Praise be to Allah.
This is an innovation (bid’ah) for which there is no basis in sharee’ah. Throwing seeds, perfume and clothes into the grave are all reprehensible actions for which there is no basis. The grave should not be opened unless there is a good reason for doing so, such as the workers forgetting their tools like shovels, so it may be opened for that reason, or if one of them has dropped something important, so the grave may be opened to retrieve it. But opening it to scatter seeds or clothes and the like is not permitted.
Women should not visit graves, because the Prophet (peace and blessings of Allaah be upon him) cursed women who visit graves. That was narrated from Abu Hurayrah, Ibn ‘Abbaas and Hassaan ibn Thaabit (may Allaah be pleased with them). So it is not permissible for them to visit graves, but that is prescribed for men, because the Prophet (peace and blessings of Allaah be upon him) said: “Visit the graves, for they remind you of the Hereafter.” (Narrated by Muslim in his Saheeh).
The reason why women are forbidden to visit graves – and Allaah knows best – is that they are a temptation (fitnah) and they have little patience.