1.) If you create fruit on a tree or bush does it need to be a ritual? thus obeying the limit of creation in which case the duration need only be momentary; & if it is D : Sun will the nutritional effects vanish at sunrise/set?
2.) Can you just use ReHe with D : Mom to bring a tree to blossom? Since fruit comes from blossom, surely Re is the technique to use?
Would you need to use Cr to 'bring it to maturity' ? (making something a better example of it;s kind)
It really depends how you do it. If you just CrHe the fruit, all the standard limits of Creo magic apply (on the other hand, you don't need a tree or bush to start with - you can directly create your foodstuff). But as you note below there are other ways to do it.
If you already have a mature tree, you can indeed use Rego to have it bloom instantly out of season, it's one of the corebook guidelines for Rego Herbam. The consensus in our troupe is that the same guideline could be used to have the tree bear fruit of out season.
Note, however, that this does not really create anything per se; it just makes the tree do whatever it could do with the resources at its disposal. Even in medieval times, there was a fair understanding of leaving land fallow, and of pruning plants (in particular grapevines) to reduce their yield while making it "better"; basically, it was understood that plants, like animals, had only so much "creative energy" in them (incidentally, "vis" is the best latin term to describe it!). So our interpretation is that you can't use a ReHe to make a tree bear fruit dozens of times in the space of a few hours. Do it once, and it's ok. The second time, the crop is considerably scarcer, and the tree suffers. The third time, you barely get anything out of it, and you definitely harm the tree. We apply the same rule to using CrHe guidelines that bring plants to maturity overnight (stuff like grain, rice etc.): overdo it, and the land becomes barren. In antiquity people could get up to three crops in the same year, so I'd say that with care and manure you could probably force a tree to bear fruit once/season and/or get one grain crop/season sustainably.
I'd say that you'd need Creo to bring a tree or bush to maturity (or a wheat or rye crop); but Rego should be enough to make a mature tree bear fruit, just as it is enough to make it bloom (and you do not need Creo to bring the flower buds to maturity).
I'd say Rego for the "causing trees to bear fruit" - if only because it falls under the "cause the plant to do something it does naturally, only faster". But as mentioned before, it's going to sap the land of (non-magical) vis.
Of course, that implies that you could use Rego to fatten up a cow, but only if you had enough grain and fodder.... which sounds odd on the surface of it, but in thinking about it more I'd actually be fine with that, as well.
Unless the creo folks have an explicit reference to the book somewhere? This does sound like something that should be covered by an actual example, but I don't know of any, one way other the other.
No explicit references, but for a cow, I'd say that making a cow produce milk would be Rego if Animal and Herbam work similarly. Fattening the cow up, however, is an improvement to the cow and Creo.
That shouldn't apply to Creo in my opinion. Rather, I'd consider Creo-grown wheat to be sorcerer's grain (prone to vanishing from inside your body tissues) unless made with a momentary ritual. In the latter case, the matured wheat isn't fed by the vis in the land, it's fed by the spell.
The corebook guidelines do make it fairly clear, I believe, that the duration of such "fast maturation" effects is the time during which the quickened growth takes place, and that at the end of it the result is pretty natural.
I agree, by the RAW you are probably right. We just apply the "life-sapping" rule at our gaming table to prevent a situations where covenants could grow really prodigious quantities of food without vis from a minor scrap of land.
Fair enough. Personally, if a gimmick like that is a problem, have the Quaesitores decide that the covenant is Making Wealth and tell them to cut it out (which creates a story).
I mean, Touch of Midas is four vis for 800 Mythic Pounds, which is more than enough to fund a covenant for several years (and if it's not, five vis gets you 8,000 MP, at least until you crash the kingdom's economy like Egypt 1324). Creo Herbam still requires the field to be plowed and planted (are magi doing that by Rego too, or using covenfolk?) and produces...uh...not nearly that much.