Winter Lighting

Carol 83

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I am a bit curious about that also. I have most of my lights on from 7:00 am until 7:00 pm and some until 9:00 pm. I have been doing it this way for about 30 years.
I can't remember who suggested that to me, or maybe I just made it up. Your way sounds better, having them on when no one is home, so they don't fry their eyeballs! Thirty years, must be working. I'll do that this year.
 

just.wing.it

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My trops are in the basement, no sunlight at all.
So I keep the lights on from 5am to 9pm, 16 hours per day.
3 "white LED grow bulbs" that I got last year, which were used last year by themselves did well....
This year I have the 2 Full Spectrum LEDs added to the 3 white ones.
 

penumbra

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A lot of people keep there lights on for tropicals 14 hours and more a day. There is nothing wrong with this but remember that the days and nights in the tropics (equator) are 12 hours sun and 12 hours dark. Unless you are keeping the plants at a tropical temperature all winter to encourage rapid growth, there is no real advantage that I have seen over a 12 hour day. For subtropical and temperate zoned plants this changes and long days are for growth while short days are for flowering.
I used to have all my plant lights at 14 hours a day, but now I run most of them at 12 hours a day. For some of my plants (mostly non bonsai) there will be no growth until spring and they can get by with a much shorter day which extends longevity of the lights. Several of my house plants and a few of my bonsai fall into this category. Examples are cactus and clivia, but there are many more. In bonsai this applies to a few of my succulent plants. I am not trying to actively grow some of these plants so I hold them at about 6 to 8 hours, and of course there are some that need no light at all, but for most of them I offer them light anyway.
 

just.wing.it

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A lot of people keep there lights on for tropicals 14 hours and more a day. There is nothing wrong with this but remember that the days and nights in the tropics (equator) are 12 hours sun and 12 hours dark. Unless you are keeping the plants at a tropical temperature all winter to encourage rapid growth, there is no real advantage that I have seen over a 12 hour day. For subtropical and temperate zoned plants this changes and long days are for growth while short days are for flowering.
I used to have all my plant lights at 14 hours a day, but now I run most of them at 12 hours a day. For some of my plants (mostly non bonsai) there will be no growth until spring and they can get by with a much shorter day which extends longevity of the lights. Several of my house plants and a few of my bonsai fall into this category. Examples are cactus and clivia, but there are many more. In bonsai this applies to a few of my succulent plants. I am not trying to actively grow some of these plants so I hold them at about 6 to 8 hours, and of course there are some that need no light at all, but for most of them I offer them light anyway.
I was taught that 18 hours of artificial light is maximum, above that there is no gain.
The green houses that grow veggies use long stretches like that, apparantly.

I understand your point about the 12 and 12 though.
I think during the summer, when my tropical are outdoors, they see more than 12 hours of sun.

I guess the bottom line for me, last time this topic of duration came up, was "more light is better indoors".

I can't remember what thread it was or who it was.....Grimmy I think was the one who convinced me, RIP bud.
 

penumbra

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I was taught that 18 hours of artificial light is maximum, above that there is no gain.
The green houses that grow veggies use long stretches like that, apparantly.

I understand your point about the 12 and 12 though.
I think during the summer, when my tropical are outdoors, they see more than 12 hours of sun.

I guess the bottom line for me, last time this topic of duration came up, was "more light is better indoors".

I can't remember what thread it was or who it was.....Grimmy I think was the one who convinced me, RIP bud.
My point is that if you are forcing a lot of new growth, and if you can keep the temperature tropical, use as much light for as long as you wish. Some cannabis growers use 22 and even 24 hours light. ( in college I was taught that 18 hour rule also) Then they cut back dramatically to induce flowering. If temperatures are lower (in my house they are) in winter, and you are basically holding your plants until spring, you just don't need over 12 hours and you could get by with less. In my bedroom I have t-5 fluorescent over ficus trees on a timer from 7:00 am to 9:00 pm, a solid 14 hours that does not interfere with my rest time. It is also warmer upstairs than it is in my basement by a fair margin as I heat with wood upstairs only. If I had a hothouse environment I would burn my lights longer and push new growth all winter long for true tropical plants. On the other hand, most sub tropical and many tropicals like a bit of a seasonal rest. I know that I can use a seasonal rest. Seasonal rest can come on from cooler temperatures or less water, but usually both. Many African plants (and elsewhere) defoliate during the dry season even though temperatures are still in the tropical range.
If you communicate with your plants you won't go wrong on either count.
 

just.wing.it

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My point is that if you are forcing a lot of new growth, and if you can keep the temperature tropical, use as much light for as long as you wish. Some cannabis growers use 22 and even 24 hours light. ( in college I was taught that 18 hour rule also) Then they cut back dramatically to induce flowering. If temperatures are lower (in my house they are) in winter, and you are basically holding your plants until spring, you just don't need over 12 hours and you could get by with less. In my bedroom I have t-5 fluorescent over ficus trees on a timer from 7:00 am to 9:00 pm, a solid 14 hours that does not interfere with my rest time. It is also warmer upstairs than it is in my basement by a fair margin as I heat with wood upstairs only. If I had a hothouse environment I would burn my lights longer and push new growth all winter long for true tropical plants. On the other hand, most sub tropical and many tropicals like a bit of a seasonal rest. I know that I can use a seasonal rest. Seasonal rest can come on from cooler temperatures or less water, but usually both. Many African plants (and elsewhere) defoliate during the dry season even though temperatures are still in the tropical range.
If you communicate with your plants you won't go wrong on either count.
Food for thought!
Thanks!

I guess for me, "forcing" as much growth as I can is best.
I do like to have a tree or 2 two trim over the winter.
 

Leo in N E Illinois

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You know, there is such a thing as a useful approximation. Perfection is the enemy of the "good enough".

Between the Tropic Latitudes, day length does not change enough that almost no plants between these latitudes uses day length to know what time of year it is. Combine this thought with the fact that even the best & brightest of indoor light set ups come up to 25% of the intensity of natural full sun. Most indoor set ups are maybe 10% of natural full sun. The studies that recommend 18 hour day length do so recognizing that to some degree, you can compensate for lower indoor light intensities with longer day length. The upper limit is 18 hours, after which tests showed no increased biomass production with day lengths long than 18 hours. Plants from the tropics are usually totally insensitive to day length in terms of governing growth cycles.

Plants, including many succulents, from regions near the 30 to 35 parallels north and south are in the regions of monsoon influenced climates. Here the rains are sharply seasonal, and many areas have 3 month or longer dry seasons, and 3 month or longer monsoon seasons, the rainy seasons. Actual it is called a wet monsoon, and a dry monsoon. Between monsoons you can have more conventional, frontal boundary influenced weather. Again, day length is not normally the environmental cue the plants use to govern growth cycles. In these regions it is the presence or absence of rainfall that governs growth. OR it is night time temperatures that govern growth. During the dry monsoon, there will be no cloud cover at night, allowing cooling at night. During the wet monsoon, the clouds hold the heat at night. SO cooling off at night is normally the signal that plants in these regions will use to signal the arrival of the dry monsoon. (dry season) These areas do not have conventional winter, spring, summer, autumn. It is either the wet season, or the dry season or the transition season(s) between.

Sub-tropical and temperate species - some actually do use day length to know what time of year it is. Some use temperature, The actual number of documented species that are truly day length sensitive is small. Chrysanthemums are definitely day length sensitive, as the floral industry has documented. Poinsettia are also day length sensitive. Marijuana, Osmanthus, Papaver, possibly some Salvia are all day length sensitive. But the vast majority not listed are either more sensitive to temperature or other environmental cues.

Interesting factoid. Globally, from the equator to the poles, there are many trees, especially conifers, that volutize some 70% of the carbon captured by photosynthesis every day as volatile sesquiterpenes. Many of these sesquiterpenes do function as plant hormones, chemical signals, that can be read by neighboring plants. The haze that gives the name to the Blue Ridge Mountains is the sesquiterpenes gassed off by the red spruce, hemlock, balsam fir, and eastern white pines of the Blue Ridge Mountains. THat haze is a soup of chemical signals from one tree to another. There are large groups of plants that have abandoned investing the chemical energy required to run biological clocks. Instead, these plants simply "read" the chemical signals the local conifers are sending, and they respond the way their neighbors do to the environment. This is why plants taken from south of the equator to north of the equator very quickly readjust their clocks to align their growth to the seasons they are currently residing in. They pick up the signals from the trees around them. So the South African spring flowering bulb will begin flowering in spring in North America in as little as 18 months from crossing the equator. It is the chemical signals floating in the air that tell the bulb what time of year it is.

SO @penumbra is correct - SOME trees are indeed daylength sensitive. And it is useful, especially if you are deliberately trying to keep your trees dormant, you should use less than 10 hours of day length. If I were to put a light in my well house, where it stays cool and I want dormancy, I would set the light for only 6 or 8 hours of light a day.
But the over all number of trees that are documented to be day length sensitive is really low. There is a somewhat larger number that are suspected as being day length sensitive, but not documented. For example, it is assumed most of the Aster (including Chrysanthemum) family are day length sensitive. The overall number of species is unclear, and thought to be relatively low.

If one is keeping temperatures up, and is looking for growth over winter, then the 18 hour day length is definitely the way to go.
 

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