Using reflective surface outdoors?

DamonS

Active Member
has anyone tried using a reflective surface such as mylar for an outdoors grow?

my outdoors garage is walled on all sides, neighbors are cool and aren't nosy, the street is pretty quiet and marijuana laws aren't very strict/enforced where I'm from so being secretive about the grow isn't an issue.

besides what is blocked out from a single tree across the road and the house and garage walls (totaling ~4 hours of indirect light per day) there is plenty of sunlight available.

im wondering if setting up wooden walls on either side of the plants, (third side towards a brick wall which doesn't overshadow the plants during day) and covering them with mylar would be of any value. i cant seem to find any info on outdoor growers using reflective surfaces. are there any detrimental effects of having too much light? increased heat maybe? ventilation?

the wooden walls themselves will be designed so their backside wont be blocking out any direct sunlight which isn't already being blocked by the house/garage walls.

though i have enough space (~20 square meters) id prefer to have as few marijuana plants as possible with maximum yield from each one (taking up ~4 square meters) and dedicating the rest of my garden to other plants.

ill be getting a 400W HPS light in a month and can do some indoor growing (have an area ready), but i would prefer to take advantage of both grow areas i have available, using the indoor grow room mainly for a mother plant, cloning and vegging, as well as extending the flowering period of the outdoors crop if outside temps/daylight drop down too much in winter. keeping the electricity bill down would also be nice.

heres two quick sketches of my grow area. the first pic shows the house/garage walls blocking out some of the morning and evening sun and reflective surface designed/positioned in such a way that they dont block out any of the sunlight. the second pic shows a bird eye view of the garage with the yellow/brown line being the "path" of the sun throughout the day, starting at the top in the morning (yellow) and moving down throughout the day. during the middle of the day (where line changes from yellow to brown) the sun is not quite above the plants but aligned so that its facing the normal of the wall, which is directly adjacent to the plants (I'm guessing the mylar surface on the brick wall alone will provide some great added sunlight during this time)

should i go ahead with the plan? any suggestions/advice would be appreciated, especially since I'm still on my first grow.
 

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DamonS

Active Member
well, its more about increasing the intensity of the available sunlight rather than compensating for indirect sunlight.

edit: the walls are going to be pretty makeshift. ill probably just use some cheap wood and might even just use some left over white paint if i cant find any mylar.
 

Inneedofbuds

Well-Known Member
you wouldnt want to do this. Light from the sun doesnt travel down onto the plants, it actually hits the plants almost parallel to the ground, at like a 3 degree angle. Anything you put to the side of the plant to reflect light would only block natural light coming from the side of the plant.
 

DamonS

Active Member
again, the added walls will be designed so they don't block out any direct sunlight from behind. the brick wall also doesn't overshadows the plants throughout the day (except for a tiny bit at sunset, during which the sun is already blocked out from buildings far off into the horizon), so adding the mylar to that wouldn't hurt.

I'm not quite getting the comment about sunlight hitting the sides of the plant...in any case, wouldn't the same lighting principals apply as those of indoor lighting?
 

Inneedofbuds

Well-Known Member
again, the added walls will be designed so they don't block out any direct sunlight from behind. the brick wall also doesn't overshadows the plants throughout the day (except for a tiny bit at sunset, during which the sun is already blocked out from buildings far off into the horizon), so adding the mylar to that wouldn't hurt.

I'm not quite getting the comment about sunlight hitting the sides of the plant...in any case, wouldn't the same lighting principals apply as those of indoor lighting?

no, with indoor lighting, as in most HID lights, the light his the plant from above, not from the sides. Most people assume the same from outdoors, but this is not the case. Light travels almost parrallell to the earth, and hits plants from the side, not from above.
 

DamonS

Active Member
i am completely confused by the idea of light traveling parallel to the earth... wouldn't that only occur at the very moment of sunrise and sunset?

im not trying to be condescending and i really am interested in understanding what you're saying, but if i were to hold up an umbrella...with the sun above me...the shadow would be below me...that by itself seems to suggest that the sunlight is coming from above...

haven't plants naturally evolved to receive as much sunlight as they can, by growing vertically with their leaves parallel to the earth/perpendicular to the sun, thereby increasing the exposed surface area towards the sun. if most of the sunlight they needed was hitting them from the side wouldn't the leaves be facing that direction?
 

Inneedofbuds

Well-Known Member
i am completely confused by the idea of light traveling parallel to the earth... wouldn't that only occur at the very moment of sunrise and sunset?

im not trying to be condescending and i really am interested in understanding what you're saying, but if i were to hold up an umbrella...with the sun above me...the shadow would be below me...that by itself seems to suggest that the sunlight is coming from above...

haven't plants naturally evolved to receive as much sunlight as they can, by growing vertically and parallel to the earth/perpendicular to the sun, thereby increasing the exposed surface area towards the sun. if most of the sunlight they needed was hitting them from the side wouldn't the leaves be facing that direction?

no... because there is always more ligth shining above the plant. The plant is already receiving as much light as it can from the side, so it grows upward in order to increase the surface area that light hits.
 

DamonS

Active Member
little edit in previous post.

i really cant tell if you are being sarcastic about plants receiving light from the side.

maybe you're confused with the spectrum at which light for plants is most beneficial and that occurs when the sun is at a certain angle.

I'm not the most knowledgeable botanist, but my understanding is that plants need light, leaves absorb light, leaves face light (upwards) to absorb light. imo, growing vertically would be a trait gained as plants began to compete with each other for light. if they actually needed light from the side then their leaves would be facing that way.
 

MonsterPot

Well-Known Member
I'm doing it. As you said, same principles as indoor growing. I've got a semi-circle of white cardboard around my plant to roughly reflect the light onto the plant. Theres definately more light when i do it...the shadows becomes alot lighter and some leaves orient themselves towards the refl'd light. I just wonder whether it makes a significant difference...i dunno...
 
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