grow lights, citrus in the arctic, and reflected light

A combination of a couple things i'm trying to understand better...


Assuming I want to grow citrus fruit in a place where it gets cold (like northern minnesota - not quite the arctic, but arctic had less letters ) my understanding is they need longer hours of light than you would have in the middle of winter as well as more intensity... two questions on my mind:

Could providing large reflectors to increase radiant energy work the same? Like the reason the winter sucks is because of the angle of the sun meaning insolation per meter is less... so just reflect more of the area back to the same grow area and that should fix part of it, right?

And could I simply have grow lights come on before the sun is up and after the sun goes down to supplement an hour to make it work? Or might the citrus grow with shorter hours as long as the intensity was stronger from those reflectors? Any opinions?

Reflecting light can add intensity, but you'll need to double your estimates for insolation gain if you have not taken into account the polarizing effect of the reflector. The light may reflect exactly as you desire, but only half of the light remains after being reflected.

I doubt daylight hours or light intensity would be a problem for growing citrus at Minnesota latitudes since they grow citrus outdoors at similar latitudes in northern Italy, Lake Lugano in Switzerland, and on the Crimean peninsula. They also grew citrus in the palace orangeries at Versailles, France and in Potsdam, Germany (52N latitude) without supplemental lighting in the 1700's.

Brian Shaw wrote:
Assuming I want to grow citrus fruit in a place where it gets cold (like northern minnesota - not quite the arctic, but arctic had less letters ) my understanding is they need longer hours of light than you would have in the middle of winter as well as more intensity... two questions on my mind:

Could providing large reflectors to increase radiant energy work the same? Like the reason the winter sucks is because of the angle of the sun meaning insolation per meter is less... so just reflect more of the area back to the same grow area and that should fix part of it, right?

And could I simply have grow lights come on before the sun is up and after the sun goes down to supplement an hour to make it work? Or might the citrus grow with shorter hours as long as the intensity was stronger from those reflectors? Any opinions?

I live in the Appalachian mountains and on average the lowest temps are around 15F (Though we did get 5F last week) , random snows, ice storms,etc. in the Winter- not near as frosty as where you are, but still not exactly "Citrus country". I am into growing citrus and various other "exotic" fruits and plants outside their normal areas.

In reference to your questions, the first thing you need to consider is dormancy. Most, if not all citrus goes dormant when the soil temps drop to 50F or so. Dormancy is also tied to the amount of light the plants receive.

To keep citrus plants actively growing/flowering/fruiting through the Winter will require much more input than keeping the same plants dormant. Also, most citrus types are much more hardy than the fruit they produce- for instance, Satsuma mandarin trees can take down to the low teens (F) with little damage, but any fruit on the trees will freeze and go bad after a freeze or two.

Citrus can survive just fine in very low light conditions through Winter if they are kept dormant.

What I do personally is both- I keep some citrus dormant- those that are planted outdoors or in my greenhouse, and I keep some active in my living room by a large window and a florescent lamp.
The hardier stuff is outside, the more tender types like lemons stay inside.

Inside lighting

Another cheep light setup for starting seedlings.  I used 1 stainless steel lift top trash can and attached an electric light to the lift lid.