Do your houseplants or seedlings struggle at times? Here's what you need to know.
With less light coming through your windows during these shorter winter days, you may be wondering if your plants are getting what they need to thrive. While the season’s weaker light may be enough for some houseplants, others need a boost to keep them growing. Still others, such as garden seedlings and flowering plants, may require more intense light than your home provides.
If you’re thinking about introducing artificial light into your home, here’s what you need to know.
How can I tell if my plants need more light?
If your plants thrive during the spring and summer, but struggle the rest of the year, it may be time to bring supplemental light to your living space. Adding a few hours of light in wintertime can reinvigorate houseplants and sustain overwintering outdoor pots until the next growing season. It can also help certain plants flower and make fruit.
Since stressed plants develop problems, here are some signs your plants need more light:
- Dying or yellowing leaves.
- Smaller than normal leaves.
- New pests and diseases.
- Tall and leggy growth.
- Variegated plants losing variegation.
To address any of the following problems, do an inventory of your plants and find out how much direct and indirect sunlight they need each day. Use a sunlight calculator or app to find out if your space provides enough light for optimal growth. If not, it’s time to consider grow lights.
Grow light basics
Grow lights give plants the energy they need to convert light into food, but not all grow lights are the same. To better understand the differences in grow lights on the market today, consider the following categories.
Light spectrum
Most plants need a spectrum of color to thrive. Although standard grow lights appear clear or white to the naked eye, they actually consist of multiple colors emitted in varying degrees. This is known as a ‘full spectrum’ light. Contained within that spectrum are some colors especially helpful to indoor plants.
- Blue light helps plants produce chlorophyll, the pigment they need to grow. It also helps encourage germination and root development in young plants and seedlings.
- Red light regulates plant growth and helps plants produce flowers and fruit.
- Green light helps maximize photosynthesis.
A standard, full-spectrum grow light will support most plant growth. Some grow lights allow you to adjust the balance of color from warm (more red light) to cool (more blue light), depending on your plant’s needs.
Color temperature
The unit Kelvin (K) measures the color temperature of individual bulbs–in other words, will the light emitted appear warm or cool? This becomes important when your grow lights also illuminate your living space. Opting for a slightly warmer color temperature will give your space a cozy glow.
Light intensity
How much light a bulb or fixture provides depends on its intensity. This is usually measured in lumens in the case of LEDs. The higher the number of lumens of your bulb, the more light that bulb will produce–and the brighter it will appear.
Other terms you may encounter when considering light intensity include:
- Watts: measures how much energy a bulb will consume when in use.
- Photosynthetic Photon Flux Density (PPFD): measures useful light intensity over a given area.
- Lux: measures the amount of lumens emitted per square meter.
- Color rendering index (CRI): measures how accurately a light bulb will render colors in a room. A CRI of 0 means all colors will appear black. A CRI of 100 indicates colors will appear as they would under natural sunlight.
Coverage
A final criteria to consider when buying a grow light is how much coverage it will provide. For LEDs, this is often measured in lumens per square meter, lux or foot-candles.
Which bulb type is best?
Grow lights come in a variety of types that range in price and longevity.
LED
LED or light emitting diode bulbs are the most effective at producing light and the most efficient to operate of all the home grow lights. They last up to five times longer than many other bulbs and have come down so much in price, there’s little reason not to choose them if you’re looking for a long-term, sustainable and non-toxic option. Choose a full spectrum LED bulb for your desk lamp or grow fixture, or opt for one of the many red-blue light combinations available for specific plant needs.
Compact fluorescent
These bulbs are less efficient than LEDs, making them more expensive to run. While they’re less expensive to purchase up front, they have a shorter lifespan and contain mercury, which can be released as vapor if broken. If using compact fluorescents, choose full spectrum for a broad range of plant needs.
Related: Eartheasy’s Guide to Energy Efficient Lighting
Halogen
While not the best choice for growing plants, halogens are brighter than standard incandescent bulbs and can meet some of a plant’s requirements for light. Given that they produce light farther along the red spectrum, they lack the blue light needed for healthy growth. However, if combined with other types of light, they can contribute to overall requirements. Keep in mind that halogens get quite hot when activated, so take care to avoid burned and damaged leaves.
Incandescent
Incandescent bulbs are not well suited to growing plants indoors. When turned on, they get quite hot, meaning they need to be placed some distance away from your plants, which reduces their effectiveness. They also produce light farther along the red spectrum. Finally, they’re inefficient and cost more to operate.
How much light do houseplants need?
Given that there are so many plants available, there’s no single answer to this question. However, there are some general rules of thumb to follow.
Low-light houseplants
Originating from shady or understory areas, these plants do well in north-facing windows or corners. They need little direct sunlight, surviving mainly in indirect light year round. These plants need 10-15 watts or approximately 50-250 lumens per square foot to thrive. They include:
- Calathea
- Pothos
- Philodendron
- Peace lily
- Snake plant
- English ivy
Medium-light houseplants
Well-suited to an east or west facing window, these plants do well with indirect light. They need 15-20 watts or approximately 250-1,000 lumens per square foot to thrive. Medium-light plants include:
- Rubber plant
- Fiddle leaf fig
- Asparagus fern
- Spider plant
- Jade
- Peperomia
High-light houseplants
Growing in direct sunlight when in nature, high-light plants do well in south or southwest-facing windows. They need more than 20 watts or more than 1,000 lumens per square foot to thrive. High-light plants include:
- Poinsettia
- Cactus
- Succulents
- Jasmine
- Orchid
- Citrus
- Hibiscus
Before purchasing a grow light, research the requirements for the plants you already own (or the plants you hope to grow). Find out what intensity of light they require, how many hours of light they need per day, and which spectrum they prefer. If your space doesn’t provide adequate light, look for a grow light to fill the gap.
Best grow lights for fruiting and flowering plants
Choose a full spectrum bulb with the option of adjusting to more red spectrum light for flowering and fruiting. Our favorite is the VITA grow bulb, which provides 1:4 blue to red light at 3000 Kelvin. For a comparable hanging option, try the Aspect Hanging Grow Light.
The Vita grow light, left (sold as bulb only) fits perfectly into most home lighting fixtures to give plants the light they need. The Aspect grow light, right, provides a versatile hanging option.
Best grow lights for seedlings and starts
Anything normally requiring full sun will need 2000 to 3000 lumens of light–and that includes seedlings. Opt for a full-spectrum bulb or something that errs towards the blue side of the spectrum. Hang your chosen grow light as close as you can to your growing trays to prevent legginess. LED bulbs are good choices, since they won’t get too hot and burn tender seedlings.
Best grow lights for tropical houseplants
Standard tropical house plants require full spectrum bulbs with a good balance of green and blue lights. Most houseplants grow well with 20 to 25 watts per square foot, or around 500 lumens per square foot. We love the versatile Uplift grow planter, with its fully adjustable (and removable) full-spectrum LED.
The Uplift grow planter lets you grow plants anywhere in the house and illuminate dark corners with an adjustable, built-in grow light.
Best grow lights for indoor herb growing
Most herbs need full sunlight to grow well. And while some may have luck in a south-facing window, bringing in supplemental light will almost always improve herb growth, making plants less leggy and more productive. Choose a full-spectrum bulb with more than 1000 lumens per square foot.
Our favorite for indoor herb growing is the wall-mounted Smart Grow frame. It includes full-spectrum LEDs at 4000 Kelvin and 1480 lumens. Or, if you’re interested in year-round edible growing, consider a hydroponic grow cabinet.
The Smart Grow frame with built-in, full-spectrum light lets you mount an indoor herb garden on any wall in your home.
Tips for growing plants under lights
- Group together plants with similar lighting needs so they can benefit from the same amount of light.
- Purchase grow lights that will fit into your regular light fixtures to help reduce costs. Desk lamps work well for houseplants. Tube lights work well for seedlings and groupings of plants.
- Choose lights with adjustable intensities and/or spectrums. Alternatively, choose a grow light with a slightly warmer spectrum for a cozy, ambient light in your home.
- Set your grow lights on a timer so your plants get the right amount of light every day. Many grow lights come with a built-in timer. If they don’t, use a plug-in timer to achieve consistent, regular light.
Frequently asked questions
Will having grow lights in my home harm our eyes?
Living with an indoor grow light is no more harmful than living with another bright light. Just avoid staring at your grow lights as you would the sun.
What is the best all around grow light for indoor use?
We love the full-spectrum VITA. The warmer light cast by this bulb provides ample light for plants and a comfortable glow for interior spaces. And since it’s sold as just the bulb (without a light fixture), you can add it to any desk or reading lamp in your home.
How far away from my plants should I hang my grow light?
The first thing to do is to research your plant’s lighting needs and purchase a bulb or light fixture that provides enough intensity and coverage. If you’re growing houseplants, this is usually 6 to 12 inches away from your plant (for LEDs and fluorescents). Place farther away and watch for signs of heat stress if using anything other than these bulb types. For seed starting, place your light 5 to 12 inches from the top of your seedlings, adjusting as needed.
My flowering plant won’t flower/fruit. Is there a light that can fix this?
Plants require enough light on the red spectrum to flower and produce fruit. Choose a light that caters to this spectrum to help your plant thrive. We recommend the Vita bulb, which fits well into standard light fixtures.
Where can I put grow lights in my home?
Installing a grow bulb into your regular light fixtures is the easiest way to introduce more light into your home. This includes desk lamps, reading lamps and more. Grow bulbs are not usually meant for ceiling fixtures or wall sconces, simply because these will be too far away from your plants. Position the fixtures in dark areas of your home or anywhere your plants need light.
