Photoperiodic plants fall into two subcategories: qualitative and quantitative. Plants that require a specific critical daylength to flower are classified as qualitative, or obligate. Without that exact amount (or more) of uninterrupted darkness, the plant will never flower.

Poinsettia plants are a classic example of a qualitative short-day plant. They will not initiate flower buds until the dark period reaches around 11 hours and 45 minutes, depending on the cultivar. Flower initiation is optimal with a 14-hour period of darkness.

Gardening Under Lights Book

Yellow sticky cards are an easy method for catching and killing many flying pests, such as fungus gnats and whiteflies. The fungus gnats you will catch are the nuisance adults, but the larvae do all the damage by feeding on roots.

If you do not want to use organic or synthetic pesticides on your indoor plants, sticky cards are a good alternative.

Gardening Under Lights Book

Want to grow kale indoors? Then you'll need to keep it cool! Kale prefers cool conditions, and is normally grown outdoors during the cool season, or in winter in hot climates. Plants will bolt once temperatures reach about 80°F (26°C).

Grow kale indoors in a space that stays consistently cool, such as a basement or a garage. You will need to cool air inside a sealed grow tent, especially if you are using HID grow lamps that generate greater amounts of light and heat. Try growing kale with LEDs, HOT5 Fluorescents, and CFLs to reduce heat.

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

Once vegetable crops or blooming plants mature and begin to flower, dial back the nitrogen fertilizers. Too much nitrogen at this stage encourages plants to put the energy into more leafy green growth instead of flowers and fruit.

When plants enter flowering mode, you can switch to a low-nitrogen fertilizer or hold off altogether until baby buds and fruits begin to appear. When fruit is about 1/2-way developed, you can begin adding balanced fertilizer back on a week (liquid) or monthly (granular) basis so that resources go to fruit development.

Gardening Under Lights Book

LED grow-light bars (in all white or nanometer-specific colors) are available with small reflectors. You can fit them under cabinets or grow shelves just like the T5 fluorescent units. If T5 fluorescent grow lamps are putting out too much heat for your seedlings or young plants, switch them out for these LED bars.

Use full spectrum LED Bars for white colored light in your living spaces.

Gardening Under Lights Book

You can use a CFL in household lamp fixtures and as grow spotlights for small indoor houseplants or cuttings. Just as with T5 fluorescents, you will have to place the CFL fairly close to your plant so you don’t lose light volume. Because of their moderate heat output, this is relatively safe.

Fitting into household fixtures also makes these lamps easy to hang horizontally or vertically if you need to get more light at lower levels between large plants.

Gardening Under Lights Book

Harvest dry seeds while still on the plant, once they have completely matured and dried. The dry pods will be easy to open or will burst open on their own, and the seeds inside will be hard and completely dry.

Keeping seeds in a cool, dry place will help extend their life. Be aware, however, that the longer you store seeds, the more their germination rate decreases.

Gardening Under Lights Book

When growing plants indoors, it is critical to understand how temperature affects your crops and how to manipulate it to improve your yields.

Your grow lights can give off heat, but you can employ high-intensity lighting in small spaces if you use an air-cooled hood. Air-cooled hoods can be connected to ducting which moves air in, through, and out of the tent, removing heat produced directly from the grow lamp.

Gardening Under Lights Book