Value Village ／ Everyday know-how
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Japanese homes keep plants — bonsai, kokedama, the ubiquitous pothos — but the humid climate and small rooms change the rules that houseplant guides written for dry Western homes assume.
| Season | Indoor humidity (Tokyo, typical) | Plant risk | Adjustment |
|---|---|---|---|
| Rainy season (June–July) | 70–85% | Root rot, fungus gnats, mould on soil, powdery mildew | Water less; no misting; fan or dehumidifier; move to the balcony under cover |
| Summer (July–September) | 65–80% | Heat above 35°C on a closed-up balcony; leaf scorch | Shade; water early morning; bring tender plants in |
| Autumn | 50–65% | Fine | — |
| Winter (heated rooms) | 20–35% | Drying, spider mites, cold draughts by windows at night | Water when dry; keep away from heater blast and single-glazed windows; humidifier helps plants and people |
[Verify] Humidity ranges with JMA normals and indoor-environment surveys; dengue/mosquito guidance with the Ministry of the Environment.
In June you are misting into 80% humidity — the result is mould. Misting is a winter-only habit in Japan, if at all.
Water when the pot is light or the top 3 cm are dry; in the rainy season that may be every two weeks, in a heated winter room every four days. Lift the pot.
Almost all bonsai are outdoor trees that need light, cold dormancy and airflow. Indoors they decline within months. Windowsill or balcony, brought in only for display.
Standing water is root rot plus mosquito larvae — a public-health concern in summer. Empty saucers after watering.
Plants add humidity and mould risk in a small humid room; a few, well placed with airflow, beat a jungle. The Japanese habit of one plant per surface, in a pot that fits the space, is climate-driven.
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https://www.env.go.jp/nature/dokuhou/
https://www.data.jma.go.jp/stats/etrn/
https://www.hokeniryo.metro.tokyo.lg.jp/kankyo/kankyo_eisei/jyuukankyo/indoor/kabi.html
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
Always follow the instructions on any product you use, and never mix cleaning products. If you rent your home, check with your landlord before making any changes.
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