In Creativerse, some trees can be grown from Saplings with a bit of patience.
Currently (R23 since October 2015) three kinds of Saplings exist in Creativerse:
To obtain Saplings, just harvest ("pull") blocks of Leaves from Ashenwood, Cragwood and/or Elderwood; eventually Saplings will be added now and then. Since R26 you can now also obtain Saplings sometimes when harvesting Wood. Saplings will even appear occasionally if you place blocks of Leaves on the ground and then pick them up again.
To make trees successfully grow, Saplings should be planted/placed on (green) Grass blocks, not too far from water (place 1 block of water nearby). They won't grow on most other kinds of soil. The place has to be on the surface with enough open space upwards ("under sunlight") and - most importantly - in a Biome that supports trees, preferably Woodlands and Forest.
Grassland is not always advantageous for trees to grow, but this will also depend on the "neighbourhood".
Take a look at the sapling right after planting it. If it stays "fallow" (written in red letters) even after placing water nearby, you can just tear it out again, as this spot will not allow the Sapling to grow.
You can use fertilizer aka Pigsy Droppings on Saplings to make them grow faster (but not on "fallow" ones, as they won't grow no matter what). After that you'll just have to wait.
Trees you grow yourself usually will be of meager size with a symmetrical shape. They might often not have any Flowers nor Beehives on them right away, however those can grow/spawn by themselves in any tree-top later on.
Since R22 (September 2015) the growth-system for crops, saplings and queen bees now functions in real-time. "No need to be in-game for nature to nurture." It will take a few RL-hours (or as much as 24 hours) until trees eventually "sprout" from Saplings (unless they are "fallow" of course). Then Saplings will turn into trees instantly which you can observe if you're close at that moment.
It is even possible to make trees grow on other trees. It can happen unintendedly when planting saplings very close to each other. Even triple-trees or higher "staples" of them can be grown deliberately too by placing grass and water on tree-tops.