In Creativerse, Cragwood trees can be grown from Saplings.
Other than that, two more tree Saplings exist: Ashenwood Saplings and Elderwood Saplings.
To obtain Cragwood Saplings, just harvest ("pull") blocks of Cragwood Leaves and Wood blocks from Cragwood trees, no matter if these trees are small and bush-like or majestic like in some Forests.
Eventually Saplings will be added now and then.
Cragwood Saplings will even appear now and then if you place blocks of Cragwood Leaves on the ground and then pick them up again. It can take quite long though, since the additional harvest will happen completely randomly.
However, Excavators of any kind will not yield any Saplings when used on Cragwood Leaves and/or Wood. Also, harvesting Corrupted Wood and Corrupted Leaves will not lead to finding any Saplings, even though they can be purified into Cragwood and Cragwood Leaves.
To make trees successfully grow, Cragwood Saplings should be planted/placed on (green) Grass or Dirt blocks. According to Playful, Saplings require moisture too, but tests did not confirm this. If you want to be on the safe side, simply place 1 block of Water or Mineral Water nearby.
In any case you can only grow trees on the surface with enough free space above and - most importantly - in a Biome that supports growing trees, preferably Woodlands and Forest.
Cragwood Saplings also won't grow on most other kinds of soil, like Mud, Detritus, Matted Needles, Canyon Floor, Rocky Dirt, Dead Grass, Savannah Grass, Sand, Sandstone, tree Leaves or Mold - if you try to plant Saplings on these types of ground, a message window will appear, telling you: "Item cannot grow on this block type.". Also, Cragwood Saplings won't grow on Snow Caps, even though Elderwood Saplings can.
Simply take a look at the Cragwood Sapling right after placing it. If it stays "fallow" (written in red letters) even after placing water nearby, you can just tear it out again; since no trees will grow at this spot.
You can plant 2x2 Saplings or even more of them together. Then a tree with a larger stem (4 blocks thick) might grow. Or maybe two trees on top of each other. The maximum size of player-grown Cragwood trees seems to be 4x2 blocks in width, but maybe you'll be able to grow even larger trees?
You can use fertilizer (Pigsy Droppings) on Cragwood Saplings to make trees grow 15 minutes faster (but you cannot fertilize "fallow" Saplings, since they won't grow no matter what). After that you'll just have to wait.
Trees you grow yourself usually will be of small height with a symmetrical shape. They might often not have any Flowers nor Beehives on them right away, however those can grow/spawn by themselves on any tree-top later on. "Home"-grown Cragwood-trees might not always feature Vines, and these also cannot grow later.
It will take ca. 15-16 RL-hours until trees eventually "sprout" from Saplings - unless they are "fallow" of course. It does not matter if you are online or nearby. Saplings will turn into full-grown trees instantly which you can observe if you're close at that moment.
It is possible to make Cragwood trees grow on other trees. It can even happen unintended when planting Saplings very close to each other. Also triple-trees or higher "staples" of trees can be grown deliberately by placing blocks of green Grass (or Dirt or Snow Cap) with Water (or Mineral Water) on tree-tops to plant your Cragwood Sapling there.
If you put Cragwood Saplings into Flower Pots, Wood Planters, on Wall Shelves, Hidden Temple Altars or Placemats, then the Saplings will not grow into trees there, but will merely be preserved and displayed for decoration.