|This article is about the Bulbo Tree. You may be looking for the Bulb Bush.|
Bulbo Trees are a terrestrial flora species found on the Floating Island and Mountain Island. The player can harvest Bulbo Tree Samples from them using a Survival Knife. Bulbo Tree Samples are edible, and a viable source of both Food & Water. Each individual slash with the Survival Knife yields one sample, until the 9th slash which instead yields two samples and destroys the tree.
Once planted, the Bulbo Tree will take 1600s (26m:40s) to mature. That is twice as slow as the Marblemelon Plant, which grows in just 800 seconds. However, the "food/water per hour" efficiency and ease of re-planting of Bulbo Trees is better than melons. For a detailed calculation of the food/water value of Bulbo Trees compared to Marblemelons, see the comparison section below.
Bulbo Trees are short trees with holes in their thick, rounded trunk. A viscous fluid leaks from these holes.
The trunk resembles bamboo shoots, until breaking up into green and blue foliage further up the tree.
Comparison to Marblemelons
An Interior Growbed has 16 "slots". The Bulbo Trees take up 4 slots each, meaning that you can plant 4 trees per growbed.
To harvest from the Bulbo Tree, you slash it with a knife. A tree lasts for 9 slashes with the Survival Knife (and the Thermoblade), with every slash giving you 1 Bulbo Tree Sample, except the final slash which gives 2 samples instead. That's a total of 10 samples (`(8*1)+2`) per tree. And since there are 4 trees per growbed, that's a total of 40 samples per full growbed, every 26m:40s (full bulbo tree regrowth cycle). But you need to replant 4 of them, so the actual amount that you can eat is 36 samples.
Each Bulbo sample gives +8 food and +10 water, meaning that the entire growbed "produces" 288 food (`36*8f`) and 360 water (`36*10w`) per 26m:40s "harvesting and regrowth cycle".
Now let's compare this to the melons. They only take 1 slot each, and you can therefore plant 16 melons per growbed.
To harvest a melon, you simply pick it up. To get more seeds for replanting, you slash the melon with a knife a single time to get its seeds. Each melon always produces exactly 4 seeds when knifed. That means that you need to knife 4 of the melons to have enough seeds to replant the 16 growbed slots. That means that you have a total of 12 edible melons per full 16-slot growbed, every 13m:20s (full marblemelon regrowth cycle).
Each Marblemelon Plant gives +12 food and +14 water, meaning that the entire growbed "produces" 144 food (`12*12f`) and 168 water (`12*14w`) per 13m:20s "harvesting and regrowth cycle". Adjusted for the fact that Bulbo Trees take twice as long to grow, and that we can therefore do two Marblemelon harvests in the same amount of time as a single Bulbo harvest, our final numbers for melons are: 288 food (`2*144f`) and 336 water (`2*168w`) per 26m:40s "bulbo cycle".
In other words, in the same 26m:40s period, the Bulbo Trees would provide 288 food and 360 water, while the Marblemelons would provide 288 food and 336 water. This means that Bulbo Trees provide exactly as much food and 7.14% more water in the same amount of time.
The Bulbo Trees are also a lot more convenient, since the final slash provides 2 seeds, and the actual seeds are the food (meaning the "seeds" are edible), meaning that you can eat one seed and then replant the final seed to begin regrowing that tree, and anytime you have excess "seeds" you can just eat them instead of having to throw them in the trash. Compared to the Melons which require you to manually slash four separate melons and then replant the 16 individual seeds, as well as dealing with the fact that you never harvest all melons at once meaning that you always have some leftover seeds which you either have to manually throw in the trash (since you can't eat them) or keeping them for replanting later, which adds even more tediousness.
Lastly, if you operate a Bioreactor, the Bulbo Tree Samples and Marblemelons both provide 420 energy, which is the maximum amount of energy of any plant/egg-based source. However, the Marblemelon Seeds only provide 70 energy, meaning that you have to throw in an entire Marblemelon if you want the equivalent of a single Bulbo Tree Sample. Therefore, Bulbo Trees are fantastic "reactor fuel" too.
Summary: The widespread belief that Marblemelons are the most potent source of food in Subnautica is incorrect. Bulbo Trees provide exactly as much food and 7.14% more water within the exact same timespan (described above).
Data Bank Entry
A bulb-based flora which roots to the ground and sprouts turquoise leaves. Analysis suggests the sap produced by this plant is poisonous to insects but can be harvested and consumed by humans for its high water content.
Assessment: Edible, high water content