As an expert on potion crafting, Lord Draco knew to highlight how very important it truly is to have a deep understanding of all the different ingredients and their relations. As he put it:

“Rosemary on sunny Sundays

Just isn't the Rosemary

on Cloudy Fridays.

"Like Lavender in winter

when a blizzard howls outside

just isn't the Lavender

in peaceful summer nights

when the waters stand still

and the air is like warm milk

and honeyed tea.

"And the Four Leafed Clover

you picked yourself

isn’t at all like

the Four Leafed Clover

that you pointed out for a five years old cousin

and who then gave it to you for safekeeping.

"People are prone to forgetting that no potion is alike. It truly happens to be so that yesterday’s medicine has a tendency of turning into today’s poison. Consequently, today’s unfortunate event is likely to transmute into tomorrow's gold. You cannot imagine how frequently it is so.”