"De oude man vertelde me over zijn relatie met een tulp."
Translation:The old man told me about his relationship with a tulip.
Never heard of anything like that. The only thing that comes close is the tulpenmanie in the Dutch Golden Age (Gouden Eeuw, 17th century) which is seen as the first well documented economic bubble. The value of Tulip bulbs rose to extreme levels and subsequently crashed.
The sentence about a relationship met een tulp indeed is an unusual case of somebody being very attached to one specific tulip. However if you change it to …zijn relatie met de tulp it suddenly turns into a normal sentence about for instance some bloemist (florist) that likes tulips a lot and tells how these flowers had an impact on his life (as with all relationships it's a bit more than simply liking them).