How to Grow Watercress Indoors

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How to Grow Watercress Indoors

Are you a fan of spicy greens? Eager to learn how to grow watercress indoors? Look no further! We’ll teach you a few different ways to grow this hardy, nutrient-dense vegetable inside your own home.

Watercress (Nasturtium officinale) is one of the most nutritious greens out there. If you’re aiming to grow at least some of your own food, then it’s great that you’re adding this plant to your list. Not only does one handful of watercress have more vitamin C than an orange, it’s also packed with a ton of nutrients. In addition to iron, it contains folate, potassium, iron, and lots of phytonutrients and antioxidants.

These plants need an environment where they’ll get a few hours of sunshine a day, but are shielded from high heat. Try to choose a window where they’ll get early morning or late afternoon sun, but not direct noon sunlight. That will fry them.

Additionally, watercress doesn’t thrive well in soil. Instead, aim for a soil-less growing medium.

Materials You’ll Need

Two Containers

Choose either plastic or glazed ceramic growing containers. One should be large, and one medium, so you can nest one inside the other. The medium-sized one should have drainage holes, while the larger one should not. Do not use terracotta pots, as they let water evaporate too easily.

Clean Rocks or Stones

You’ll need a handful of these to place inside the larger pot.

Soil-Less Growing Medium

Organic coconut coir is perfect for growing watercress. Alternatively, find or mix one that has equal parts perlite, vermiculite, and peat moss.

Watercress Plants

These plants don’t propagate well from seed. Instead, buy a bunch of fresh watercress from the grocery store. As long as the plants are still green and not wilted, you can root them in water. If you can’t find them locally, try a specialty Asian supermarket.

A Sharp Knife

Use this to cut the watercress stems so they can root.

Glass Jar

You’ll need this to help your cuttings develop roots.

How to Grow Watercress Indoors Step by Step

Step 1: Prep Your Plants

Take the watercress cuttings and use the knife to cut their stems at a downward angle.

Step 2: Put the Cuttings in Water

Fill the glass jar with room temperature water, and pop the cuttings into it.

Step 3: Let the Cuttings Root

Place the jar in a spot where it’ll get partial sunlight during the day. Let them grow until new rootlets are about 1″ long, changing the water every few days.

Step 4: Prep Your Container

Wash and clean your containers with soapy water, and let them dry.

Step 5: Add the Rocks

Place your clean stones in the bottom of the large container, about 1″ deep. This will allow the medium-sized container to perch on top of them nicely.

Step 6: Pour the Growing Medium

Add the soil-less growing medium, and saturate it well with water.

Step 7: Add the Plants!

Gently transplant your rooted watercress cuttings into this medium. If the container you chose is 10″ to 12″ in diameter, add three cuttings. In contrast, if your pot is 6″ to 8″ in diameter, only plant one.

Step 8:

Add water to the larger container so it comes halfway up the medium-sized pot. Don’t water inside the smaller container: just add water to the larger, external one whenever it needs to be topped up.

Step 9:

Place this container in a sunny location, and let it grow! Watercress needs quite a bit of sunlight in order to thrive, so keep the pot in the brightest location you can find.

Watercress Care Tips

Keep it Wet!

Make sure there’s always at least 3″ of water at the bottom of the container, and change this water out every two to three days. This is because watercress thrives in moving water: if it stagnates, the plants will rot.

Feed it Occasionally

Feed your watercress with a very diluted water-based fertilizer like this one once every couple of weeks. Seriously, use about 1/4 of what’s recommended on the fertilizer bottle’s label. Mix this with water and then pour it into the outer, larger container.

Prune it Regularly

Prune or pinch the plants back every time they get bigger than 4″ or 5″ high. This will make them grow thick and bushy rather than tall and leggy. You can eat these trimmings, or wait until the plants are about a month old. Then harvest them thoroughly and start a new batch.

Option 2: Grow Watercress Indoors with Hydroponics or Aquaponics

Another super easy way to grow watercress indoors is in a fish tank.

What You’ll Need

A Fish Tank (Empty, OR Full of Pet Fish)

Now, this can be an old fish tank that you happen to repurpose solely for growing awesome greens. This is known as “hydroponic” gardening. Alternatively, you can grow your watercress in a tank that’s currently housing some fishy friends. The latter approach is known as “aquaponics”, and is a great symbiotic approach to growing food.

Tank Aerator

This is the bubble-making thinger that adds oxygen to water.

Watercress Plants

Just like in the previous method, you’ll need live watercress plants from a grocery store.

Hydroponic Growing Containers

For this method, you’ll need hydroponic growing containers like these. They’re small baskets full of eco-friendly foam that holds the seedlings in place. These are then semi-submerged in the water, so the plants can draw all the liquid and nutrients they need.

How to Grow Watercress Indoors in a Fish Tank

Step 1: Clean Your Equipment

If you’re growing your watercress in an empty fish tank, give it a good scrub with hot, soapy water. Clean the aerator and tubes thoroughly as well.

Step 2: Root Some Cuttings

Trim the watercress roots like in the previous method, and place them in a jar of water. Let this sit in a sunny spot for a couple of weeks until rootlets develop.

Step 3 : Fill Up the Tank!

Fill the tank with water and get the aerator set up.

Step 4 : Let the Water Settle

Let the water oxygenate for a couple of days. This will also allow any chemicals in the water to evaporate.

Step 5: Transfer the Cuttings

Transfer the now-rooted cuttings into those little, individual hydroponic baskets.

Step 6: Place the Containers in the Tank

Place the baskets into your tank’s water, and hold each one in place for about 30 seconds. This will let everything saturate and settle well before you let them go.

Hydroponic/Aquaponic Watercress Growing Tips

Feed Your Plants!

If you’re growing your watercress in an empty tank, you’ll need to add nutrients to the water to feed the developing plants. With aquaponics, the greens draw nutrients (fish poop) out of the water to help them grow. In turn, they release oxygen back into the water. This keeps the fish happy and healthy. As you can see, it really is a great interdependence.

Related Post: Why is Lettuce Good for Aquaponics?

Keep the Aerator or Fish Happy

If you’re using an empty tank, the aerator should keep the water moving happily. This will keep it from stagnating, so you don’t have to worry about algae blooms or rotting roots. Similarly, a tank fill of fish will serve the same purpose. Just make sure to keep the fish healthy, and remove dead ones immediately!

Wrap Up

Now that you know how to grow watercress indoors, you’ll be able to cultivate it whenever you like. Add it to soups and salads, toss it into sandwiches, or just graze on it as a healthy snack.

Just snip some off whenever you’re ready to enjoy it!