Hardening Off Indoor Veg Plants: What LED Spectrum/Intensity Allows Direct to Outside

Douglas.Curtis · Jul 14, 2019

Anyone who's moved indoor plants to outdoor knows what I'm talking about. The sun is a different spectrum than most indoor lighting, and making the transition from indoor to outdoor can be rough. Especially rough in some of the less comfortable areas of the planet.

What spectrum and intensity of LED lighting will harden off a cannabis plant indoor? The proper set up would allow moving these plants directly outside with minimal to no shock or damage.

I ask, because I have moved other plants from indoor to outdoor, without hardening off. They came from under intense LED lighting, but I have literally no hard data on what happened.

Grnhlthnhapyns · Jul 14, 2019

I would imagine a major factor in how well a plant performs outside is dependant on how strong and healthy its been brought up to be indoors. My opinion leans towards maximizing root strength and volume (myself using a soil I try to maximize the lively health of the root one as insurance when the forces of nature are at play and not so plant friendly..

Whats your latitude and altitude like? Maybe playing a role in transitions of plants behaviour from in to out.

Are temps (day and night / highs and lows) extreme?

Are the plants significantly structured inside before they go out? Strong stems /stalk,

fans blowing indoor? Stress reducing feeds(fulvic/ humic acid) good balanced supply of macro/micro nutrients all the time?

What about some sort of semi sheltered environment in your transition stage? Makeshift frame greenhouse? Shed to ease your plant into becoming adjusted to a new environment? Hope you find a way for them to thrive

Grnhlthnhapyns · Jul 14, 2019

I chimed in because from my cfl Rubbermaid 'incubation' grow box I start seedlings on a 1L water bottle. Move them nder my
Timber 3VL 3500k
PPFD: 912 μmol/m²/s to get bigger.
Been moving stuff outdoors at 43degree lat with 2 days of slight droop before they reach for the sunshine

Douglas.Curtis · Jul 15, 2019

Yes, the healthier the plant the more quickly it adapts to the lighting change. When it's healthy enough, temp/RH changes are much less stressful than spectrum. I'm looking for the data on what's needed to allow a 3-4' plant to be moved without stress.

I guess a good place to start would be the maximum IR and other spectrum levels available outdoor. Anything adapted to this should jump when put in milder conditions, no?

PDX Dopesmoker · Jul 15, 2019

I had success with keeping the formerly indoor clones in the shade outdoors for 5 days before letting them get into the sun directly.
Maybe you can go directly into the sunlight if you trim some foliage? I haven't tried that.

xxPeacePipexx · Jul 16, 2019

Ultraviolet light is what burns plants that are not hardened off even with greenhouse grown specimens and the roots often can't keep up with the changes in environmental stress during hardening. So I don't think that with even the brightest of LED and spectrum one could completely make this fool-proof omitting the process of hardening.

Noonin NorCal · Jul 16, 2019

I agree with PDX. Give them 4-5 days on the side of your house or wherever it gets some sun and shade too

Noonin NorCal · Jul 16, 2019

If you go straight to outdside from inside, they will get blown around and not be happy at all

OG_NoMan · Jul 16, 2019

My personal experience... I have them under a 315 cmh and put them out between 1-2 ft tall. They go in a spot that gets about 3 hours of morning sun and then a splattering of direct sun the rest of the day. Ideally I would leave them in this spot for 2 days then into the garden under direct sun. I had to speed the process up this year and the one batch only had a day then into the garden with no problems. IMO you need high light intensity right before they go out and it isn't as stressful when they hit full sun. Another option is to plant when it will be a bit rainy for a couple days and they should acclimate fine :tiphat:

troutman · Jul 16, 2019

My hardening tip: :tiphat:

Place your plants in a totally shaded spot outdoors for 4 to 7 days before exposing them to full sunlight.

CannaRed · Jul 16, 2019

I asked HydroGrowsLeds this question about their lights.
They said you don't have to harden off with their lights.

I can't tell you if it worked or not because it was cloudy here for days.

Talk to HydroGrowsLeds he's helpful with info

ambertrichome · Jul 16, 2019

Solacure 32w Flower Power bulb is the strongest UVA/B light available. 20+ times stronger vs Arcadia 54w Desert Dragon bulb, which is the most powerful Reptile bulb, but for precaution sake, I still wouldn't put them directly into full bright sun. Many times you only get 1 chance, and why not just suck it up, and gradually introduce them to high UVA/B

When its known that its going to be cloudy for several days, that's the perfect time. Showers don't hurt either.

Douglas.Curtis · Jul 17, 2019

CannaRed said:
I asked HydroGrowsLeds this question about their lights.
They said you don't have to harden off with their lights.

I can't tell you if it worked or not because it was cloudy here for days.

Talk to HydroGrowsLeds he's helpful with info

This is interesting, ty.

Douglas.Curtis · Jul 18, 2019

I directed them to this thread... I don't quote PM's, so you'll have to ask them what their reply was.

UV for sure, Infra red possibly, say a board which can be turned on, and slowly dialed up in strength for 3 days? I'm guessing seasonal spectrum changes would be a minimal issue.

Koondense · Jul 19, 2019

Cloudy days or partial shade will do the trick.
I usually veg(not seedlings) under mixed spectrum led bulbs(3000+6500K), with around 30w/sq ft and have never had problems when transplanting outdoor.
I think the problems come from lightning with reduced spectrums like hps or purple leds mostly.

Cheers

Douglas.Curtis · Jul 19, 2019

Though I appreciate all of the hardening off information, I really do, the thread is about LEDs and not having to harden off.
:thank you:

ambertrichome · Jul 20, 2019

NO way Id trust the UVA/B to be strong enough from LED to harden my plants. IMHO, even using the most powerful UVA/B bulbs ( Solacure ) you will still risk burning them if you plant them in direct sunlight.
Shade, putting them out when its cloudy, and light showers is my recommendation.

But theres just no way Id trust any bulb to harden my plants vs the sun.

Douglas.Curtis · Jul 20, 2019

ambertrichome said:
NO way Id trust the UVA/B to be strong enough from LED to harden my plants. IMHO, even using the most powerful UVA/B bulbs ( Solacure ) you will still risk burning them if you plant them in direct sunlight.

Interesting, it may very well turn out there isn't a way with LEDs (at least not yet). Perhaps all we can do is reduce the time. FWIW, it's actually not so difficult to replicate the sun UV/AB when you're quite close to the plants. Plants burn easy when you bring the Solacure lights too close, yes?

ambertrichome · Jul 20, 2019

Solacure will Totally Fry them if to close. Will make them totally crispy critters dehydrated, like a raisin that been in Death Valley for a week.

It also takes a special type of very very expensive glass to transmit UVA/B correctly.

At 32w, the Solacure is 20x-30x more powerful that the Arcadia Desert Dragon Reptile 54w Bulb, which is the most powerful Reptile bulb made.
Solacure is also made to be plant specific vs for Reptiles.

These bulbs will blind you like tanning bed bulbs. We run them 8 hours out of 12, and never more than 8 hours in veg, as its simply not necessary, and can probably get away with less than we use.
In 12-12 we let the lights come on for 2 hours, then the UVA/B comes on for 8 hours, and then OFF for the last 2 hours of the light cycle. We work with the plants during these times. Plants in nature usually don't get anymore than that.
Solacure recommends 1 x 1000w HID, or equivalent, and 2x 4 foot Bulbs for every 4 x 4 area. 24 inches off the canopy. Any closer reduce time exposure.

'Boogieman' · Jul 20, 2019

I take them outside for a hour or two in the sun every day, starting when they are seedlings. Then in late may I transplant outdoors and never had problems.

Hardening Off Indoor Veg Plants: What LED Spectrum/Intensity Allows Direct to Outside

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