Intro.. this hobby escalated quickly!

[ShadyStump]

Your hibiscus will be ok with the humidity, but not the others. Brightest window you have. You'll hear people say they don't make good bonsai, but you can't beat waking up to those flowers on a winter morning, so go for broke. I've got a few of them nowadays.

Portulacaria Afra are technically succulents, so treat them like a cactus almost. Dry, hot air, water thoroughly, but rarely. You can actually just watch the foliage, and when you see it start wrinkle ever so slightly, that's when you water. And those things are impervious to sunlight. Come summer they'll be the one thing you won't have to worry about leaving outside and forgetting for a week. They also are about as easy to start from cuttings as anything in the world, so whenever you trim, or accidentally break it, just stick in some soil, water only once, then wait for it to grow into a new plant.

 

[ShadyStump]

I totally forgot about answering the actual question.

No, you generally don't put them in the pretty bonsai pots until they're more developed. Part of the function of the traditional bonsai pots is they're small so can restrict root growth, which slows top growth, keeping your tree in your chosen style longer.
While developing your trees, larger pots are preferred so they can grow freely and quickly.
Different species react differently, of course. Your p. afra could go into bonsai pots now and you might never know a difference. Your hibiscus, however, you might want to slip pot into something bigger to give them lots of room for the time being.

A thing to remember is these are tropical species that grow profusely in the summer, but sort of stagnate when the weather cools down. So these you'll want to work on in the summer when they're actively growing.
That said, p. afra are damn near bulletproof as long as they have plenty of sun and you don't over water. Seriously, let the soil dry out 100% between watering.
It's hard to over water hibiscus, but it is possible. Remember the chopstick trick.

 

[Sammy V]

Your hibiscus will be ok with the humidity, but not the others. Brightest window you have. You'll hear people say they don't make good bonsai, but you can't beat waking up to those flowers on a winter morning, so go for broke. I've got a few of them nowadays.

Portulacaria Afra are technically succulents, so treat them like a cactus almost. Dry, hot air, water thoroughly, but rarely. You can actually just watch the foliage, and when you see it start wrinkle ever so slightly, that's when you water. And those things are impervious to sunlight. Come summer they'll be the one thing you won't have to worry about leaving outside and forgetting for a week. They also are about as easy to start from cuttings as anything in the world, so whenever you trim, or accidentally break it, just stick in some soil, water only once, then wait for it to grow into a new plant.

Brightest window I have for the hibiscus, or the Afra jade? I've been keeping the hibiscus under the grow lights so far, since that's where the humidity is at. Indoors (as you know, being in CO) is pretty dang dry, usually 10-30%.

My wife and I gave out 2" tall succulents at our wedding 7 years ago, and we had some leftover. She's been the succulent master all these years, and they've turned into monsters next to a west facing window. I bet the Afra will do great next to these guys. I even think one of the succulents that has a couple 1" diameter trunks and is about 22" tall is also a Jade, wonder if I can use the bonsai shrink ray on it.

 

[Sammy V]

I totally forgot about answering the actual question.

No, you generally don't put them in the pretty bonsai pots until they're more developed. Part of the function of the traditional bonsai pots is they're small so can restrict root growth, which slows top growth, keeping your tree in your chosen style longer.
While developing your trees, larger pots are preferred so they can grow freely and quickly.
Different species react differently, of course. Your p. afra could go into bonsai pots now and you might never know a difference. Your hibiscus, however, you might want to slip pot into something bigger to give them lots of room for the time being.

Gotcha, thanks! The only follow up question about that, the hibiscus and jade (from Eastern Leaf) don't seem to be in bonsai soil, but more organic potting soil that doesn't allow great drainage. If I put them in bigger pots for development, should I use bonsai/akadama/pumice/lava blends or keep them in potting soil? I guess the root of that question (ha, unintentional pun alert! ) What's the rhyme or reason for switching from the soil they came in to bonsai soil?

 

[ShadyStump]

Yup, that's a great place for it.
And that is definitely a jade plant. Some people like to use those for bonsai too. Treat them just like the portulacaria afra.
P. afra is called dwarf jade because they have obvious similarities, but they're not actually related at all. P. afra is native to Africa, if you hadn't guessed yet, and also called elephant plant. Jades are south Asian.

If your hibiscus seem to be doing ok with the lights, then stick with it. I'm struggling with humidity in my living room, and it's definitely taking it's toll.
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So, the rhyme and reason of inorganic substrate vs more organic traditional soil.
There's a thing we call soil wars. They can be brutal.
I'll try to make it as quick and non-controversial as possible.

People grow plants and trees in traditional soil all the time, no problem. So long as you're watering PROPERLY - not just "enough" - there's rarely a problem with it. Don't panic, and don't rush into anything. Remember the chopstick trick.
That more organic potting soil tends to also be full of perlite, the styrofoam looking bits that are actually a type of stone. Why?
The inorganic hard bits help keep the soil from compacting and suffocating the roots. (Yes, roots need oxygen, even though that's not taught in 6th grade science.) It also helps with water drainage so your soil isn't a sopping swampy mess that will drown your tree. Organic matter breeds mold and fungus, and these can be helpful sometimes, but can also eat your tree's roots. This what's known as root rot.

When you're trying to get a relatively large tree to grow in a relatively small pot, you have to optimize conditions.
Now, with an inorganic, we'll draining substrate of proper particle size, it's virtually impossible to over water, and it lets air move into the roots.

There's a resource somewhere here from our own @markyscott, who is a geologist by trade, detailing the physics of soil and water interaction as it applies to bonsai in mind blowing detail. I'll try to link to it when I get a chance.

 

[bonsaichile]

Just wondering what you did with your trees tonight... it will be 8 degrees here, after some weeks of milder temps!

 

[Sammy V]

Just wondering what you did with your trees tonight... it will be 8 degrees here, after some weeks of milder temps!

Hi! Sorry I forgot to reply earlier. We were in the teens as well, so I put everything in the greenhouse box for the night. My garage is usually at least 50°, and with both grow lights on full blast and the doors closed, it can get up to 100° pretty quickly. I added a small fan that will kick on when the temp gets above my set range, and it works like a champ to bring it back down with cool garage air. I'm finding that having a bunch of options for lighting and temperature is helpful, and will just bring some of my (future) trees out into the sun during the day.

 

[Sammy V]

If your hibiscus seem to be doing ok with the lights, then stick with it. I'm struggling with humidity in my living room, and it's definitely taking it's toll.

It's doing great... dare I say, it even has some new leaves! I'd say I'm pretty much a pro at this point.
Except bugs. I found 1 aphid on the Hibiscus that probably hitched a ride on the tree. Killed it, and haven't seen any more, but I am seeing a bunch of spots on some leaves, and they're turning really bright yellow (independent of the spots, I'm not thinking yellow leaves is a Fall thing, since the leaves with spots are all the yellow ones). I'm hoping it's not burn spots, these seem to love being really close the grow lights. I haven't seen any new damage since I killed the one critter, but I think it's time to educate myself about pest control.

Great info on soils, thanks! That's my next dive down the rabbit hole (after pest control).

 

[ShadyStump]

The yellowing leaves may be normal, old leaves dying off to be replaced by new ones. The only reason to question that is the black spots.
I don't think they're from aphids. They usually feed at the base of the stem, or at the veins in the leaves. Maybe fungal from the original nursery, but I don't think it's too much to worry about.
HOWEVER, the aphids aren't gone, I promise. Just slow and hiding. Any reasonable pesticide should take care of them, but treatment like that can be problematic indoors. Over winter I go with the old school gardeners' trick of spraying with a strong tobacco tea. The nicotine is a neurostimulant that's toxic in high enough levels. Thankfully, the levels needed to keep aphids well under control are barely enough to make your kids or pets mildly uncomfortable for a couple hours.
About a cup of any cheap tobacco steeped in a quart of hot water. Filter well, add a drop or 2 of dish soap as a surfactant, and a few drops of alcohol to make sure any viruses or the like present in the tobacco leaf gets killed off. Spray the plant thoroughly from all angles. I treat mine about once a month starting as soon as they move inside for winter. February seems to be the big time for aphids to go nuts, so you'll likely wind up doing it every week or so.