I agree that the score to Evening Primrose is excellent. There are only four songs, but every one is perfect. I've also seen the Tony Perkins version and agree that it's imperfect, but the 2001 recording from Nonesuch, with Neil Patrick Harris and Theresa McCarthy, is quite good. I think I prefer "If You Can Find Me I'm Here" to "I Remember Sky," but it's close.
And then there's "Take Me to the World" and "When." Gotta love it. Sondheim just got better after this one, of course, but he was already brilliant in 1966.
By the way, this wasn't a "special," in the conventional sense of the term. It was an episode of ABC's wonderful 1966-67 anthology series Stage 67. It featured plays by writers like Truman Capote and Murray Schisgal. It even featured a musical episode by Burt Bacharach and Hal David, though Sondheim blew those guys away. (Despite which, I love Burt Bacharach and Hal David.)
"A world of skies that's bursting with surprise."