Hilchos Shabbos - Windowsill Plants

QUESTION: I have flowers growing in soil in flowerpots on my windowsill. Can I open the window shades to give them sun?

ANSWER: Poskim write that one may not uncover a greenhouse on Shabbos to allow sunlight to shine in, since the intention is to cause the plants to grow. Actions which cause plant growth are included in the prohibition of Zorei’a (planting). Some poskim maintain that this would be a Torah prohibition (see Sefer Shvisas HaShabbos – Zorei’a 10). However, the Har Tzvi (OC 1:133) argues that letting in sunlight is not a direct melacha but rather only a grama (causative), which is only Rabbinically forbidden. Either way it may not be done on Shabbos if the intention is to cause the plants to grow. Har Tzvi writes that if one’s intention in opening the shade is for personal use and not for the plants, this is permitted. He explains that an unintended grama is permitted on Shabbos. Rav Ovadya Yosef (Yechave Daas 5:29) writes that although there is good reason to be lenient, still it is best not to leave plants on the windowsill where they will directly be affected by the opening of the shades, even though your intent in opening the shades was not for the plants. However, if the plants are away from the window, and your intention is not for the plants, you may open the shades.

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