How would plant control powers/magic work?

Question

In my fantasy world everyone has several (three?) magic powers that they're born with, and one of them could be control over plants. About 1/4 to 1/5 of the population will have this. They make the plants grow mostly however they like, though bigger projects will be harder.

Specific examples:

Giant trees could be made to grow into houses (think the elven houses in the Inheritance Cycle)

Living boats (self repair!)

Food grown quicker, and out of season

Throwing the seeds on the ground, and making them sprout (perhaps they are vines that can suddenly wrap around the enemy!)

Limits:

Plants keep certain characteristics; if a plant has yellow flowers, it keeps having yellow flowers.

Growing a plant too much might kill it

things can't be undone (you can't make a tree absorb a branch you just had it grow)

Significant knowledge of how plants work required

What are more practical applications of this power? What other limits? What sort of plants would be particularly suited for this? What kinds of rules of biology will I be breaking? Any cool new plant species that could be magically created?

Answer 1

Naturally it would depend on how magic itself works within your setting. My own ideas on similar magic have rely on an ability to manipulate something very much like the Force in Star Wars. It is tied to all living things, and while affecting matter, it would be particularly useful when manipulating living things. It could both be used forcefully and more through gentle coercion of natural processes.

One possibility is that the magic user manipulates the water inside the plant such as in the Avatar series. But in order to cause plants to grow and to control that growth, you would have to manipulate the plant on a cellular level and have control over its genetic expression. I would consider looking at some books on cellular biology and particularly at how cells grow and interact with their environment. For example, how when a cell multiples it does so according to cues it gets from nearby cells. It is hard to explain simply but cells react according to chemical cues they get from their neighbours. Obviously you wouldn't have to include all this stuff in your writing but having an understanding of how it works might help you to set limits and create a more convincing magic system. If the magic user has to understand plants intimately, then maybe you can go into biology (in which case you will need to have a deep understanding). Perhaps the magic user sees/feels/senses the cells and can control their function by overriding the chemical cues. Alternatively, magic itself could have a certain level of awareness and manipulates the plant's cells according to the magic user's will (but still within physical limits).

In terms of breaking biological rules resources would be a major issue. One of the reasons trees don't grow over night is because they spend much of their energy gathering resources. They must collect energy from the sun and carbon from the air to produce sugars. They must gather nitrogen and a wide variety minerals from the soil to produce cells. Without these resources the plant can not grow. Perhaps the magician could stimulate rapid growth briefly, but the plant would very quickly run out of reserves and ultimately die (that could be a risk). As such, the magic user would need a way of providing the extra resources needed (perhaps created magically through some process that can manipulate atoms into new from but then you would likely have issues with energy and radiation but if you were that powerful why would you bother manipulating plants). One possibility is that the magic user has limited power to increase the speed of the plants growth but that the magician's main power is to control genetic expression and cellular functions. For example: you could magically cause a tree to grow into a bridge, but it would still take decades perhaps even centuries. This slow magic approach would work well from a long lived species like Elves but would have limited practical applications for shorter lived species like Humans.

I hope this helps

Answer 2

An interesting idea might be that, since plants vary in how fragile they are and their uses, people with this ability carry certain types of plants with them in unique ways.

For example, perhaps one such 'plant-controller' or however you want to term them, may find that the flexibility and relative strength of a tough jungle vine mimics rope well and has a variety of uses from the mundane to the combative, as well as defensive. They know they'll be journeying into an area that lacks much plant growth beyond scrub brush and stunted trees in the mountainous crags, so they seek to find a way to bring such a useful plant with them. In the end they decide to bring a moderate belt-pouch or, perhaps more reasonably, a backpack filled with the rich soil of their jungle home in which they transplant such a vine. They then encourage it to grow, wrapping it around them in coils much as one might do with a length of rope, offering some light-weight protection, while also keeping it at hand should it come in handy.

Various iterations of such a practice could come into place with other useful or rare plants, and could also be used for a sort of fashion or status display as well.