The European nettle tree likes deep and infrequent watering. You would want to soak them in a gallon of water each time, especially when they are planted in pots. The water storage of flower pots is limited and the soil will dry out faster. Watering is required every 3 to 5 days when living in a cold region. Water it early in the morning when the soil is dry, outdoors or indoors. You can also determine if watering is needed by checking the soil inside. When the top 2-3 inches of soil is dry, it is time to give the plant a full watering. During hot days, you may need to check the moisture daily, as the heat can quickly dry out the soil in the pot. Irrigation of the soil is also required if you have a garden. When you live in a hot climate, you might want to water once a week. Only water when you notice that about 2 to 3 inches of soil become too dry outdoors or indoors. Consider the amount of rainwater on the plant and ensure not to add to it to prevent root rot.You may not need additional watering of the plants if there is a lot of rainfall.European nettle tree generally grows during spring and fall. When they are outdoors, you need to add mulch about 3 to 4 inches deep to conserve more water. You need to water the plants more frequently in sandy soil because this type tends to drain faster. However, with the clay one, you need to water this less frequently where you could go for 2-3 days to dry the plant and not develop any root rot. You could mark the date on the calendar whenever you water and when you notice that the leaves are starting to droop. This can mean that you might be a day late.