Oxalis and Euphorbia Ammak Variegata in a Bright Position

The importance of light for the health and wellbeing of your Indoor Plants cannot be understated. In many cases, it is the reason for issues as the plant grows. Most people don’t realise how quickly and easily the light level can impact plant growth, and how dark it really feels for the plant! Just like a dark room for us would be enough light for an Owl to see clearly, a room we think is bright enough for our plants could actually be the cause of their issues. Let’s explore some images that help to elaborate this point and some common signs in many indoor plants that the light where they live simply isn’t enough.

Lux Meters

Before we go into examples and specifics, let’s take a look at Lux Meters. These apps can easily be found on Smartphones and Verdant Dwellings use ‘Lux Light Meter Pro’, found in the Android App Store. This is a very quick, accurate, and simple way to determine what light your plants are actually getting. Obviously, the level will change on overcast days compared to sunny days, different times of the year, etc, so it is good to take multiple readings to get an idea of the fluctuations in the space.

Lux Meters read the level of luminous flux per unit area, the area of which is one lumen per square meter. In simple terms, it is a measure of the actual light (or lumens) in an area as perceived by the human eye. This level is given a number and the higher the number, the brighter the position is. The reason Lux Meters are so useful is they take all the guesswork out of positioning a plant. If you think the position is bright, but the reading is not, then it is bright for your perception, but not for the plant and the plant will show the effects.

Indoor Plant Lux Ranges

For Indoor Plants, these Lux readings have a range from low light to bright light, remembering bright indoors is very different from bright outdoors. Outdoors on a Melbourne blue sky day with some passing white clouds sits on an average of 80,000 to 90,000 Lux. For Indoor Plants the guide we use is as follows.

Lux of 1000+ - Bright
Lux of 400-1000- Medium
Lux of 100-400- Low
Lux Below 100- Very Low

Using the above range with a Lux meter takes any guesswork or uncertainty out of the light in a certain position. If it feels bright, but the Lux Meter says the reading is 399, it is low light and, depending on the plant, may cause issues. What is bright to us is relative to plants, all of which originate outdoors in an abundance of light. So now we know the ranges for Indoor Plants, let’s take a look at some specific examples of light indoors.

Lux Indoor Readings

It is also worth noting that the Euphorbia, just a few centimeters closer to the window than the Oxalis, has a Lux reading of 3254. This is obviously a significant increase and shows how small changes make a world of difference in the world of plants. These photos are taken facing the window and you can clearly see the Oxalis have turned to face the light. This is why plant rotation is helpful so that plants get an even light all the way around.

This next example is important and demonstrates how close to the window this Sanseveria Superba and Zamioculcus Zamifolia Jungle Warrior are to the window and plants first shown. Taken on the same day and only a meter further into the room, you can see the light level in this position is lower. To our eyes, this spot is still very bright and filled with light. Not so much to the plants.

As you can see in the second photo, the Lux reading here, facing the window side of the plant, is 309. This is a drop of thousands of Lux and this position to a plant is LOW light. When we talk about low light plants such as the Sanseveria, Zamioculcus, Spider Plant, Spathyphillum, etc, this is what we are describing as low light. It is not a dark corner where the light needs to be turned on for us to see clearly. This position is bright for us, easily enough light to read by. For plants, this spot is too dark to thrive for most. The Lux meter gives us the opportunity to see light as the plant does and, as plants require light to transform into energy and grow, this is vitally important.

Most plants will not survive and grow in very low light in our homes. The one example of a plant that will SURVIVE, but not THRIVE is the Sanseveria. This hardy and water-conscious plant can live in a position with a very low Lux reading as seen in these images. The VERY LOW light in this position is only 64. For our eyes, this hall position between an East and a West facing window may be considered medium light. It is obviously a very different story to plants.

Watering requirements reduce drastically when a plant is in a position of lower light. This Sanseveria is bareley ever watered and has not grown in three years. When it does get water, it is a small amount directly over the base of the leaves so that the roots are wet, but the soil is not sitting soggy. It is almost in a state of suspended animation and would not survive if not mature when placed here.

The important thing to remember is the leaves need to be in appropriate light. This doesn’t have to mean all of the leaves either. With some varieties you can have a trailing plant on a windowsill that is sustained by light at the top of the plant, or a plant that doesn’t mind low or medium light in a partially lit position. This can be seen with the below Sanseveria Laurentii. If the Lux light meter was held at the base of the plant, far less light would be available. However as a large portion gets light, 332 on the Lux meter, enough light is available to these large leaves to photosynthesise for the entire plant, keeping it sustained and growing.

“Most people don’t realise how quickly and easily the light level can impact plant growth, and how dark it really feels for the plant! ”

For most plants, the majority needs to be well lit to survive and thrive. This is most important in variegated plants that display white. This applies to popular plants like the Epipremnum Aureum Snow Queen right through to rare mutation based variegation like Monstera Deliciosa Albo.

The next photos are of three variegated plants, a Monstera Standleyana Albo, a Monstera Borsigiana Albo and a Monstera Adansonii Albo. All of these plants have large sections of white variegation and, in the case of the Adansonii and Borsigiana, thinner leaves. They require a great deal more light than their all green family members. The white in their leaves cannot photosynthesise as it does not contain chlorophyll. Any green sections need enough light to sustain themselves as well as the white sections of leaf. If light levels are heading into medium, under 1000 on the Lux meter, you will start to see the variegated sections of the plant suffer. The white will brown and die off back to the green of the leaf.

This placement is a corner position between two windows. Trees and buildings mean that neither window is direct harsh light but filtered and dappled enough in Summer and bright enough in Winter. One is North East facing and the other North West facing meaning it is bright all day long. This photo was taken with the light meter facing the North West window on an overcast day in the late morning. This shows it is a BRIGHT position with the Lux meter reading 1239. Obviously on a sunny Summer day, the reading would increase substantially meaning the plants are getting all the light they need. This also highlights that the Monstera Standleyana Albo has dried out too much recently with the slight leaf curl and yellow/brown tips seen. When issues arise, if you know the light levels are good, light can be ruled out as the cause of the issue.

Watering Issues in Low Light

Another reason, other than photosynthesis and energy production, that insufficient light can cause issues is with watering. Plants use the available water in their soil, drawing it up into their root system, and then require more. However, water is also lost to evaporation. The brighter and more direct the light, the warmer the weather, the more water is lost to evaporation. This can be frustrating when you feel you’re watering all the time in Summer, but it means plants are not sitting in water for prolonged periods of time, which most plants don’t like. Some plants do not mind being left in water for longer periods of time, liking to be constantly damp, such as Ferns or Spider Plants. For many plants however, they like to dry a little or a lot before another water is given. If light is lower, the amount of water given becomes vital as rather than being lost to evaporation, it is sitting in the soil and around the roots, for extended periods. A tropical plant, in medium light and especially in cool weather, will suffer quickly if large amounts of water are given. In fact, if the light is too low, the plant wont have the energy to draw up water as quickly for growth, as it is sitting mostly dormant. Problems arise with overwatering far more easily and frequently if the plant is also in a position of low light.

Customers often note that plants coming out of the nursery are damp in the soil, far more than they would be in a home setting. This is due to the heat and the light of a growing space. More water is required as the warmth and abundance of light mean plants are growing quickly, using the available water in a much faster manner. These photos show random positions around our Nursery. It can be seen that on an average and overcast day the Nursery light is around 3500 Lux. Even the darkest corner is over 1100. These three photos were taken on an overcast day at the end of Winter with light just starting to increase. You can see in the next image, taken on a Sunny day in early Summer, the light has increased by a very substantial amount, now sitting at 23280.

This abundance of light means the plants are growing quickly, consuming more water than they would in a lower light. In Winter, the lower light means a more dormant plant, not in its growing phase. The high light levels keep them happy and slowly moving along in a growing space, light levels not often seen in homes.

Often growers are asked how plants look so vibrant and healthy, with such strong growth. Obviously soil, watering, pest management, fertiliser and more, are important for plants to grow healthy and strong, however the number one element that Indoor Growers have over residential homes is an abundance of light, especially overhead light.

Some Specific Examples of Plant suffering in low light

The number one issue with light being too low is that plants don’t have the ability to photosynthesise and produce energy in an abundant manner meaning watering issues and over feeding can easily arise. Many plants start to show you that their position is too dark for them to thrive by growing slowly. When a plants growing season comes around and plants remain dormant, barely producing new growth, it is a good sign the light is too low. This is more true if the plant has just been fed as you know having fertiliser is not the cause. Some plants give more specific signs however that the light is just not bright enough. Below are just a few, of so many, examples.

Vine families including Epipremnum, Rhaphidophora, Hoya, Philodendron, Monstera - These plants will begin to grow smaller and smaller leaves, sometimes growing only vine with no leaves at all. This is a definite sign that the light is too low for them and they need to be moved.
Monstera - Monstera plants develop holes and fenestrations in many of its varieties. The main, and most obvious, two are the Deliciosa and the Adansonii. These varieties will stop producing as many holes and fenestrations if the light is too low. An Adansonii will get smaller and smaller holes in less number as well as growing small leaves. Deliciosa have no fenestration as young plants and will not develop them until older and light is sufficient. A Deliciosa in the wrong light position will have little, sometimes no, fenestration and the stems will be long and stretched as the plant searches for light.
Ficus Lyrata (Fiddle Leaf Fig) - This Ficus has a very specific way of letting you know that the light is too low. It will develop brown spots on the leaves, as if someone has put out a cigarette or cigar on the leaf and burnt it. People often mistake this for overwater, but the edge of the leaf will brown when the plant is overwatered. The brown spots on the leaf are not enough light, every time.
Ficus Elastica (Rubber Tree Plant) - This Ficus, with her stiff and shiny leaves, shows lack of light differently to her cousin. In an effort to conserve the energy and gather as much light as possible, the Elastica, of all colours, will drop her lower leaves. The top leaves remain and often continue to grow, but all lower leaves, starting at the base of the plant, will systematically drop as the plant struggles to survive in an area without sufficient light.
String of Pearls (Senecio Rowleyanus) - String of Pearls, like almost all Succulent Senecio plants, require a very large amount of light to thrive. If the light is too low, the pearls will begin to turn to mush, rotting like microwaved squash. People often mistake this for overwatering and hold back on watering the plant thinking it will improve. As it is not water at all, but the light being too low, the plant continues to rot and die away. Simply moving it to a windowsill will stop the issue and allow new strings to grow. Mushy pearls is an insufficient light issue every time. See our full blog on Succulent Senecio here.
Oxalis - Seen in the initial photos of this blog, Oxalis love light. In a bright position they have an abundance of energy meaning they can produce more leaves and fowlers. It also means they develop rhizomes under the soil, further bushing out the plant. If the light remains high year round, they won’t die off in Winter either. Our pictured plants, in Southern Coastal Victoria, never loose size in Winter. Oxalis are tough, a weed to some, so they are survivors in lower light. They will not produce many leaves however and will look sparse and possibly spindly, maybe not flowering. This is a sure sign the light is too low for the plant to thrive. Move your Oxalis to a bright spot in direct, non harsh, light and it will grow thick and fast.

A solution for lack of natural light is quality Grow Lights. These mimic sunlight with a range of light spectrums offered through a multitude of LED’s. Often these lights have a purple tinge due to red and blue light LED’s in the composition. Grow Lights can be purchased as a lamp or a bulb and can be used to boost the light a plant receives to help it thrive and grow. Grow Lights can also be used at night but giving plants time to rest, as they do at night in nature, is important and Grow Lights should not be left on 24/7. They are a good alternative, but need to be close to the plants to produce the required light and are not a permanent substitute for natural light. Like anything supplementary, the real thing gives the most benefits.

Remember that your plants are talking to you visually all the time. They tell you when they are thirsty, hungry, over watered, under watered, suffering a pest and definitely when the light is too low. Watching colour changes, leaf changes, growth quality and speed, and more give vital signs of the plants in your home as they tell you how they are and what they need. No matter what we perceive, our plants will tell us and we can choose to listen to them or not. Light however is key and light for plants is not light perceived by humans. So grab your Smartphone and download a Lux Meter to help you and your plants. It’s a wonderful thing when, using the meter, you find a position they love without the guess work.

Please Note: Plant Lux Ranges are based on the ‘Lux Light Meter Pro’ app and levels may vary for different phones and applications.

Happy Growing!

The Importance of Light

Lux Meters

Indoor Plant Lux Ranges

Lux Indoor Readings

Watering Issues in Low Light

Some Specific Examples of Plant suffering in low light

Verdant Dwellings

EXCELLENCE IN INDOOR PLANTS