Planning plant lighting

Plant lighting can be complex but does not have to be. With this guide you will learn step by step how to tackle the planning.

Anyone wishing to grow, cultivate or winter plants indoors usually needs plant lighting to compensate for the lack of natural light. Some varieties also benefit from a certain light spectrum that does not occur in nature.

To achieve an optimal result, plant lighting should first be planned carefully. We show step by step what is important.

Step 1: Focus on the plant

It is actually logical that we first consider what we want to grow in the first place. For example, there are significant differences in lighting requirements between Microgreens and medical cannabis. The former thrive excellently even in low light, after all, harvesting is done in the early stages of vegetation. The latter, on the other hand, is one of the most demanding plants in terms of lighting.

Furthermore, one should be aware of the individual characteristics of the plant. The growth form and height should be taken into account when planning the lighting. Will the plant grow to room height? Or cultivated in several layers (see vertical farming)? This will affect the possible height and arrangement of the lighting modules.

In the case of a dense canopy, it can be helpful to also light from the side or between the plants ("interlighting").

Step 2: Intensity

As already indicated: For different plant varieties - different cultivars - there are different recommendations for the optimal intensity. The intensity of plant lighting is measured in PPFD. This is a measured value that describes how much photosynthetically active radiation hits a surface. Manufacturer's specifications for PPFD are easy to gloss over and are often not adapted to the individual application scenario. This is because different wall coatings, angles and heights can cause the values to differ greatly from the manufacturers' data sheets. However, they can usually provide a rough orientation.

PPFD and photosynthesis
The rate of photosynthesis is an important indicator of the growth potential of plants

It would be best to measure the photosynthetic photon flux density itself with a sensor. This is where much can be optimized in terms of energy efficiency and yield. For example, at higher intensities it will be necessary to add CO2 in order to further increase the photosynthesis rate. Otherwise, the additional energy input is out of all proportion to the additional yields from the higher intensity. At normal CO2 levels, a PPFD of up to 800 µmol/s²m² in the generative phase is recommended, depending on the cultivar. One can also go up to 1000 µmol/s²m², but the expected advantages are marginal compared to the increased electricity costs.

Step 3: Area

In this context, the question naturally arises as to how large the illuminated area will be. In combination with the previously determined requirements of the cultivar in terms of light intensity, we can estimate how many LED modules or lights we will need for the project. For our DIY LED module FLUXengine you can easily find the required lighting with this tool calculate.

Step 4: Spectrum

White light: Colour temperature

With white light sources, the colour temperature alone usually gives an indication of what the spectrum looks like. Here, cold white (4000 K or more) means that the blue component is higher. This light is particularly suitable for the cultivation and growth phase of plants. It prevents the plants from shooting up too much (horny) and ensures compact healthy growth.

Plan plant lighting 1
3500K Spektrum - the all-rounder between warm white and cool white

Warm white (3000 K and less) is mostly used as flower lighting. The higher red light content is equivalent to a higher number of photons and also gives the plant the signal to develop flowers and fruits. However, this can lead to accelerated growth at higher altitudes.

Neutral white (3500 K) can be used both in growth and in flowering. It is a balanced all-rounder.

Special wavelengths

Plan plant lighting 2

Some growers use special wavelengths to control photomorphogenesis, metabolites and active ingredients in plants. These include near UV (350-400 nm), blue (~ 450 nm), red (~660 nm) and near infrared (700-750 nm). More about the effects of special wavelengths follows in this article.

Step 5: Type of room

Much depends on this point as well. What kind of premises are available? Basically, you can grow indoor plants in all possible environments. But the lighting requirements differ. With large wall surfaces, the lamps should be as close as possible to the plants. In large rooms the reflection losses at the edges are hardly noticeable and the lamps can be mounted directly under the ceiling. If there are surfaces that should be left out of the lighting, one should buy optics (lenses, reflectors) to direct the light. This is the case in living rooms, for example, or if corridors between rows of plants should not be illuminated.

A hall

Plan plant lighting 3

Ratio of wall area to floor area: very small, therefore best lamp position: directly under the ceiling, optics not required. Corridors between the rows of plants should be as narrow as possible, otherwise optics might be advisable. There is usually commercial interest in plant lighting in halls. The indoor gardener or vertical farmer will try to optimize the costs by all means. LEDs are therefore more likely to be given a higher current in order to save investment costs.

A special grow room

Plan plant lighting 4

Basically the same as the hall, but in a smaller format. Here it may be advisable to build the lamps height-adjustable, because the wall surface is proportionally larger. This prevents unnecessary reflection losses on the walls.

A living space

Plan plant lighting 5

The requirements here are completely different. Anyone who illuminates plants openly in living spaces will prefer a light spectrum that is also pleasant to the eye. White plant light is well suited for this - as with the FLUXengines. In addition, optics will be advisable to bundle the very bright light where it is needed. For plants that grow in height, you should also plan a height-adjustable suspension.

A tent or cupboard

In these "mini greenhouses" the wall area is very high compared to the base area. Therefore, you should definitely plan for a height-adjustable light. It is also important to ensure that the wall surface is as reflective as possible. We do not use optics because the light of our FLUXengines is well distributed over the entire base area.

Even smaller: PC-Growbox and Co.

Plan plant lighting 6

As in all areas of life, there are also fans of miniaturisation among amateur gardeners. For example, disused computer housings can be used for micro growing. To ensure that experienced tinkerers have fun with their project, the LEDs should be kept as low as possible. This is because space is limited and the plants will be very close to the light sources. Of course we want to do without heat sinks, suspensions and optics in order to gain as much space as possible.

Step 6: Budget

Money comes into play at the end. And craftsmanship and the desire to build your own home. Those who have a lot of the former and less of the latter can and should fall back on Plug & Play products. But many gardeners see it as a challenge to plan and implement plant lighting themselves. With this article you already have a good overview of the problems and how to plan ahead. We have already written about the various designs reports that are suitable for DIY LED plant lighting.

Our offer

If you want to make the planning a little easier, take a look our DIY kits on. We've thought of everything and you can start right away. If you belong to those who prefer to buy a finished lamp, we can supply pre-assembled versions on request. In the future there will also be plug & play plant lighting from Crescience.


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