<P><B>Abstract</B></P><P><I>Arundo donax</I> L. (giant cane) is a suitable feedstock for sugar production because of its high biomass yield and low agronomic input requirement. Eight <I>A. donax</I> clones were studied at full field scale for sugars production. 1‐ethyl‐3‐methylimidazolium acetate ‐ [C<SUB>2</SUB>C<SUB>1</SUB>im][OAc] ‐ and enzymatic treatments were used to obtain the sugars. Highest glucose yields were obtained for pretreatment performed at 160 °C for 3 hours, with glucan conversion yields from 40.8 % to 76.2 % for most productive <I>A. donax</I> clones (AD10 and AD 20). Differences in cell wall structure measured by micropore surface area (pores of 0.3 ‐ 1.5 nm) explained both ionic liquids and enzymatic performances of clones. Structural differences were due to the guaiacyl (G) and syringyl (S) units that determined different lignin cross‐linking affecting cell wall microporosity and so enzyme accessibility. Total glucose and xylose yields (11 Mg Ha<SUP>−1</SUP> and 4.84 Mg Ha<SUP>−1</SUP>, clone AD20), were impressive and about 3.5 to 4.5 times more than those obtainable from switchgrass and corn stover.</P>