Indoor plants accumulate dust on their leaves, mineral deposits on their soil, and a general staleness from living in the same spot with poorly ventilated air for months. Some suggest that spending time in warm summer rain gives houseplants a spa day, as soft water reaches their roots, dust is washed away, and they get a rare dose of outdoor conditions.
The method recommends waiting for a warm day when the temperature outside is close to indoor conditions, moving plants to a wind-protected spot, and letting them enjoy the rain for 20 minutes. However, British summer showers are often not warm and are unpredictable in intensity.
In a test, tropical plants were placed outside during a light summer shower. The rain was colder than expected, causing one Calathea to develop darkened patches on its leaves. A Monstera fared better but was knocked about by the rain, while other plants were fine.
The verdict warns that a cold downpour on plants acclimatised to stable indoor temperatures can cause chill damage and waterlogged soil, especially in pots without drainage, leading to root rot. There is also a risk of outdoor pests like vine weevils and slugs hitching a ride back inside. The advice is to stick to a lukewarm shower indoors, which provides the rinse without the risks.
