not unless the light is within inches of the plants ... otherwise its not useful to the plant ...

when i used to grow plants indoors on my light stand.. i often ran the lights 24/7 ...

i dont think you have anything to worry about in this regard ...

ken

As noted, unless the light is inches away from the plant, it makes NO DIFFERENCE. A lamp many feet away is hundreds of times fainter than sunlight. That is, as far as the plant is concerned, a porch light at night is essentially darkness. Your eyes open way up at night to let more light in, to make very faint things look brighter.

Any chance you can turn the light off? Well None of what you're growing have photoperiodism tendencies, where light and dark length are measured to trigger a growth change such as flowering, so no problem there.

Something you will see at night if the plants get to much light is the plants exhibiting Phototropism, and they will bend toward your porch light when the chromophore in the photoreceptors are triggered altering plant activity. Photosynthesis will also be triggered so Phototropism is a signal your plant thinks it's daylight. There is a threshold of light required to trigger photosynthesis and at that point they think its daylight.

if the plant thinks it's daylight it will disrupt the dark respiration process and this is where you will have a problem. Respiration is constant, night and day but at night it's more intense because photosynthesis has ceased. To a plant it's like Oh boy, now that I've photosynthesized all day I can get some serious respiration in. In the day light it's called photorespiration and isn't enough so why a dark period is important to plants.

Your plants will become stressed and damage the plants. So yes the light at night can effect your plants, and also warm nights can do the same thing and disrupt dark respiration. Your plants need cooler night temperatures than day temps for a good night of respiration just like you need cooler nights for a good nights sleep.

A full moon isn't effectively darkness and emits approximately 0.3 lux per square foot and the intensity of a porch light could disrupt dark respiration. A candle one foot away is enough to trigger photoreceptors in plants and proven by Darwin and his son in 1913. The candle is one lumen so I'd say anything under one lumen and over 0.3 lumens could cause stress and blossom drop, but haven't yet found any studies made for a definitive answer.

I don't think that's the case. Lots of gardens are illuminated by streetlights, night-illumination, and it has no effect on them whatsoever. Triggering photoreceptors and stressing plants are two entirely different things.