They’re not local, but we *love* the folks at Cortesia – http://www.solomonsseal.net
They make amazing quality stuff, and if we can’t wait for our own, we buy from them.

We don’t really understand how it works, which is true for many plants! Here’s what Jim McDonald has to say about it:
So how does it work? Long years ago, I believed that the gooey mucilage in the roots finds its way to the enflamed tissues and coats and lubricates them, which reduces friction and irritation and soothes the tissues themselves. But this certainly can’t be, as it wasn’t long before I Iearned that a.) mucilages aren’t extracted by alcohol very well, and the dosage of tincture is far too small for it to be working on a physical level and b.) mucilages don’t get into the blood stream and thus into joints. Matthew Wood speculated that Solomon’s Seal might stimulate the body to produce cortisone, and my current belief is that it acts on the synovial glands, improving the production or quality of synovial fluid in some way and thus lubrication in the joints. Often you can clearly perceive a notable lessening of friction in the joint shortly after a dose is taken. On a few instances I’ve seen this friction cease entirely for a short period after the dose. But who knows exactly what’s going on; what is clear is that it works, and if that’s the case, understanding why isn’t entirely necessary (though it can be nice). In regards to the aforementioned use of helping tendons/ligaments tighten or loosen as needed, I think this has to do with its moistening effect. Dry tissues loose their pliability; they’re “stiff”… think of an old dried out piece of leather. It doesn’t want to stretch, but if you do stretch it, it doesn’t want to go back to its original shape. But, moisten that leather and its pliability is restored. It can stretch out or tighten back to its natural length.

So the key indication for its use is inflammation associated with dryness. Maybe the dryness causes the inflammation, or maybe vice verse… it doesn’t seem to matter. Solomon’s Seal seems to moisten connective tissues and lubricate joints, and in so doing ease attendant inflammation.

In our own experience, we have found the “restoring connective tissue” aspect to be true both with dryness and without – I’m not certain dryness is absolutely requisite. Here are some examples that come to mind: in the case of a sprained ankle, there’s no particular dryness there (though the sprained ankles in question were in people who were constitutionally dry, now that i think about it). Also in the case of overtight fascia (throughout the body) we’ve used both dry constitutions and reasonably neutral. I’ve used it for a rotator cuff injury in a person with damp constitution. We use it to help folks develop flexibility (emotional/psychological) regardless of constitution. Although I didn’t mention any respiratory aspect in my article, we’ve also seen it used regularly for tightness in the chest related to asthma: here I think this has a good deal to do with the pulmonary fascia, frankly. That case was a damp individual in the extreme. I have not tried Solomon’s in someone with Rheumatoid Arthritis – that would be a good test, though!

That’s probably not the clear-cut answer you would have liked, but perhaps it will be helpful anyway!
As for getting some, try http://www.mountainroseherbs.com – they stock it dried and it’s very good quality. It’d be nicer to make it fresh, but like you say, winter in Vermont (or, in our case, Boston)!

I do mean the tinctures, yes. It’s a little trickier to get the lotion to emulsify when you’re using all tinctures, so if it’s difficult, you can also just make your lotion with the oils (calendula and plantain) and use rosewater for the water, and then mix the tinctures in a separate bottle – apply the tinctures first (as if they were a liniment) and then put the lotion on top. sometimes that’s easier than emulsifying the alcohol.

or, in our house, i will do it that way sometimes because then the whole family can use the lotion – it’s also great for plain dry skin – and i apply the tinctures separately.
hope that helps!