Learn Italian: Voglio che voi innaffiate il prato stasera. - I want you all to water the lawn tonight.

The phrase voglio che expresses a desire or will. In Italian, when you express what you want someone else to do, you must use the subjunctive mood for the second verb.

Innaffiate looks exactly like the normal present tense for voi. Is it really the subjunctive?

Yes! For regular -are verbs, both the noi and voi forms in the present subjunctive are completely identical to the regular present tense. You only know it is the subjunctive here because it follows voglio che.

The English translation uses the infinitive 'to water'. Why does Italian use a conjugated verb instead of innaffiare?

In English, we say 'I want you to do something'. But in Italian, if the subject changes between the two verbs (from io wanting to voi watering), you cannot use the infinitive. You must use che followed by the conjugated subjunctive verb. You only use the infinitive if the subject stays the same, like voglio innaffiare (I want to water).

Since innaffiate only goes with voi, do we really need to include the pronoun voi in this sentence?