Quote

sarveshaam api pushpaanaam / sahasragunam utpalam
tasmaat padmam tathaa raajan / padmaat tu shatapatrakam
tasmaat sahasrapatram tu / pundareekam tatah param
pundareeka sahasraat tu tulasi gunato 'dhikaa
(Mahabharata- Ashwamedhika Parva 14.96.15).

"Of all the flowers, O King, the bluish lotus flower (Utpalam) is thousand times more qualified for My worship. Greater than that is the red lotus (Padmam) flower. Of the red lotus, the lotus with hundred petals is more qualified. Better than that is the red lotus with thousand petals. Better than this is the white lotus flower (Pundarika). And better than white lotus flower with thousand petals is the Tulasi leaf, which is even more qualified for My worship".