Grow lights have been used to aid germination and growth in plants for decades. The common household light bulb we used beside our seed trays each spring have been replaced by much more effective bulbs. We no longer have to turn our leggy seedlings in hopes of them not growing into 4" tall plants with two leaves before we scrap them and start again, with similar results the next time. No more lamps turned on their sides while being held in place (hopefully) but other solid objects. For just a few dollars we can all afford to have grow lights in our homes.
Seed Starting Under Grow Lights
Unless the seeds you’re starting specifically need light to aid in germination, wait until the sprouts break through the soil to turn your grow lights on. Unnecessary light doesn’t help seeds that require darkness. If light is required for germination, such as in lavender and lettuce, turn your lights on as soon as you’ve seeded the tray or container. Adding bottom heat to aid in germination is simple with a small heat mat.
When I use grow lights I have my stand set up and the lights hung for the sake of convenience. I lower the bulb to 1" above the soil surface. It’s easy to push the bulb out of the way for watering. When 50% of the seeds in a tray have germinated I turn the lights on. Waiting as little as a day too long to turn on lights can result in leggy seedlings with weak stems. When germination is complete I raise the light to 2" above the top of the tallest seedlings. This prevents seedlings from stretching to reach the light without them being too close to the light. Lights and seedlings should be checked daily. Raise the lights as needed and preferably, never more than 2" above the tallest seedlings.
When seedlings are grown indoor they lack the movement a breeze would naturally provide. Stems need movement to build strength and be ready to be moved outdoors. You can simulate this movement by setting up a fan blowing gently on the seedlings for a few hour each day. Or, you can brush your hand gently over the tops of the seedlings. Remember to be careful so that stems aren’t damaged or broken.
Grow Lights in Winter
Grow lights are used to increase light for house plants in the winter. Plants need light to produce sugars, starches and other substances they need to survive. I like smaller, round bulbs when I use them in the house. They don’t take up as much space as the longer, narrow bulbs, they're less noticeable, and they still serve the same purpose. You can buy a 60 watt bulb for under $10. A 150 watt bulb is a good deal for about $12. Each bulb should last a minimum of 3,000 hours.
Commercial greenhouse growers use grow lights to extend the length of day light during short winter days. Warm air isn’t enough to keep plants growing well, although fast growth usually isn’t the goal in winter. The lights are to keep photosynthesis from slowing too much while the plants are in an artificial greenhouse environment. In addition to the length of natural day light comes the quality of light. A stretch of several cloudy days in a row can be countered by the use of grow lights to improve the quality of light the plants receive.
Electricity Consumption
Figuring out the amperage your grow light is using is simple. The formula is: wattage divided by voltage equals amperage. Watts divided by volts equals amps. It’s that easy. The average household circuit breaker is rated at 15 amps. One kilowatt hour equals 100o watts for one hour. To figure out how much it costs to use a grow light for one kilowatt hour (kW/h) you’ll use this formula: If you are charged .10¢ per kW/h, a 1000 watt fixture will use 1.1 kW per hour. Grow lights are turned on for 14 hours a day. Multiply 14 hours times .10¢ equals $1.40 a day. That’s $42 a month. When you make your own calculations be sure to check your light bill to find out how much you’re charged per kilowatt hour.
Wavelengths
Incandescent bulbs, the kind of light bulbs commonly used to light our homes, are not suitable for growing. They produce enough red rays but not enough blue rays. The high amount of heat they produce can quickly damage plants, they have a short life compared to fluorescent bulbs, and are inefficient producers of energy.
Fluorescent tubes specifically designed for indoor growing provide the most efficient source of artificial light suitable for growing plants. These tubes are the best choice but combining one of these with one less expensive cool white tube can also work well too. These tubes are less expensive to use because they use less electricity. They also produce less heat making them safer for the plants. Fluorescent tubes produce the most light in the center of the tube. Reflectors in the base of the light help direct the light toward the plants instead of throughout the entire room.
High end grow lights can be very expensive. Metal halide lights are the best high intensity discharge (HID) lights for growing in low or no light situations. They’re readily available from 100 to 1000 watts per bulb. These lights flow electricity through high pressure vaporized gas. They resemble natural light the best. High-pressure sodium (HPS) lights are also metal halide lights. Metal halide lights can be used from seed germination, growth and through the bloom cycle. High-pressure sodium lights are usually used during the bloom cycle only. These lights are so expensive that they’re unlikely to be used by home growers. The set up of ballast, bulb and base cost around $300. In comparison, a fluorescent bulb, its ballast and base cost around $20.
Timers
Timers are very helpful when it comes to regulating the amount of time your grow lights are running. Fourteen to sixteen hours of light is enough for plants. More light than needed isn’t beneficial and adds up on your electric bill. If you’re using several lights you must make sure your timer or timers will support the number of lights you use. There are wattage limits. Standard wattage per timer is 1875. Timers plug into a normal outlet without requiring anything extra. I paid $15 each for my timers. Their convenience alone is well worth the price.
Other Materials You Might Need
Regular fluorescent grow lights had a low output and were too large and inconvenient for anything more than seed starting. There are new compact and T5 full spectrum fluorescent lights available now. These are much better than the old standbys. To use these new bulbs in old fixtures you’ll need mogul adapters. The mogul socket adapter allows you to screw a compact fluorescent grow light bulb into a standard light socket. You screw a compact fluorescent light into the mogul socket and screw the adapter into a regular household light socket. Mogul adapters cost about $15.00.
Make Your Own Light
You can put your own light stand together inexpensively. It probably won’t be something you want to use in the house long term but for seed starting this will work well. The stand is made from pieces of one-inch PVC. I learned how to make these at a workshop held by my county’s Cooperative Extension Service.
Supply List:
- 2 J hooks
- 2 PVC elbows
- 2 PVC T joints
- 2 PVC end caps
- 1 inch diameter PVC pipe. Length varies depending on how tall and long you want to make your stand.
- PVC cutter if you have one. If not, a hack saw will work.
- PVC adhesive, if you don’t want to take your stand apart.
- Shop light
- Light weight chain to hang the lights from
- Drill
Cut the first piece of PVC pipe to the desired height. This is the first leg. Cut two shorter pieces to the same length. For decent stability I cut these two shorter pieces no less than 6” long each. These are the “feet” of the stand. Connect the two shorter pieces to the long piece using a T joint. If you aren’t going to take your stand apart for storage you should use PVC adhesive to secure the pieces together. Repeat this for the second leg.
Cut a piece of PVC pipe four inches longer than the length of your grow lights. This is the crosspiece that runs across the top. At equal distances, drill two holes in the under side of the crosspiece. You’ll secure your light to the crosspiece using the two J hooks.
Attach an elbow joint to each end of the cross piece. Make sure the joints are going in the same direction and that the holes are in what will be the bottom of the crosspiece. If you’re using adhesive, use it in the elbows.
You should now have two legs and one crosspiece. Attach the legs to the crosspiece by using the elbows.
Attach the J hooks. Then attach the light-weight chain to the shop light. Hang the light from the crosspiece. Shorten the chain as plants grow. There you are! A simple, economical grow light. I don’t use adhesive on my stands. When I’ve finished with them for the season I take them apart, put all the pieces in a box and pack it away in the cellar for the rest of year. If you leave your stands together you can hang them from the wall or ceiling of the cellar or basement. They’re so light they won’t need much to support them.
To make the best use of inexpensive fluorescent lights you need to buy one warm bulb to go with the cool bulb. The cool bulb gives off more blue light. This is good for leaf growth. The warm bulb gives off red light which is needed for flowering.
Grow Light Kits
Grow light kits make getting started with grow lights simple. You can purchase attractive kits that include everything you need. It takes just an hour or two put these kits together, put them in place, add your plants and turn on the lights. I like the looks of the sleek under-the-cupboard kits that are available now. They look nice on a tidy cupboard. There are a lot of kits that aren't intrustive. That is, they aren't so noticeable that they detract from the plants.
Gardener’s Supply carries several models and replacement parts. A small light would be great for growing herbs on a kitchen window all winter. Having fresh herbs year round is almost a luxury in some parts of the country. I think these herb seed disks from Thompson & Morgan would be great to use for a window sill garden. Not a chef extraordinaire? How about a table model for your desk? I’m looking at my desk right now and wishing I had one! It would liven up my work space and remind me of warmer weather.
Our choices in grow lights now have taken them from being a working tool to an attractive piece of furniture or addition to our decor. No matter what your need, I'm sure there are lights that will suit you.
Resources
University of Minnesota, Cooperative Extension
Starting Seeds Indoors
The Green Thumb
Calculating Electric Usage of Grow Lights