I'm confused as to what should be the correct sentence here.
A row of trees were to be planted in front of the house.
A row of trees was to be planted in front of the house.
I'm confused as to what should be the correct sentence here.
A row of trees were to be planted in front of the house.
A row of trees was to be planted in front of the house.
It is true that notionally, each tree is planted, so it would be ok to say that
A row of trees are planted.
Most often, however, when the row is considered as a whole and the action of the verb hints to the whole, not to each item of the whole, then you can safely use the singular.A row means ONE row, so it is singular.
Cambridge has a similar example:
A row of tall fir trees shuts off the view of the street in front.
It is as the rule of verb agreement with the collective nouns:
When all the members of a collective noun are performing an action as a unit (and that’s usually the case), use a singular verb.
- The chamber orchestra often plays at the Art Centre.
When the members of a collective noun are performing an action as individuals, use a plural verb. In this case, all or some members of the group are doing something independently of the other members; the group is not acting together as a unit.
- The orchestra are tuning their instruments. (source)