In most online publications, the author of var. sibiricum is listed as (L.) Hartm., but IPNI does not give a reference, so dates could not be compared to var. sibiricum (L.) Garcke (1849).
I looked at publications by C.J. Hartman and found his earlier publication (1843) in Handb. Skand. Fl. (ed. 4) 102-103.
Here is a screen shot of the entry on pages 102-103:
Unless Hartman's combination is illegitimate or invalid, Allium schoenoprasum var. sibiricum (L.) Hartm. (1843) should have priority over A. schoenoprasum var. sibiricum (L.) Garcke (1849).
In most online publications, the author of var. sibiricum is listed as (L.) Hartm., but IPNI does not give a reference, so dates could not be compared to var. sibiricum (L.) Garcke (1849).
I looked at publications by C.J. Hartman and found his earlier publication (1843) in Handb. Skand. Fl. (ed. 4) 102-103.
A pdf of this publication can found at: https://bibdigital.rjb.csic.es/en/records/item/15933-handbok-i-skandinaviens-flora-fjerde-4ordf-upplagan-rattad-och-forokad
Here is a screen shot of the entry on pages 102-103:
Unless Hartman's combination is illegitimate or invalid, Allium schoenoprasum var. sibiricum (L.) Hartm. (1843) should have priority over A. schoenoprasum var. sibiricum (L.) Garcke (1849).