|MadSci Network: Botany|
Plants need light as the energy source for photosynthesis. Most houseplants are shade plants that normally live in forests. Shade plants have lower light requirements than plants that live in full sun, or sun plants. However, some shade plants are very adaptable to higher light levels. Some aren't however. African violet (Saintpaulia spp.) will be harmed by more than about 10% of full sunlight. A houseplant's shade tolerance often depends on how quickly they are transferred from high to low light. If they are transferred gradually to low light, or acclimatized, they survive much better. The reverse is true as well. People often damage or kill houseplants if they move them from a shady indoor location directly into full sun when they set them outside for the summer. Scientists measure photosynthetically active radiation (PAR). Full sunlight is about 2,000 micromoles per square meter per second of PAR or about 10,000 foot candles. Some foliage houseplants can survive with less than 1% of full sunlight or less than 20 micromoles per square meter per second of PAR or under 100 footcandles. Some of the low light houseplants are Philodendron, pothos (Epipremnum aureum), Chinese evergreens (Aglaonema), ferns and parlor palm (Chamaedora elegans). The website cited below has lists of low light houseplants. Houseplant books often group houseplants based on their light requirements. The book by Hartmann and others has five levels: Low 25 to 75 footcandles Medium 75 to 200 footcandles High 200 to 400 footcandles High + 400 to 600 footcandles High ++ 600 to 1200 footcandles The above scale ranges from about 1% to 12% of full sunlight. Other books sometimes use the direction the window faces to group plants by light requirements. South windows get more light than north windows for example. References Hartmann, H.T. et al. Plant Science: Growth, Development, and Utilization of Cultivated Plants. Englewood Cliffs, NJ: Prentice Hall. Light and Houseplants
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