Yes he has Weak Spontaneous Magic.
The spell could also be made concentration duration and I believe Avery knows "maintain the demanding spell" to extend it.
This doesn't help the fact that the base individual for herbam is still tiny.
Yep - that was the general plan: to use D:Conc (moon) to get the wood to last for a month. That would be a lvl 3 spell (base 1 + Touch + Conc), and St. Avery can spont a lvl 5 Maintenance spell that will keep it active for a month.
Also - I believe the general interpretation is twenty-seven cubic feet worth of tree - For example, Transformation of the Thorny Staff (muHe, pg 137), affects a staff of up to 6 feet in length. Similarly, Dance of the Staves (pg. 138) affects "a pole, staff, haft, or any other long, thin, non-living wooden object."
Not that these are huge numbers - rather, this shows that something with T:ind can affect something longer than 1 pace - which tells us that the T: Individual of Herbam is a general volume, rather than a strict, per-dimension size.
Also - I'm pretty sure this is a general rule - when creating something with CrAq, for example, you don't need to restrict yourselves to the literal dimensions set by a small pond - you could summon a blast of water that is more than a few paces in length. And summoning a the maximum amount of gold you can (CrTe) in a sphere (Touch of Midas, pg. 153) would require that you break out of the hard limitations set by a cubic volume. (ie a sphere with the same volume as a cube will have a larger diameter than the cube's length, breadth, or width.)
If the plan relies on Avery spontaneously casting several maintenance spells -- because we will need a fairly large number of pieces of wood to make furniture -- then you hit the problem that repeated castings of a spontaneous spell. That brings a much higher risk of botching.
Is Avery willing to risk gaining a point of Warping so that we can make our own furniture from magical wood, when we can probably obtain that wood from nearby trees with much less risk?
I'm not saying this cannot work; I'm simply saying that it contains an element of statistical risk that seems to outweight the reward.
Particularly since the making of the furniture riquires additional stress Finesse rolls that may simply waste the created wood...
I believed there was no risk of botching when using /5 spontaneous cadting (because there is no dices)
Sure, if he can achieve the result with a Fatigue-less spontaneous spell, then there is no risk. But remember that sustaining another magus' spell doesn't use the same guideline as sustaining his own (which is what Maintaining the Demanding Spell uses).
With T:Touch and D:Moon, the (level of your sustaining spell + 1 magnitude) needs to be double (level of the spell to be sustained).
I think it works in that case, but you might want to check my math to be sure.
Oh, good point. It uses half of (level +5 magnitude) guideline, doesn't it. Hm. Well, that would be (Base 3 -5 Magnitudes + 1 Touch, +3 Moon) x2 = (3 -5 +1 +3)x2 = 2x2 = difficulty 4.
Huh. So, actually, it's easier. So....yay for quirks in the AM magic system?
Pretty much what I figured. (snorts) Low-level spells are one spot where the guidelines tend to break down in meta-magic.
Much in the same way, a pibbly level 1 Unravelling the Fabric of (Form) has a fair chance of dispelling a level 10 spell at Voice range, since it only needs to get 10 on a stress die + 3 (with no botch possible).
Pretty much what I figured. (snorts) Low-level spells are one spot where the guidelines tend to break down in meta-magic.
Much in the same way, a pibbly level 1 Unravelling the Fabric of (Form) has a fair chance of dispelling a level 10 spell at Voice range, since it only needs to get a total of 10 on a stress die + 3 (with no botch possible).
Question for Pralix: Will we be introducing some Companion characters at some point? I have the beginnings of an idea for one, and I'd like to know if it's worth it to try and develop it some more. 
You can hire whoever you want, and then do the book-keeping if you want to have more detail. But don't expect me to run clever companion stories. I think your characters' flaws give me enough to work with (and juggling too many balls means dropping more)
I was thinking more along the lines of having a companion character that can get included in whatever stories the other magi are playing. From my experience, not having a character to play when another magus' story drag on for weeks and months can get pretty boring.
Unless you plan on having us have all the magi involved in each story? That seems unlikely (and unrealistic) considering the somewhat diverging interests of our magi. 
Well, I'm mainly running Emily as an excuse to have someone for St. Avery to talk to that I also control - in order not to have to wait up to several days to engage in any sort of back-and-forth conversation. So she's sort-of a companion, at this point.
Yeah, I think we're done talking about our general positions - I think the next step is to go out, hit up our Houses and gather information on the various positions. Our current trending seems to be the following:
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Chapter Houses - slight negative; we're not going to have one any time soon. If you want to camp a vis source, put a new covenant there.
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Interference with mundanes - neutral: the current system seems to work fine. If you want to join the Reconquesta, don't bring down wrath on the rest of the Order.
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Cathars: slight positive - if you want to have a few Cathar grogs, that's fine - as long as they don't make a fuss about it and call down the Church on you.
Yup, so I suppose we'll go to each of our relations of our respective house and ask about these three issues and then ask about any other issue specific to the house that is desired I suppose?
Agreed
Deluge of work, expected to last for a week.
First week at my new responsibilities at work, so I expect I will be slow to respond as well.
School is super busy today. Also tomorrow. Also every Tues+Wednesday for the next few months. Should've posted on monday...
I'm gone. skiing. Internet unreliable. back in 1 wk or 2
I have major internet connection issues (changing provider + issues on the line), I don't now when I'll be able to answer.