Growing Under Lights
We all know plants need light to thrive yet finding enough light indoors can be tricky -- especially in the darkness of winter. Luckily, today’s grow lights can help, and they’ve come a long way in quality, style and affordability. Read on to learn how plants use light, how to choose the right indoor light to fit your needs and how to adjust them.
How Plants Use Light
First off, a little botany lesson on sunlight and how plants use light to make their own food. It’s an amazing process called “photosynthesis” with “photo” meaning light and “synthesis” meaning to put together. Plants tap the sun’s energy using chlorophyll found mostly in their leaves. Chlorophyll reflects green – hence the green color of plants – and absorbs blue and red light. Plants then use the light energy to change water and carbon dioxide into 1) nutrients for their food and 2) oxygen to release into the air – a perk for us. Plants vary in how much light they need to thrive from low-light houseplants like peace lilies to high-light fruiting plants like tomatoes. To learn more about photosynthesis, check out this short National Geographic video, this deeper Khan Academy lesson or this cool microscopic peak inside a leaf.
When to Use Supplemental Light
Artificial light can help plants grow indoors when there’s not enough sunlight. They can ensure your veggie seedlings get off to a great start, coax a flowering houseplant (e.g., begonias and orchids) into bloom, and provide enough light to satisfy herbs and succulents even in the darkest spaces. Darryl Cheng, author of the New Plant Parent, offers this chart on light needs for various houseplants.
Choosing the Right Light
When shopping for grow lights, we recommend full-spectrum LED lights which produce a balance of cool and warm light that mimics natural sunlight. LED lights also are more energy efficient and longer lasting than traditional florescent grow bulbs, plus they won’t shatter or buzz like the florescent ones. When evaluating options, consider size (how many plants to light), wattage, price, aesthetic and type (desktop, portable, hanging or complete system shelving unit). Shop for grow lights at your local garden center, hardware store or online source.
- Screw-in bulbs: Labeled “sunlight” or “daylight” on the package, these inexpensive LED bulbs can easily be swapped out with traditional light bulbs for a desk lamp or floor lamp. ($4-$30)
- Clamp lights: These lights are the next easiest and inexpensive option. Plus, they’re simple to clamp to a cabinet, a shelf or table. Go for the industrial look with an aluminum reflector lamp or choose a more modern style with a light bar and flexible gooseneck. ($12-$30)
- Panel lights: Ranging from 10-inch squares to two-foot rectangles, these panels can be attached to a stand, suspended from the ceiling, or mounted under a shelf or cabinet. Match the panel size to the size of your plant collection. ($30-$150)
- Table-top units: For herb growing or seed starting, try a tabletop unit with hydroponic or soil container options. They range from one foot (ideal for a kitchen countertop) to three feet (better suited to a laundry room counter, basement work bench or folding table set up in an unused guest room). ($80-$300)
- Complete stacked systems: To accommodate a lot of plants or seedlings, consider a stacked system with multiple lighted racks. Many feature adjustable lights, roller feet for portability and easy assembly to tear down when not in use. ($300-$1,000)
Adjusting the Light
Most grow lights include a timer or can be outfitted with one or a smart plug, so you don’t have to remember to turn them on and off. Set the timer for 14-16 hours of light daily for bright-light plants (seedlings and flowering or fruiting plants) or 10-12 hours for low to medium-light plants. Experiment with the location of the light source, depending on the plants’ lighting needs. While seedlings should have the light source at least 6 inches from the plant foliage, other lower-light plants can be positioned farther from the light source.
Seed Starting Under LightsWith seed starting season just around the corner, make sure you have the right lighting set up to ensure strong seedlings. Without sufficient light, seedlings can grow weak and leggy. For beginners, start small with a countertop kitchen unit and position lights 2 inches from the soil then raise the lights to 4 inches once the first leaves sprout. Continue raising the light source as the seedlings grow. For more details, check out this seed-starting video with Pam Bennett, associate professor with The Ohio State University.