Really, exactly how much experimentation can you do on your adenium before it actually keels over and dies from repeated assault?
Actually, quite a lot. There are many ways to grow the seedlings; it really all depends on what look you want to produce. You can grow them large, keep them compact or just see what they grow into, given basic plant care.
|The actual seedlings, sans tail.|
You can usually tell very early if a seedling is going to turn out well. The one on the left, for example, is only 6 months old with its trunk already two inches wide even though it was grown in what could be considered normal care. It is in a pot of 50 percent potting soil and 50 percent perlite, watered when the pot is very light and fed once a week at half-strength. Within five months it had outgrown its first pot and had to be potted up. It has never been pruned.
Meanwhile, the one in the middle is 2.5 years old, grown in the same half and half substrate with regular watering and feeding. It has a substantial trunk but was kept short with regular pruning, to encourage branching. In the winter, it was kept lit inside the house where night temperatures did not fall below 16C at night. It slowed down growth but did not entirely stop.
On the other hand, the third one on the right is also 2.5 years old, grown very hard in the 5:1:1 mix. It received only occasional and irregular watering in summer and whatever it got when it rained. When it was first moved into the 5:1:1 mix, it took this seedling most of the growing season to adjust, failing to sustain more than six or seven leaves at a time. Growing hard also means this seedlings was artificially lit in winter but not warmed. This one and several others under the same treatment, stayed semi-dormant on a shelf where temperatures ranged between 10C to 16C. The leaves only started growing more vigorously on their second summer. By this past summer, they have fully adjusted to the 5:1:1 mix, growing heavy foliage while staying compact.
Now, what this shows is that different cultivation methods produce radically different results in adeniums. Among all the factors that affect growth, the strongest, most rapid response is to temperature and light. Withdrawing fertilizer and water will not bother them for a very long time but persistently low temperatures will
Down to Earth
|Adenium seedlings in the ground since May 2015|
In autumn, they will be dug up and transferred back into pots for more indoor misery. If they survive the winter, they'll go back in the ground.
For a lot of growers, adeniums are all about the flowers and only secondarily, the caudex. For me, though, they're all about the caudex and the roots; the flowers only need to be tolerable.
My first experiments with roots involved putting plastic discs under them, cut out from various deli cups. The roots did grow horizontally over them (they had no choice); but then wrapped around underneath and formed something that looked like a death grip that reminded me of Ripley's baby alien. So I took the discs out and put lava rocks under them instead. They're still in their pots.
This root experiment below was suggested in this forum thread. The plan, basically, is to spread the roots out quickly and evenly by slicing everything off.
First, pick a seedling at least a year old. Dig it up and clean it. The one picked for this experiment had only just been pruned.
Mark the soil-line on the seedling--where the dark exposed skin meets the pale part buried under the soil. Then, with a sharp box cutter, slice slightly below that line so that you have at least half a centimeter of gradually-darkening skin left. This will be under the soil when you repot it.
When dry, this is what it should look like. The edges should slightly fold in and the glue should feel thoroughly dry to the touch, covering all parts of the exposed area.
Now, prepare your substrate of 50 percent potting soil and 50 percent perlite or pumice. It is better to use a clay pot because it is rigid and the whole set-up will move less. Hard plastic is also good, just make sure it is stiff enough to keep the soil steady.
The original experiment in that forum thread also used discs. But I already know how that turns out so I opted to use a Christmas ball instead, to make the roots grow less death-grip-ish.
Fill up the pot to near the top of that ball, place the seedling flush on the surface and continue filling it up with potting material up to about a centimeter of the stem is covered.
If you have a lot of seedlings to experiment with, you should definitely try grafting. The process is the same (you can read this post) except easier because you are working with young plants and they tend to respond faster.
It is usually better if you pick a seedling that is at least half a year old. Most growers wait until the seedlings are a year old before they do this, usually until they have bloomed at least once just to see what kind of flower it produces. Growing these plants from seedlings is largely a crapshoot--you know you're sowing a certain cultivar but whether it produces the flower you expect is wild guesswork.
So if you do not mind sacrificing a seedling of unknown bloom potential, then by all means, graft away.
There is one difference between grafting on an adult plant and grafting on a seedling, however. Seedlings will tend to be more aggressive trying to push new growth below the graft point. Going forward you may want this new growth, if only to see what flower that produces if you haven't seen it. But do not allow the stock growth until you are absolutely sure your graft has successfully taken. Otherwise, your grafted scion will have a harder time competing for energy with the natives. As in human societies, taking over a territory necessitates killing the natives to ensure your success. It's a total dick move.