ALL of your observations deserve careful consideration:

Witchy was what I intended, but withy is interesting.  Hadn't seen that word before.

~ I think you're right that some of the lines are too dependent upon careful observation of the punctuation, and I may have to provide full-stops in a place or two to remove the complexity.  May lose something in that, but may also gain ease of reading.

~ I'm pondering the masculine vs. feminine, not having pondered the fact that wizard is masculine; I was thinking generic!

~ Whence is a problem, I admit.

~ My eye will consider opening the other one. 

deLighting in your visit, Daniel  8)

I'm reading withy. . .minus the c. . .a slender stalk. . .thus making the scansion of the line. . .read fine.

I'm having a bit of trouble with two words. . .splayed and grit. . .not their correct usage in the work. . .but the tonality of the words with regard to the subject matter. . .I'd rather say sand. . .smoother I feel.  And splayed feels too. . .Penthouse. . . 

I agree on the lack of  "from" prefacing whence. . .if you wish to use the feminine. . .perhaps

from palaces of ice from whence she's sent. . .and switch wizard to goddess.

and. . .I know I've done things like this before.  . .but. . .for some reason I"m tripping over the eye hearing the black hole blink from sight.

Overall, however, this is a beautiful poem. . .just lovely.  .and one of my favorites of yours, Daniel.

~Rene~

a scent of yesteryear 
 
Sweet rose of summer, stirring love and dreams 
but weeks ago, stands withcy now, stripped stark with >> also,  I read "stripped" in the old two-syllable method to keep the meter - which  I think is fine
of all her petals, leaves… mere thorny bark 
remains to cast a spell in silent screams. 
The winter wizard shows her cool descent 
from palaces of ice whence she was sent.  
 
Another year has slipped into the night 
of yesterdays that fade beyond the stars 
splayed out in silken nothingness as far 
as eye can hear a black hole blink from sight. 
The grit of time can never pause; it's caught 
between the gears… naught but an afterthought. is the "grit" the antecedent of the "afterthought"?

L2 is bumpy unless the modern reader doesn't trip on "stripped

The enjambments are pretty smooth -- you are good

There is a lot of non-forced alliteration which I always like though L10 seems a bit contrived IMHO -- yes, the "hearing" part I like but the 3 B's might be over the top.

I love, no change that, I REALLY love the final couplet. It has such power and conjures up so much.

Fine piece, Daniel --- can't find any major nits.

Norm