Crux Fidelis (Faithful Cross) is a part of the longer Pange Lingua credited to the Christian poet Saint Venantius Fortunatus, Bishop of Poitiers (530-609).
The translation I found at Thesaurus Precum Latinarum reads:
above all other,
one and only noble Tree!
None in foliage, none in blossom,
none in fruit thy peers may be;
sweetest wood and sweetest iron!
Sweetest Weight is hung on thee!
Lofty tree, bend down thy branches,
to embrace thy sacred load;
oh, relax the native tension
of that all too rigid wood;
gently, gently bear the members
of thy dying King and God.
Tree, which solely wast found worthy
the world’s Victim to sustain.
harbor from the raging tempest!
ark, that saved the world again!
Tree, with sacred blood anointed
of the Lamb for sinners slain.
Blessing, honor, everlasting,
to the immortal Deity;
to the Father, Son, and Spirit,
equal praises ever be;
glory through the earth and heaven
to Trinity in Unity. Amen.
Also at Thesaurus Precum Latinarum was this note:
“There is a charming ancient legend that is hinted at in the second verse of this hymn. According to this legend, the wood of the Cross upon which Christ was crucified was taken from that tree which was the source of the fruit of the fall in the Garden of Eden. When Adam died, the legend states, Seth obtained from the Cherubim guarding the Garden a branch of the tree from which Eve ate the forbidden fruit. Seth planted this branch at Golgotha (the place of the skull), which is so named because Adam was buried there. As time went on, the Ark of the Covenant, the pole upon which the bronze serpent was lifted, and other items were made from this tree.”