble salt build-up and root injury is by watering correctly and not overfertilizing.

• Use rainwater where possible, as rainwater doesn’t contain dissolved minerals.
• When watering plants, water thoroughly until water flows out though the drainage holes at the bottom of the pot to wash excess soluble salts out from the growing medium.
• Don’t leave pots sitting in a saucer of water, they’ll reabsorb the drained water containing the washed out soluble salts straight back into the growing medium.
• Do not over-fertilise houseplants, follow the application rates indicated on the label. Over-fertilising is just as bad as under-fertilising and does not benefit the plant.
• Remove salt crusts and deposits from the potting mix surface, scrape away some of that potting mix showing salt accumulation and add fresh potting mix to the pot.
• Potting mix doesn’t last forever, so it’s important to repot houseplants every couple of years using fresh, premium quality potting mix.

Leaching Out Accumulated Salt Build-Up in Pots

Salt buildup in pots can be reduced by leaching the potting mix by pouring plenty of water through it and allowing it to drain out completely, to flush out all the excess soluble salts.

To leach the growing medium in a pot of soluble salts, pour a volume of water equal to twice the volume of the pot through it, repeat once a year. Use a watering can as it makes it easier.

For more information on what the volume of standard pots is, and how to calculate pot volume, please see article – How Much Potting Mix Does A Garden Pot Hold?

How much salt accumulation can plants tolerate? In general, houseplants may be injured by salt concentrations of 200 ppm and higher, but this will vary depending on the type, its age and how it is being grown.

For more information, please see article – What Are The White Deposits On The Surface Of Houseplant Pots?

5. Plant Fluoride Sensitivity

Some houseplants are sensitive to the fluoride that is added to municipal tap water for the purpose of preventing tooth decay in humans.

The symptom of fluoride toxicity in plants is leaf necrosis (yellowing, then browning, leading to dead, scorched areas on the leaf), which appears mainly at the tips of the leaves and along the margins (edges), spreading inwards. This is typically described as ‘tip burn’.

There’s no easy way to remove fluoride from the water, so if plants are sensitive to fluorine they can be watered with rainwater or distilled water instead. Another helpful tip is to keep the pH of the growing medium above 6.0, because under these conditions fluorine becomes chemically bound and therefore unavailable to the plant.

List of Fluoride Sensitive Plants

• Calatheas, such as Zebra plant (Calathea zebrina)  and others (Calathea spp.), Marantaceae family
• Dracaena species: Lucky Bamboo (Dracaena sanderiana), Madagascar Dragon Tree (Dracaena marginata), Dracaena ‘Janet Craig’ (Dracaena deremensis ‘Janet Craig’), Dracaena ‘Warneckii’ (Dracaena deremensis ‘Warneckii’), Happy Plant or Corn Plant (Dracaena Massangeana) Agavaceae family
• Good Luck Plant (Cordyline terminalis), Agavaceae family
• Lilium species Liliaceae family
• Never-Never Plant (Ctenanthe oppenheimiana), Marantaceae family
• Parlor Palm (Chamaedorea elegans), Palmae family
• Peace lily and others (Spathiphyllum spp)., Araceae family
• Prayer Plant (Maranta leuconeura), Marantaceae family
• Spider Plant (Chlorophytum comosum), Liliaceae family
• Tahitian Bridal Veil (Gibasis pellucida), Commelinaceae family
• Yuccas (Yucca spp.), Agavaceae family

For more information, see article – Which Indoor Plants Are Sensitive To Fluoride In Tap Water?

References

• Clemson University Cooperative Extension Service, Houseplant Diseases & Disorders Factsheet HGIC 2251 Updated: Sep 10, 2021, https://hgic.clemson.edu/factsheet/houseplant-diseases-disorders/
• University of Tennessee, Tennessee Master Gardener Handbook, Chapter 13, Houseplantshttps://extension.tennessee.edu/MasterGardener/DocumentsAgentResources/Houseplants/Instructor_Chapter_PDF_(2011)_Houseplants.pdf
• Virginia Cooperative Extension, Piedmont Master Gardeners, PMG News, Houseplants With Brown Leaf Tips, January 19, 2022, https://piedmontmastergardeners.org/houseplants-with-brown-leaf-tips/