What base effect would you use if you wanted to mow the grass in a field - N.B. not to destroy it, but to cut it, so as to later make hay bales? I'm not even 100% sure whether it should be Perdo or Rego.
And once it's cut, what would be the base effect to make hay bales (I guess one small bale is approximately the size of a Herbam Individual, i.e. a cubic pace)? From covenants, I'd say either ReHe5 ("treat and process items made of plant products") or ReHe4 ("treat items made of plant products" for drying the hay) followed by ReHe3 ("control an amount of wood" for actually making the bales)?
Note that there can be multiple solutions to this, all are welcome. In general, I'd rather achieve the desired final effect via multiple steps each requiring lower-level magic, insted of employing a single higher-level effect that "does it all" in a single step, because I am trying to see if this can be done with non-fatiguing spontaneous magic.
A Day's Work for a Farmer, ReHe 10/15
ReHe 3: Manipulate items made of plant product
Group +2, Touch +1, Inst (+0), possibly a +1 for size considering how large can be a field (if you don't want to cast it multiple times).
You get a pile of hay at your feet (or in front of you considering the size).
If you want some versatility, you can toss in another +1 for Flexibility and you have One Day Harvest in a Snap - you can harvest any type of food (one type per casting): apples from an Orchard, wheat from a field, grapes from a vineyard.
But if somebody find this Flexibity a bit too generous, I am fine. Not a hill I will die for.
Then a second spell, same baseline to turn the harvest wheat/hay into nice hay bales. One bale at a time.
Most Finesse roll should not be higher than 6 (one day's work, no more) and the base EF is pretty low.
The problem I see with this is that before being mowed, grass is not an item made of plant product. It's a (living) plant. That's part of the reason I'm not 100% sure Perdo is out of the picture. I mean, if you can do this without Perdo, you can probably cut down trees just with Rego magic, including "treant-like" trees...
Since you are doing it with Craft Magic then it does not matter if the grass is alive or not. Unless you think that a Craft Magic spell to sheer sheep would require that all the sheep be dead before it could be used as well.
I'd say Rego Herbam with +0 Perdo Requisite, or the opposite, if you want to turn it into a single spell.
Were you looking for spells or item effects? The following is assuming you're using a series of simple items to avoid any need for significant management.
Or, PeHe to kill the plant by cutting off it's stalk base.
Then ReHe to process the stalks by drying them out.
Then ReHe to gather all the dried hay into bales.
And finally ReHe(on twine) to bind the bales firmly.
Since you are doing it with craft magic, it matters very much if the grass is alive or not.
Rego craft as rearrangement of
materials means that some functions of
the mundane craftsman are outside the
province of craft magic. For instance, a
butcher can kill an animal with a knife,
but craft magic cannot do this, as life-
into-death is not a rearrangement but a
destruction (which falls in the realm of
Perdo magic). (Non-craft Rego could,
however,, with enough Finesse, wield
a knife to similar effect.) Covenants p49
Perhaps craft magic with a Pe requisite. Or the other way around. I just have this idea that pure perdo would produce gras that was shredded, wilted, or in some other way destroyed and not neatly cut in baleable hay.
Hay in bales would seriously confuse any farmer prior to the 1900s. There was an art and science to building haystacks. And cutting hay and stacking it into haystacks would definitely be Rego craft magic. With a decent finesse requirement to do it properly, so rain came off of it without damage.
Group is problematic here. You cannot just cast multiple times because each target has to be a distinct group. Without looking it up, I would guess that one hay ball takes about one standard size group of straws. If a field yields ten hay bales, it would then be size +1, and if it yields eleven it would be size +2.
Boundary target feels more logical, but takes a ritual so it is not going to happen.
OTOH hay bales sounds utterly non-medieval, and IIUC requires plastic vacuum packing because the hay is not dried.
Good point! In fact, there are some out-of-the-way places in the mountains, close to where I live, where bales where unheard of before the second world war, and in fact as late as the early 60s. Haystacks all the way.
Then again, it's crucial to understand whether the bale was something medieval folks could not even conceive of, or instead something that was fairly obvious and equally obviously "not worth it" given their technology level - so that a Hermetic farmer would immediately think of it.
I was about to say that when mowing, you damage the plant (but crucially, you must not kill it), whereas you don't damage sheep by shearing them; in fact, sheep need to be sheared even if you have no use for their wool and must dispose of it - at least modern sheep. Furthermore, sheep will naturally shed hair, but grass does not naturally shed its blades (I think? I am woefully ignorant on the matter).
Then again, if I look at the PeAn guidelines, removing all hair counts as superficial damage so you do have a point. Still, do we have any canonical example that shearing sheep can be done via vanilla craft magic, without Perdo?
For bales to be worthwhile, you need to know how to handle them. Before tractors round bales were not something that could be moved, therefore not usable. Square bales require large barn spaces because the rain can make them spontaneously combust, or just rot. There are a whole series of technologies that are necessary prior to hay bales being better than haystacks. Barns, vermin control, proper stacking to prevent collapse, proper curing to prevent the barn from burning down, enough workers to get all the bales in before the rain, etc.
But I do believe your idea has merit for haystacks.
Though Hermetic magic can easily move 1-cubic pace bales.
Meaning the savvy Hermetic farmer will just ward the barn (with D:Ring spells) from rain.
This all seems doable with simple Hermetic Rego magics.
So, yes, the question would be: would a Hermetic magus knowledgeable in farming understand all this? I think he would, in the sense that I have the impression that farmers of old understood why they did things in a certain way (e.g. made haystacks neither too large nor too small), so that as soon as a solution to avoid the problems inherent in doing stuff in a certain, otherwise more efficient, way became available, they'd switch productive framework.
Actually hay bales of certain sizes were much more convenient than loose hay for moving by hand. What is necessary however was a hay press to form the bales (originally square bales held by twine or wire)
The first hay presses were horse powered in the 1800s, long before tractors were developed, and they made teh hay more convenient to store and transport. The process was within the capabilities of 13th century machinists, but it simply wasn't developed until the 1800's.
PeHe to kill a plant is base 5 (Though it says destroy a plant, you could argue a different level to shear down a stalk.) Instead Rego Terram 4 or 5 (base 2 like Unseen arm, +1 Touch[or voice], +1 concentration) to control a sharpened scythe-blade to do the reaping. You could also just have peasants do this.
Rego Herbam base 3 to control the shorn stalks into piles, gather them into haystacks. Needs +2 group and you could do it by touch if you walk to each pile. That'll be ReHe 10. Probably the same level of spell to dry the hay out.