Plants react adversely to drastic change; in particular, decreases in temperature have a profound effect. Plants that have been grown in a controlled environment are tender and the risk of tissue damage from exposure to sudden temperature decreases is great. This is most prevalent in herbaceous plants such as annuals and perennials. Gradual exposure is the key to success. For home owners the most practical method of acclimatization involves movement of plants outdoors for increasing periods of time. If purchasing plants before the recommended planting date (usually towards the end of May), plants will have to be moved outside during warm days and inside at night. During the second week place plants outside and leave outside at night if there is no chance of frost. This method can be modified as required but should suffice for most plants. Keep the plants well watered as they will dry out quickly. Movement of the plants inside during extreme conditions (heavy rain, hail) during the first two weeks is also recommended.