seedling grow box

Seedling grow box

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Note: We’ve recently updated this article to include the latest LED grow light technology in addition to common fluorescent shop lights which can also be used as grow lights. Since this article was originally written, the price of LED grow lights has decreased significantly, making them competitive with or in some cases even less expensive than fluorescent lighting.

Get a jumpstart on the warm and cool weather growing seasons AND grow food indoors year round with this DIY grow light setup.

Video: introduction to a simple, indoor DIY grow light setup

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Our family grows a lot of organic food in our yard. By virtue of the fact that we live in Agricultural Zone 7b in Greenville, SC, we get to enjoy relatively warm/moderate temperatures throughout the year, although our winters can get quite cold (nighttime low temps have hit the single digits the past few years).

Nevertheless, we’re able to grow food indoors AND in our yard 365 days per year. Yep, the afternoon after it hit five degrees, we uncovered our low tunnel beds and harvested spinach, kale, miner’s lettuce, chickweed, and cilantro for a salad.

Gardening: An Investment Worth Making

The National Gardening Association estimates that for every $1 you invest into your garden, you get $8 back.

It’s so gratifying to get daily garden harvests like this!

We love helping people learn how to maximize their Return On Investment (ROI) in their garden, get huge yields, and do it all using organic/permaculture growing methods. Of course, organic gardening has a range of benefits that extend far beyond money, as we’ve stated elsewhere.

The highest ROI comes from the stuff you can get or use for free. For instance, most people bag and throw out their fall leaves. However, leaves are an incredible source of free nutrition that you can use to feed your beneficial soil microbes, which ultimately produces more delicious organic food for you. With a couple hours of work, you can get hundreds or even thousands of dollars in return if you use those leaves for your garden.

Some of the other high-ROI things you can do in your garden do require an initial upfront investment of cash. For us, one of the things that has made the biggest difference—and created the highest ROI—is making an indoor DIY grow light system.

Our DIY indoor grow light system. The shelves are lonely in this picture, but for most of the year, they’re full of plants and seedlings.

Three Reasons to Make Your Own DIY Grow Light System

You don’t HAVE to have a grow light system in order to have great gardening success, but it certainly helps. Here are three reasons we recommend serious/more advanced home gardeners make a DIY grow light system:

1. Get a Jumpstart On Each Growing Season

In our Ag Zone, we start our spring and summer seeds indoors in late January through February, then transplant them outdoors after the last frost date.

This gives us (and our plants) a 2-3 month head start on the warm weather growing season. Translation: we get to start harvesting much earlier and for much longer than if we were to direct sow our seeds outdoors once the weather warmed up.

Trays of fall seedlings started indoors in late July/early August under our grow lights will be transplanted outdoors in September.

The same thing is true when we start our fall/winter seeds indoors in July-August, then transplant the seedlings outdoors in September-October. Also, if you’ve ever started seeds indoors without grow lights, you might also realize how hard it is to get enough sunlight through your windows (even south-facing windows) to keep your plants from getting weak and leggy.

2. Grow Food Indoors

There are indoor grow light systems you can use to grow large plants like tomatoes, but that’s not what we’re discussing here. The grow light system we use and recommend is designed for starting seeds for transplanting OR growing smaller plants like lettuces and other greens for indoor harvests.

Using the grow light system in this article, you can easily grow enough greens and/or microgreens to get a nice daily harvest. If you live in a particularly cold climate, this benefit might be especially attractive since it’s more difficult for you to grow outdoors during the winter.

An array of colorful microgreens growing under our indoor grow light system. Microgreens aren’t just beautiful and tasty, they also pack some serious nutrition. You can read our article about how (and why) to grow microgreens here.

3. Improve Seed Germination Rates

We start a lot of seeds indoors and outdoors. No matter where you live, an outdoor growing environment is always going to be a little less “stable” than an indoor growing environment— varying temperatures, soil moisture fluctuations, etc.

You’ll use less seeds and have a higher germination rate by starting your seeds indoors under grow lights. Not to mention, there might be hungry insects that are more than happy to chew down an emergent seedling soon after it punches through the soil surface in your garden—not so when you start your seeds indoors.

No matter how many times we see it happen, we still get a sense of joy seeing seeds germinate – especially if it’s still freezing cold and dreary outside!

You can improve your seed germination rates and plant survival rates by starting your main seedlings indoors, then transplanting them outdoors once they’re 6-9 weeks old. Plus, if you have an edible landscape, more mature plants are more immediately attractive.

How To Put Together Your Own Grow Light System

The grow light system we use has the following benefits/features:

  • Relatively inexpensive and can easily pay for itself in a single growing season.
  • Easy to break down and set up.
  • Made with parts that can be ordered from Amazon or found at large home improvement stores like Lowes or Home Depot.
  • Made with parts you never have to replace (except for the lightbulbs which need to be replaced every 10,000-50,000 light hours depending on manufacturer’s recommendations or visual signs that your plants are getting inadequate levels of light).
  • *Fluorescent bulbs produce 3x more light than incandescents, are energy efficient and non-heating. e.g. they’ll grow your plants without really impacting your energy or heating/cooling bills. (*Since this article was first written, the price of LED grow lights has come WAY down, so we also have LED grow light options listed below. LED grow lights are even more energy efficient than fluorescent bulbs.)
  • Made with adjustable parts so you can raise or lower each row or each light, AND remove or add shelves as needed.

1. The Parts for Your Indoor DIY Grow Light System

Below are the parts you’ll need to put together the exact grow light setup we use. Note: We’re providing info for two different sized grow light setups using the same materials (option 2 is just a miniature version):

  1. Option 1: LARGE Grow Light System – Five shelf system (74-in H x 48-in W x 18-in D). Technically, this system has 6 shelves, but you can’t hang lights above the top shelf, so there are only five shelves to put seed flats on. This LARGE Grow Light System is ideal if you’re growing plants for a large garden/edible landscape or if you plan to start/grow hundreds of plants indoors at the same time.
  2. Option 2: SMALL Grow Light System – Two shelf system (30-in H x 24-in W x 14-in D). Technically, this system has 3 shelves, but you can’t hang lights above the top shelf, so there are only two shelves to put seed flats on. The SMALL Grow Light System is ideal if you’re growing in a smaller garden/edible landscape or if you only plan to start/grow less than a hundred plants indoors at the same time.

Parts you’ll need to purchase and their cost via Amazon ( *please note that prices on Amazon change, sometimes daily, depending on sales and product availability ):

Materials List for LARGE Shelf Grow Light System:

  • 48″ Multi-Tier Steel Shelving Unit (48″L x 18″W x 82″H)/ there are a few product options here:
    • A tall 82″ chrome-colored unit with 6 adjustable tiers and wheels – product link | cost: (*since this is the lowest cost, we’ll use it in our total costs below)
    • Same tall 82″ unit as above (82″), but black-colored – product link | cost:
    • A shorter 72″ high steel unit with 6 adjustable tiers and wheels – product link | cost:
  • 10-Outlet Power Strip – product link | quantity needed: 1 | cost: (it’s a 2-pack)
  • Open Oval Chain (black finish) – product link | quantity needed: 1 ft strips x 20 total strips | cost: (whole roll, 50′) Depending on the lights you get, you may not need the chain since chains are sometimes included with the lights.
  • 20 S-hooks (can be easily adjusted with pliers) – product link | quantity needed: 20 | cost: for a 20-pack
  • Zip Ties – product link | quantity needed: we used 10-12 but they come in a bag of 30 (you can never have too many zip ties around) | cost:
  • LIGHTING: Choose EITHER LED OR Fluorescent Lights. LEDs may be a touch more expensive up-front, but costs are quickly coming down on them and the benefit of having healthier plants and lower energy costs probably outweighs any difference in upfront costs. IMPORTANT: Since the LEDs are hung about 24” above the plants/seedlings (versus fluorescents which can hang 2-3″ over seedlings) you can’t set up all 6 shelves. You can only use 4 shelves, three of which have plants on them. Therefore you only need 3 LED lights.
    • LED Lights – These options assume 1 LED light strip per shelf. We’ve included a few options in case one is out of stock:
      • 48″ 64W Full Spectrum LED Light Strip – product link | quantity needed: 3 | cost: per unit
      • 48″ 60W Full Spectrum LED Light Strip – product link | quantity needed: 3 | cost: $45.99 per unit
      • 4 pack – 48″ 60W Full Spectrum LED Light Strips – product link | quantity needed: 1 | cost: per unit
    • Fluorescent Lights
      • 48″ Fluorescent Shop Light Housing – product link | quantity needed: 10 | cost: $15.50 per unit
      • 48″ COOL LIGHT Fluorescent Bulbs – two options depending on pricing and what’s in stock:
        • product link | quantity needed: we used 1 cool light bulb in each housing unit, or 10 total cool light bulbs | cost: /ten-pack
        • product link | quantity needed: same as above | cost: /ten-pack
      • 48″ WARM LIGHT Fluorescent Bulbs – product link | quantity: same as above | cost: /ten-pack
  • TOTAL COST: about $350 depending on current Amazon pricing

If you use fluorescent shop lights, S-hooks and chains allow you to hang your grow lights and adjust the distance between the bulbs and the plants as-needed (and as the plants grow taller).

Materials List for SMALL Grow Light System:

  • 3-Tier Steel Shelving Unit (13.11 x 23.15 x 29.90 inches) – product link | cost: (*Note that the reason this unit is so much less expensive than a 5 or 6-tier shelf is that the width and depth are much smaller, so you won’t be able to put as many plant trays on it)
  • 10-Outlet Power Strip – product link | quantity needed: 1 | cost: (it’s a 2-pack)
  • Zip Ties – product link | quantity needed: we used 10-12 but they come in a bag of 30 (you can never have too many zip ties around) | cost:
  • 24″ LED grow light unit – product link | quantity needed: *1 | cost per unit: per unit. (*As mentioned above in the large grow light setup notes, LEDs are hung higher about the seedlings/plants (24″) than fluorescent lights (2-3″), so you’ll only have one planting shelf with this smaller setup, rather than two.)
  • Note: You may be able to find fluorescent shop light housing + 24″ warm and cool light fluorescent bulbs at you local Lowes or Home Depot, but those items seem to be very rare now. Plus, that setup will actually cost about twice as much as the LED setup we recommend above.
  • (optional but recommended) Heavy duty shelf wheels | Note: these wheels allow you to easily move the entire grow light shelving system whenever, wherever you want – even when it’s full of seed trays. | product link (4-pack) | quantity: 1 | cost: $19.45
  • TOTAL COST: About $150 before taxes

2. Getting the Proper Bulbs

If you’re getting full spectrum LED grow lights, you can skip this section. If you’re getting/using fluorescent lights, you’ll want to carefully read this section…

As you probably know, light is essential for plant health/growth. Sunlight contains ROYGBIV, the full spectrum of colors of the rainbow that we all learned about in kindergarten.

The two most critically important light spectrums are RED and BLUE light.

  • Red spectrum light stimulates growth and flowering, but too much red light leads to tall, weak plants.
  • Blue spectrum light regulates the proper amount and distribution of plant growth, ensuring that all parts of the plant take on the proper size, shape and density.

The color of light created by each type of fluorescent bulb is determined by its interior phosphor coating. When using fluorescent bulbs, we recommend using a combination of these two types of fluorescent bulbs:

  • “Cool white” fluorescent bulbs offer Y/G/B (yellow, green, blue) spectrum lights for your plants. Cool bulbs have a kelvin range between 5000 – 6000K.
  • “Warm white” provides O/R (orange, red) spectrum light. Warm bulbs have a kelvin range between 2700 – 3500K.

So, install alternating cool and warm fluorescent bulbs into your light housing as indicated in the materials list above and shown in the image below. This way, you can mimic nearly the entire color spectrum of the sun, thus growing healthy seedlings and plants.

Alternating cool and warm fluorescent shop light bulbs. The bulbs don’t actually look red or blue to the naked eye.

3. Other Indoor Grow Light FAQs

Below are answers to the most frequently asked questions we get about our DIY indoor grow light setup:

1. How much indoor light hours do your plants need?

Answer: Each type of plant is a little different, but generally speaking, your edible garden plants will do fine with 10-14 hours of indoor light per day. You can buy a timer if you want or just set an alert on your phone/calendar to remind you to turn the lights on in the morning and off at night. Just like people, plants need darkness/rest, so try not to forget to turn your lights off.

More tips: 1) Plug one power strip into the other power strip so that you can just flip a single switch to turn all the lights on or off. 2) Use zip ties to attach your power strips to the side of your shelving unit AND to keep the power chords neat and organized.

2. How close do you let your plants go to the fluorescent grow lights?

Answer: Keep your plants about 2-3″ from your fluorescent lights. If your plants start looking thin, leggy and weak, move the lights closer to the tops of your plants using your adjustable chains and S-hooks. If the leaves get scalded, move your lights higher (very unlikely to happen unless your plants are directly touching the bulb).

Tomato seedlings being started indoors in February. Notice how close the lights are to the top of the plants – we keep the lights a few inches overhead. If the lights are touching the plants, your plants may get sunburn; if they’re too far away, your plants may become weak and leggy.

3. How often do I have to replace my fluorescent bulbs?

Answer: It depends on the bulbs you buy. Each manufacturer puts the estimated “lamp life” on the specs, which are often 20,000+ light hours. After a few years, if your bulbs are still working but your seedlings seem like they’re not growing as well, you may want to consider replacing them early.

4. What about growing under LED bulbs/lights?

Growing plants under LED bulbs is a little more complicated.

  • Sprouts & young seedlings – For sprouts and seedlings, you’ll want the tops of your plants to be 24-28″ overhead.
  • Growth stage – After your seedlings are a few weeks old, you can lower the LED lights to 18-24″ over the top of your plants.
  • Flowering/fruiting – If you’re growing plants all the way to production (ex. growing strawberries or tomatoes), you’ll want to lower your LED lights to a height of 12-18″ during this stage of development.

5. What trays, cells, etc. should I get and what starting mix should I get/make?

Answer: Since we’ve had comments and emails from this article asking what seed starting trays, etc we use, we’ll quickly provide a bit of info here, then refer you to more detailed articles/videos we’ve created on that topic:

  • Trays – Because we got tired of throwing away flimsy trays after one or two growing seasons, we now prefer these extra strength trays because they’re BPA-Free, SUPER durable, and also created by a local (to us) NC farmer who needed supplies that lasted longer than the current options: 5 pack & 10 pack
  • Heat mat – Essential for getting good seed germination when starting tomatoes, peppers, and other summer nightshades indoors: 48″ x 20″ heat mat & thermostat to control temps
  • More info – We have three free seed starting video classes (plus a free ebook) if you want to get the answers to all your seed starting questions. Plus, we also have a detailed guide showing you how to use Ladbrooke Soil Blocks.

Get a jumpstart on the warm and cool weather growing seasons AND easily grow food indoors year round with this DIY grow light setup.