Starting Seeds Indoors Under Fluorescent Lights

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Posted by @DavidLMO on
Starting seeds indoors over winter can give you a leg up, save lots of money, and give you something to do in the dreary period. I grow from 500 to 1000 plants in my basement each year. A decent set up can be put together without spending a fortune.

I am in Zone 5B, Northwest Missouri, and grow plants in my basement December - April. The normal unassisted temperature is 60 - 65 degrees and humidity 40 - 45 %.

I have run into several posts here where people wonder about growing under fluorescent (Abbreviated below as Fluor.) lights when they run out of windowsill space. Aside from watering, lighting is the biggest problem of growing from seed indoors, and the biggest lighting problem is not enough light, which results in leggy plants. (One trick to help prevent legginess is to run an oscillating fan towards your seed trays, especially once the seedlings grow to an inch or so in height.)

This article summarizes what has worked for me. I start between 500 - 2,000 or more plants from seed each year in my basement. In my grow area, there is one south window, 2 ' x 4', which provides just a bit of light. My entire regular grow area is about 12 ' x 20 '. More area is available if needed and for storage.

One can spend a lot of money on lighting systems, but I am just going to address relatively cheap setups. For that, you can start with a standard 2-bulb 48-inch "shop" light. (If you need the width, you can go with a 4-bulb unit.) Under one of these, you can start 144 plants using two 72-cell trays. Replace the bulbs if your unit comes with them and use them in your basement or shop. They are ineffective. Yes, I have tried them. I do not buy the absolute cheapest fixture. If there are 3 prices available, I buy the middle one. The cheapest will be the least efficient and will "break" the soonest because it has the cheapest ballast - the guts of a Fluor. light.

Thumb of 2015-11-09/DavidLMO/988005

In general, you also do not really need fancy grow or plant light bulbs. If you want, though, to shell out the added bucks, go for it. Grow bulbs do provide better light, but for the average person just wanting to start a couple of seed trays or so, it may not be worth it. A grow/plant type bulb can be 2 or more times the price of "natural" or 3 - 4 x the price of cool or warm bulbs. Based on my experiments, natural light bulbs provide almost as good results as grow or plant bulbs.

I have tried about everything that is available and in combination. Do not use plain cheap bulbs. You will get no joy and they do not last. (In fact, though a bulb may be "rated" at xxxx hours, you will likely never see that. If you get 50 % of xxxx, consider yourself lucky.) From my experience, using just cool or just warm is not effective. Using one of each is an improvement. But nowadays, I use bulbs called "natural." They work better for me than using a combo of cool & warm. They are also referred to as full spectrum.

Whether you use T-5 or T-12 is just a matter of size and choice. I have stayed mostly with T-12 because that is what I have the most of. I have fixtures that are 5 or more years old. While fixtures will "wear out" over time, the bigger problem is the ballast going out. If you are handy, you can replace them. While I am handy, I simply replace the entire unit.

Buy some small cheap chain and some S-hooks. Lightweight rope or twine can also be used. Attach your lights to ceiling or shelves in the best way that works. On my top shelves, my lights hang from the ceiling, where I attached them to rafters with eye hooks. However you set things up, you want to be able to adjust the height of the Fluor. fixture above your seed trays. When you first start the seeds, the light bulbs should be only a couple of inches max above the seed tray. As germination occurs, start adjusting the lights up, but maintain them at a few inches (and no more) above the plants. Once germination occurs and the seedlings are an inch or so tall, check what you are growing. Some things require the bulbs to be closer or farther.

You can get a timer and run the lights on/off. I typically run mine 12 hours on and 12 off. A multiple outlet box will be useful too, so that a timer can turn everything on and off at the same time.

I typically am running 6 - 10 fixtures. Fewer in December and January and most by March. I start moving things outdoors to my "pretend" greenhouse in mid to late April. We typically cannot be considered frost-free until about Mothers day.

You can go whole hog and literally spend several hundreds or even thousands of dollars on lighting. Today there are many choices and numerous options. I don't use LEDs or any other fancy new tech lighting.

Obviously there are many other things needed depending on how fancy you want to get and how much control you want. Lighting is just one important factor.

In addition to my fluorescent lights, I also have 2 - 500 watt metal halide warehouse lights (which I picked up, including bulbs, for $ 25 each Smiling )
3 oscillating fans
Small heater unit
4 standard seed tray sized heat mats
Controller for heat mats
Two timers

And an understanding wife who is also a plant lover.

I start all my seeds in 72 cell trays and use only seed-starting media. Be aware that if you use standard trays with plastic dome tops, you should keep the light a bit away from the dome. I don't use domes much anymore and I personally now have better luck. Domes can help with moisture retention. If you use them, remove them or open them up for an hour or so each day. In my experience, they can cause too much moisture retention and damping off. You can help to prevent damping off by adding hydrogen peroxide to your water. A typical mixture is 1/2 cup of 3 % (2 teaspoons of 35 %) hydrogen peroxide to a gallon of water

Lots of useful info here:


By far, for me, the biggest benefit of starting seeds indoors is that by early June I can have seedlings from a couple of inches to as much as six inches tall. Much of what I grow is for commercial purposes, so this is a significant advantage.

Comments and Discussion
Thread Title Last Reply Replies
T8 bulbs are a better choice by DonShirer Nov 21, 2018 12:23 AM 1
Led Lights by robertmirabi Mar 14, 2018 11:54 AM 0
Great Explanation! by Azgarden Feb 27, 2016 8:36 AM 0
Thank you!! by BetNC Feb 23, 2016 8:57 PM 0
Always good info by Oberon46 Feb 22, 2016 10:50 AM 0
Nice article by kqcrna Feb 21, 2016 7:49 PM 0

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