The number of hours of indoor light that plants need varies depending on the type of plant. Most houseplants require between 10-16 hours of light per day. The optimal amount of light allows the plant to photosynthesize efficiently and thrive. Too little light will result in slow, leggy growth, while too much can scorch leaves. The intensity or brightness of the light also impacts how many hours are required.
How many hours of light do common houseplants need?
Here is a breakdown of the recommended hours of indoor light per day for some popular houseplants:
- Succulents and cacti: 12-14 hours
- Orchids: 12-14 hours
- Peace lily: 10-12 hours
- Chinese evergreen: 10-12 hours
- Snake plant: 8-10 hours
- Pothos: 10-12 hours
- Philodendron: 10-12 hours
- Dracaena: 10-12 hours
- Croton: 12-14 hours
- Rubber plant: 12-14 hours
As a general guideline, flowering plants and those with colorful leaves need more light, while plants with more foliage and fewer flowers can get by with slightly less light per day.
How to determine if your plant is getting enough light
The best way to determine if your indoor plants are getting adequate daily light is to observe the plant itself. Here are some signs that indicate whether your plant needs more or less light:
- Leggy growth means insufficient light. If stems are stretching and spaces between leaves are excessive, increase light.
- Wilting or drooping leaves can indicate too much light. Move to a shadier spot.
- Bright green foliage signifies adequate lighting. Rich green without yellowing is ideal.
- Vibrant blooms and flowers show the plant is getting the light it craves.
- Variegated leaves with well-defined creamy stripes require bright light to maintain coloration.
- If leaf scorching or burn occurs, reduce light intensity and duration.
Pay attention to how your plant responds over time and adjust the light levels accordingly. The hours of light needed may change somewhat depending on the season as well.
Optimal hours of light by season
Outdoor light levels shift throughout the year, and houseplants respond similarly to these seasonal changes. Adjust indoor lighting to mimic the seasons for optimal plant health and growth.
| Season | Hours of light |
|---|---|
| Spring | 14-16 hours |
| Summer | 12-14 hours |
| Fall | 10-12 hours |
| Winter | 8-10 hours |
During the brighter seasons of spring and summer, give plants longer days by providing light for 14-16 hours. In the darker fall and winter, reduce the duration to 8-12 hours to mimic outdoor conditions.
Factors that influence light needs
The number of hours plants need to be illuminated depends on a few key factors:
- Plant variety – Certain plant species have higher or lower light demands.
- Growth stage – Young plants need longer days to promote development. Established plants can get by with slightly fewer hours.
- Time of year – Light requirements decrease in fall/winter when outdoor light is less intense.
- Sunlight intensity – Bright sun provides more usable light so fewer hours are needed than lower indoor light.
- Day length sensitivity – Some plants initiate blooms based on day length or photoperiod.
Optimizing these factors for each plant ensures they get just the right amount of light to remain healthy and achieve desired growth patterns.
Using artificial light to supplement natural daylight
When indoor light through windows is insufficient, plant grow lights can boost light levels. Here are some tips for utilizing artificial plant lights effectively:
- Choose broad spectrum LED grow lights that provide full light spectrum similar to natural sunlight.
- Position lights 6-12 inches above foliage for best coverage without burning.
- Run grow lights for 12-16 hours per day unless plant requires less light.
- Use a timer to ensure consistent daily photoperiods.
- Adjust duration to align with seasonal day lengths or specific plant needs.
Grow lights should deliver 100-200 foot candles of intensity. Measure with a light meter to determine optimal placement. Combine artificial light with bright, indirect natural light for the healthiest indoor plants.
Providing adequate darkness for plants
Getting the right amount of total light is only half of the equation. Ensuring an adequate period of uninterrupted darkness is also critical for indoor plants. Some reasons plants need dark periods include:
- Initiating flower buds and blooming for some long-night plants.
- Promoting stomatal closure at night to retain moisture.
- Allowing the photosynthetic process to reset overnight.
- Avoiding metabolic stress and leaf scorching from constant artificial light.
Most plants should have 8-10 hours of continuous darkness each night. Use dark curtains or shades to block ambient light from streetlights, lamps, and electronics. Turn off indoor lights near plants at night including holiday lights which can confuse photoperiodic flowering.
Signs plants are getting too much light
While insufficient light is more common, providing too much light can also negatively affect plants. Look for these clues that light duration or intensity is excessive:
- Yellow or burnt leaf edges
- Dry, crispy foliage
- Wilting, drooping leaves
- Leaf scorching or whitish areas
- Sudden leaf drop
- Bleached or faded leaf color
If any signs of light stress appear, immediately move the plant to a shadier spot and reduce hours of artificial light. Introduce the plant to brighter light gradually over time to acclimate it.
Adjusting indoor light for plant health
Optimizing indoor lighting requires paying close attention to how plants respond and making adjustments. Here are some tips for regulating light effectively:
- Start conservatively with less light then increase duration and intensity gradually as needed.
- Rotate plant orientation to evenly distribute light exposure.
- Use sheer curtains or movable screens to diffuse harsh light.
- Move plants closer to or further from light source to regulate intensity.
- Remove shade cloth or reflectors if leaves show signs of scorching.
- Group plants with similar light needs together for easier care.
Adapt lighting conditions through the seasons as outdoor conditions change. Respond promptly if plants exhibit symptoms of too much or too little light at any time of year.
Using a light meter
A light meter takes the guesswork out of determining if plants are getting adequate daily light. This device measures the photosynthetic photon flux density (PPFD) of light in micromoles per square meter per second. An ideal PPFD reading for most indoor plants is between 100-200. Here are some tips for using a light meter effectively:
- Take measurements at the top of the plant canopy where leaves receive light.
- Test at multiple times of day and in various weather conditions.
- Move plants or lighting to achieve target PPFD levels.
- Refer to manufacturer recommendations for specific plants.
- iPhone light meter apps provide ballpark readings when a professional meter is unavailable.
Light meters take the ambiguity and subjectivity out of providing optimal daily light for indoor plant health and growth.
Considerations for outdoor plants moved indoors
Plants acclimated to growing outdoors generally require more light than indoor varieties. Here are some tips for transitioning outdoor plants into interior living spaces:
- Gradually expose plant to increased light levels over several weeks.
- Avoid sudden relocation to a low light area which can shock plants.
- Boost light with wide spectrum grow lights to maintain health.
- Rotate plant orientation to distribute light evenly to all sides.
- Monitor for signs of insufficient light such as leggy growth.
- Be prepared to move plant back outdoors or into a greenhouse if extra light is inadequate.
With attentive care and sufficient light, most outdoor plants can adapt to indoor environments long term.
Innovative lighting options for indoor plants
Beyond traditional overhead grow lights, some cutting edge options for providing indoor plants the light they crave include:
- Full spectrum LED panels – slim fixtures deliver balanced, intense light ideal for shelves and walls.
- Strip lights – flexible strips allow positioning light at ideal angle and distance from leaves.
- Floor and table lamps – direct light upwards for better coverage of hanging and tall plants.
- Fiber optic lighting – transfers sunlight indoors from rooftop collectors via cables.
- Light therapy bulbs – designed to treat seasonal affective disorder in humans but also benefit plants.
Advancements in lighting technology are making it easier than ever to give indoor plants the light they need to stay healthy and grow strong.
Conclusion
Determining optimal indoor light requirements depends on the needs of specific plant varieties, seasons, and growing conditions. Look for signs of insufficient or excessive light and adjust artificial lighting accordingly. Aim for 10-16 hours of illumination with 8+ hours of darkness for most common houseplants. Supplement with adjustable LED grow lights as needed to deliver 100-200 PPFD. With a balance of daylight and darkness tailored to each plant, an indoor garden can thrive year round.
