This section is from the book "British Wild Flowers In The Four Seasons", by Thomas Moore. Also available from Amazon: British Wild Flowers.
H. bifolia: stem 1-1 1/2 foot high; leaves two, rather large, broadly ovate or oblong; flowers pure white or with a slight greenish tinge, large and sweet-scented, in a loose spike, 3-8 inches long; lip linear, entire, the spur slender, twice as long. - Moist pastures and meadows. Fl. June, July.
H. albida: stem 6-8 inches high; leaves few, oblong; spike dense, cylindrical, 1-2 inches long, with numerous small, yellowish-white, sweet-scented flowers; lip with three deep acute lobes, the middle one largest. - Mountain pastures. Fl June, July.
H. viridis: stem 6-8 inches high; leaves few, ovate or oblong; flowers yellowish-green, in a close spike; lip linear, with three teeth, the middle one smallest. - Frog Orchis. - Dry hilly pastures. Fl. June, July.
 
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