A few weeks ago I started an experimental grow without any fancy equipment; no discount storage boxes or bins. I’m using recycled coffee tubs! This is a cheap hydroponics DIY setup that anyone can handle making. Aside from the seed, I think I have about $1 invested per plant.
No, I’m not using a grow light, because I want to see just how well the plants do in a very bright, south-facing window. Shady areas simply won’t work. There is no circulation pump; it’s a super simple setup that you can put together in an hour or two. This is passive hydroponics, a method known as Kratky.
First, you’ve got to start your seeds, which means you need a germination chamber, and some 1″ Rockwool starter cubes. You can buy a strip of 24 for about $8 – which translates to 30 cents per lettuce you grow. Still cheap, and you’ll be ready to start a fresh crop with supplies on hand.
You have to soak your Rockwool for 24 hours in water to get the pH to the right level. I used distilled water but adjusted the pH with lemon juice to bring it from the 7.0 pH level that all distilled water has down to the recommended 6.0 pH. Once that’s done, you’re ready to plant.
A domed plastic clamshell with a flat bottom from the store is perfect if the number of grow cubes you’re starting will fit inside and close with a couple inches of headroom. I used a cookie box that had a clear top and a black bottom; good for soaking up the warmth of the sun!
- Remove the plastic wrapper from around the Rockwool cubes.
- Drop your seeds in the pre-drilled hole.
- Take a couple of paper towels and fold them to fit the bottom of your container.
- Add enough water to saturate the paper towel but not so much you’ve got standing water.
- Sit your seeded cubes inside the box.
- Close the lid, and set it in a dark spot where no sunlight can reach it.
- After 3 days, check your cubes to see if you’ve got sprouts yet.
It doesn’t take long for lettuce to germinate. If only a couple of sprouted, you need to give them light, so get them in the windowsill inside your germination chamber.
Seeds need no nutrients for at least two weeks. They’re fine with just the moist cubes and paper towel in the box. Keep the lid on it to maintain good humidity, and put it in a south-facing windowsill – right against the glass. If your paper towel starts drying out, remoisten it – this maintains the moisture in the grow cubes just enough to keep your baby lettuce happy.
Once the seedlings are tall enough to touch the lid, it’s time to remove that part of your homemade germination chamber. I left my lettuce in the recycled cookie box for three weeks after they all sprouted.
The seed was sown on March 27, and they finally went into hydro pots on April 18. But for a week before I ‘planted’ them, I gave them a half-strength nutrient solution. Just enough to re-moisten the cubes and then saturating the paper towel with it. The cubes were dunked twice a day, and growth started happening faster.
Now you need 2″ net cups, which will cost about 25 cents each. Put them upside down on the coffee tub lid and trace around it with a marker. Make a slightly smaller circle inside so the net cup won’t fall through. Use an Exacto or utility knife to cut out the circle. Best to start a little farther in than you think it needs – you can always trim it back so the pot sits flush with the lid.
Now mix up some grow nutrients solution. If you use a one-part kind like GroTek Solo-Grow or Botanicare Pure Blend Pro Grow you’ll only need 1/4 teaspoon per quart of water for seedlings, and 1/2 teaspoon once they start filling out until harvest.
Before you add your nutes to the coffee tubs, you need to mark a line where the bottom of the pot will sit once it’s all put together. You want to keep the nutrient level just above that line until the roots of the lettuce grow long enough to reach the moisture and nutrition below. If it drops too low, you will have wilted plants!
On May 6, only one of the 4 in my windowsill has roots that reach out past the plastic net, but the plants are growing like crazy. Look how small they were when I moved them into the pots below. I’m using Solo-Grow, which is working very nicely. So far, I’ve had to add nutrients twice in 6 days.
Best guesstimate on when this lettuce will be ready to harvest is in 4-6 weeks (it takes 3 months in the ground). They would probably grow a bit faster under a grow light, but that’s not part of this experiment.
Since it’s working well, it’s time to sow another 4 seeds, and build up a steady supply of fresh dirt-free lettuce 😉
Last updated by Catherine Sherriffs on 04/05/2020.