If you have a very sunny south-facing window, with day-long direct sun, you may be able to do without the grow light, but depending on the quality and intensity of the light, you may struggle with slow growth and leggy, floppy, unhealthy-looking plants. Also, if the conditions are too hot, it will encourage the plant to bolt to seed sooner.
For indoor growing, we highly recommend a good full spectrum LED or fluorescent grow light. Unfortunately, you can’t simply use regular household lighting. Plants need specific wavelengths of light that aren’t usually found in regular light bulbs. Grow lights are designed to provide the full spectrum of light needed for a plant.
There are two styles of grow lights: pink and white. The pink lights are more efficient, as they project only the necessary wavelengths of light. They can be hard on human eyes, however. We recommend putting your plants where you’ll see them every day, and a white light will probably look best.
Next, you should consider the kind of bulb. Fluorescent bulbs may be the cheapest, but LEDs last considerably longer and have been coming down in price. HID (High Intensity Discharge) lights are commonly used in commercial hydroponics but are probably not a good fit for your home.
Then, you must consider the housing and hanging of the light. Think about where you plan to host the plants, how many you will have, and how you will direct the light at them. Grow lights do come in standard bulb sizes, both LEDs and CFLs. You could put one in a shop light or desk lamp over the plants. The most common lights come in a rectangular housing that must be hung from above. You can also find lights, mostly LEDs, that include a base (either a clamp or freestanding) with a gooseneck for positioning the light.
Finally, the most important consideration is the intensity of the light. This gets confusing fast, because lights may be labeled in watts, lumens, foot-candles, or lux. Just know that lower intensity lights must be positioned closer to the plants, while higher-intensity lights need to be further away. The highest-intensity lights may also be uncomfortable for your eyes, so choose accordingly.
Your greens will want about 12 hours of light every day, and twelve hours of dark. Fancier lights will come with a timer, others will not, and many will require you to turn them on every morning. You can always buy a cheap mechanical timer, or commit to turning the lights on and off manually.
Here are some lights that we recommend ourselves, or have had recommended to us by hydroponics experts. Note that most of these products are imported from overseas, and usually bear the brand of the importer, not the manufacturer. If one becomes unavailable, you can often find the exact same product under another name.
Lights with Stands
These lights are free-standing, and good for a small collection of 3–4 plants. Pick a height that will work well with your setup. Keep in mind the height of your mason jar plus the mature height of the plant (figure at least 6 inches or so, or find this on your seed packet). You’ll want the light to hang just a few inches above your plant.
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Hanging Lights
Hanging lights are more complex to set up, since they must be suspended from something, but they can accommodate larger setups more easily, especially models that can be chained together. You will usually hang multiple lights and add their wattage together to figure roughly how much light they’ll emit.
Barrina brand lights come highly recommended. These are just a few, but you’ll find many more options at the Barrina Store.