I have one question and that is whether or not you think some varieties might not be able to take the amount of light on young leaves? Since I'm treating them all the same and watering the same. Or is it possible the ones that wither just have leaves but not enough roots and what they do have just can't take the heat I had them on so the watering I'm doing wouldn't help anyway?
I don’t think it matters by variety, but by the state of the plant itself. I usually do not put mine under lights until I am certain they have roots. This is because you need both roots and leaves to regulate moisture.
Very thin cuttings can lose moisture very fast. They also have a lower store of carbohydrates, so these can peter out very quickly with just a small amount of growth. They don’t gain enough growth fast enough to replenish the used sugars. They can die because of lack of strength or because of desiccation. Many choose to graft with these instead because they can get more water and nutrients from the rootstock than they can on their own. That said, I have had some great plants come from rooted small cuttings, so it is not impossible.
If you only have leaves, but no roots, the plant will lose moisture through the leaves. Sunlight, or strong grow lights, will cause the plant to put out more moisture. So in a case where I have some top growth, but not enough to indicate roots as well, I keep them bagged and exposed to ambient light only. You do not want darkness because you want the leaves to be able to do a little photosynthesis to get energy for root growth. I keep them bagged to help prevent moisture loss until they can get water from roots.
It’s only after I am certain that I have roots too that I remove the bag and turn on the grow lights. I realize that can be hard to know with a treepot. But there are indications to look for. Sometimes with bagged pots, you will see roots coming out at the bottom or even out the top because of the humidity. The top growth also will progress with roots. Usually if there are no roots, the top growth can happen to an extent but it is minimal and halts at a certain point. So once I see continual progression, that usually is an indication that there are roots too.
A cutting will eventually wither though if it never develops roots, even if it has a small leaf or two. There’s nothing you can do about that, it’s just what the cutting did for reasons unknown to us. It used up what little it had and didn’t have whatever it needed for roots to grow. It could be that it desiccated too much, it could have rotted, it could be that it was low on stored nutrients, or it could be that it didn’t have the hormones needed. The same is true in the opposite situation if you have roots but no top growth.
If you have roots, but no top growth, you want to lower the heat mat temp and expose the top to warm ambient air because it is the air temperature that will help to stimulate top growth. Without the leaves, the plant will not fully pull up water and nutrients from the medium. The leaves are what drive that upward pull and help to regulate moisture throughout the plant.
All of that said, you do need to be careful that your
grow lights are not too strong. This does not happen often, usually they are not strong enough. But if someone gets a professional grow setup with a lot of professional grow lights, it can be too intense for a young plant. Usually in a set up like that though, there can be something that lowers the intensity or that allows you to raise the lights up higher away from the plant.
You do need to watch the
heat level. Grow lights can put out a lot of heat. Usually, you can feel the light yourself with your hand to see if it is warm or even hot, this will give you an idea of what your plant is experiencing. I do put a little small temperature thing next to my plants so I can check it. I have some grow lights now that for some reason are really warming up one corner of my grow set up, and it was the thermometer that let me see the difference because from where I was, I couldn’t tell on my own.
Heat mats are usually only used to stimulate root growth. Once you have roots, you can turn it off completely if the ambient temps are warm enough. If they are not, then you can keep the mat on, but lower the temperature on it so that the roots do not “cook” from too much heat exposure. In a normal outdoors soil environment, the roots are kept cooler than the leaves which are exposed to warm air and sun.
Hope that helps! If I ran off in a different direction and didn’t answer your question fully, let me know.
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I take my rooted cuttings outside once low temps are consistently over 40-45° and any danger of frost has passed. I use my outside trees as a marker as well, if they are waking up and leafing out, it’s usually a good sign weather has become conducive to growing.
can't thank you enough!
