Im curious too? I have never had too because I can never provide enough light for them. I hope all of you are ok these days. I can almost feel fall in the air. In fact, Lowe's already has their Halloween display up. I almost puked..lol

I knew better but I over-watered because I was busy and got bugs causing some issues, leaf drop and branch die back issues and noticed 5-1-1 burnup after a single spring to fall season outside, and then found a sort of range by putting spotlights aimed at the pots warming the rootstock. I did get growth using all artificial light. I definitely intend to pull pots and refresh pot bottoms with fresh 5-1-1 material, drench and spray, and watch the watering but I'd rather my spot light were on the plants not heating rootstock. I intend to try one tree in a northeast window unheated area that will stay in the 60-65 range and see if I can kind of dormant it through. But whoever is using heat mats with success would love to hear from you.

I'm not an expert at this, but I dual use my lights and pads... for plant maintenance and seed starting. I have two triple band UFO lights that I hang aerial. 4 Costco 4ft LED around the sides. I put a reflectix house around the lights. And I have 5ft heat pads from hydrofarm that I put on raised plywood platforms that the plants sit on top of. If you buy your 4ft LEDs at HD or Lowes, you can mix them so you have different light bands, not quite as balanced as a UFO or specific grow light, but better than my purchase of all the same from Costco. My citrus and tropicals get the light (and heat as necessary). Then in very late winter, some plants move way to get garden seedlings started. I got my first heat pad and UFO for seed starting eons ago, before I got the citrus bug and now, it's a money pit (worse than boating) LOL.

I use warm water and I insulate the soil surface from heat loss. This seems to work. I also keep my plants 3 feet or more off the ground

Fruity Paws - thanks for the heads-up about the longer heating mat! I have one of those in a smaller size that I use for seed starting but didn't realize they offered the longer one! And I would think for this particular use, some type of rheostat (or better, thermostat) for temp control would be needed (and they do have those). The one nuisance I can see with these however, is watering since although they are waterproof/resistant, it would be the matter of working out a routine to lift the tree off the mat to water/fertilize/drain and then move back to the mat. For the smaller trees, doing that would be easier and this might also be good as a way to get them better established in a smaller soil volume. As the tree ages and is up-potted, I would think the larger volume mitigates some of the temperature swings and the mat might might not be as necessary.

I think I just realized what I could use to put the mat on and make it easier to water - metal wire closet shelves. I have a long one (6ft) outside that some of my trees are sitting on and could consider getting a shorter one (4ft) for inside under my light structure in the basement. Place mat on that, trees on mat, and would just need to slide the mat off, irrigate/fertigate, drain, slide the mat back on without having to do too much moving of the trees.

I have a small greenhouse I keep my plants in over the winter. It faces south so gets lots of sun. I keep the thermostat set to 50° - 52° in the winter, but during the day the sun heats it up a lot. So far, I haven't noticed a lot of leaf loss in the winter.

I'm approaching the point where I don't have more room for Citrus (need room for cactus and succulents, after all) so I'm eyeing a rather large square LED light my son has (and isn't using presently).

During winter I've set my pots on top of a brick or two inside of a individual plastic washbasin of sorts, keeps pot dry and I let the excess water slowly evaporate for humidity, a nice time saver not particularly attractive but its a basement. However, would those extra distances render a heat mat ineffective or would the warmer wash basin warm the water and brick and ultimately the roots in pot..............I've also seen people do the pot wrap

Jenny_in_se_pa and Bklyn citrus - I put the thin washer/dryer white plastic pans on top of my heat mat on top of my plywood platforms. The thin plastic conducts heat fine and keeps water in. Bricks are too big will prevent any significant heat transfer. Normally pots sit directly on the pan. But when I do a full flush, I will raise the pots on small plastic 1/2 shims. Let the plants drain and collect the fertilizer salt water in the pan - that then gets dumped into my garden. The excess salt and any fungus or bacteria goes outside. If you let your fertilizer salts, fungus, and crud collect and evaporate, you have to really scrub the pans in the spring. Think of the hard scale that builds up on your glass shower doors.

While heat mats sound like a good idea, I've found that for very small plants, mats end up causing the plant to dry out fast. When the soil temperature is higher than the surrounding air temperature, it causes water loss (this is similar to the phenomena of freeze drying). It ends up creating a lot more work to more frequently check on the plants and make sure there's enough moisture in the soil.

I've had better success putting them in a humidity enclosed little tent and then warming the entire surrounding air. This doesn't cause drying out because the area inside is relatively small and the air already saturated with humidity.

Maybe mats make more sense for areas outside or in a greenhouse that have higher levels of humidity or moisture in the air. Even seed trays with a covering over them, warmed by a heat mat, need to be checked periodically (every 2-3 days) to make sure the soil hasn't dried out.

Last year, I had the citrus pots that were in the basement balanced on some large river stones in their saucers and then the saucers were sitting on some plastic boot trays that were placed on a couple layers of 6 mil plastic laid on an indoor/door rug (the finished part of the basement where this setup was had laminate floors). A humidifier was then plopped in the middle of the reflective structure -

Before -

With citrus -

When Steve mentioned using a wet vac to suck air through his pots, that gave me an idea for using it for a different purpose. So I ran out and got a 1 gallon one and used it to suck out any excess irrigation/fertigation from the saucers and then could discard it (there is a stationary tub in the part of the basement that has the washer/dryer).

In the upstairs area, I had the trees, in their saucers propped on river rock, each sitting in one of those HD concrete mixing tubs (medium sized, which are 20" wide by 27.5" long) that I saw Evan recommend in a post, and that was propped on a boot tray that was placed on 6 mil plastic (the floors there are laminate as well) -

I eventually added my Tango mandarin to the above setup.

Like the basement plants, I could use the 1 gallon wet vac to suck out any excess liquid from the saucers and discard.

So if I could actually run the mat under those light-colored trays and sit the trees on that and they can get some heat that way, that might be an option. It's hard to find some of those larger white dish tubs though and I'm not sure if the 14"ers would fit in them but they might.

socalolympia - you had posted before I posted above... If I ever did decide to go with a heat mat, I would definitely get a thermostat to go with it and then along with a soil thermometer, the temp could be adjusted to correspond with the air temperature.

As for humidity, my setup in the basement had a humidifier that kept the humidity at around 50% around that structure. With too much humidity though, the fungus gnats have a field day and a party! lol

points to ponder

A simple set up for heating citrus roots. Seedling mat and thermostat available on Amazon. Hooks available from Lee Valley Tools.

Look for seedling mats that have a higher IP rating and reinforced power cord.

I am with Al on this one.

Steve

Brooklyn,

I use heat mats but for rooting plumeria cuttings. I have several of Ipower brand and they last and last. But they do tend to dry out smaller pots.

To heat, or not to heat: that is the question:

Whether 'tis nobler in the growers mind for citrus to suffer

The slings and arrows of dormancy,

Or to take arms against a sea of troubles,

And by opposing end dormancy? To die: to sleep;

No more; and by a sleep to say we end

The heart-ache and the thousand natural shocks

That citrus indoors is heir to.

Well, I did find a goldilocks range at some point, by shining lights right on the rootstock at base of pots ( a PIP suggestion) and some growth and blooms in winter. I do not have that truly sweet 50 to 60 degree spot with low natural lighting available to imitate a mild Citrus winter, although I'm going to trial one spot with a northeast window in an unheated hallway which leaves me in the 62 night at worst to 70 degree day range, I'm 100% artificial for winter in a basement away from any windows....so technology has to be the answer here and heat mats kept on a low setting may help...again maybe trial one or two

For lemons and limes, the time from bloom to edible fruit is in the range of 6-9 months, oranges take 9-12 months and Grapefruit take 14 months. If you live in a Northern growing zone you can bring the citrus in and enjoy beautiful fragrant blooms but you will never be able to bloom, set fruit, and wait for a ripe harvest in your living room when the plant is getting marginal light for 9 months. Blooming and fruiting is dependent on sufficient light and heat. Citrus trees in a dark or shaded window space may produce foliage but not even flower. If you do not have a bright (preferably South facing) window, skylight or greenhouse, you may need to supplement indoors with grow lights (you need 3500-65,000 LUX for sweet orange or 4000-65000 LUX for Meyer Lemons). Citrus ideally require 50%+ humidity. If you are heating the leaves with artificial lights, your roots are cold, and your humidity is low, your citrus will have three major problems which will lead to WLD. You can't grow the top of the tree like Florida and the bottom of the tree like Buffalo. For best results indoors, I simulate California weather by providing a minimum of 8-12 hours of grow lights each day. You want to keep the leaf and root temperature within a moderate range. Where people have problems is when the leaves heat up in a window and the root activity has slowed down to the point where they can not supply enough transpiration of and nutritional uptake.

One thing that might catch some people off guard is the UV emitted from artificial lights. Some brands and types are worse than others.

If anyone is using T5 or LED Strip lights if you turn them vertically so they run from the floor to the ceiling the citrus will grow much better than if you placed them over top.

In my photo further up in this thread, that reflective structure (top and back using this material and sides using this) includes a fixture with a pair of 4ft long 54W T5s (6400K) and then I eventually had 16 spotlights (pointed from above, lower down, and within the center), with a mix of LED & CFL bulbs, that were a mix of daylight (6500K for CFL & 5000K for LED) & warm white (2700K for CFL & LED). The comparative lux in the center of the structure (measured from a lux meter) came out to about the equivalent lux measured for an overcast day outside on my a NE-facing patio at about 2 hours past mid-day. With the lights on (~16 hrs/day), within the center of the structure about 3.5ft above the floor (where I had a temp/hygrometer sensor hanging), the temp rise was about 7 - 10 degrees F over ambient. Soil temp (from a soil probe) with lights on, was ~68F. Didn't get chance to check soil temps with the lights off (ambient room temp with lights off was ~67F).

Due to the height of at least two of the trees, I may consider running the T5 vertically (the structure height was about 5.5ft), although the logistics of doing that with the unit that I have, would need some MacGyver tinkering. Still trying to decide which trees will go where in any case and may end up putting the shorter trees there and taller ones elsewhere.

I talked with the resident horticulturalists at a one manufacturer of T5HO lighting. He ran an experiment with citrus where one set up horizontal and one setup vertical. The vertical set up did much better as the plant had better coverage. They put one T5HO in each corner vertically.

Amazon has grow tents at a very reasonable price. The advantages of a grow tent is the increased humidity and the reflective light surfaces.

One thing that Steve had shown with some of this seedlings and grafts (including the bucket light) and that I found myself last year with positioning spotlights down lower on the trunk, is that you can wake up and/or accelerate growth on dormant and/or newly-sprouted buds in the area where the light is concentrated.

many different ways to skin a cat. personally, a grow tent ain't working for me, and the mylar seems a bit much too, hanging all over the place. Neither is strip fixtures running up walls. I like to enjoy looking at the damn things in winter unencumbered. A big factor for me is don't own to many. If I have a tree thats big enough I'm just looking to hold it and I intend to try a northeast window unheated spot for one, it may mean watering monthly but walking by daily to check for bugs. New lights going in today.

Al, you could not of worded it better !

Therefore, the reason I leave my trees to rest in much cooler temps when light levels are low.

I use 'heat mats' when starting seeds or trying to root cuttings.

Mike

I use an item used for beer making called a Brew Belt. Only uses about 20 watts of power and wraps nicely around pretty much any container.

https://www.amazon.com/Brew-Fermentation-Heating-Belt-1-Count/dp/B001D6IUB6/ref=sr_1_5?ie=UTF8&qid=1534786030&sr=8-5&keywords=brew+belt

Vapour Pressure Defecit

https://youtu.be/k5bb3lazp6A

When the stomata shut to prevent water loss, photosynthesis cannot occur since CO2 cannot be taken in from the surrounding air. Plant growth and yield will be slowed if this occurs too often. On the other hand, plants won’t thrive in an overly wet environment (low VPD), as this slows transpiration and can result in increases in disease outbreaks.

Leaf temperature is extremely important as it directly affects the VPD. The problem for most people growing indoors in the winter time is the sunlight and artificial light and limited humidity will put the VPD in a danger zone for citrus.

Everyone's situation is completely different and this is why you have to look at your humidity and temperatures (room, leaf, and root). VPD has to be set up differently for

Low Transpiration (Propagation / Early Vegetative Growth)0.4—0.8

Healthy Transpiration (Late veg / Early Flower)0.8—1.2

High Transpiration (Mid / Late Flower)1.2—1.6

Danger Zone (Over / Under Transpiration)<0.4 >1.6

Lemon Lime Orange - thanks for the video links. The guy who did the vapor pressure one is a piece of work! LOL

Ken - thanks for the heads up on that belt heater. What's even more interesting is that at that Amazon link, there were links to pad heaters including a 12" round one that could be a potential too (as an alternative to the rectangular ones), e.g., this. Amazing what stuff is out there!

Get ready for indoor growing. Handy tip of the day: 1 L Spray bottle for storage and mixing + Neem oil + chemical free dry disposable Lens cleaning tissue = excellent spot treatment of spider mites. Wipe on wipe off.

i put up additional lights yesterday 2- 2x4 ft 4 bulb LED light fixtures with bulb blends hanging from chains, so I have a 4 x 8 coverage area, but after thinking it over I decided to order that mylar jenny suggested for a backwall behind the lights and maybe sides, I still want the trees visible

bklyn - what I did when I hung that mylar is that I draped it at the back of my structure and hung it so that I could roll it up and clamp it out of the way to access those trees along the back (I had 2 rows of trees within it - total 5). The front was left open for the taller trees that didn't completely fit under the T5s. The structure was ~4ft wide and ~3 ft deep. The back had 2, 4ft tall x 4.5ft wide (as 3, 18" wide panels) foldable tomato trellises like these to form an openable "fence" along the back -

These were secured to the pedestals holding the T5 lights and allowed the mylar to drape down over them like a cabin tent -

Rear - mylar sheet clamped up -

I had pieces of 2ft wide "Infrastop" (similar to "Reflectix") reflective insulation hung along the sides.

my set up is right against a white wall so I have no back access, perfect to line the wall only using the mylar using carpet tape, maybe a side or two. I brought my stuff in early last year and learned a few lessons, applicable only to my basement which is technically a cellar with an 8 ft ceiling, it will never be bone dry humidity wise so thats a non concern. #1 don't overcrowd, #2 don't overwater - using warm water and vinegar on a 10 day cycle seemed to work best for me, #3 after you sprayed them before bringing them in, do it again twice, #4 anything not bearing fruit may get a pot pull because I had amazingly had soil breakdown in 5-1-1 in only 6 months......you can't control pots left out in the rain, microorganisms, etc., I had arrested dieback at some point and got all to grow, but lost two (never let a baby meyer fruit before two years old it forgets to grow)and ditched a few cuttings that made no sense. I don't want to be lifting things and unzipping things, I just want to walk over and look and if needed take action.

If the inside of your setup is already white then the mylar will not make very much of an improvement in reflecting light.

Many citrus rootstocks like Flying Dragon TF or Trifoliate perform poorly in high PH soil. To lower the PH some people use vinegar. I have tried it myself and had disastrous results. In the wrong concentration, it is an herbicide. In an experiment conducted at Swedish Agricultural University, it was found that addition of 24 % vinegar to a peat soil decreased the pH of the soil from 7.3 to 5.6. However, after 48 hours the pH values of the soil returned to 7.0-7.5.(David Hansson, personal communication).

I've heard mylar is about 95% reflectivity and flat white paint creeps in somewhere around 85%?

If pots outdoors are getting too much rain you can lay wood dowels across pots and cover pot with two half circles of plastic with a hole cut in the center for the trunk. Tape the two halves together. That will control rain. You have to make sure the slats of wood raise the plastic enough to prevent roots from overheating and to allow proper off-gassing of soil. Another way is to bend plastic in the shape of a funnel around the trunk so water runs off.

I second Ken's view. Difference between mylar and flat white is a few percentage points. Over the years I have tried many methods and eventually settled on just flat white. The biggest advantages are it is easier on the eyes (so you can enjoy the plants) and easier to clean (I use good quality exterior grade paint). Plus you can always paint over if need be. If you need to hang something to enclose - I prefer Panda film which is flat white on one side and black on the other side. You can attach grommets and hang them like shower curtains. They do not crumple, not make noise like thin mylar when brush past them and easy to wipe clean.

Thin mylar sheets are a pain. First year they are good but they crumple easily. They stain easily too (from over sprays) and not easy to clean. Basically they lose their reflectivity over time. Mylar sheets with thicker backing as posted above may not have this problem. I have not used those.

In my case, the floor is also white - actually a bit off-white ceramic tiles. Easier to clean too. The shelves are painted white too.

I try not pack plants too close for better air flow. I want to keep all plants accessible so that I get to inspect them periodically for pests. If needed I will prune the plants to improve air flow and light penetration. I still have too many plants and trying to get the number down.

I also have two fans on timers.

To limit the amount of water your pot holds with little to no effort, you can simply tip the pot at an angle and secure it in place by resting it against an object - Compare B to A to see how much perched water this simple operation removes. Figure D shows one of an infinite number of ways ballast can be put to work (when you're establishing the planting) to limit the amount of perched water a pot can hold. Figure E illustrates the effectiveness of using a wick, which can be added at any point in time. Or, simply make a soil that isn't so water retentive a rain shower is automatically a concern. Rain is better at flushing soils of accumulating dissolved solids than tapwater is because it is much lower than tap water in dissolved solids, and more often than not rain is slightly on the acidic side, which makes it better at removing/flushing carbonates from the soil. Lots of rain is like hitting the fertilizer 'reset' button - a good thing.

Al

I'll save a paint job, using some mylar for now which I need to do anyway for the time being. I have perlite & bark on standby, neem, fertilizer, spray bottles and insectical soap, etc. I'm getting ready , but I have an outdoor garden too

BKLYN I have a big kumquat and big grapefruit that is now blooming and setting fruit so I will experiment with heating both in an effort to keep some fruit over the winter. I'm lucky to have my all glass sun room dedicated to plants but it is unheated. My citrus winter well there but certainly couldn't hold fruit.

I found the mats posted above on Amazon so it will be here shortly. Let's see in the January 2019 pictures post and compare lol.