The flowers smelling sweet in the garden attract many visito

smelling sweet in the garden 是分词短语做后置定语修饰the flowers.
主语：the flowers .
后置定语:smelling in the garden.
谓语:attract.
宾语：many visitors.
非限定性定语从句：which makes Tom very happy.
因为smell是感官动词,平时都说the flowers smell sweet.所以在这句中the flowers 是smelling的逻辑主语,用现在分词形式.
再问： the flowers 是smelling的逻辑主语，用现在分词形式。为什么是逻辑主语？？？？为啥不能直接做非谓语动词的主语？？我觉得the flowers 可以做smell的主语