Both answers are grammatically correct, but it's much better to say "there are no flowers." It simply sounds better. Usually, when people say "there aren't," it's common to add the word "any" after it. For example: there aren't any flowers on the table. Hope this helps.

There are no flower

'There are no flowers on the table' is correct. 'There aren't flowers on the table' is non-standard but makes sense. It is technically correct to add 'any' after plural countable nouns in a negative sentence like this so that it becomes 'There aren't any flowers on the table'. Hope that helps!

As everyone else has said, 'there are no flowers on the table' would be the better phrase. Just to put a finer point on this question, the only time I would prefer the use of 'there aren't flowers on the table' would be in a negative response the the statement 'There are flowers on the table'. The reason being is that you mirror the word 'are' in the first statement to link the two statements together, making it clear you are providing a response to that statement.