When to Prune Seedlings?

[dbonsaiw]

How long after germination do you typically wait before the first pruning and can it be done earlier? All things being equal I would just let the seedlings grow to thicken the base, at least the first year. But I have these Vachelia Caven seedlings that are basically beanstalks. I planted the seeds on January 8, 2023, and as of yesterday some are over two feet tall already (by far the most aggressive grower I've seen). I've staked them best I could, but at this rate they won't fit in the grow tent in a few months and I will have a hard time bringing them back in next winter. Not to mention that watering is becoming a juggling act as I bring 8 of these up and down the stairs individually (I will likely need to change up that routine soon).

Plan is to grow them as long as I can. At some point, they will just be too tall and I'll have no choice but to prune em back. At that point, I'll trim them back as little as I can and wait for some trunk thickening before cutting low. Or should I figure out a way to keep them growing without a pruning (I can have the leader circle the tent like a root)?

Is Nigel Saunders on this site? I used his Acacia videos to scarify and germinate these and would love to ask him some follow up questions on his Acacia.

 

[Kievnstavick]

Speaking with some inexperience, but I figured I'd chime in.

In general, the "first" pruning begins when you are satisfied with the trunk thickness. Another first prune could be when you are doing clip and grow method with an out of placed branch.

Instead of pruning them, you could put some wire on them to get some interesting shapes while they are still young and easily manipulated. Doing so will give you more time before the plants overtake the grow light.

You could also just prune them to keep them short enough for your grow tent. Do remember that the more you reduce the folliage, the longer it will take to reach a desired trunk thickness.

For some context, I have done some minor pruning on my tropical seedlings (Over 1 year old at this point) in order to try and achieve maximum photosynthetic ability inside the grow tent. That is I pruned the seedlings with the intent of making sure other trees and the lower limbs recieved enough light to not abandon them. I also did a prune with the aim of trying to divert vigor into some weaker branches. My latest pruning was to control their height as they are growing too close to the grow light now and I am too lazy to adjust the shelf height currently. So I performed a slightly aggressive "chop" to them manageable.

Sometimes you have to perform some pruning due to circumstance or future goals, but the main idea is not to cut them until they are good and ready. Use your best judgement. If your fingers getting twitchy, then go get yourself another tree to play with in the meantime.

 

[eugenev2]

How long after germination do you typically wait before the first pruning and can it be done earlier? All things being equal I would just let the seedlings grow to thicken the base, at least the first year. But I have these Vachelia Caven seedlings that are basically beanstalks. I planted the seeds on January 8, 2023, and as of yesterday some are over two feet tall already (by far the most aggressive grower I've seen). I've staked them best I could, but at this rate they won't fit in the grow tent in a few months and I will have a hard time bringing them back in next winter. Not to mention that watering is becoming a juggling act as I bring 8 of these up and down the stairs individually (I will likely need to change up that routine soon).

Plan is to grow them as long as I can. At some point, they will just be too tall and I'll have no choice but to prune em back. At that point, I'll trim them back as little as I can and wait for some trunk thickening before cutting low. Or should I figure out a way to keep them growing without a pruning (I can have the leader circle the tent like a root)?

Is Nigel Saunders on this site? I used his Acacia videos to scarify and germinate these and would love to ask him some follow up questions on his Acacia.

I don't think there is a right or wrong answer on this subject, i would say it would depend on your goal, if thickening is the goal then letting it grow out is the answer.
But personally i understand the space limitations, i have seedlings and saplings that grow 6 feet easily in a year and due to space limitations have to cut them down, knowing that i'm slowing growth but unfortunately i have no other option.
Also be mindful when these finally graduate to the outside world as they together with their brethren Vachelia karoo are super invasive in the right climate

 

[ShadyStump]

Is Nigel Saunders on this site?

Technically, yes, but he hasn't been active in years. You might just comment some questions on his videos, and maybe drop an invite to return.

 

[Shibui]

The answer here is like so many other bonsai subjects - It depends.
It depends on whether the species buds from bare wood. Need to prune more on pines, etc that don't bud back well to maintain viable shoots to cut back to after the grow phase.
It depends whether you will be happy with large scars or can work out a way to disguise them. Many really high quality bonsai are developed more slowly with regular pruning to minimize cut scars.
It depends if you want speed above all else - don't prune until thickness goals are reached and hope you can salvage something from the results.
It depends whether you value taper in the trunk. I've found that pruning is the most useful tool to develop taper.

In my experience fastest thickening is not always the fastest way to a finished bonsai.

 

[dbonsaiw]

Thanks to all. I will let them grow as long as I can. If I indeed have a 12 foot tree at the end of the season I'll address it then.