Famous last words heard by houseplants:
“Bright indirect light?” This spot seems bright enough.
Your interior light levels form the growth potential of the plant. Your care efforts realize that potential (watering, fertilizing, repotting). Good light is the PREREQUISITE for a plant to grow but the term “bright indirect light” fails to convey anything concrete.
The worst part is the term “bright indirect light” makes you think just any place the sun doesn’t shine is considered indirect light. And our eyes adjust to a wide range of light levels so you will NOT feel the difference.
Instead, those with huge, unobstructed windows and/or skylights are patting themselves on the back at how good they are with houseplants while those with smaller windows living between buildings are struggling to figure out why their fiddle leaf fig always ends up with 90% of their foliage lost.
After measuring light, I realized there’s no such thing as a ‘greenthumb’ – just people with large, unobstructed windows.
Step 1: Get a light meter and get to know how bright your indirect light actually is.
A light meter is so critical to understanding light that I designed and manufactured my very own:
The LTH Meter
Light | Temperature | Humidity
I designed and manufactured the LTH Meter with houseplant owners in mind. When you know your light situation, you will know where to put plants (and where NOT to put plants) – and you can start using grow lights properly!
Disclaimer: this article contains Amazon Affiliate links. Earnings from qualifying sales goes to support the work of House Plant Journal – thank you!
This is the Dr. Meter LX1330B Light Meter that I used before. It’s not as compact as the LTH Meter, has limited measuring ranges (need to manually select the range), and does not measure temperature and humidity. The pricing has been varying wildly on Amazon but it should be around $40-60 [US Link] [CAN Link]. An alternate model: [US Link] [CAN Link]
What about apps? Android devices do not have standardized ambient light sensor hardware and the iOS platform doesn’t give access to the iPhone light sensor, which means those apps are doing a rough calculation based on the camera brightness value. An app might be able to give you a rough idea, but a dedicated device will do the proper cosine correction for the angle of incident light (that’s what the white dome is for).
Step 2: Bookmark this page so you can look up the levels of indirect light necessary for various plants. I don’t have every possible houseplant but after reading a few of these, I think you’ll get the idea.
Commercial Light Levels: most of our typical “houseplants” are grown in greenhouses with varying layers of shade cloth. To give you a rough idea, “50% Shade” would measure to 5000 foot-candles (FC) and “90% Shade” comes to 1000 FC – this is the strength of the sun shining through different layers of shade cloth, which is a black net-like material. These numbers are easily searchable on the internet – I’ve included the source links where applicable. ***Don’t expect to achieve these light levels indoors from your indirect light.***
Interior Light Levels: plants can technically survive in a wide range of light levels so do not take the numbers listed here as prescriptive – they aren’t strict requirements. You should think of them as guidelines for good growth. Another consideration is that “good growth” is subjective as any plant will take the shape of its light situation – up to a certain point, it’s not entirely under your control! These numbers are gathered from my own observations and measurements. ***Use these as guidelines.***
How to measure natural light:
- Sensor placement: top of the plant
- Sensor orientation: should be pointed straight up but if you find that you have to turn the sensor to get a higher reading, it just means over time, the plant will tilt towards that direction
- WHEN to measure: the purpose of the light meter is to measure the strength of INDIRECT light so you want to get a sense of the average strength of this light while the sun is NOT in view (and also not too close to sun rise or sun set – when the overall sky is darker)
- DIRECT SUN: also take note of the total duration the sun shines directly on the plant
Analysis for natural light:
- If the average indirect light is above “Good for Growth”, then expect good growth
- If the average indirect light is at or below “Minimum for Maintenance”, then don’t expect strong growth
- If the duration of direct sun is above the “Tolerance of Direct Sun”, then block it with a white sheer curtain
- If the duration of direct sun is at or below the “Tolerance of Direct Sun”, then there’s no need to block the plant (just be sure to keep up with watering)
For white LED grow lights:
- For good growth: set the distance of the grow light such that the reading at the top of the plant is at or above “Good for Growth” and keep the light on for 12-16 hours a day
- For maintaining over winter: set the distance of the grow light to get a reading around the “Minimum for Maintenance” and keep the light on for 8-12 hours a day
Note on FC (foot-candle) vs PPFD (PAR Photon Flux Density)
After using a spectrometer, I realized that illuminance (FC and lux) and PPFD correlate nicely for natural light and white LED light (approximate PPFD = 0.2 x FC – for those two light sources). So as long as you’re using either of those light sources, you can use whatever light meter you have (traditional foot-candle/lux or PAR meter) and refer to the chart.
Discrepancies between FC and PPFD only arise when using these grow lights:
- Red/Blue (“blurple”) LED grow lights
- Ceramic metal halide
- High pressure sodium
- Fluorescent
So you can expect good growth results even if measuring with a traditional foot-candle meter as long as you’re using either natural light or white LED lights.
Note: the full unit of PPFD is “µmol/s/m²” but, for this chart, it is shortened to “µmol”
Looking for a sensible and logical approach to houseplant care?
Find it here:
| Plant | Good Growth | Minimum for Maintenance | Tolerance of Direct Sun | Commercial Light Levels | References/Comments | |
|---|---|---|---|---|---|---|
| African Violets | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 1000-1200 FC (200-240 µmol) | https://mrec.ifas.ufl.edu/foliage/folnotes/africanv.htm | |
| Aglaonema (Chinese Evergreen, and several species) | 200 FC (40 µmol) | 100 FC (20 µmol) | 1-2 hours direct sun is tolerable | 1000-2400 FC (200-480 µmol) | Classical “low light” tolerant houseplant. Plant dies slowly below 100 FC and will look ugly after a year or two. | https://mrec.ifas.ufl.edu/Foliage/folnotes/aglaonem.htm |
| Air Plants (Tillandsia – many species) | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 3000-7000 FC (600-1400 µmol) | my air plant care video here https://youtu.be/sjNVLgEbvOY | https://bromeliadsocietyhouston.org/genera-intro/tillandsia/ |
| Alocasia (several species) | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 2000-5000 FC (400-1000 µmol)(estimated based on ‘part shade/part sun’) | Leaves will very likely die back. Calmly repot the base into fresh soil and new leaves may sprout. | https://edis.ifas.ufl.edu/fp033 |
| Anthurium (several species) | 400 FC (80 µmol) | 100 FC (20 µmol) | 1-2 hours direct sun is tolerable | 1500-2000 FC (300-400 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/anthuriu.htm | |
| Aspidistra (Cast-Iron Plant) | 200 FC (40 µmol) | 100 FC (20 µmol) | 1-2 hours direct sun is tolerable | 2000-5000 FC (400-1000 µmol) | Classical “low light” tolerant houseplant. Plant dies slowly below 100 FC but will look fine for many months, possibly years. | https://ufdcimages.uflib.ufl.edu/UF/00/08/93/74/00001/EP14700.pdf |
| Areca Palm | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 5000-6000 FC (1000-1200 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/areca.htm | |
| Arrowhead Vine (Syngonium podophyllum) | 200 FC (40 µmol) | 100 FC (20 µmol) | 2-3 hours direct sun is tolerable | 1500-3000 FC (300-600 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/nephthyt.htm | |
| Begonia (several species) | 400 FC (80 µmol) | 200 FC (40 µmol) | 1-2 hours direct sun is tolerable | 2000-2500 FC (400-500 µmol) | https://mrec.ifas.ufl.edu/foliage/folnotes/begonias.htm | |
| Bird-Of-Paradise (Strelitzia) | 800 FC (160 µmol) | 400 FC (80 µmol) | 4-5 hours direct sun is tolerable | 2000-5000 FC (400-1000 µmol)(estimated based on ‘part shade/part sun’) | http://hort.ufl.edu/database/documents/pdf/shrub_fact_sheets/strrega.pdf | |
| Calathea (several species) | 400 FC (80 µmol) | 200 FC (40 µmol) | 1-2 hours direct sun is tolerable | 1000-2000 FC (200-400 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/calathea.htm | |
| Cordyline (Ti Plant) | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 3000 FC (600 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/cordylin.htm | |
| Croton (several species) | 800 FC (160 µmol) | 400 FC (80 µmol) | 4-5 hours direct sun is tolerable | 3000-5000 FC (600-1000 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/crotons.htm | |
| Dieffenbachia (Dumb cane; several species) | 400 FC (80 µmol) | 100 FC (20 µmol) | 3-4 hours direct sun is tolerable | 1500-3000 FC (300-600 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/dieffenb.htm | |
| Dracaena (several species) | 200 FC (40 µmol) | 100 FC (20 µmol) | 3-4 hours direct sun is tolerable | 2000-3000 FC (400-600 µmol) | Very low-light tolerant – I’ve seen one last for years at 30-50 FC. It had very long, thin and dark green spindly foliage but it was alive. | https://mrec.ifas.ufl.edu/Foliage/folnotes/dracaena.htm |
| English Ivy (Hedera helix) | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 1500-2500 FC (300-500 µmol) | lower leaves will drop off – generally doesn’t look nice after a year. | https://mrec.ifas.ufl.edu/Foliage/folnotes/english.htm |
| Hoya (several species) | 200 FC (40 µmol) | 100 FC (20 µmol) | 3-4 hours direct sun is tolerable | 1500-2000 FC (300-400 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/waxplant.htm | |
| Ferns (Boston Fern, Bird’s Nest Fern, Maidenhair Fern) | 200 FC (40 µmol) | 100 FC (20 µmol) | Bird’s nest fern/maidenhair fern – 1-2 hours direct sun is tolerable but must keep soil evenly moist | 1500-3000 FC (300-600 µmol) | my Maidenhair fern care video here: https://youtu.be/Q1FecMy2zXE | https://mrec.ifas.ufl.edu/Foliage/folnotes/bostonF.htm https://mrec.ifas.ufl.edu/Foliage/folnotes/birdnest.htm |
| Ficus (Rubber plant, elastica; Fiddle leaf fig, lyrata; benjamina) | 800 FC (160 µmol) | 400 FC (80 µmol) | 3-4 hours of direct sun is tolerable | 2000-6000 FC (400-1200 µmol) | if you don’t have at least 400 FC of indirect light, your fiddle leaf fig will lose most of its lower leaves. If you have small windows, save your money. | https://mrec.ifas.ufl.edu/Foliage/folnotes/ficus.htm |
| Fittonia (Nerve Plant) | 200 FC (40 µmol) | 100 FC (20 µmol) | 1-2 hours direct sun is tolerable but must keep soil evenly moist | 1500-2500 FC (300-500 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/fittonia.htm | |
| Jade Plant (Crassula ovata, other Crassula) | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 5000-6000 FC (1000-1200 µmol) | Book "Tropical Foliage Plants" by Lynn P. Griffith Jr. - https://www.houseplantjournal.com/recommended-product/reference-books/ | Jade will stretch with indirect light levels below 200 FC most of the day - it won't die but you may not enjoy the stretched look. |
| Maranta (Prayer Plant) | 200 FC (40 µmol) | 100 FC (20 µmol) | 2-3 hours direct sun is tolerable | 1000-2500 FC (200-500 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/maranta.htm | |
| Monstera deliciosa | 400 FC (80 µmol) | 100 FC (20 µmol) | 2-3 hours direct sun is tolerable | 1000-2500 FC (200-500 µmol) (estimated based on ‘shade/filtered sun’) | my detailed monstera care article – https://www.houseplantjournal.com/2017-1-25-monstera-deliciosa-house-plant-journal/ | https://edis.ifas.ufl.edu/pdffiles/HS/HS31100.pdf |
| Norfolk Island Pine | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 5000-6000 FC (1000-1200 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/norfolk.htm | |
| Parlour Palm (Chamaedorea) | 400 FC (80 µmol) | 100 FC (20 µmol) | 1-2 hours direct sun is tolerable | 1500-3000 FC (300-600 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/chamaed.htm | |
| Peace Lily (Spathiphyllum) | 200 FC (40 µmol) | 100 FC (20 µmol) | 1-2 hours direct sun is tolerable | 1500-2500 FC (300-500 µmol) | Very “low light” tolerant – down to 50 FC, but will just barely survive and have high risk of root rot. Overall plant will gradually lose leaves and become thinner in low light. My peace lily care video – https://youtu.be/GpIsAhmWDbQ | https://mrec.ifas.ufl.edu/Foliage/folnotes/spathiph.htm |
| Peperomia (many species) | 200 FC (40 µmol) | 100 FC (20 µmol) | 2-3 hours direct sun is tolerable | 1500-3500 FC (300-700 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/pep.htm | |
| Phalaenopsis (Moth Orchid) | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 1000-1500 FC (200-300 µmol) | http://www.aos.org/AOS/media/Content-Images/PDFs/GrowingtheBestPhalsPart_3.pdf | |
| Philodendron Vines (Heart-leaf, Brasil, etc) | 200 FC (40 µmol) | 100 FC (20 µmol) | 2-3 hours direct sun is tolerable but leaves may lose color. | 1500-3000 FC (300-600 µmol) | Very “low light” tolerant – down to 50 FC, but will just barely survive. | https://mrec.ifas.ufl.edu/Foliage/folnotes/philo-hl.htm |
| Philodendrons (Moonlight, Imperial Red, Prince of Orange, Pink Princess, etc.) | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 1500-2500 FC (300-500 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/philo-sh.htm | |
| Pilea (Aluminum plant, cadierei and others; NOTE: Pilea peperomioides not specifically mentioned) | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 1000-2000 FC (200-400 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/pilea.htm | |
| Polka Dot Plant (Hypoestes) | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 3000-3500 FC (600-700 µmol) | should be cut back every few months to keep bushy, otherwise will grow leggy. | https://gpnmag.com/article/culture-report-hypoestes-hippo-series/ |
| Pothos (Epipremnum aureum, Scindapsus pictus) | 200 FC (40 µmol) | 100 FC (20 µmol) | 3-4 hours direct sun is tolerable | 3000-5000 FC (600-1000 µmol) | Very “low light” tolerant – down to 50 FC, but will just barely survive. | https://mrec.ifas.ufl.edu/Foliage/folnotes/pothos.htm |
| Sansevieria (Snake Plant, Mother-in-law’s Tongue) | 200 FC (40 µmol) | 100 FC (20 µmol) | 5-6 hours direct sun is tolerable | 1000-6000 FC (200-1200 µmol) | Very “low light” tolerant – down to 50 FC, but will just barely survive and be at high risk of root rot. New leaves grown at low light levels will be long, thin and floppy. | https://mrec.ifas.ufl.edu/Foliage/folnotes/sansevie.htm |
| Schefflera (Mini Umbrella Tree, Schefflera arboricola; Umbrella Tree, Brassaia actinophylla) | 200 FC (40 µmol) | 100 FC (20 µmol) | 2-3 hours direct sun is tolerable | 5000-7000 FC (1000-1400 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/scheffle.htm | |
| Schlumbergera/Rhipsalidopsis (Christmas/Thanksgiving/Easter Cactus) | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 1500-3000 FC (300-600 µmol) | https://www.plantgrower.org/uploads/6/5/5/4/65545169/holiday_cactus_production_guide.pdf | |
| Spider Plant (Chlorophytum) | 400 FC (80 µmol) | 200 FC (40 µmol) | 2-3 hours direct sun is tolerable | 1000-2500 FC (200-500 µmol) | https://mrec.ifas.ufl.edu/Foliage/folnotes/spider.htm | |
| Staghorn Fern (Platycerium) | 400 FC (80 µmol) | 200 FC (40 µmol) | 3-4 hours direct sun is tolerable | 1000-2000 FC (200-400 µmol) | my staghorn fern care video here: https://youtu.be/bTM3WLwfq78 | http://edis.ifas.ufl.edu/mg015 |
| Succulents (Aloe, Echeveria, Euphorbia, etc.) | 800 FC (160 µmol) | 400 FC (80 µmol) | 5-6 hours direct sun is tolerable | 5000 FC (1000 µmol) | Aloe and Euphorbia can stay looking mostly the same down to 200 FC; Echeveria will stretch when grown indoors after several months – it’s inevitable. You can propagate by taking leaf cuttings and stem tip cutting – they simply do not stay compact and cute forever. Here’s a video on succulent leaf propagation: https://youtu.be/laAtQf8kwEA | https://hort.ifas.ufl.edu/floriculture/pdfs/crop_production/Cacti%20and%20Succulents_ENHFL04-006.pdf |
| Yucca | 800 FC (160 µmol) | 400 FC (80 µmol) | 3-4 hours direct sun is tolerable | 6000-7000 FC (1200-1400 µmol) | often confused with Dracaena fragrans (Corn Plant), which is far more low-light tolerant. Yucca will not perform well below 400 FC. | https://mrec.ifas.ufl.edu/Foliage/folnotes/yucca.htm |
| ZZ Plant (Zamioculcas zamiifolia) | 200 FC (40 µmol) | 100 FC (20 µmol) | 3-4 hours direct sun is tolerable | 1000-2000 FC (200-400 µmol) | often classified low-light tolerant, ZZ plant will survive with 50 FC but will be at high risk of root rot. | https://edis.ifas.ufl.edu/ep252 |
I designed a light meter that also displays temperature and humidity, giving you unparalleled awareness of your growing conditions:
Get your LTH Meter HERE
