I have never had an issue with silk plants. Like already said wash them well with hot water and soap, making sure all the soap is rinsed off. There will be a lot of dye residue that will wash off, that's what you want. The reason it is best to use live plants is because they help keep up humidity but silk works well as long as you don't have a plant muncher. Just clean them regularly to make sure you don't get any mold.