Light Banks & Grow Lights for Seedlings
Author Ellen Vande Visse
Light Banks
For Indoor Seed-Starting & Maintenance
Old style shop lights
Fixture: a shop light that is four feet (48”) long and holds 2 fluorescent bulbs each
that are 40 watt.
Fluorescent bulbs: one warm and one cool light, 40 Watt (=40 W).
Never mix 40 watt and 32 watt bulbs in the same fixture! You’ll burn the ballast.
More modern shop lights
1. There is no need to spend the extra money for a “Full Spectrum” bulb.
2. Moreenergyefficientshoplightsareavailablenow.
3. Don’t mix fixtures and bulbs. Choose the bulbs that match the watt called for on
the fixture you have.
Fixture: a four foot length shop light
Here is one kind of recommended fixture found at Lowe’s, (2012) — Item # 313520
4’ T-8 Electronic shop light built for a pair of 32 watt bulbs
Fluorescent bulbs
The following are for a goal of providing light of a wave lengths that promote seed starting and good leaf growth, rather than wave lengths that stimulate blooming or blossoms.
Each shop light fixture needs two different bulbs in it. (Put 2 kinds of bulbs in one lighting device.) Look for these specifications on the label of the fluorescent tubes.
F32 T8
Energy used: 32 watts Light output: 2800 lumens
Life: 20,000 hours Color Temperature: 3500 K
Cri: 78
F32 T8
Energy Used: 32 watts Light output: 2950 lumens
Life: 20,000 hours Color Temperature: 4100 K
Cri: 86
More about Indoor Seed-Starting
Set Up
I recommend shelves or shelving unit or rack. A handy size for horticultural flats: set of four shelves, four-foot length and 12” to 14” width. Mount a pair of shop lights under the shelves.
Use the shop light chains and hooks to adjust the height of the shelves. The leaves of your seedlings need to almost touch the fluorescent tubes. Move the light fixtures higher as the plants grow higher.
To enhance lighting, use aluminum foil or a space blanket around the light banks. This will help reflect more light intensity to your seedlings.
Every Day Maintenance
As soon as you see the slightest germination, get seed flats immediately under shop lights for 14 to 16 hours per 24-hour cycle. Set up a timer to help you with this. The lights must nearly touch the tiny leaves to prevent spindly growth.
After germination, keep the air temperature at 60-650 F.
Water your plants deeply every day as needed. Sometimes this means twice a day.
Set a fan on low setting, directed at your plants, for about 45 minutes or so each day, preferably right after watering your flats. Again, a separate timer can help you do this.
By early April, you may have enough daylight to transfer your seedlings from shop lights to a sunny windowsill, but be sure they don’t fry there.
Another note– If you are on a water softening system, your tap water is very salty. It is best to use a water source that is not so high in sodium, such as melted snow, collected rain water, or stream, lake, or untreated well water.
What’s Next? Hardening Off
As your outdoor garden soil warms and air temperatures warm to a plant-friendly range, you’ll need to get your seedlings acclimated to wind, sun, and the shock of big change. This process is called “hardening off”. Expose your flats of seedlings to 1 hour of sun the first day, 2 hours the next day, and so on. Please read more on this. Soon you’ll be ready to successfully transplant into your prepared garden soil.