How to Grow Watercress Indoors: 17 Simple Steps

Watercress is a water-loving perennial herb that can easily be grown indoors. It’s part of the Brassicaceae family of plants and has a flavor like green pepper, wasabi, and spinach. People in the Mediterranean region have been in love with it since ancient times. 

Besides its characteristic peppery flavor, it packs a ton of nutrition in its tiny green leaves. It contains vitamins B, C, and K, polyphenols, terpenes, and tons of antioxidants. If you’re a foodie or a health-conscious person, try growing watercress at home. Even if you’re a novice gardener, you’ll have no problems growing this semi-aquatic herb. 

Let’s dive into the 17 simple steps to grow watercress indoors. With a little attention, you’ll get a constant supply of delicious and nutritious greens throughout the year. 

Watercress Seeds

With a peppery and pungent flavor, this ancient plant is popular around the world for its nutritional and medicinal value. High in vitamins A, C, and K, as well as providing potassium and calcium, watercress has been studied for its antioxidant properties. At home along streams and lakes, watercress can also be grown in moist, partly shady gardens and indoors in containers.

Buy at Epic Gardening

Step 1: Buy Your Seeds

Start growing watercress indoors by buying high-quality seeds from a reputable company. You should be able to find them online or at your local nursery without a problem. 

Make sure the seed packets are less than a year old. If you buy them in person, check to see if they’re in good condition. Look for stains, watermarks, rips, or signs the packets were left outside in the sun. If you see signs of damage on the packets or they’re over a year old, don’t use them. 

Step 2: Collect Your Containers

The first step to growing this power food in your home is collecting its pots. Salad trays or other deep rectangular containers work well.

These makeshift bottom trays will hold water while smaller pots are placed inside. You’ll start your herbs in the smaller ones. 

For the smaller pots, make sure they have enough drainage holes at the bottom. This will allow enough circulation of water and nutrients in the plant’s roots. You can also purchase durable 3″ cube pots that already have drainage and airflow holes.

Step 3: Prepare the Inner Container

The second step to growing healthy watercress indoors is preparing the pots. Start by poking drainage holes in the bottom. 

Place a coffee filter or a thin piece of cloth at the bottom. This will trap the soil from escaping out of the drainage holes. 

Step 4: Fill With Soil or Hydroponic Growing Medium

Once your pots are prepared, it’s time to fill them with a soil blend. Watercress isn’t picky about its growing medium.

Choose a well-drained soil mixture of potting soil and sand, clay, chalk, or perlite. The soil’s pH should be neutral. If you want, you can use a soil testing kit like this one to measure the pH. 

You can also grow your plants in hydroponic gravel or other soil-free mediums like coconut coir. They will thrive in both types of mediums, so choose what’s easiest for you. 

Step 5: Plant Your Seeds

Open your seed packet and carefully remove the tiny seeds. Make small holes with your finger in the growing medium about ¼ inch deep. 

Gently sprinkle your seeds in the holes, about 3 or 4 per hole. Cover them with a very thin layer of soil or a growing medium. 

Make sure you don’t overcrowd the holes or plant them too deep. The seeds won’t germinate if they’re too deep inside their medium. 

Step 6: Cover the Pots

Cover your watercress seeds with plastic or plastic domes. Make sure there’s some aeration through small holes or openings. 

This will help lock in moisture for the seedlings to germinate. Continue spraying or misting the growing medium to keep it moist throughout the germination period. 

Step 7: Stack Your Containers

Once you planted your seeds and covered them with a humidity dome, you’ll place them inside the bottom trays. Start by arranging a few clean stones at the bottom of your larger trays to provide good oxygen circulation. 

Place your smaller container on top so it’s sitting on the stones, roughly ½ inch to an inch off the bottom. Fill the bottom trays with clean, fresh water about halfway to the top. If you’re using a hydroponic growing medium, fill it with a hydroponic nutrient solution instead of water. 

This setup will water the plants from the bottom and keep their growing medium moist. As they grow, keep the water filled to about the same level. 

Step 8: Place in Light

Place your containers in front of a large window or grow light. These plants love full sun to partial shade. Aim for over 6 hours of direct sunlight or light from grow lights. 

I love growing my watercress in my kitchen windowsill. It gets plenty of bright light through the windows. My plants produce tons of bright green foliage right in my kitchen. 

Step 9: Wait Until They Germinate

Watercress takes about one to two weeks to emerge. You’ll see tiny green shoots growing out of your growing medium. 

Sometimes, I like to harvest the tiny seedlings as microgreens. They have a nice flavor and make great garnishes for special meals. 

Step 10: Thin Your Plants if Necessary

If your seedlings are overcrowding each other, it helps to thin them out. Choose the strongest-looking seedlings when they’re at least one inch tall, and carefully remove the others. Leave about one plant per 4 inches. 

This will prevent your plants from competing for nutrients. With enough space, they’ll grow big and healthy leaves packed with nutrients and flavor. 

Step 11: Harvest Your First Greens

Now, the fun part is harvesting your first greens! Watercress is incredibly resilient, so don’t be afraid to give it a good pruning. 

You can harvest the foliage when it’s young or let it grow longer for more flavorful leaves. Sometimes, the healthiest plants pack a spicy punch. 

Step 12: Divide Your Plants

After your plants have matured, you’ll probably be surprised by how full their growth is. Try propagating your plants to new pots by dividing them. This is incredibly easy, and if you don’t have room, give the new plants away as gifts. 

Start by finding a healthy batch of foliage and roots. Carefully separate it from the growing medium. 

Set up another double container setup as before and prepare a new container with a soil or hydroponic growing medium. Plant the divided watercress in the new pots and give them a good misting. These new plants should flourish with enough light, water, and nutrients. 

Step 13: Keep Up With Watering

Watercress will grow best when its roots are in contact with water. That’s why it’s important to keep the water levels on your trays up to the base of the smaller containers containing your plants. 

To help prevent disease, bacterial growth, or growing issues, change your water frequently. Give your plants clean fresh water every few days. 

If you’re growing your plants hydroponically without soil, you’ll use a nutrient solution instead. Keep the growing medium hydrated throughout the process. 

Step 14: Feed Your Plants

As your plants grow, they may need an extra boost in nutrients, especially if they’re growing in soil. Do this by adding an organic liquid fertilizer to the water every couple of weeks. 

The water will absorb the fertilizer, making it easy for your plants to absorb the nutrients. With the extra nutrient boost, you’ll see lush foliage with deep green coloration and vigorous growth. 

My favorite fertilizer to use with watercress is liquid kelp fertilizer. This organic fertilizer is made from the Atlantic kelp species Ascophyllum nodosum. The fertilizer will absorb quickly into the water, giving your plants an easily absorbed source of balanced nutrients. 

Step 15: Aerate Your Watercress

Besides changing the water frequently, you’ll want to aerate your plants. To do this, simply lift your small pots out of the water a few times. This circulates the water in the roots and lets oxygen flow freely.  

If you forget this step, water will become stagnant in the small spaces between the roots. When water is stagnant, it will become less oxygenated. 

Step 16: Watch for Diseases or Pests

Indoor grown watercress can still succumb to a variety of pests and diseases. Check your plants for whiteflies, which can quickly infest your water-loving herbs. Spider mites can also be attracted to the moist growing conditions. 

Remove these pests by hand if the infestation is small. Or apply a little organic neem oil to the infested foliage. Rinse the greens off well before eating and avoid using anything chemical. 

The most common disease is damping off disease. Fungal pathogens infect the young seedlings and cause them to wilt. There’s no cure, so it’s best to start your seedlings over again from step 1. The best way to prevent this disease is by oxygenating the water and changing it several times a week. 

Step 17: Clean Your Containers 

The final step is cleaning your trays and pots every month or two. Algae and bacteria can grow easily in room temperature water. That’s why it’s important to clean your containers thoroughly to prevent buildup. 

Remove the smaller pots and give the larger containers a good scrub. I like to avoid soaps and use a white vinegar and water solution. After cleaning, fill them up again with water or a nutrient solution and return your plants.