Vapor pressure deficit (VPD) and its function in plant growth can be used as a tool for increasing your harvest. VPD isn't new, but historically farmers relied on the natural climate. Only more recently, with the rising popularity of indoor commercial farming and greenhouses, it's become possible to precisely control environmental conditions, including VPD. With the best genetics and nutrients globally, your plants can't reach their potential without dialing in humidity and temperature. Knowledgeable cultivars manipulate VPD to encourage the stomata on their plants to open, allowing them to take up as many nutrients as possible, resulting in increased growth.