Millet, I think I have encountered the other side of your formula for preventing WLD-- Since I have been using the Christmas lights to warm the roots of my seedlings I have had several try to grow new leaves, but the new leaves are just curling-- the tip of the leaf curls under back toward the stem and makes a complete circle.

I think the problem is that the plants have not been able to get outside to get direct light because of the rain and the 4 ft fluorescent shop light that I have recently suspended about 2 ft above the plants is just not enough light to support the growth. The leaves are trying to grow but just don't have the photons to support it.

Skeet

Skeet, the problem is that you have the fluorescent lights located much too far from your trees. Poor results obtained with fluorescent lights can be traced to two problems, not enough bulbs to cover the growing area and the bulbs not close enough to the plants. Most plants can be grown using about 40 fixture watts per square foot. With fluorescent bulbs you need a minimum of four 40 watt four foot long bulbs to cover a 1 by 4 foot area. However, because fluorescent bulbs tend to disperse light you are fooling yourself if you think your light is only covering the 1 by 4 foot area. In reality it is covering 11/2 to 2 by 4 feet so 6 to 8 bulbs are what is really required.

With all artificial lights the light intensity is greatest near the bulb and diminishes with the square of the distance as you move away. Thus, a light that gives 1000 lumens 1 foot away will give only 250 lumens at 2 ft. In addition, fluorescent lights give more diffuse light, like the light on a cloudy day. This scattered light looses its’ energy quickly, so to obtain good growth under fluorescent lights the plants must be within a FEW INCHES of the light. Because fluorescent lights need to be close to the plants their usefulness is limited to low profile plants such as African violets and to seedlings. It is difficult, but not impossible, to grow a high profile plant, under fluorescent lights. (10 lumens = 10 foot candles = 1 lux). - Millet

I was originally just trying to keep the seedlings from getting cold roots by putting them in my shop at night -- then I would set them back outside during the day for direct sun if it was warm enough.

After I did the test with the small Christmas lights I decided to keep them going, thinking that warmer roots (70-80 F) would grow faster--still setting the plants out during the day. But then we had a series of rainy days so that I could not set them outside. So, I left the Christmas lights on lowered the one shop light that was over that part of the shop just for temporary help.

The leaves started curling under in just a day or 2. I have since turned off the Christmas lights and still use the shop light for a little help at night. Some of the small leaves (less than 1/2 in long) have fallen off, but most remaining growth is back to normal.

I think the warm roots was definitly speeding growth, but as you say I just did not provide sufficient light intensity. I may go buy a couple extra shop lights and make a rack to hold them a few inches above the plants, especially if it looks like we are going to get another long spell of rain or cold.

Skeet

Millets resoning is exactly why I use high intensity flouresence and keep them as close as i can to the plants, also it is good to replace the flouresence bulbs about every year or every two years they loose intensity with age.

Plants do not “see” light the same way that people see light.. Plants are not concerned with how bright the light is, but are more concerned with the ENERGY of the light. The energy of light is measured as joules or watts per square area. The intensity of light is NOT the same as the amount of energy in the light, because blue light has more energy than red light, so that 2000 foot-candles of red light has less energy than the same 2000 foot-candles of blue light. HID lights are available as either MH (metal halide) or HPS (high pressure sodium) lights. Both of these are acceptable for growing plants. The MH bulbs have a more blue spectrum that looks more like daylight, while the HPS bulbs are more golden. They both are over 30% efficient at turning electricity into light. The price of MH fixtures are a little cheaper than the HPS fixtures but the MH bulbs do not last as long so the operating cost is about the same.

HID lights produce an intense point source light that is not as diffuse as fluorescent bulbs and includes significant amounts of infrared radiation (heat). This means that HID bulbs are most effective when combined with a sophisticated reflector and are kept a minimum of 1 foot from the tree. In general HID lights are better for taller plants and plants requiring a higher light intensity. All HID lights require a transformer (ballast) to ignite the bulb and keep it lit. Some ballasts are built into the light fixtures while some are kept remote. Most Ballasts are designed to work using 120V with other voltages available. HID light systems are simple to use. I have one hung over my Fina Sodea Clementine in the greenhouse. Many people place their high light plants directly under the HID light and their lower light plants such as orchids farther away. - Millet

sorry millet that is what I meant by intesity I use the blue light flourence with 6400K. Not the best as MH, HPS are the best but very costly.

I had quite a few days of cloudy days.. I have a citrus that has lights wrapped around the pot *root rot recovery*.. I noticed after quite a few days of clouds the leaves went limp and kinda curled.. I checked the soil to make sure it wasn't dry.. No.. After a few days of sun the leaves perked back up..
the effects of lack of sunny days was not as damaging (no leaf loss) and took longer to show effect (2 or 3 days of clouds) as skeets seedlings..

my plant was larger so it took longer and had less effect??

I was trying to figure out the reason..
ok. with cool temps and high light the roots are not active and the canopy is active.. tree drops leaves so the canopy is not requiring so much from the roots (something like that)...
With warm very active roots and low light.. the roots are producing more than the canopy requires.. the cells OD on moisture.. with the overly wet foliage the cells are not as firm holding the leaf stiff...
is that about the sum of it???
I have been pondering this since reading this post.. and again my tree has limp leaves due to the low light days.. Today was sunny so I'm hoping that maybe tomorrow will be sunny as well and the plant can recover a bit before the next set of cloudy days..
if a tree suffers too long with out sufficient lighting and higher temps will it cause cell damage to the leaves??
I think I will unplug the lights tomorrow because we are suppose to get more nasty weather..

There is sufficient natural light (south picture window and small east window that gives it am sun as well..) on sunny days.. I'm running in to more cloudy days now and do not have supplemental lighting for the plants in that room..
So far the only plant really effected is the one that has the pot wrapped in lights..

Thanks for any input/ explanations!!

Gina *BabyBlue*

I think there are 2 options-- stop the heating, or supply sufficient light. Initially I just stopped the heating until I got a couple more shop lights and set them up so I had the lights only a few inches above the plants.
I haven't had any problems since, but I also have not had any new flushes.

I'm just guessing as to the cause, but I think the roots were supplying nutrients but the leaves were unable to turn that into new leaf tissue. In my case the leaves rolled end over end--like they were being pushed while the end was tied--then they dropped. The last leaf from that flush that stayed on my biggest lemon is now at least twice the size of all other leaves. Most of the leaves that died and dried up were less than a 1/2 long when the sunlight was stopped.

Almost all of the seedling were starting a big flush due to a couple weeks of 70's with sunny days. I was bringing them in and heating the roots at night to keep them active-- root temps were getting into the 80s at night.

I was able to leave them out all weekend last week, but they were inside again until yesterday--now were have 4 more days of rain forecast. I am just beginning to see some seedlings starting a new flush. We will see how it goes.

Skeet

>>>>>>With warm very active roots and low light.. the roots are producing more than the canopy requires.. the cells OD on moisture.. with the overly wet foliage the cells are not as firm holding the leaf stiff...
is that about the sum of it???<<<<<<<<<<

Gina the above is not correct. Leaves become turgid (stiff) when the cells are filled with water, and leaves become "limp" when the cells are deficient in water. Just because the root zone temperature is warm, the roots will not, and do not, send more water than the canopy requires, and the cells do not OD. Actually the tree uses two different forces to supply the tree with water from the soil. One by the roots, called root pressure, and the other by the leaves, called transpirational pull. The latter force (transpirational pull) is far stronger than the upward pressure from the root system. Transpirational pull lifts vast quantities of water against gravity to the topmost leaves. Although root pressure may push water up to the leaves of very low growing plants, it is insufficient to elevate water into the foliage of trees. On cloudy days the transpirational pull will not be as strong and on sunny days. Also because your tree is in *root rot recovery* it probably does not have the root structure to send much water, let alone cause leaf OD. Lastly, because the tree has experienced root rot, you are probably being very cautious and keeping the soil overly dry. I've come to believe that root rot almost never develops because of over watering, but rather from compaction of the growth medium causing restricted drainage. The root damage is from a lack of oxygen and a high level of carbon dioxide. in the root zone. A highly porous fast draining "soil" will always maintain good root zone aeration, even with a lot of water poured through it. - Millet

Thanks Millet!!!

That was a guess on my part.. I'm glad you cleared it up for me.. that makes since..

I did unplug the lights.. We got some decent sun today and it has perked back up again..
Guess I need to move it back in to the room where it may not be as warm but it will get a little supplemental light.. The rest of my trees are doing fine there.. The Meyer is pouting.. but that is what meyers do best right?? LOL

Gina *BabyBlue*

I have had to keep the seedlings inside for most of the past 2 weeks, but since I lowered the shop light to just above the plants I am getting new growth that seems to be holding up just fine. The small Christmas lights are only good for about a 20 degree boost, so the last couple mornings the soil temps have been in the upper 50's to low 60's. I don't have an ambient thermometer in the shop, but it probably got into the upper 30's when it got into the upper 20's outside.

Skeet

Skeet just a thought........The method that nature uses to produce strong trunks and firm branches is the tree's resistance against the wind, and to a lesser extent by the branches the tree produces at the bottom of the trunk. Therefore, citrus trees grown indoors without enough air movement often require a stake to hold them up. Place a fan to blow enough wind across your seedling trees to cause them to flicker back and forth. This will give a strong firm structure to your trees. - Millet

I have lost a couple seedlings that I had in small pots-- I had them under a shop light with a bunch of annuals (tomatoes and peppers) but without heat-- so even fluorescent lights can cook the leaves when they are close and the roots are unheated.