Underground Greenhouse

[Sir Vice]

Has anyone ever set up an underground greenhouse to grow food? I figure it would be mostly fungus. Would continual light nourish plants?

[Oli Ironbar]

Not sure about continual flame since it specifies ‘as torchlight’. If torch light allows normal plants to grow, then yes, if not, then I’d ask the world’s GM.

Also, this! Magic Dirt

[Pizza Lord]

I have never set up an underground greenhouse (or a regular greenhouse), either in real life or in game. Fungus would be the easiest and most likely plantlife in an underground situation.

It's a hard question to answer, because not all plants need sunlight or at least as much. How much they need for photosynthesis and growing varies wildly. They mostly need photons or light, it doesn't have to be sunlight, but not all interior lights are the same (That's why special grow lights exist for indoor terrariums and greenhouses).

Potato plants aren't going to need the same light as sunflowers or corn or grapes (and there's numerous strains and varieties of each of those).

Assuming we are talking about plants that need light, a continual flame (I know you said continual light), or a light probably won't do it. That's about torchlight level. A continual daylight effect probably could. It's as bright as daylight (note that it doesn't count as sunlight or daylight for creatures affected by it), so it probably is bright enough light, but whether any magical light gives off enough photons or whatever 'real' light gives off is not something I can state definitively.

Obviously if you get into spells that do function as daylight, like sunbeam or morning sun, and assuming you could capture or create an item that emanated such light, that's pretty much a fair 'yes'. But otherwise, it really comes down to the plant and how much light it needs for how long (some plants need a full day of light (at least 8 hours or more). Some won't.

So I'd say that a continual lightsource can work, but it would probably have to be at least daylight strength and it depends on the plants.

[Dasrak]

Fungi do not conduct photosynthesis. While that does mean that you don't need sunlight, it also means that their metabolic processes consume oxygen and release CO2. You'd need very good ventilation to bring in fresh oxygen from the surface to avoid deadly CO2 build-up. Given the availability of effects like Daylight, it might actually be easier to setup an underground farm for plants than for fungi.

I would rule that plants require bright light conduct photosynthesis, and most forms of magical lighting only exude regular light levels. You'd need a Daylight spell or equivalent for your underground farm.

[Azothath]

Aeon Towers on Kortos uses orbs from Orv. see alse Deep Tolguth.

[Set]

Sir Vice wrote:

Has anyone ever set up an underground greenhouse to grow food? I figure it would be mostly fungus. Would continual light nourish plants?

I don't think you can get a suntan (or sunburn) from continual flame, so it'd probably be pretty crappy as a 'grow-light.'

BUT, any group that's been in the darklands for centuries, has access to magic, and wants to practice darklands agriculture, has no doubt come up with a solution. A researched higher-level version of light or continual flame that *does* produce light nourishing to surface world plants. Some alchemical solution spread on a normal light source to *make* it nourishing to plants. Plants that have been 'fleshwarped' to be sustained by other forces, such as the arcane residue leaking from cheapo magic items made for this express purpose (to radiate arcane energy that nourishes the plants). Just egregious use of plant growth type spells. Stuff like that.

Many darklands races are going to have zero interest in this sort of experiment (being purely carnivores or whatever), or lack the arcane resources (troglodytes, dire corbies, etc.). But the ones who do have advanced cultures, magical resources and / or an interest in new and different things (instead of just living on bugs, fish, fungus and each other for 10,000 years) will have come up with a solution.

If a PC wants to develop such a thing, they'll have to do their own research, or discover a group that already has, and learn how *they* did it!

[Senko]

I would say no. If you look at the higher level daylight spell . . .

You touch an object when you cast this spell, causing the object to shed bright light in a 60-foot radius. This illumination increases the light level for an additional 60 feet by one step (darkness becomes dim light, dim light becomes normal light, and normal light becomes bright light). Creatures that take penalties in bright light take them while within the 60-foot radius of this magical light. Despite its name, this spell is not the equivalent of daylight for the purposes of creatures that are damaged or destroyed by such light.

I believe it used to function as actualy daylight but that's by the by. If the daylight spell doesn't work as daylight for creatures damaged by daylight I can't see the lower level continual light being different. To me if it wont harm undead/plants then it can't nourish plants like daylight would normally. So you'd need to homebrew some new spell or magic item/s to allow light into your greenhouse.

[Azothath]

In the Game there are several ways to go about this;

1) GM/writer caveat as a setting. Yesss... it's mythic in quotes. How the writer rationalizes it is usually pretty funny but it is almost universally based on magic from a nostalgic mythic past.

2) PC based using daylight (or another spell) and permanency. It'll take some trial and error to determine the radius of normal sunlight and growth and a secondary area of lesser growth along with how much water, gas exchange, and natural fertilizers will be needed to sustain long term growth. You'll also need some crop rotation and inter-cropping. Likely leshys are your maintenance guys.

3) science based magic empowered. Like #2 but we're talking a permanent gate near a sun/on a plane to pass a decent amount of energy (EM(light), plasma, high energy particles, etc) into transducers & an energy distribution network in a static environment to provide benign light & energy. PC normal skills don't cover this so it falls to #1. You need about 1000-1400 W/m^2 (1367 W/m^2 ≈ 128 klux) mostly in the 450-600nm wavelengths. Multiplying the figure of 1,050 watts per square meter by 93 lumens per watt indicates that bright sunlight provides an illuminance of approximately 98,000 lux (lumens per square meter) on a perpendicular surface at sea level.
Hopefully you also got (from #2) that it takes more than light to make a sustainable garden.

4) switch environments and organisms. A novel approach but there are thermal vents and low oxygen environments on earth.

5) switch planes. Yep, Create Demiplane and permanency spells offer a simple RAW solution.

[Senko]

If you don't mind taking inspiration from a story based on a show about magic ponies take a look at the last maretian on fimfic. Its a crossover between My little pony and the last martian. One of the things they do in there is use magic to set up a greenhouse in a cave of mars with some successes and failures as its trial and error.

[Mysterious Stranger]

One way to grow food underground would be to use the create demiplane line of spells. Lesser create demiplane does not start with plants, but if you bring them in and the set the light to at least normal they will continue to grow and produce food. The full create demiplane can have the bountiful property which gives it a thriving ecosystem. Use a Permanency spell to make the duration permanent you have a garden.

For races that have powerful spell caster this should not be a problem to setup. Once it is setup it can last for centuries.

[Coidzor]

This thread from 2017 about creating an underground ecology touches on more than just PF1E material, but is still potentially of interest.

Ultimately, though, GM adjudication is the biggest factor, followed by how much anyone at the table is willing to research real world plant requirements.