The best Autoflower light intensity

For Autoflowering plants we recommend PAR intensity of about 550 µmols/m²/second and a 20 hour light period. To achieve this light intensity with LED grow lights you need about 20 watts per sq. ft. or 230 watts per sq.m of plant canopy. This is a DLI of 40 Mols, close to the limit a plant can absorb in one day

The advantage of Autoflower plants over photoperiod plants

Autoflower plants are so called because they automatically start to produce flowers or buds after a period of time. They do not require a switch of daily light schedule from 16 hours to 12 hours as photoperiod plants do. The benefit is the light schedule can be setup as 20 hours light and 4 hours darkness per day all the way from seedling to harvest. Therefore autoflower plants receive more light energy per day and grow quicker than photoperiod plants.

An additional benefit of growing autopflower plants is the light intensity can be reduced as both autoflower and photoperiod plants can only absorb a limited amount of light per day.

Maximising the Daily Light Integral DLI for autoflowering plants

The measure of the amount of light plants can absorb over a light cycle is called DLI (Daily Light Integral, the amount of PAR reaching the plant over the total light cycle).

This is an important measure because, although plants can absorb PAR intensity up to at least 1,500 µmols/m²/second for a period of time, plants are limited as to how much light they can absorb over the total light cycle. 40 DLI is generally accepted as the upper limit for plants to absorb in one day.

Recommended PAR intensity for auto flowering plants

Autoflowering plants do not require switching to a 12 hour light cycle to stimulate the plants to flower. For Auto flowering plants the typical light cycle is 20 hours on and 4 hours off. This maximises the time the lights are on while still allowing a few hours darkness for the plant to 'sleep' and metabolise.

Because the day is longer the PAR intensity can be relatively lower to reach the same maximum 40 DLI. Here is the table for the recommended grow light system wattage to achieve our recommended PAR intensity of 550 µmols/m²/second for Autoflowering plants.