LED & Nutrient Requirements in Ficus

[hemmy]

Has anyone experienced nutrient deficiencies growing ficus under full spectrum LED?

On the tail end of my first indoor ficus season and hope to have to them all outdoors in a few weeks. But it was not without challenges!

Scale and whitefly were persistent. Soaps didn’t cut it and I had to use a neonictinoid.

I wasn’t acidifying my hard water or fertilizing until the last several weeks.

My largest are Ficus microcarpa mostly working on secondary branching. But I lost a lot of smaller branching on a F. microcarpa in a shallow box (red circle) and a F. benjamina in a bonsai pot (red circle). Both of these were the better trees and kept under the lights (300W, SE3000, Spider Farmer (back when they were slightly more affordable in the early Fall)). I would move the lights around somewhat, but I’m noticing that the F. microcarpa that gets the most light has lost color and branches (red circle). It also dries out quickly. The same variety ficus next to it in a large nursery can (blue circle) is a much deeper green with more leaves.

I have a hard time thinking the light intensity was too much for a ficus, but maybe I wasn’t keeping them wet enough for the higher transpiration rates. That combined with nutrient lock in the substrate from drying out and harder water.

I was hoping to get it corrected before they went out so I’d be more confident going into next Fall. But acidifying the water and weekly miracid hasn’t done much. Any advice is appreciated.

Cheers!

 

[Glaucus]

You have a light that was made to grow cannabis plants, who can take about the most light of any plants out there.
Ficus are shade plants. So how are you sure your light level isn't too high? Did you measure it?
Can you estimate the PPFD you are providing based on the specs and the dimming setting?
Your light can give them 1200 µmol/m²/s while Ficus spp. should be ok with 120 µmol/m²/s. That is a factor 10 too much light on the max setting at the recommended hanging height.

 

[hemmy]

You have a light that was made to grow cannabis plants, who can take about the most light of any plants out there.
Ficus are shade plants. So how are you sure your light level isn't too high? Did you measure it?
Can you estimate the PPFD you are providing based on the specs and the dimming setting?
Your light can give them 1200 µmol/m²/s while Ficus spp. should be ok with 120 µmol/m²/s. That is a factor 10 too much light on the max setting at the recommended hanging height.

Fair point and probably confirmed by the greener color of the ficus that is getting less light. I was going off a table of light requirements for various household plants (link below). It lists 3 categories, "Good Growth", 'Min. for Maintenance', and "Commercial Light Levels". The PPFD levels (µmol/s/m²) listed for Ficus benjamina are 160, 80, and 400-1200.

So I thought I’d be good at the 1100-1200 range. I did confirm the output with a phone app (which I know are crap, but it was recommended online as being the least crappy).

I have moved the light up higher last week, so we’ll see if that makes a difference. The ficus burtt-davyi which are much shorter and farther from the other light all look great. Although the Willow leaf ficus, also short, has been a lighter green all winter.

Post in thread 'Winter Lighting'
https://www.bonsainut.com/threads/winter-lighting.40016/post-997949

 

[Shibui]

Given the differences between trees close to the lights and further away sound like there's a good chance this is light related. My ficus always look a bit sad toward the end of winter. I put that down to colder temps. I also have problems with leaf drop if the soil stays wet through cooler months.
Why not fertilize through winter? These are tropical and grow all year round given reasonable conditions so they need nutrients all year round too. Even if soil pH locks up nutrients adding more will give free nutrients for the roots to take up. You may need to reduce fert when altering pH as that will usually unlock some elements and can occasionally provide nutrient overload.

 

[Glaucus]

It could be that Ficus can actually take the high light intensity. But if you have issues, I would go with the 'good growth' value. So the 160 µmol/s/m² for example. Staying below 250 µmol/s/m² seems smart. So being 4 times higher to me is immediately a red flag. Your canopy/most affected area might be getting above 1500 µmol/s/m²?
You can always give it longer days to get a DLI on the higher end, to try to optimize for more growth. But apparently even for the DLI, they like to stay below 15 mol/m²/d.

And even if a plant can take 1000 µmol/s/m² of light, it would also put stress on it in terms of CO2 and nutrients. It would be like operating a jet engine.
It would be easier to keep it healthy at a lower growth rate.

 

[Paradox]

I keep mine under fluorescent tubes (haven't upgraded to LED yet). One table has 3 tubes the other has 6. They are daylight 6400K, 32 watt bulb.

Lights are on for 14 or 15 hours.

I don't use a humidity tent.

I water them every day or every other day depending on their needs.

I feed them weekly when they are actively growing. They do seem to have a semi dormant/slow growth period in January and February.

I don't have the issues you are seeing other than they do get a scale outbreak sometimes while inside.

 

[MSGhero]

My trees and setup are much smaller (30-40% output on SF-1000), but it looks like your lights are too close. Is the heat managed, or are they getting hot in addition to likely receiving too much light?

Indoors fulltime, I fert weekly-ish in the growing season, and once a month or twice a month at lower doses during the colder months. My leaves drop around late Dec- mid Feb.

 

[Michigan Tree Murderer]

I have my ficus under a spider farmer SF1000D LED Grow Light, and I only see leaves that color on new growth. I did feed them once a month starting in Feb. I'm really impressed by the grow light, it's on 12hours a day in the winter.

Before and after of two .
TBF in Dec 2022

Same one a few days ago. The aerial roots fattened up.


F. microcarpa from Nov 2022


Now May 2023


I've trimmed them both several times over the winter.

 

[hemmy]

Is the heat managed, or are they getting hot in addition to likely receiving too much light?

Yes, I have a positive exhaust at the top and passive on the base of the other side. Plus a rotating fan inside to circulate air. I needed an oil heater this winter at night. Highs of mid-70s in winter.

 

[hemmy]

It must have been too close lights/intensity. I raised the lights 2 weeks ago and the yellowing one has gotten much greener. They should be outside soon but I’m low on full shade where the other trees are acclimating.

 

[ShadyStump]

Just conversation thinking of next winter: Ficus can take damn near anything. I keep my heart around 65F in winter because I'm broke and doing laundry is cheaper than the heating bills. The strongest light I have is about equal to the lowest setting on yours, and it's spread thin supplementing a north facing window. Never had issues with ficus.

Things to remember:
When you read the recommended height for the light, that's height from the top of the plants, not the base.

If you move them outside into full sun right now, you'll see a bit of sunburn, but then they'll bounce right back. Remember that ficus CAN handle full shade, but in the wild they're usually growing in the shade of other ficus that are soaking up all the sun they can get.

Just use osmocote or the like in winter. They can't really take more from it than they need when they're half asleep.
And they can take plenty dry conditions. You really only need the sort of setup you have if you're trying to keep them actively growing 100% of the time.

 

[leatherback]

Remember that ficus CAN handle full shade, but in the wild they're usually growing in the shade of other ficus that are soaking up all the sun they can get.

THIS