How to Grow Lettuce Indoors with Hydroponics
Some of the easiest crops to grow hydroponically are lettuce and other leafy greens like chard, kale, and arugula. They don’t take up much room and are quite fast growing. Rich in micronutrients and diverse in color and flavor, they are versatile in sandwiches or salads.
Fresh Facts About Lettuce
First we need to know a little more about our crop. Lettuce is a cool season vegetable, meaning they grow best between 45° and 80° F, perfect for indoor growing. They typically grow in a shape called a rosette, a tight spiral similar to rose petals. Lettuce is harvested prior to bolting, or flowering, since during that time it loses shape and the stem thickens and lengthens. The best thing about lettuce and greens is that your crop will be ready in 20-30 days, allowing for quick turn over and multiple crops throughout the year.
The following hydroponic techniques are ebb and flow systems, which work by pumping water up around the roots and then draining it away to pull in fresh oxygen. Water soluble fertilizers are dissolved in the reservoir to provide nutrients to the plants. In the case of multi-step fertilizers, each addition should be fully dissolved before adding another. The pH and electrical conductivity of the nutrient solution should be checked regularly and often, at least 2-3 times a week, in case it needs to be adjusted. For lettuce, choose a fertilizer that favors vegetative growth.
Beginner
| Stuff You’ll Need | |
| Lettuce seeds – any variety | Mega Garden by HydroFarm |
If you’re looking for an easy fix, nothing could be simpler than the Mega Garden. It comes with everything you need to propagate, grow, fertilize and finish your crop all conveniently together. The Mega Garden is excellent for baby greens (lettuce and other greens harvested while leaves are still small) or mature lettuce, since the pots can be arranged either tightly or spaced out.
When propagating lettuce seeds in the rockwool cubes, set the timer to flood the tray 1-2 times a day and use just the overflow drain head without the extenders. This will keep the water level low and not flood your seedlings. DO NOT separate the cubes. Simply soak until evenly moist. Add the RapidStart Root Stimulator to the reservoir, and place cubes in the flood tray, 2-3 seeds per cube, with the hole facing up. Set grow lights to give your seedlings 12-18 hours of light per day.
Once the seedlings are about 1 to 1.5 inches in height, fill the pots with clay pebbles and place 1 plug/seedling in each, so that it sits in the pebbles at least 1 inch from the top of the pot. Now you can add an extender or two to the overflow drain to raise the maximum fill level as desired. Dump out the old nutrient solution and replace with fresh water, adding the FloraNova Solution as directed. Place the pots in the flood tray and set your pump to run between 3-7 times a day as needed.
Intermediate
| Stuff You’ll Need | |
| Lettuce seeds – any variety | Starter plugs/rockwool mini-cubes |
| Propagation tray with dome | 36L Hydroton Pebbles, rinsed |
| 4x4” Rockwool Blocks | Active Aqua Flow Grow System |
This pre-made ebb & flow system from Active Aqua features a control bucket to ensure the correct flood height and a 55-gallon reservoir for even dilution of nutrients. The buckets can be set up in a variety of layouts to fit any grow space. Soak starter cubes until evenly moist but not soggy. Start your seeds in the rockwool cubes, 2-3 seeds per cube, keeping the dome on for added humidity. Set grow lights to give your seedlings 12-18 hours of light a day.
Thin out the weak sprouts. Once the seedlings are about 1 to 1.5 inches in height, fill the pots with clay pebbles and place 1 plug/seedling in each 4 inch cube. Place the cube in the pebbles to sit at least 1 inch from the top of the pot. Set the pump timer to flood the pots 3-7 times throughout the light cycle. The secondary pump should be set to return the water to the reservoir as soon as the water reaches the max fill height. Add your fertilizer to the reservoir. As the lettuce grows larger it may need more flood cycles per day.
Don't forget the lights. Our earlier article will help you pick the right grow lights for your grow room. “Lettuce” help you with your greens! Whether your philosophy is “Start small” or “Go big or go home,” our knowledgeable staff is on hand to help you choose the right hydroponic system. The only thing greener than your thumb will be your salad or perhaps your neighbors’ envious faces! Questions or comments? Drop us a line through Facebook, Twitter, LinkedIn, Pinterest!
