[Grammar] How long + negative?

[Nudrat Nazeer]

Can we say " The plants are dying. How long haven't you watered them?" OR " Since when haven't you watered them?"?

 

[Rover_KE]

These don't sound natural.

Stick with 'How long is it since you watered them'.

Rover

 

[Heterological]

I would ask, "how long has it been since you watered them?"

 

[Nudrat Nazeer]

Can we replace " how long" with "since when"?

 

[Heterological]

It's grammatically correct to say "since when have you watered them?" but "how long has it been since you watered them?" sounds more natural. The reason for the verb change is that in the "since when" sentence, "have" is conjugated for "you;" in the "how long" sentence, "have" is changed to "has" to go with "it."