How to Grow a Non-Stop Supply of Salad Greens in Your Classroom

If you’ve ever dreamed of bringing fresh, healthy food into your classroom but felt limited by time, space, or resources, I have great news for you: it’s absolutely possible. In fact, you and your students can grow a continuous supply of salad greens, indoors, year-round, without an outdoor garden, expensive grow lights, or fancy equipment. And I mean salad greens not just microgreens!

This isn’t theory. I’ve tested it myself, and I know it works beautifully in classrooms too. Let’s break it down step by step so you can see how simple (and rewarding) it really is.

Why Salad Greens?

Salad greens are one of the easiest and most practical crops you can grow indoors. They germinate quickly, grow fast, and don’t require much depth of soil. In as little as six weeks, your students will be harvesting, and with the right system, they’ll keep harvesting week after week.

This project teaches more than gardening. It connects kids to food, health, and sustainability. It shows them how a small daily or weekly effort creates long-term results. And it sparks excitement every time they walk past their “classroom garden.”

Step One: Finding the Right Window

The most important ingredient in your setup is sunlight. You’ll want a bright, sunny window, ideally south-facing in the northern hemisphere. South-facing windows catch the maximum amount of light throughout the day, which is crucial during shorter, cloudier winter months.

Not sure which direction your windows face? A quick check on Google Maps or your smartphone compass app will solve that. If your classroom doesn’t have a suitable window, get creative. Consider the library, staff lounge, an office, or even a colleague’s classroom. A little resourcefulness will go a long way here.

Tip: East- or west-facing windows can still work, but they’ll be more limited, especially in winter. North-facing windows don’t provide enough light, EVER!

Step Two: Choosing the Right Seeds

Not all salad mixes are equal. A good seed mix means faster germination, better flavor, and stronger plants. I’ve personally had success with salad mixes from OSC Seeds (Canada), and teachers I work with in the U.S. recommend Sow True Seeds.

You’re not limited to those two sources, most reputable seed companies carry mixes labeled as “salad greens,” “cut-and-come-again mixes,” or “mesclun mixes.” The key is variety: a blend of lettuces, mustards, and other leafy greens ensures continuous growth and a more interesting harvest.

Step Three: Potting Soil

Choose an organic potting mix with no added chemicals. This doesn’t need to be fancy. The kind you find at your local garden center, hardware store, or even big-box retailer will work.

Since you’ll be reusing soil across multiple planting cycles (I’ll explain how later), you don’t need to stockpile huge bags. Just make sure you plan ahead if you want to keep growing through winter when many garden centers close.

Step Four: The Sub-Irrigated Planter System

This is where the magic happens. Consistent watering is the difference between thriving greens and failed crops, and in a classroom, it’s too easy to over- or under-water. The solution? A simple double-container sub-irrigated planter system.

Here’s how it works:

• Outer container (reservoir): A sturdy plastic bin or bucket that holds water.

• Inner container (planter): A slightly smaller container with holes drilled near (but not at) the bottom. This holds the soil and plants.

When you pour water into the reservoir, it seeps up into the planter through those side holes. The soil absorbs exactly what it needs, and the roots stay consistently hydrated. No guesswork, no accidents, just steady growth.

For reference, I’ve used 14" x 10" x 4" containers as reservoirs and 12" x 9" x 3" containers (repurposed from grocery-store salad mixes) as planters. Yours don’t have to match these exact measurements. Just make sure the inner container fits inside the outer one, leaving a little room beside the planter to pour water into the reservoir.

Step Five: Planting and Maintaining

Now comes the fun part, getting your students involved. This is a 100% hands-on activity, and the more they do, the more they learn.

1. Fill the planter with potting soil.

2. Water the soil so it’s evenly damp.

3. Sprinkle seeds across the surface.

4. Cover lightly with a thin layer of soil.

5. Water gently from above just once, to settle the seeds, and wet the covering soil.

6. Place the planter into the reservoir and add about two inches of water (in the reservoir).

7. Move it to the sunny window.

From this point on, you only need to keep an eye on the water level in the reservoir. Top it up as needed, and that’s it. No more overhead watering required.

Step Six: Harvesting and Replanting

Here’s the secret to a non-stop supply: staggered planting.

Start with 18 containers and plant three of them per week (for example, every Monday, Wednesday, and Friday). After six weeks, your first set will be ready to harvest, and by then, you’ll have new containers coming up behind them.

To replant, simply:

• Cut the greens.

• Pull out the roots.

• Remove and replace the top 2–3 cm of soil.

• Plant new seeds in the same container.

This cycle means fresh salad greens forever, with just a few minutes of effort a few times a week.

Why This Project Matters

Yes, your students will love the salads. But the real value is much deeper. They’ll learn:

• Science in action: photosynthesis, soil cycles, and plant biology.

• Healthy habits: the joy of eating what they’ve grown.

• Responsibility and teamwork: shared care for a living system.

• Resilience and empowerment: the knowledge that they can grow food, anytime, anywhere.

• Work ethics and grit: deep knowing that small persistent action, rewards them over time.

And for you? A project that’s low-maintenance, cost-effective, and profoundly rewarding.

Ready to Get Started?

With nothing more than a sunny window, a few containers, some potting soil, and the right seeds, you can transform your classroom into a thriving mini-garden.

Your students will thank you, not just today, but for years to come. Because this simple project leaves a lasting impression about food, nature, and what’s possible when we work together and keep showing up.

🌱 Want to hear me walk you step by step through the process? Listen to Episode 64 of School Gardens with Ease: Click here to listen .