Whether greenery is hung in the heat of your house or the cold air outside, these winter environments are intensely dry, and the plant has no source of moisture. Once you've conditioned the cuttings, treat them with an anti-desiccant spray (sold at nurseries). This seals the pores on the leaves and bark and helps the foliage retain moisture.

-From Martha Stewart, http://www.marthastewart.com/274907/holiday-greenery-101/@center/307034/christmas-workshop