Gosh what a question!
It is difficult to pin-point any particular double-entendre but the whole premise of the book is written around the aesthetic movement, which had historic links to Oscar Wilde himself and homosexuality. The entire book is a fountain of underlying (wicked) sexual/homoerotic prose. Wilde was known for his homosexuality and for his trademark wore a green carnation which became one of the first symbols adopted by homosexual men to identify themselves. Note Noel Cowards verse:
Pretty boys, witty boys,
You may sneer
At our disintegration.
Haughty boys, naughty boys,
Dear, dear, dear!
Swooning with affectation ...
And as we are the reason
For the Nineties being gay,
We all wear a green carnation.
In the book itself, the opening chapter emphasises the �prettiness� of Reggie himself and his �dandy� ways and his �delicate walk�. The Coward-ess form of written text is rather subtle in modernity and I think when most recall such lines they have preconceptions of verse germane to being homosexual. In the book, there are several references to wickedness, saints and sinners and acting according to nature, to sin is exciting - and lots of talk about buns and strawberries which might have sexual connotations.
��.youth is not passionate it is merely sticky and excited.�
http://www.yorku.ca/inpar/green_carnation.pdf