Translation:There are many trees around my house.
I just got marked wrong and was corrected with "There are a lot of trees around my house." But "there are" can only be used with plural nouns and "a lot" is singular. Elsewhere in the course, users are insisting that "there's" must not be used with plurals, so this is both wrong and inconsistent.
I think that depends upon what you mean by "a lot."
It so happens that English does have a singular word "lot" which would work here, best described as a vacant lot, or a plot of land. If you are saying that your house is surrounded by a (mostly) vacant lot, one which is devoid of buildings but otherwise full of trees, then you could indeed say that "there is a lot of trees around my house," and it would be grammatically correct (although 'there is a lot of trees surrounding my house' would be a better way to express it). However, this sentence doesn't mean the same thing.
This Chinese sentence uses 很多, which translates into English as "many" or "a lot". However, you can't unequivocally say that this usage of "a lot" is singular - it's actually a collective noun. Some collective nouns can be treated as singular grammatically, but this isn't one of them. "There is/there's a lot of trees around my house" is NOT a grammatically correct sentence. That doesn't mean people don't say it; I have heard many native speakers, both British and American, say things like "We was at the pub." It's a construct that exists in some dialects, but it is grammatically wrong, and it sounds slightly uneducated.
In short, "lot" can be a very confusing word, because it can be used in different ways, in terms of meaning and grammatical constructions. In this case, it modifies 'trees,' and thus, since the modification is "many," the plural form of the verb is correct.
Thanks (a lot 8-) for this explanation. Duolingo should think about non english people who are here to learn Chinese, not English. So they should not be too picky in the accepted replies and later provide a better sentence, for those who are interested.