Tchaikovsky’s favourite flower was lilies of the valley.  The local musical society at Tiflis was extremely enthusiastic to have the presence of Tchaikovsky at a gala concert of his works at the Opera House:

Ippolitov-Ivanov had thought of everything, even finding out by devious means what his favourite flower was.  This flower did not grow in the Tiflis area, so Ippolitov-Ivanov sent to Kutasi, some three hundred miles away.  He ordered an entire railway carriage to be filled with them.

When the composer entered the theatre, he was simply staggered by the look of it.

Spring that year [said Ippolitov-Ivanov] had been marvellous and the wealth of flowers was almost unbelievable – in particular, of Pyotr Ilyich’s beloved lilies of the valley.  So the theatre was decorated with greenery and an assortment of flowers and the box set apart for our dear guest and his relations was filled with lillies of the valley – Tchaikovsky was seated in an absolute bower of them.

Sharp at eight o’clock [Ippolitov-Ivanov continues], Pyotr Illyich, his brother Anatoly Ilyich and his wife and daughter entered the theatre in which the whole of musical Tiflis had been waiting in impatient expectation for the best part of an hour.  Everybody rose to their feet, and choir, chorus, soloists and audience burst out with “Glory to our dear and honoured guest” which we took, with suitably altered words, from the first act of Mazepa, “Praise to our great genius!”

Cited in: Hanson, Lawrence and Elisabeth (1965) Tchaikovsky: A New Study of the Man and His Music. London: Cassell & Company, p.246-247.