Yellow Flowers (also called "Cragwood Flowers") are cubic natural blocks consisting of dark green small leaves with yellow flowers embedded in them.
These flower blocks can be found in many biomes, but mainly Woodlands and Forests on Cragwood-trees amongst and on their Cragwood Leaves. Yellow Flowers can occasionally be obtained from Leafies, Night Leafies and Night Twiggies too. Additionally to that, they can often be found in Wood Treasure Chests that randomly spawn on the surface at night-times in dark places.
The actual flowers on this block glow softly in the dark, which makes them well visible at night, but they cannot illuminate their surroundings.
These blocks of flowers "regrow" on Cragwood Leaves and can also be multiplied by placing and collecting them again. Yellow Flowers can be placed into the world as cubic blocks just like they are, but are able to (rarely) make aggressive and non-aggressive Creatures spawn.
They are flammable (but no Fuel) and can be used as a crafting ingredient for some recipes in the crafting menu and/or can be placed as decoration or even for building purposes. Yellow Flowers can be processed into Yellow Pigment in a Processor without requiring a crafting recipe.
How to obtain
For one thing you can gather Yellow Flowers from naturally occurring Cragwood trees in Forests, Woodlands, Grassland, valleys between Mountains, but also growing in a small bush-like shape in Canyons and Savannahs.
These trees are part of any newly created Creativerse game world, since they are fixed elements of the prefabricated template worlds that every newly created Creativerse is a copy of.
Since the flowers on this natural block glow faintly in the dark on Cragwood trees, this makes them easy to find, even when it's night ingame.
For another thing, Yellow Flowers can also occasionally be obtained by killing or pet-harvesting from Leafies, Night Leafies and Night Twiggies. While Night Twiggies can usually only be encountered at night in Woodlands and neighbouring biomes, common green Leafies can spawn in many surface biomes on, under or next to tree Leaves, and Night Leafies will often spawn at night at these same places - on or around tree Leaves.
You can also "grow" Yellow Flowers by placing Cragwood Leaves into the game world in suitable biomes (not too hot, too cold or too high up). A certain minimum number of Leaves blocks is required to make Yellow Flowers grow though.
You will usually have to wait for a few (real time) days until you can collect one or two Yellow Flowers every couple of days or so. Also, staying close the area where you've placed the Cragwood Leaves is recommended since it seems to speed up the growth of Yellow Flowers. The same goes for Wildwood Flowers, Blue Flowers and Red Flowers; not for Autumnwood Flowers nor Weepwood Flowers though.
No more whole Cragwood trees are added to the world after world generation (they do not grow by themselves), but these trees can be grown by players from Cragwood Saplings and will usually feature a few Yellow Flowers then. You can place several Saplings next to each other (like 2x2 for example), which will occasionally cause a thicker and larger tree to grow from this arrangement, naturally providing more Yellow Flowers then.
Please note that trees will only grow from Saplings in fitting environments. Grassland is often not a good place to grow them, but Woodlands and Forests are. Cragwood trees can be grown on Grass blocks or Dirt blocks on the surface under open sky; different to ingame hints they do not even require any moisture nearby.
Cragwood Saplings can be fertilized by Pigsy Droppings, but only if the Saplings aren't fallow, because in this case no tree will grow from them at the chosen spot anyway. If Saplings are placed into unfit areas, they will not start to sparkle and stay fallow. The word "fallow" can be read written in red letters when pointing your crosshair cursor at the Saplings that do not sparkle.
Yellow Flowers can also often be found in Wood Treasure Chests spawning in the night on natural blocks on the surface in unlit spots.
However, the fastest method to obtain more of Yellow Flowers is to place blocks of these flowers on the ground and pick them up again - once in a while you will receive 2 flower blocks at once when doing that.
How to use
These flowers can also be used as an ingredient in Basic Health Potions, Stone Mining Cells, Taming Collars, Golden Potions, Speed Potions, Heart-Shaped Boxes, Candy Skull Statues, Grumm's Temple Garden and in other such crafting recipes that will accept any type of Flowers in your crafting menu (to be opened by typing "Q" as the default key).
Yellow Flowers can be placed as building blocks too, since they have a cubic shape. They can be fully rotated into all directions by pointing your cursor at them, then pressing and holding R (as the default key) and then moving the mouse while holding down the left mouse button. The chosen rotation angle can be "locked" too by simply typing "r" while looking at an already rotated block or item, so that all flower blocks of the same stack in the chosen quickslot will then face the same direction when being placed.
However on top of these natural flower blocks non-aggressive ordinary green Leafies might rarely spawn during the day, and rarely possibly also aggressive Night Leafies during ingame-nights in darkness.
Since Yellow Flowers glow only faintly and will not illuminate their surrounding even a bit, they cannot be used as a light-source.
Yellow Flowers can be put on display in display containers like Placemats, Stone Wall Shelves, Hidden Temple Altars, Galactic Grav-Chambers, Frozen Containers, Holiday Decorative Trees, Snow Buried Containers, Wood Planters, Flower Pots or the like, where they will be displayed in a smaller size and won't be able to spawn any Creatures. Anything that is placed into slots of display containers cannot be rotated.
Yellow Flowers can be processed into Yellow Pigment in a Processor. No crafting recipe is required for this. Simply carry blocks of Yellow Flowers in your inventory or quickbar when activating a Processor in the game world by pointing your cursor at it and clicking your right mouse button or typing "f" (as the default key). Then you can click on the icons for Yellow Flowers in the list of "processable" items in the left window in order to move them to the slot of the Processor.
Yellow Pigment is used for crafting Yellow Beacons, Yellow Lamps (Wood Burning Lamps emitting yellow light), Yellow Fireworks, Yellow Stained Glass, Yellow Beds, Yellow Concrete, Yellow Mosaic Tile Wall, Yellow Adobe Floor, Yellow Adobe Roof, Yellow Adobe Wall, Yellow Carpet, Yellow Wood Wall, Golden Swords, Golden Potions, Golden Wall, Banded Golden Wall, Studded Golden Wall and other items.
Attention: like nearly all plants and flowers in Creativerse, including whole trees, blocks of Yellow Flowers are flammable!
When placing Yellow Flowers close to (or especially directly above) torches or any other items with open flames or fiery blocks like Hardened Lava, then Yellow Flowers can easily catch fire and burn to nothingness in hot environments that make a heat meter show up, like Oceans, Jungles or the Lava layer, but also in much cooler Swamplands.
Placing several torches or heat sources with open flames next to each other can even raise the chances to set flammable objects like Yellow Flowers on fire. Liquid Lava or Fire Bombs will immediately burn Yellow Flower blocks.
If Yellow Flowers start burning, the flames are then able to spread to other nearby flammable blocks, even across gaps of 1-2 blocks on game worlds and player claims where the "fire spreading" option is enabled. This way a whole wooden building or forest (especially Wildwood, Weepwood, Parchwood and Shorewood) can burn down in the worst case.
Fire cannot be extinguished by using liquids, but it can be stopped from spreading by claiming the area and making sure that the claim (advanced) option "fire sim/spreading enabled" is disabled (by default). Fire Bombs will have no effect on these claims either.
It is also possible for owners of the game world (F2P players included) to toggle the spreading of fire on a whole game world in the basic world options ("edit world" and "disable fire spread"). Another option to stop fire from spreading would be to create forest aisles/swaths wide enough so that the flames cannot leap over.