Learn from Acharya Indu Prakash in Vastu Shastra about the reason why dried flowers from the house should be removed immediately. He states that dried up flowers are like a carcass and in the same way as dead bodies are not kept in the house, similarly dried flowers should also not be kept in the house as they might become the cause of various problems.
The famous Tantra treatise 'Mantra Maharnava' states that all flowers offered to God become instantly clean. It is further stated that the Nirmalas should be removed immediately, otherwise the negative powers like Chandali, Chandanshu, and Vishwakasena can enter your house.
Nowadays it is the fashion to keep dried pot pori flowers, but putting fake flowers or the poles of pori are similar to poisons. Therefore, only fresh flowers should be used.