?-Watering/nutrients acer palmatum seedlings under grow lights help

Sean Walker

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I have my sprouting seedlings in an equal mix of fine sifted peat, vermiculite, and perlite in very good draining flats. They are placed uncovered 5-7 inches under 5000 lumen led shop lights 24 hrs a day with a periodic fan on a rack in my forced air heated basement around 60-70 F.
Right now I’m only misting once a day not to drench just to top of dirt looking wet with a pump sprayer.

I am looking for watering frequency and amount recommendations along with when to start giving nutrition. I have a 5:2 kelp/humic mix I was thinking of using as a foliar spray. What about a “Root Rucus” type product?
 

Shibui

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Watering seedlings is the same as indoor plants and outdoor plants. Misting is not enough. It won't allow water to exchange air in the soil and won't allow the normal and necessary soil moisture fluctuations. It is likely to promote fungal problems in roots or above or both.
Check sub surface soil moisture to decide whether to water. Either dig the tip of a finger down 1/2" or keep a wood skewer or chopstick in the soil as a moisture gauge. pull it out to check before watering. Water only when the soil starts to dry but water well to saturate the soil right through.
Your soil mix has no nutrients in it. By the time the seedlings have their first true leaves they will be in need of nutrients so start feeding as soon as true leaves emerge for good health and growth. you can apply fert as a foliar spray but nutrients are taken up by roots so some of the fert really needs to be washed down into the soil to be properly effective. Kelp, humic and Root Rucus are all soil conditioners. They don't have much, if any of the basic nutrients that growing plants need. In soil they may stimulate some release of the required nutrients but your seedling mix has very little nutrient available to be stimulated. You should get far better growth rates by using a real fertilizer. It certainly makes a big difference to seedling trays here.
 

cbroad

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Sorry @Sean Walker, I was hoping cmeg could give you a little direction for feeding these. He's done a lot of research for seedling propagation indoors, mostly hydroponic, but there's some cross-over there I'm sure for soil.

Check out his thread about his adventures if you haven't already: https://www.bonsainut.com/threads/extended-season-starting-trees-indoors.39965/

Plus you guys are basically neighbors.
 

Bnana

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Fertilizing is simple, just give standard liquid fertilizer (with micronutrients) like you would house plants. What they don't take up will was away when the trays are draining.
 

Arlithrien

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In my 2nd year of growing maples from seed here's what I did:

Watering: Look into "bottom watering". I fill a shallow baking sheet with about an inch of water and set my seed tray in there for ~10 minutes to let it soak up until thoroughly wet. How often you do this will depend but I find every 5-7 days they need to be rewatered or saplings start falling over.

Airflow: Get a cheap desk fan on Amazon and keep air on your seedlings. Not too intense only enough to make them slightly sway in the breeze, supposed to strengthen and thicken the trunks.

Timers: I keep my grow lights and fan on timers. Fan alternates between 30min on, 60min off although this isn't a science. I aligned lighting time with the outside sunrise/sunset times to be safe at first but as they grew I gradually increased the sunlight hours. Plants need 6-8 hours of darkness a day so I maxed out the light hours to 16hrs a day.

Feeding: I sprayed the leaves with diluted liquid kelp every so often when they grew true leaves. I also used old potting mix my first time so maybe that has nutrients in it.

Transplanting: I waited until 2nd or 3rd set of true leaves before transplanting. I've read you can keep them in the tray for up to a year if you need to. I moved them into 4inch pots, surrounded the peat "plug" with bonsai aggregate and then topped it off with some fertilizer and moved them outside. They exploded in size after doing this. Some of my 1year old whips are almost 2ft long!
 
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Leo in N E Illinois

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A couple thoughts. Contrary to some opinions, after reading studies done at the Forest Products Lab at University of Wisconsin - Madison, For the vast majority of trees, 24 hours of light is "too much", it is wasteful. Increased daylength over 12 hours does result in increased growth, to a point. The magic number is 18 hours. Day cycles longer than 18 hours do not result in better or more growth. There is a "dark cycle" in photosynthesis, that does not require light. It does not require darkness, but it is the bottle neck for production of carbohydrates. THe health of the seedlings will benefit from having at least 4 hours of darkness per 24 hours in order to clear system of "backed up intermediate photosynthetic products". Plants do need a rest.

Item 2 - 5000 lumen is about equivalent to 1/4 to 1/2 outdoors sunlight. (much depends on distance from the plants where this is measured. Good enough quality to raise a wide range of trees. Here you can make up for low intensity by using the longer day length. But 24 hours is too long. Reduce day length to 18 hours. Do not reduce to match outdoor sunrise - sunset. You have seedlings, you want them to "think spring", want them to grow. Ideal day length for growth is 18 hours. Day lengths less than 12 hours are only used when trying to force dormancy. Less than 12 hours tells plants it is "winter".

Item 3 - fans. I keep a fan going 24 hours a day, 7 days a week. Even when ambient air is low humidity, the constantly moving air really helps to keep down pathogens, and insects. Results in healthy roots. And the moving air allows the leaves to be closer to the lamps without heat build up. Less issue with burning leaves if fans are on. Keeping fans on 24/7 will largely eliminate issues with damping off.

Fertilizer, yes you should fertilize after first true leaves become visible. I prefer dilute, but frequent. You do not have to be elaborate as CMeg1, Craig is over the top, near perfection in the way he grows seedlings. Commercial chemical fertilizers will work, a higher nitrogen number is preferred, I use a 12-1-4 with full complement of micronutrients. You can also go "organic", with fish emulsion and other organic nutrients. The kelp/humic acids are not fertilizer, but are very helpful. Do apply them the way Craig (@cmeg1 ) suggests. He's got it right.

Raising seedlings does not have to be complicated. I would never go through the trouble of supplementing CO2, carbon dioxide. You can keep it simple. The 2 biggest issues with out of season, or winter sprouting of seed is insufficient light, and lack of air movement.

Have fun with your project.
 

Pitoon

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24hrs of light is too much.......... 16hrs on / 8hrs off to replicate summer. Fertilize 50% dosage once first true leaves have harden off. But really not necessary, once you repot to put them outside give them a small dosage of osmocote and they will be good for the rest of the growing season.
 

cmeg1

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Sorry @Sean Walker, I was hoping cmeg could give you a little direction for feeding these. He's done a lot of research for seedling propagation indoors, mostly hydroponic, but there's some cross-over there I'm sure for soil.

Check out his thread about his adventures if you haven't already: https://www.bonsainut.com/threads/extended-season-starting-trees-indoors.39965/

Plus you guys are basically neighbors.
Thanks!
Busy couple days.
It is fun to check in though
 

Bnana

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Indeed 24 hours of light is harmful. The dark cycle of photosynthesis does not need darkness (but also doesn't need light). But plants do have a circadian rhythm and some processes occur in the dark. One example is DNA-repair.
Plants grow less with 24 hours of light, not better.

The light intensity you need depends on the species. But day light can be 100.000 lumen. That's not needed thankfully, 5000 is reasonable.
Measuring light in lumen does not really make sense in this context anyway, that's a measure how bright it is for our eyes. Two light sources that give the same lumen value on a leaf can have vastly different photosynthetic values. Often PAR is used for this, but that's pretty poor as well as it, incorrectly, gives all photosynthetically active wavelengths the same value. But for your bonsai, PAR is a reasonable approximation.
 

Sean Walker

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Good stuff from everyone! Very helpful !
I appreciate the time and knowledge you’ve given !
The lights are 6000k ish and I had read that is in a suitable range for JM’s
@Bnana I’ll have to read up on PAR thank you!
 
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Leo in N E Illinois

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Good stuff from everyone! Very helpful !
I appreciate the time and knowledge you’ve given !
The lights are 6000k ish and I had read that is in a suitable range for JM’s
@Bnana I’ll have to read up on PAR thank you!

As a long time orchids under lights grower, 5000 K thru 6700 K is great, good color temperature for growing a wide range of species. JM are shade tolerant, so the 5000 lumens is just fine if you run a long day length, I think 18 hours maximizes potential growth.

You have a good set up
 

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