This article covers the PPFD (PAR) targets I aim for with my orchids and houseplants (on a 12h daily cycle); please understand these are my personal estimations and guidelines—they’re not coming from a book or study. I’ve simply cross-referenced the foot candle recommendations for various orchids and houseplants, extrapolated those numbers in relationship to full sun, adjusted those values to PAR, and then finally made additional refinements based on my plants, lights and some real-world PAR readings.
If you’re not familiar with PAR and PPFD, you may want to refer to this detailed post about orchid light, first. Alternatively, maybe you just want to know the visible signs your orchid is/not getting enough light.
For general interest and perspective on light intensity, “full sun” on a bright day (no clouds) is about 2,000-2,200 umol/m2/s. Many “tomato” (cannabis) growers run their plants at a PPFD up to 800 umol/m2/s (which is generally too bright for most orchids or tropical houseplants). Your goal with the majority of tropical plants should generally be to target about 15-30% filtered sun (removing 70-85% of direct sun’s intensity – like how leaves and clouds would naturally outdoors in a rainforest). When considering light intensity for indoor plants, be careful and analytical as you will have to contend with conditions unique to your home and area of the world, such as ambient room light, window direction (and angle of sun into your home), seasons, spectrum, distance from lights, time period, and so on. In other words, light will vary greatly in almost every home.
Outdoor & Greenhouse PAR Readings for Relational Insights
A huge thanks to Kelly McCracken (from High Desert Orchids in Albuquerque, New Mexico)— she captured PAR data at different times of day within her greenhouse, home and outdoors. Her readings have greatly helped me verify and improve the accuracy of this post. Hop over to her site or follow them on Facebook!
A Summary of Kelly’s Greenhouse PAR Readings
(so you have context and understanding of light intensity)
- 50–70 umol/m2/s PPFD – Greenhouse, Low Light (Under Bench)
- 100 umol/m2/s (morning/evening) up to 250 mid-day maximum – Greenhouse, Moderate Light (Bench Level)
- 200–500 umol/m2/s average with a peak intensities reaching 800-900 – Greenhouse, High Light (Roof Level)
- 2,000–2,200 umol/m2/s – Outside Direct Sun (Unshaded/Full)
Light Suggestions for Orchids (PPFD or PAR Recommendations)
- Low-Light Orchids (Mottled-Leaf Paphs, Jewel Orchids, Phals)
40–80 umol/m2/s PPFD (20 umol/ft2/s) - Moderate-Light Orchids (Onc, Phrags, Epidens, Dends etc)
80–150 umol/m2/s PPFD (30-40 umol/ft2/s) - High-Light Orchids (Cattleya)
150–350 umol/m2/s PPFD (50-100 umol/ft2/s) - Very High-Light Orchids (Vandas)
350–600 umol/m2/s PPFD (50-100 umol/ft2/s) - *Converting meters to feet: 1m = 3.28ft
**NOTE: These are general suggestions not EXACT numbers; you can expect that +/- 50-100 umol/m2/s is likely okay and individual orchid species may be adapted to a range beyond these numbers—for example, a lot of strap-leafed paphs can take closer to 150 umol/m2/s. I encourage you to use this information to help you benchmark where your light should be, but as with all things related to horticulture and plant care, adjust based on your conditions and how your plants perform, look and grow.
How Much Light (PAR) for Aroids & Tropical Houseplants?
Start low and work up. You’ll know if your plant is stressed if the leaves become pale and chlorotic. A good benchmark should echo the orchid brackets:
- Very Low-Light Houseplants (Begonia pavonina)
20–40 umol/m2/s PPFD (20 umol/ft2/s) - Low-Light Plants (African Violets, Tropical Begonias)
40–80 umol/m2/s PPFD (20 umol/ft2/s) - Moderate-Light Houseplants (Low-light Aroids like Anthuriums and Pothos)
80–150 umol/m2/s PPFD (30-40 umol/ft2/s) - High-Light Houseplants (Tropical Succulents like Christmas Cactus, Philodendrons, Monstera)
150–350 umol/m2/s PPFD (50-100 umol/ft2/s) - Very High-Light Houseplants (Tropical Trees like Chocolate, Citrus, etc)
350–600 umol/m2/s PPFD (50-100 umol/ft2/s) - Full-Sun Plants (Cannabis, Fruiting Trees/Shrubs, Eucalyptus, Desert Cacti)
600–2,200 umol/m2/s PPFD
Infographic: Light Comparisons Home, Greenhouse & Outdoors
