You get a lot more than that. T: Group does not produce 10 seeds - it produces a number of seeds equal to the mass of ten standard Individuals of Herbam -- which is a pace by a pace by a pace. That's a lot of seeds!
Mark
The biggest "cheat" on the Creo system comes form Creo Animal: You can bring an animal to full maturation within a single moment.
That's calf --> cow --> cheeseburgers in an hour. You can afford to have cattle, sheep or pig herds of dozens of times the size of what you'd expect to be able to sustain by mundane foraging, grazing or hay-feed.
You can combine this with some Scinnfolk magic (every covenant needs a friendly fertility maga/magus) to boost their productivity by 3x.
With hermetic magic, the real question is what do you do with all the leftovers?
Keep in mind, too, the possibilities of Muto. If you're a magus, you don't need the food to be good, just nutritious. A person can get by on rough porridge and roots. A magus can use Duration: Sun, however, to make it a delicous Steak-pot pie, with wine (water) and sweet honey cakes. Its yummy when you eat it, and when its been digested, it doesn't matter that it was actually porridge; its still nutritious.
A covenant can feast like a King for the price of a peasant's bread and soup.
Ah, even better, then. CrHe5 (instant spell, 1 vis pawn) to create 100 cubic paces of seeds, wheat, for example. In fact, that is enough for NOT having to even plan them: you just eat them.
Who said covenants needed rto move stuff around? Just fill up your granary with a pair of CrHe5 spells
Xavi
...Except that rituals are always level 20 or higher.
which might eg. make 100,000 cubic paces of seeds of wheat, making storage a real problem.
While I agree that that (and the equivalent with plants) works very well here, I still think Imbued with the Spirit of Animal/Herbam can be a bigger Creo "cheat" to be applied to food, though not nearly as much as when applied to Corpus, Terram, or Vim for various purposes.
I happen to be playing a Jerbiton who has put a lot of effort into cooking right now, so I'm toying with lots of these ideas. That Jerbiton is an insanely good cook/baker/vinter/brewer. But I'm still working on clever ways to increase productivity. Right now the few momentary Rego craft magic spells are not the choke-point. The choke-point is on the raw ingredients. I require too much variety of ingredients, making CrAn/CrHe rituals with Imbued with the Spirit of Animal/Herbam ineffective. Right now getting stuff from our peasants and importing some things protected by circles to prevent pests and rotting is working. But I'm still very limited. So I'm paying a lot of attention to the ideas in this thread. Keep the ideas coming!
Chris
Again.... Muto!
Food needs to be eaten in a Moon, generally speaking, so you can turn any basic nutritious material into the greatest culinary masterpiece in Mythic Europe, so long as its eaten in a month, and it won't cause the hunger pangs either. All you need is one source of protien, basic bread materials and one type of veggie and you're set.
A reasonable storyguide will give you a strong bonus on any finesse roll if you're a brillian chef.
And a fair amount of yearly warping as well for eating highly magic-ed food.
Cheers,
Xavi
Yes. I've been trying to avoid that. So far I have avoided it just using naturally produced stuff and applying Rego craft magic. But if I push it further I expect we'll hit the 1 warping point per year thing for anyone who keeps eating this food.
Chris
Gaining warping for eating highly magicked food is really fuzzy. I would say that is covered by the warping point you gain for living in a high aura. For mages, you would get the warping point until you get your potion, at which point your whole life is "highly magicked".
Saxonous has a good point. It is indirect, which does not necessarily cause warping. Myself, I've been trying to avoid the food itself from even being warped. I figured if I can keep the food itself from even being warped, then it's likely not magical enough to warp those who eat it. So right now that the food merely has one spell cast on it, and only Rego craft magic at that, should mean no one gets warped from it. That's how we've been playing it. If I were to use Muto on the food so every bit of food consumed is under a magical effect while consumed, I could see the potential for the warping to arise. Similarly, if I had a plant that were under a magical spell continuously for many years producing fruit I use, I could see the potential for that fruit to cause warping. But as Saxonous said, that may still be covered by the high aura if you're getting those points.
So I'm trying to think through ways to avoid warping the plants and animals I'm using, too. I don't mind a little bit of warping, like the Rego craft magic cooking spells. I'm mostly concerned with grapes since my primary area is wine-making. (Let's ignore the other ingredients for the moment.) I've considered growing grape vines non-magically and using those as a source for more but not generally for their grapes. Then I could transplant some of those each year (or grow new ones from their seeds), making sure not to overly disrupt the process. So far I'm safe. Then use CrHe to grow them to maturity as needed. That's probably 1 warping point. Then use a low-level ReHe spell to have them produce fruit repeatedly over the appropriate seasons (looks like about 3-4 months naturally, potentially adjusted further). That would pick up 1 warping point for continuous low-level spell usage. Then I use a spell to make wine from them, which definitely adds 1 warping point to the product. So the barrel of wine should be at 2-3 warping points, not even enough to reach the first level (5 points). At the end of the growing season I would get rid of the warped vines, planning to repeat the process the following year. I would think I ought to be able to produce wine that someone could consume for a year without risk of warping.
Too bad wine isn't at today's kind of prices (as far as I've been able to tell). In a couple years I should be producing wine around the level that today would sell for hundreds of dollars a bottle, and a barrel is far more than a bottle. Overall, even though I should be making the best wine in Europe soon, the income probably won't be that large compared to what we can get other ways.
Chris
What is this "protien" of which you speak? 
I would think it would be the balance of humors, as described in Arts and Acadime that matters. So you could change bread into beef and not cause a humor inbalance once the spell wore off, but if you switched bread to lettice, the eater would be either imbalanced before or after the food changed back.
Also, I would think parma would keep transformed food from being eaten by those who have Parma Magica
If you want a greenhouse to grow stuff in , use Conjuring the Mystic Tower (page 153) ,
but make the stone quartz.
To go one better use Conjuring The House of God (page 133 , Art & Academe).
You will easily be able to grow Size +03 trees inside , with room to spare.
I'm not sure how far the Finesse Roll will go in altering basic size and shape however.
You would need to reinvent either spell for major differences , i suspect.
Being as a Mystic Tower is still a tower , i dont think rorting by casting it sideways into a hill will work.
With the cathedral option , you could also raise exotic birds for fun and profit.
For grape-growing you can use InHe to determine the best possible nutrients to add to the soil.
Though InHe(Te) for info about the soil itself possibly.
You can also determine the maximum number of grapes per vine that will not hinder nutrient intake for the fruit.
Either pick any excess (Rego Craft) or use ReHe in controlled bursts to cause the best fruit growth.
Bountiful Feast is a good example of an effect that "naturally" boosts the yield of plants. As written in the book it's an expensive ritual but it's based on a magnitude 1 creo herbam effect that keeps a plant healthy and thriving for the duration. A ring/circle version of the spell (From MoH) is below magnitude five and easily cast by magi or put into a magic item. With a little work you could create thriving gardens inside large inlaid magic circles.