Certified Professional Horticulturist (CPH) Practice Exam

During the summer, how often should most indoor plants typically be watered?

1. Once a week

2. Every day

3. Every two weeks

4. When the top inch of soil is dry

The correct answer is: When the top inch of soil is dry

The most appropriate guideline for watering indoor plants during the summer is to do so when the top inch of soil is dry. This method takes into account the varying needs of different plant species and the conditions within the indoor environment. During warmer months, factors such as temperature, humidity, light, and air circulation can significantly affect how quickly soil dries out. By checking the moisture level in the top inch of soil, a gardener can assess the plant's actual needs rather than adhering to a strict schedule, which may lead to over or under-watering. Most indoor plants prefer to dry out slightly between waterings, as excessive moisture at the roots can lead to issues like root rot. In contrast, watering weekly, daily, or every two weeks does not universally apply to all types of indoor plants. These approaches ignore the specific moisture requirements of each species and the environmental factors influencing water evaporation and absorption. Therefore, consistently checking the soil's moisture level is a more reliable and effective practice for maintaining plant health during the summer months.