Horned Melons are one of 4 types of Crops in Creativerse that are usually used for Cooking many different types of Food. These Melons can also be consumed directly for some Stamina bonus, or can be fed to Pets.
Other than that, Horned Melons can be placed on display containers, but not directly into the game world.
How to obtain
Horned Melons can be found on the ground of Jungle Biomes.
Since these Crops are pretty rare in the beginning, it is advised not to just consume the first Melon/s you find, but to process them into 2 Horned Melon Seeds (each) in the Processor, from which you can grow more Horned Melons yourself "infinitely".
Horned Melons are quite rare at first, but the longer you play on a Creativerse world the more of those will spawn. If players are staying somewhere close to Jungle Biomes it seems to increase the chances of Melons spawning there. Sleeping on a Bed to skip days and nights will not help speeding up this process though.
The "Pro" world option "more regrowth" should make more Horned Melons spawn in the game-world even faster.
Unfortunately, it seems that Melons cannot easily be made to spawn in artificial "jungles" made from Detritus, so to collect your first Horned Melon you will have to explore the Creativerse Worlds a bit to find Jungles and then cross these biomes a few times until Melons will spawn there.
You can use your Map and compare it with the maps of template worlds ( http://steamcommunity.com/sharedfiles/filedetails/?id=634088783 ) to see where the closest Jungle might be.
When Horned Melons are captured with a Capture Block, they will be captured in the shape of Horned Melon Seeds (1 Seed instead of 1 Horned Melon). This applies to Melons found in the wild in Jungles as well as to Melons grown on plowed land.
Melons cannot be bought as grown Crops with building kits for Blueprints, since they cannot be placed directly into the game world, but only into the slots of display containers. If display containers are captured as Blueprints, the building kits will not contain the items in the slots of the display containers. Instead, the display containers will show "ghost images" when the Blueprint is built.
How to use
Horned Melons can be fed to Pets just as they are.
Some Pets even prefer Melons as their favorite fodder, which is pretty convenient. Pets will only provide players with their best harvest when being fed their favorite type of Food after all.
Horned Melons can also be consumed directly to grant "Pro" player characters a small bonus of +20 to their maximum (possible) Stamina, but only +10 maximum Stamina for F2P player characters.
However, this is not an efficient way to use Horned Melons.
The better option is to use Horned Melons in order to cook even more useful Food like Melon Pie (grants poison resistance and +200/100 max. Stamina and is the favorite Food type of a number of Pets) or Melon Sandwiches (these will grant +200 max. Health and +200/100 max. Stamina) in a Cooking Station.
Melons can also be used as secondary ingredients for many other types of Food with a large range of different buffs in a Cooking Station.
The Cooking Station only provides 4 cooking recipes, but by selecting/inserting different ingredients, you can cook up to 36 types of Food with different positive effects (buffs) when consumed (either right click on the Food after putting it into a quickbar, or drag a stack of Food from the inventory over your character's portrait on the right side).
Horned Melons can also be put on display by placing them into the slots of display containers like Placemats, Stone Wall Shelves, Hidden Temple Altars, Galactic Grav-Chambers, Frozen Containers, Holiday Decorative Trees, Snow Buried Containers, Holiday Mantles, Flower Pots, Wood Planters or the like.
How to grow Horned Melons from Seeds
First place such natural blocks over a body of Water or Mineral Water, or alternatively place these liquids directly adjacent to each block of Dirt, Grass or Mud (like directly below for example, or at least corner to corner).
This can even be done underground in complete darkness and/or in a building, but not at too high altitudes, not in too cold nor too hot biomes/layers, and not too close to Swamplands or pools of Bog Water. In these cases, Seeds will stay "fallow" and won't grow. They cannot be fertilized either in this case, but can be picked up again.
Next craft a Plow and use it on the solid blocks of Dirt, green Grass and/or Mud to till them; they will turn into "tilled land". Then place Seeds on the tilled land with right-click from a quickslot just like you'd place any block.
You can, but you do not need to fertilize Seeds in order to make your Crops grow faster. You can also fertilize Seedlings (the second growth stage of Crops) alternatively - but you can only use fertilizer once on any Crop, not twice (so either Seed or Seedling of one Crop, but not both). Fertilizing will reduce the growth time of Horned Melons for ca. 10 minutes. Fertilizing the Seeds will let them grow into Seedlings immediately, while fertilizing Seedlings will reduce the all-over growing time just as much as when you fertilize the Seeds.
Wait a bit until the Crops are ripe to receive the best harvest. While Wheat grows the fastest and needs approx. 50 minutes (real-life-time) to grow from seeds into ripe plants, even if you're offline, Crisphead Lettuce requires about 60 minutes, Turnips not much longer (ca. 61 minutes), but Horned Melons take the longest - ca. 90 minutes until they're ripe.
The Melons can be harvested by being "pulled" with the gauntlet and left mouse button (by default) just like any other type of block, item, plant or liquid. You won't even need to equip any Power Cell for this.
If Crops stay "ripe" for 24 RL hours, they will turn into "grown" Crops. The harvest will become a little less then, but Crops will never wither.
Please refer to the article Farming if you want to learn more about growing Crops and please read the article Food if you want to learn more about how to cook up to 36 types of buff-granting Food by making use of the 4 types of Crops that you can plant.