Succulent Light Needs – Natural vs Artificial Light

Not every place in the house is optimal for succulents. It should be borne in mind that light is not only important for photosynthesis, i.e. for energy generation, but also the development of flowers, leaves, and body size. Therefore, we need to look into succulent light needs if we are to produce great looking plants.

The plants also become more susceptible to disease due to a lack of light. Remember that succulents are used to getting a lot more lighting in their natural habitat than in our living rooms.

How much sunlight do succulents need?

The minimum light intensity for cacti and succulents should be between 1,500 and 3,000 lux.

Here are the light requirements of some succulent plants. Some are low light succulents.

  • Sansevieria Trifasciata – 300 lux.
  • The dragon tree, Dracena Deremensis – 600 lux.
  • Genus Tillandsia  – 800 lux.
  • Crassula Falcata and the money tree (Crassula Ovata) – 1,800 lux.
  • Euphorbia Trigona and mostly other cacti – At least 2000 lux.

In the summer, we usually have an illuminance of around 100,000 lux, which can drop to around 20,000 lux on duller days. A home with a south-facing window with 10,000 lux of light on the windowsill, we only have about 2,000 lux directly behind the window in autumn and winter. On such days, we only get about 500 lux if we are 1 meter away from the window. At a distance of 3 meters from the window, the value drops to 100 lux.

If you want to set up your cacti 2 meters from the window, you can only achieve these values ​​on a very bright summer day and only with open curtains and straight light. A reduction of 90% reduction in illuminance can be anticipated otherwise.

Many room windows also have a film integrated into the laminated glass, which filters out the UV component so that the rooms are less heated, and the harmful UV component remains outside.
It is good for us humans, but fatal for most plants.

do solar lights help plants grow

Not everyone has a lux meter on hand to test the amount of light entering a certain area of space, and our human sensors can only help to a limited extent. We still feel comfortable at 50 lux, which is the value of a simple light bulb.

You can use the growth habit of your crop to determine whether the amount of light is sufficient. Indicators of insufficient light are:

  • A previously spherical plant continues to grow pointedly.
  • Columns grow towards the window.
  • The areole distance in cacti has increased.
can succulents grow in full sun
The left specimen of Crassula Ovata forms a longer stem due to lack of light; the leaves are too far apart. On the right, a healthy specimen.

If you still want to keep cacti and succulents away from the window, you must supplement them with artificial light. In the past, sodium vapor lights or MH lights that come with high purchase costs, large space requirements, high power consumption, and poor efficiency were used for this. A lot of energy was converted into heat instead of light.

A good alternative is cheaper fluorescent tubes, such as the Lumilux daylight with 3,250 lumens and a color spectrum that matches daylight. But since these lights contain mercury, they are harmful to the environment. They will disappear from the market in the future.

Nowadays, LED research has already outgrown its infancy and very useful features have emerged, such as longer life, and lower power consumption.

can succulents be in full sun

How many lumens does the sun produce?

Without the sun, there would be no life on earth. It radiates with such energy that its warmth can be felt on the earth despite being around 150 million kilometers away. But how bright is the sun's light? This question can be explained with the help of Lux, Lumen and Candela.

how many lumens does the sun produce
The light of the sun is considered the motor of all life.

Understand Lumens and Other Light Units

The light is measured in different units. There are three important things you are sure to know from physics classes: Lux, Lumen and Candela. The question now is to what extent these units differ from each other.

  • The main lighting unit is lumen. The reason for this is that only this unit denotes the actual light energy that is emitted by a body. So, no second component comes into play here – it is only about the pure “power” of the light bulb, the fire, or the sun. For example, a 100-watt light bulb sends out 1,400 lumens, a candle only around 10 lumens.
  • If you want to know what effect the emitted light has, another unit comes into play: Candela. With the help of this unit, the pure light beam is not measured but is related to the emission angle and other adverse factors. An example: If an incandescent light has a beam angle of 100 °, it has a lower candela value than a light with an angle of 50 ° because the illuminated solid angle is larger.
  • The third important unit is Lux. This unit is very tangible because you can imagine its factors. When it comes to lux, it calculates how much a certain area is illuminated. If you want to calculate the lux intensity, the luminous flux is divided by the area. Lux is equal to lumens by square meters.

Now you understand how important the unit lumen is when calculating light. But how many lumens is direct sunlight?

The Luminous Flux of the Sun

  • If you look at the units explained above and wonder how many lumens is direct sunlight, you will have noticed one thing: The lumen value of the sun should be constant, since it always shines with approximately the same intensity and no second component is involved in lumens. It is the same. The lumen value of the sun is constantly around 6.3×1028 lumens.
  • From the large number, you can see how huge this value must be. If you want to know the luminosity with which the light arrives at you, the calculation is quite complicated, because you certainly do not know the exact radiation angle of the sun. As a guideline, you can remember that the sun burns down at 90,000 to 100,000 lux when the sky is clear and around noon.
  • In the shade, the value drops rapidly and quickly below 10,000 lux. For comparison, which shows you the power of the sun again: Ordinary office lighting shines down on you at around 500 lux. 

Do succulents like full sun?

can succulents take full sun light
Most succulents feel great in the sun

Most succulents come from the hot, sun-drenched regions of the world. As a result, they are the ideal choice for planting in sunny locations, or at the balcony. Where other balcony plants suffer in the blazing sunshine in summer, cacti, houseleeks, milkweed plants, and stonecrops grow healthily. That is why if you are wondering can succulents take full sun, you need not worry. The drought specialists, on the other hand, should be protected from constant rain, like in the rain shade of a house wall.

How long can succulents go without light?

Light, besides water, is an elixir of life for plants, without which nothing can be done. Without light, photosynthesis cannot occur and the succulents cannot produce energy for growth and / or sustenance. Succulents in particular need a lot of light, although not necessarily direct sunlight. They can survive about a week without light, after which their health will be severely threatened.

If you notice your succulent leaves pointing down, this is a clear indication that it lacks light. When this happens, gradually move it to a brighter place. Be careful not to expose it to too much light at once – its leaves will get burned if you do so.

Do solar lights help plants grow?

Succulents need a bright and sunny location. A south window or even a greenhouse is ideal. Aloe, gasteria or haworthia, on the other hand, prefer partially shaded locations. If there is too much sunlight, they will begin to turn brown.

In summer you should water succulents in small quantities, but regularly with lime-free water. The upper substrate should be kept dry until the next irrigation. If there is too much moisture, the roots might start to rot.

Watering is restricted in winter. One serving of water a month is enough. It is better to water too little than too much. The succulents are, after all, thirst artists. In the cold season, the plants tolerate somewhat lower temperatures. However, you should not expose them too much to cold weather, as it could eventually damage them. A bright location is important in every season.

Do succulents need a south facing window?

As the Earth rotates during it's 24 hour cycle, from late morning to mid afternoon the planet becomes closest to the sun. Therefore the strongest rays from the sun flow through South facing windows during this part of the day.

Succulents which demand full sun will thrive here, it provides optimum levels of light for photosynthesis, so growth can be pretty fast.

So if you are planning to plant your succulents indoors, the ideal location will be a south-facing window – that is if you're located in the northern hemisphere. The opposite is true if you're living in the southern hemisphere.

Besides south-facing windows, East and West-facing windows also receive very good light levels and natural sources of heat without either being extreme.

Do plants grow better in sunlight or artificial light?

There have been many debates about whether sunlight or artificial light provides the best lighting needs for plants. Neither one is better than the other, and at times they might even complement each other.

Artificial lighting for indoor plants

Every plant needs light to grow. As a rule, plants thrive best under natural sunlight. However, this is often not available in sufficient quantities. Additional artificial lighting can then help to increase the growth and quality of plants. However, not every light brings the desired effects. Only certain spectral ranges of light, namely the violet-blue and the orange-red spectral range, can be used by plants for photosynthesis.

In turn, photosynthesis is crucial for the growth of the plant. The plant uses the light energy supplied to produce glucose and oxygen from water and carbon dioxide (CO2), which are needed for healthy growth and flowering. The light requirement can vary greatly depending on the type of plant. However, many plants need a lot of light, namely about 16 hours of light a day. Natural daylight is not enough, especially in winter.

How you can increase the growth of houseplants with LEDs

Plants cannot thrive when there is insufficient light. Many plants then form long shoots, the leaves turn light green, later yellow or brown and eventually fall off. With suitable LED lighting, you can give your houseplants exactly the light they need for healthy growth. However, the differences in the light spectrum of different light-emitting diodes can be large. Special LEDs for plant growth offer exactly the light spectrum required for photosynthesis, at the right illuminance.

Since LEDs generate little heat, they can be placed near the plants without causing any damage. Also, LEDs have very good energy efficiency: they can be left on for a long time, and the lights do not have to be replaced as often due to the long service life. For your plants, the additional LED light means healthier growth, faster flower formation and better quality.

Can you use normal lights to grow plants?

A daylight light imitates the daylight of the sun. Such lights were originally not intended specifically for plant lighting, but for a more natural illumination of living space.

If you do not place too high demands on the light for the plants, commercially available daylight lights can be sufficient. However, you must be aware that this variant was not designed for plant lighting. Thus, a daylight light does not necessarily provide the light that plants need to grow. You risk power consumption that misses the mark.

Energy Saving Lights as Plant Lights

can you use normal lights to grow plants

Energy-saving lights are practical, but not suitable as plant LED lights.

The same applies to the energy-saving lights. They are known as room lighting, and the consideration of converting them into plant lights is understandable since they can all be turned on with just a flick of the switch.

However, the concept of conventional energy-saving lights misses the purposes of plant lighting.

It is advisable to use LED plant lighting. Due to the low power consumption and much higher efficiency, more watts in the form of usable photons reach the plant cells.

Besides, energy-saving lights (as well as fluorescent tubes, by the way) contain mercury, which is dangerous if handled carelessly.

Does a black light help plants grow?

Black light only emits UV-A light and affects plants like any other UV-A light source. However, they are a weak source.

Most plants cannot grow under black light if black light is the only light source. If there is other light, they can grow under the black light, if it is not too strong or near the plants. However, the black light itself does not contribute to growth.

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