Given that many LED grow lamps combine only red and blue light, the pink- or purple-colored light they produce might not be the most attractive choice for your kitchen or living room. Pink light also causes your plants to look pink or purple instead of green.

This pink or purple light makes it hard to identify a nutrient deficiency, fungal disease, or pest problem. A multicolor white LED, or RGB LED, will give you a more standard white-colored light.

Gardening Under Lights Book

Seeds germinate at different speeds depending on the type of plant. Your seed packet will offer estimated germination times based on optimal temperature ranges, but you will likely germinate seeds much faster in a controlled environment with heat mats.

For example, I often have germination occur on lettuce seeds and mixed seeds of microgreens within only two to three days of seeding. Other seeds, such as bluebonnets, can take weeks. Temperature influences germination speeds.

Gardening Under Lights Book

Different plants have different heat tolerances, so you may find that your tomato transplants can tolerate hotter temperatures while your lettuce plants scorch. If you notice browning, scorching, curling, or crispy leaves close to the lamp, increase the distance between the lamp and the plant.

This tomato has grown about 12 inches too close to the hot 400-watt HPS lamp, and its leaves are beginning to curl because of excess heat. I must raise the lamp to create more distance from the plant.

Gardening Under Lights Book

Place the pellets in a seedling tray and cover them with water, and the pellets will expand. Once they have soaked, set the pellets in a solid seed tray (no need for an additional container), drop your seeds into the opening at the top of the film, and keep moist.

Seed plugs are sold with small seed-germinating greenhouse kits.

Gardening Under Lights Book

While citrus is easy to grow in containers, they hate living indoors. They require bright light. When you see photos of a beautiful fruit-filled lemon tree next to a small indoor window, know that it most likely did not grow and fruit in that location.

If you happen to have a very large south- or southwest-facing window that gets direct full sunlight for more than 6 hours a day, you might be able to keep your citrus happy.

Getting cannabis to produce flower buds requires a strictly controlled lighting regimen. Cannabis sativa is a qualitative short-day plant. To remain in a vegetative state, plants require 16 to 18 hours of continuous light followed by 6 to 8 hours of uninterrupted darkness.

Once you are ready to force them to flower, reduce their daylength to 12 hours, followed by 12 hours of uninterrupted darkness, for about two weeks.

Gardening Under Lights Book

In warm climates, cilantro can be grown outdoors only in the cooler fall and winter months. In cool climates, it can be grown in spring and early summer. Once temperatures reach about 70 F, cilantro will go to flower and seed, then plants will expire. If you live in a hot climate like I do, you must grow cilantro through the winter outdoors. BUT, that means I don't have any cilantro in summer when my tomatoes and peppers are ripening. My solution? I grow some cilantro indoors during the warm months.

You'll need a cool spot in the house to grow indoor cilantro, and use low-heat grow lights such as LEDs or CFLs. Use moderate light for harvesting foliage, bright light for flowering if you want to collect seed.

New BOOK! Gardening Under Lights: The Complete Guide for Indoor Growers

Plants that bloom only in summer, such as coneflower, are typically long-day plants; those that bloom only in early spring or fall, such as chrysanthemums, are typically short-day plants. Plants that can flower continuously through the growing season—such as roses, cucumbers, and tomatoes—are day-neutral.

Gardening Under Lights Book