Building a DIY Hydroponics System Part 6: Planting

Building a DIY Hydroponics System Part 6: Planting

This is Part 6 of a 7 Part Series of how to build and manage a DIY Hydroponic Lettuce System!

Other Articles in this Series:
Part 1: The Rail System
Part 2: The Support Structure
Part 3: The Reservoir
Part 4: Lighting
Part 5: Nutrients
Part 7: Harvesting

Note about links: We have linked to certain products that we have found useful when building our hydroponic systems. Some of these links may be affiliate links and as an Amazon Associate we earn from qualifying purchases after clicking one of these. We take great care to only link to products we have found to be useful - products we would recommend to a friend or family member building this system - but you are more than welcome to use other products instead.

Now that you've got everything up and running, all that's left to do is the FUN STUFF!!!! Here's everything you'll need to know to get some real food growing in your new delightfully awesome DIY hydroponics system!


  1. Growing Medium
    "Growing Medium" is where you plant the seed, and what the initial roots first grab onto when lettuce starts to grow. The rail system is designed to handle a variety of commercially available grow plugs. We have used both rock wool and tree bark starter plugs (we would recommend Rapid Rooters or Viagrow Plugs). The tree bark starter plugs have worked best, with faster germination time and less algae growth. They're also compostable & therefore have a very low environmental impact. We order a batch of 50 or 100 tree bark starter plugs at a time. A pack of 100 lasts almost half a year when harvesting 4 heads a week.

  2. Net Cups
    "Net cups" serve as a container to hold the growing medium in the rails. We use these 1.5" net cups because they fit grow plugs perfectly, without any open space around the edges. This prevents algae growth by blocking light from passing through into the rails. These net cups are reusable, so you only need one for each plant site plus a few extra for harvesting and planting.

  3. Seeds
    We have always had great experiences ordering seeds from Johnny's Seeds. We have tried lots of different varieties of lettuce but have found Muir, Rex and Monte Carlo to be the fastest growing with the best flavor, and they fit within the system (some heads grow too tall and tip over or grow too wide & block too much light from other heads of lettuce.) These are some good starting options, but feel free to experiment with different varieties to find what you like best! We've found that trying different lettuce varieties is one of the most fun parts of this hobby, so go crazy!

Planting Process

When you're first starting out, you'll want to stagger your planting to about 4 seeds per week. (We don't want all of your lettuce heads to reach maturity all at once! Because what are you going to do with 28 heads of lettuce in one week?) What you can do is choose a consistent day of the week where you usually have a bit of free time in the morning (Saturday, for instance), and for 7 weeks in a row, plant 4 seeds on Saturday morning. By the 7th week, you'll have all your plant sites in the hydroponics system filled up with lettuce, all at different stages of development.

You'll want to cover any unused plant sites to prevent algae growth. We like snap-in plugs to fill in unused spots and to give a clean look. We've used 2-inch and 1.5-inch hole plugs and would recommend them. Otherwise cardboard or other opaque materials work well.

Once you're able to start harvesting, you'll plant one seed for every head you harvest. Plant seeds right after you harvest that day.

How To Plant

Place a fresh seed plug into a clean 1.5" net cup. Add 1-2 seeds per plug. (If the seeds you chose have a low germination rate, it can be helpful to have 2 just in case one doesn't germinate. We usually do just 1 because most of the seed packets we order have a germination rate of 95-99%.) Place the net cup into one of the holes that are closest together. The seed should germinate within 3 days. As each lettuce plant grows, and as you harvest, you'll move plants through the system as shown in the diagram below:

planting to harvest

Once your lettuce has grown to maturity, it's time to harvest!