Flowering Lights

Lights used for flowering are almost always red; consisting of light between 600nm and 750nm wavelengths.

After your plants have been growing and building up energy during the vegetation stage, they are ready to enter flowering (or fruiting). Redder lights gently stimulate this change in function, mimicking the change in sunlight from summer to autumn/fall. Using a properly designed flowering light greatly reduces plant stress, thus improving yields.

Benefits of using a flowering light

  • Triggers a much stronger flowering response
  • Higher yields over regular grow lights – up to 50% more
  • Plant is less stressed, resistant to rot/infection

Not only does this type of light stimulate photosynthesis in the chloroplasts, but also stimulates metabolism and energy generation in the mitochondria of plant cells. This is incredibly effective during a flowering period, helping the plant to efficiently achieve its goals.

How flowering works

Two of the primary factors that contribute to when plants (including trees, bushes, herbs, cannabis, etc.) start flowering are the photoperiod and the light spectrum.


The photoperiod is the length of day, or the amount of hours that a plant spends in light vs darkness. In nature, this is controlled by the sun, the rotation of the earth and therefore the seasons, which leads to different lengths of days. For growing indoors however this process has to be stimulated by restricting the hours the light is turned on (manually or with an automated plug-in socket timer).

As most of us know, nights gradually get longer (and days shorter) towards late summer and autumn. This is a big cue for plants to begin flowering and spreading their seeds before winter. In some cases though, plants will even begin flowering regardless of the photoperiod.


Light Spectrum

The spectrum of colour in a light also has a smaller but still significant effect on a plant’s flowering and growth phases. In nature, sunlight during spring and summer is towards the blue end of the visible light spectrum, whereas light in late summer and autumn shifts towards the red end of the spectrum.

As plants have evolved with this cycle of seasons, replicating the light spectrum of nature when growing indoors has been shown to produce better results and healthier plants. If you only use 1 light or spectrum for the entire lifetime of an indoor plant, it should still grow and enter a flowering period, although size, potency and other results will not be optimal. This is due to the blue wavelengths found in most standard grow lights, which have a slight inhibitory effect on flowering and general metabolism of a plant, despite working well for photosynthesis/growth.


How do I choose a quality flowering light?

Using a standard grow light at first and then switching to a flowering light when your plant starts (or is ready to start) flowering works wonders. Flowering lights can still be used to grow a plant at any stage, however.

There are several flowering lights on the market but most are not powerful enough or don’t use the optimal wavelengths of red light.

If you are looking to grow the biggest, healthiest, highest yielding plants then be sure to pick up a powerful red light that outputs wavelengths optimised for flowering, such as the one below:


Recommended Flowering Light

£ 300.00 £ 240.00 Ex. VAT £ 200.00
red light man red light device photosynthesis chlorophyll
Graph showing Redlightman’s Red Light Device spectrum with chlorophyll absorption

See growing page for information on further grow lights.