What type of plants are you growing? Do they require that much light?

I use two 2-bulb fixtures per 18" shelf and this is works just fine. Some of my fixtures are overdriven for plants that like more intense light.

You can purchase 24" deep wire shelving but they are much more costly.

Regards,

Rokal

Sunslight,

"Checking the actual, inside, dimensions of the shelves, I came up with approximately 46x16."

Actually, I have one of those shelves right here beside my computer, in use to hold my computer, scanner, video camera, CD drawers, and a bunch of books. I bought three of those shelf units, and I have one of them in use as a fluorescent plant stand right now.

The distance between the posts is actually a bit less than 16 inches. I measure about 15¾" between the chrome posts.

The distance between the heavy wire structure at the bottom ends of the shelves is about 46¾ inches, maybe a hair more. However, that should be not problem, because you hang the fixtures from the wire shelf above the shelf, and the fixtures can extend well beyond the end of the shelf, if need be. I use 1" S-hooks to hook over the wires of the overhead shelves, and the lightweight chains that came with my Home Depot shoplights. The chains let you adjust the height of the lights to keep them reasonably close to your plants for the best results.

That leaves the problem of how you fit three fixtures in the relatively narrow space of 15¾ inches. There are several possible solutions. For your 50" x 6" fixtures, you hang them in a "staggered" configuration. Hang two of your fixtures snug against the poles, down a few inches lower than the minimum hanging distance, and hang the third fixture higher up and centered so that its light can come down between the other two fixtures.

A variation on that would be to hand the outside fixtures at enough of an angle to allow the third fixture to fit between them. That would put your three fixtures in sort of a "hip roof" configuration, fitting between the poles and protruding a bit beyond the end of the shelves.

A third possibility would be to hang all three of your fixtures at an angle, in a sort of "venetian blind" configuration.

A fourth possibility is to buy some narrower fluorescent shoplights. Home Depot has $8 48-inch T8/T12 shoplights that are only 5 inches wide, and three of them fit neatly between the chrome wire posts. Since Home Depot sells a box of 10 Philips Cool White T8 bulbs for $19.95, they cost only $2 each. They draw only 32 watts each, contain less mercury, and are more efficient than T12 bulbs, so they put out as much or more light. And their lifetime is rated for 20,000 hours, which is a long time.

Another advantage of the Home Depot Commercial Electric shoplights is that they can be converted to "overdrive" your tubes for at least 50% more light output per tube. That would give you the light equivalent of 9 tubes per shelf.

MM

Maine Man --

Been following you on Dave's and now over here.

I bought bulbs at Home Depot last night, and at my local HD, the T12's are 19.99 a box, but the T8's are almost double that. The deal on the shop light fixtures is the same -- $8 for the T1 fixture; $21 for the T8 fixture. I went T12, even though we're a highly energy efficient and solar driven household, because I'm under the lowest tier of electricity pricing in the winter, and I can't imagine the 8 watt per bulb different being cost-effective given the big difference in pricing of both bulbs and fixtures. Will keep an eye out for cheaper T8's for the next light shelf system.

Now to my question: I have a shelving unit that is 18" deep and was planning on hanging one double bulb shoplight fixture per shelf -- 4 shelves, 4 double fixtures, one cool and one warm bulb per shelf. Now I'm thinking that will be insufficient. How many bulbs per 18" shelf do I need?

If more than two, the next question is whether to use a four-light fixture, or 2 two-lighters -- or whether I need 6 bulbs, though it sounds like that applies only to 24" deep shelving.

Thoughts? Or advice in general?

This is my first year germinating and putting cuttings under light, so this part is new. I remember my dad having all kinds of stuff under lights in the basement 30 years ago, but I will confess that I wasn't really paying attention until called upon to help plant what seemed at the time to be an ungodly number of bedding plants. I garden in Sacramento now, and try not to fight mother nature, so that means most of the garden is low irrigation. I'm propagating agastaches, sages, and lots of natives because I'm replacing half an acre of lawn with more interesting and more environmentally responsible vegetation.

In August, when it's too hot to think outside, I'll set up an overdrive system for next year. Have saved your instructions -- thanks!

Tokoro

P.S. Happy ground hog's day, everyone! And if you're in a state with a February 5 primary (not Maine), don't forget to vote.

Tokoro,

I'm surprised about the price discrepancies. I've bought dozens of $2 Philips F32T8/TL741 Cool White T8s from our local Home Depot and lots of their $8 2-bulb fixtures as well. The ending "41" in the model number of the fluorescent tubes indicates a color temperature of 4100°K. Incidentally, the $8 Commercial Electric (a Home Depot brand) Shoplights can use either T8 or T12 bulbs.

"I have a shelving unit that is 18" deep and was planning on hanging one double bulb shoplight fixture per shelf -- 4 shelves, 4 double fixtures, one cool and one warm bulb per shelf. Now I'm thinking that will be insufficient. How many bulbs per 18" shelf do I need?"

The number of bulbs you need depends on the light requirements of the plants you will be growing. Some plants, like coleus for example, don't require a lot of light intensity and might do well under a single 2-tube fixture. Pretty much everything I grow except coleus likes "full sunlight" and benefits from as much light as I can get over them. So I hang as many fixtures over a shelf as I can. For an 18-inch shelf, that is three fixtures (six bulbs). For a 24-inch shelf, that is four fixtures, for 8 tubes. And when overdriven, that is the equivalent of 9 tubes per 18-inch shelf and 12 tubes per 24-inch shelf.

Incidentally, I bought a few warm white T8 bulbs (they cost a little over $3 each) and discovered that my seedlings leaned very preferentially toward my cool white bulbs. I still use the warm white bulbs, but I am very glad I didn't buy very many of them. I have grown zinnias from seed to bloom to seed again under just overdriven cool whites. Maybe overdriving the bulbs boosts the warm spectrum output of the bulb. But, in any case, I won't be spending more to get warm white bulbs again.

"If more than two, the next question is whether to use a four-light fixture, or 2 two-lighters -- or whether I need 6 bulbs, though it sounds like that applies only to 24" deep shelving."

I use 8 tubes over a 24-inch shelf and 6 tubes over an 18-inch shelf. I use two 2-bulb fixtures instead of one 4-bulb fixture because they cost less ($8) and they are more flexible in how you can hang them. For example, you couldn't get 6 bulbs over an 18-inch shelf if you had 4-tube fixtures.

Our groundhog gave us 6 more weeks of Winter. Oh well, we were going to get that anyway. Good thing I've got a lot of fluorescent lights.

MM