Since no one else seems to have tried this, I guess I'll be the guinea pig and post my experience here.

One week ago I filled my 6 slots with Ashe Juniper (AKA Mountain Cedar) cuttings.* A rooting gel was used prior to insertion into the Aerogarden, although the efficacy of doing so is debatable due to being immediately washed off. Wounds were not made. This may have been a mistake due to how woody the cuttings are. As of today, my results are as followings:

--4 of the 6 cuttings have experienced no change in appearance that I can see. No drying out or dying, but no hint of roots either.

--1 of the cuttings appears to me to be dead or well on the way. The foliage appears to be a darker green, as though dried out. This is also a logical outcome because in my experimentation I decided to leave more foliage on this one than the others, and it also has the woodiest stem. I think maybe my thinking at the time was that having a woodier stem would allow it to retain more moisture. But I think having a woodier stem actually caused it to not uptake enough water, and that combined with the extra foliage seems to have spelled its demise. This is one that could have benefitted from some wounding, if only to give a larger surface area to absorb water.

--1 of the cuttings has some small hints of root formation. It's so tiny that I can't say with certainty that it is the beginnings of root formation at all. It could just be a small shard of leaf material that got left behind. I don't remember it being there on previous inspections, but it's possible I just missed it before. I should know by next week for sure if roots are forming. This was the most tender / least woody of the cuttings, so it does makes sense that if anything was going to start rooting this fast, it would be this one.

--On a negative note, that same tender cutting that is possibly showing signs of roots also caught the first case of mold. Fuzzy area just above the water line. I brushed it off with a foam brush dipped in a solution of 2 cups of water and 1 cap of bleach.

I'll report again in another week.

* I now realize that this tree is one of, if not THE, most hated plants in the world. It is the cause of a great deal of misery due to allergies here in Central Texas. I did not know what the tree was when I decided to propagate it. Before you get on me about that, I actually thought I knew--I thought it was Arizona or Leyland Cypress, but I have since become about 100% sure that it is actually Mountain Cedar. This tree covers a lot that I purchased, and my goal with the cuttings was to propagate it to add more of the same tree to the property line of the lot where there is a bare space. Based on this tree already being ubiquitous in the area and being one of the few trees that grow in the soil there (caliche at about 6 inches), I will likely go ahead and plant any cuttings that do survive. I'm sorry if this offends anyone.

I have been wondering about doing something like this too. I have an aerogarden at work, but nothing is in it right now. I'm not sure the air stone is allowing enough air through (it has been dry for about 2 years, but seems to be very weak when I fill it and turn it on). I did a big version of rooting this way in 5 gallon buckets with big airstones a couple of years ago with tomato plants, but, like you said, they'll grow roots just about anywhere...

Okay, weekly update.

Essentially nothing to report. The tiny root formation that I thought I saw on one cutting is still there and still looks like a root trying to come out to me; however, it has not grown at all in the past week. Not even a tiny bit. So that leads me to believe that it wasn't a root after all. If it is, it popped out very quickly but then decided not to grow after that.

I just did a few things with the cuttings. For one, I reapplied rooting hormone to all cuttings. This is something I usually don't do--usually you don't have access to the bottom of the cuttings once you place them in the media, but with the Aerogarden you have constant access. Read some posts by a guy who has great success with cloning machines, and he says he does this, so I figured I'd give it a try.

In addition to reapplying the cloning gel, I also wounded (scraped bark) the cuttings that I felt were too woody to be likely to root as they were. On one of the cuttings, I made a split in the bottom of the stem, maybe one inch long. This is another trick that I read about for particularly tough to root cuttings.

So I'm two weeks in and essentially nothing has happened. Then again, I'm trying to root something that for all I know can't even be rooted at all. I searched around the internet and found some references to Juniper, but nothing about this particular species when it comes to rooting cuttings. I also read that conifers, if they do root at all, can take up to a year to do so.

One detail I didn't mention previously: I am currently supplying light 24 hours a day to maximize photosynthesis. I have also not added any nutrients to the water. My plan is that if roots do form, I will back the light down to 17 hours a day and add nutrients to the water. The theory is that once roots have started forming, less daylight will encourage root growth.

Any thoughts on the light plan? I'm having second thoughts about it. What does the science say on this? On one hand I'm told that photosynthesis is essential for root formation. On the other hand, I'm told that shorter days trigger a focus on root formation. That's where I came up with my current strategy. I've read a lot of people say they have had success with 24/7 light, but I've also read people saying don't do it.

Still no sign of roots on anything. In addition, I got some feedback on another garden forum that other people's attempts to root cuttings in the Aerogarden have not been successful. Since I have no pressing need to put anything else in the Aerogarden, I'm just going to leave them in there until something happens or they die. Changed the light cycle to 17 on and 7 off, and added the recommended nutrients as though they are regular plants. Basically settling in for the long haul now.

Probably won't update this thread again unless there is something significant to report.

Final update. I gave up on this experiment. After a month and 7 days, there was no sign of rooting. One of the cuttings appeared to be dead. As I came here and saw that my first post was only 5 or 6 weeks ago, I was surprised. I thought it was longer than that. I guess with conifers there is still a chance they could have done something later. But I needed the grow light from the Aerogarden, everything I have heard from others says the Aerogarden is no good for propagating, and I really had no practical use for these cuttings other than as an experiment anyway. I stuck the cuttings in a shady area outside just as a why not sort of thing rather than throw them out.

So in my opinion, the cloning machines out there that provide mist to the root area are worth the money because just water and an air stone is not going to get it done for anything other than plants that would root in plain water anyway.