How to Build a DIY Grow Light for Starting Seeds

Have you struggled with leggy seedlings after starting them by seed? You may have read that using a grow light will help when you grow seeds indoors, but seeing the costs of grow light systems makes your eyes bug out. What if I told you that you could easily make your own grow light system for a fraction of the price without having to invest in fancy systems?

This blog details how to make your own grow light with purchased materials that are a fraction of the cost of ready-made seed starter lighting kits. A search of the internet for ready-made seed starter kits with LED lights found a large variety of prices, beginning at $75! A seed starter light, as illustrated and discussed in this post, costs approximately $50 in materials (although as low as $35, depending on the cost of the light). The seeds, trays and soil are extra.

Figure 1. Assembled seed light.

Materials List for DIY Grow Light, with costs

(Purchased at Home Depot, 1/21/23)

(1) Schedule 40 PVC pipe 3/4” x 10’ $6.29

(2) Schedule 40 PVC pipe 3/4” tee (.80 each) $1.72

(4) Schedule 40 PVC pipe 3/4” elbow (.61 each) $3.00

(1) Two-lamp LED shop light fixture 4’ $30.97 (recently found this 2-pack on Amazon cheaper than just one I bought)

(1) Electric timer $11.25 (similar to this one)

TOTAL: $53.53

In this set-up, an LED shop light is used. A fluorescent shop light can be used as well, although LED is more energy-efficient, but a bit more expensive.

A timer is included in the materials list since the lights need to be on for up to 16 hours per day. A timer ensures that the plants receive sufficient light per day. One could forego the timer but only if the light source is consistently turned on and off at an appropriate interval daily. I don’t know about you, but the less that I have to remember when it comes to daily life, the better.

PVC glue may be used when connecting the pieces of piping for a permanent bond. However, if you wish to disassemble the pieces for storage, do not use PVC glue. I don’t use glue for mine.

Cutting the PVC

Do this step first. From the 10’ length of PVC, have the home store cut, or cut at home with a hack saw, hand saw, PVC cutter, or any power saw:

• Four 12” legs – cut evenly!
• Four 6” cross bars – cut evenly!

When finished cutting, you will have approximately a 4’ length of PVC pipe. This will be the light support bar from which the light is suspended. It can vary by several inches and will be okay.

If after growing seeds with this set-up, you may find that you need more height after the seedlings grow a bit and you’ve pulled up the chain as far as it can go, especially for taller seedlings like tomatoes. You can easily cut various lengths of pipe (e.g. 14”, 16”, 18”) and trade out the legs as they get taller or use a PVC extender on each of the legs and put shorter sections to add to the initial 12”. It’s better than what I did which was place books under the legs as I needed more height.

Assembly of PVC Frame

(Note: if using PVC glue for a permanent bond, use in a well-ventilated area)

1. To make a leg assembly, take one tee and insert two of the 6” pieces of PVC pipe into the crossbar of the tee.
2. Insert elbows on the ends of the two PVC 6” pipes.
3. Insert a 12” long PVC leg into each of the two elbows. (See Figure 2)
4. Repeat steps 2 through 4 to create leg assembly.

Figure 2. Side detail

Installation of Shop Light onto Frame

1. Unpack the light.
2. There should be instructions with the light fixture, and generally, they will follow the instructions here: pull out the chains (there should be one for each end) and the “S” hook type of fastener. Loop the end of the chain through the “S” hook so that you can create a loop that is large enough for the PVC pipe to go through. The height can be adjusted as much as the chain will allow. (See Figure 3)
3. Insert the “S’ hook with the chain attached into the slot on the top surface of each end of the light fixture.
4. Install the lamps in the light fixture.
5. Thread the approximately 4’ long piece of PVC pipe through the two chains that will support the light fixture.
6. Insert the approximately 4’ long piece of PVC into the open end of the tee on one of the leg assemblies. Do the same for the opposite end twisting the leg assembly pieces as necessary to align properly.

Figure 3. Detail of chain and "S" hook attachment.

Tips on Planting Seeds

Here are some tips for planting seeds effectively:

1. Before starting seeds indoors check the seed package to learn how many weeks before the last frost date the seeds should be planted.
2. Select your containers. If they have previously been used, clean them using a 10% bleach and water solution to destroy any disease organisms present.
3. Use a sterile, well drained planting medium. Commercial mediums especially formulated for seed starting work well.
4. Add tepid water to your planting medium so that it is evenly moist but not wet.
5. Fill your containers with the seed starting medium and tamp it down so that the surface is level and within ¼ to ½ inch from tops of the containers. This will prevent water run off.
6. Plant your seeds to the depth the seed package recommends. This is usually 2 to 3 times the diameter of the seed. Tiny seeds can be pressed into the medium. (Check to see if the seeds need light to germinate and if so sprinkle them on the surface).
7. Plant at least 3 seeds in each container because not all seeds will germinate and any extra seedlings can be thinned out later.
8. Gently tamp the medium to obtain good seed to soil contact.
9. Label your pots with the type of seed and the date sown.

Figure 4. Seed-starting materials - seed tray with lid, heat mat, labels, and soil.

Tips on Maintaining Seedlings

Once your seeds are planted, you need to maintain them. Make sure you are checking on them daily and following these recommendations.

• Water the seeds. Bottom watering, if possible, is best because it doesn’t disturb the seeds but bottom watering is not recommended for paper or peat pots.
• Misting is also effective. You can cover the containers now until the seeds germinate to help maintain moisture.
• Try to keep the growing temperatures at 60 to 75 degrees Fahrenheit during the day and above 50 degrees during the night unless the seeds need cool temperatures to germinate. Adding bottom heat can help germination but too much heat, once germinated, can cause leggy plants.
• Once they have germinated keep the seedlings 1 to 3 inches below the fluorescent light bulb for 12 to 16 hours a day. Remember that the light in the center of the bulb is stronger than the light at the ends so rotate your plants. If you are using full spectrum grow lights, check to see the manufacturers’ recommendations for growing seedlings.

Figure 5. Light a few inches above seedlings.

• To prevent “damping off,” a fungal disease that attacks seedlings, maintain good air circulation. Using a small fan at low speed helps. (See Figure 6)

Figure 6. Damping off on basil.

• When true leaves form, fertilize the seedlings at ¼ the recommended strength.
• When two sets of true leaves form, it’s time to transplant seedlings into individual pots if they were started in flats.
• Before planting your seedlings harden them by gradually exposing them to outside growing conditions for a week or so (See Figure 7).

Figure 7. This is one day after transplanting lettuce from smaller cells. I'm starting to harden them off.

Conclusion

Growing seeds indoors can be a rewarding or defeating task, depending on the results. By using a grow light and following these recommendations, you can have healthy, happy seedlings that can turn into food for your table. 

Check out some of these other post on seed-starting:

• Mastering Indoor Seed Starting: 8 Common Mistakes to Avoid
• Starting from Scratch: The Pros and Cons of Starting Seeds vs Transplants in Your Vegetable Garden
• Protect Your Garden Using Disease-Resistant Seeds

Want to know the easiest vegetables to grow? Download my Seed Starting Cheatsheet: 12 Easy Vegetable Seeds to Start Indoors.

Disclosure: Some of the links in this blog are affiliate links. This means that, at zero cost to you, I will earn an affiliate commission if you click through the link and finalize a purchase.