How to Grow Herbs Hydroponically: From Seed to Harvest

  • By: SFUAA
  • Date: April 15, 2022
  • Time to read: 11 min.

Hydroponics is a method of growing plants without soil. Instead of using dirt as a medium to anchor roots and provide nutrients, hydroponic systems grow crops in nutrient-rich water. The goal is to provide the right balance of oxygen, water, and nutrients to maximize how quickly the plant grows and how much food it produces.

When done right, hydroponics yields healthier plants with higher production rates than growing in dirt. Soil contains fungus and bacteria that can cause disease in plants; hydroponic systems are sealed off from these organisms and allow farmers to monitor conditions more carefully. Hydroponic systems also have fewer weeds, require less space, use less water, and produce more vegetables per square foot than soil-based farms.

Herbs are especially well-suited for hydroponics because they tend to prefer slightly moist environments regardless of whether you’re growing them indoors or outdoors. As long as you know what you’re doing and take care of your system properly, herbs will flourish in a hydroponic environment.

red rubin basil hydroponic
Red Rubin Basil (A Few Weeks Old), Grown Hydroponically | Source: My Aerogarden

But What About the Flavor?

No matter which method of growing you use, your herbs will be healthy, fresh and flavorful as long as you give them the proper care. Hydroponic herbs can taste just as good as (or even better than) herbs grown in soil.

The flavor of herbs grown in hydroponic systems is controlled by how hot it is where they are growing as well as how rich a concentration of nutrients there are in the water your herbs have access to.

Because of this, it’s important to make sure you keep the water in your system topped up to avoid too high a concentration of nutrients.

Can I Grow Any Herbs Through Hydroponic Systems?

It is possible to grow almost every herb hydroponically. But some herbs, like basil and cilantro, thrive in hydroponic systems and lend themselves well to this method of growing. Herbs with high water requirements, such as chives and mints, also flourish in a hydroponic environment. Herbs grown for their leaves or seeds are particularly well suited for growing hydroponically.

Herbs that are grown for their roots – such as turmeric or onions – may not fare as well in hydroponic systems as leafy or stem-based plants do.

A few herbs that grow well in hydroponic systems include:

  • chives*
  • rosemary
  • lavender
  • chamomile
  • tarragon
  • fennel
  • sage*
  • marjoram
  • lemongrass
  • basil*
  • oregano*
  • cilantro*

Herbs marked with a * are especially good to start off with using the Kratky hydroponic method we’ll discuss below.

What Type of Hydroponic System Should I Use For Growing Herbs?

There are lots of different hydroponic systems out there, but the best system for growing herbs is the one you can get and use easily.

Since the Kratky method uses mostly things you should already have on hand, we’ll discuss this one in the most detail for teaching you how to grow herbs hydroponically.

Nutrient Film Technique (NFT)

An NFT system consists of channels that are sloped enough to allow solution to flow past the roots by gravity. The solution is pumped up from one end and slowly flows down through each channel.

If you don’t yet have any experience with hydroponics, NFT systems require a bit more effort than some other options and may be something you want to avoid.

They are excellent for growing more plants in a given space with less water, however.

The Kratky Method

The Kratky method is also known as non-circulating hydroponics because it doesn’t require pumps or electricity. In this system, plants are placed in small containers that are then filled with nutrient solution so their roots are covered.

As plants grow taller and take up more space in their container, they push the water level down below their roots while they continue absorbing nutrients from the solution left over at the top.

This technique was invented by Dr. Bernard Kratky at University of Hawaii and is perfect for people who want to experiment with hydroponics without investing lots of money or equipment upfront (and it’s great for kids too!).

This method is better for smaller plants with a short lifecycle than larger plants with a longer lifecycle (like tomatoes or lavender).

Because the plants require air space between their roots and the top of the water as they start growing, it makes refilling the water a bit trickier.

Aquaponics Systems

Aquaponic systems use water from fish tanks to provide nutrients for plants—they’re great if you already have an aquarium or plan on setting one up anyway!

In an aquaponics system, water flows through a fish tank into a grow bed where seedlings are planted in grow media like lava rock or clay pebbles (you can also use inert materials like perlite).

Plants’ roots absorb nitrogen and other nutrients from waste released by fish as they swim around in their aquarium home. Once cleaned by plants’ roots, water then drains back into the tank to keep your growing environment almost entirely self-contained!

All you have to add is the fish food (and enough water to keep your system topped up.

On the other hand, it’s a bit complicated to properly set up and maintain, so it may not be for beginners.

Deep Water Culture

Another relatively cheap hydroponics system is the deep water culture system.

Deep water culture systems – at their most basic – are just 5 gallon buckets filled with water with an aquarium air pump inside of them.

The pump provides the oxygen to the plants through the water. Plants are grown in net pots that are hung over the bucket so their roots can grow down into the water.

A lid on the bucket keeps light out and a hole in it fits the air tubing from the pump to keep it above the water level.

There are more complex variations of this system, but they all share this basic idea.

At scale, you can use a styrofoam raft to put your plants in and a larger tub of water rather than a hole drilled into the lid of a bucket so you can grow a bunch of herbs in a very small spot.

These systems are great for beginners. The only downside is that diseases that any of your plants get will spread to all of your plants in that system because they all share the same bucket of water.

Germinating Herbs for Hydroponic Systems

To begin growing your herbs hydroponically, you will need to germinate your seeds.

Rather than dropping seeds directly into most types of hydroponic systems like you’d do with soil, you’ll want to start your seeds in a seed starting plug to make sure they start off on the right foot.

The two most common are rockwool cubes and Rapid Rooter brand peat moss plugs.

For each herb plant that you want to grow hydroponically, drop 3 seeds into a rockwool cube or rapid rooter plant starting plug (if using rockwool, make sure to soak it in water with a pH of 5.5 to 6.5 for an hour before adding the seeds).

Place your plugs with the seeds in them in seed starting trays with a little water in the bottom of them and a lid on top to keep the humidity in.

If you live in a cold area, a heat mat can help your seeds germinate faster

Once your seeds have started germinating, you can add a LED grow light 6 inches above your seedlings, set on 18/6 light cycle (18 hours on and 6 hours off) for 24 hours per day until they sprout their first true leaves.

Once this happens and you can see the roots emerging from the rockwool (or rapid rooter plugs), then they are ready to transplant into your hydroponics system!

Growing Herbs Hydroponically in a Kratky Setup

Note: for the rest of this guide, I’ll focus on how to grow herbs in a Kratky setup, as it is the easiest and cheapest setup to grow in.

For Kratky systems, you can actually germinate your seedlings in the Kratky setup. This makes it super easy to get started, as you don’t need separate equipment to start your seeds.

With Kratky systems, you’ll have one plant per bottle, jar, or bucket of water. This makes it very easy to move your plants around and harvest as necessary.

Step 0 – What You’ll Need

Here are the items you’ll need to start:

  • A plastic bottle, mason jar, or 5 gallon bucket to grow your herbs in.
  • A net pot that fits your jar.
    • For mason jars and a lot of plastic bottles, the 2 inch net pot is the perfect size. You will need the ones that advertise having a wide rim, though, as ones with narrower rims won’t fit standard mouth mason jars.
    • For wide mouth mason jars, 3 inch net pots with wide rims should work.
    • For 5 gallon buckets, you can buy a special 5 gallon bucket net pot lid.
    • For jugs with very small mouths, you can get one of the pre-seeded aerogarden net pots.
  • Aluminum foil, duct tape, or plastidip spray to prevent light from getting into your bottle or jar. This will prevent algae growth.
  • A hydroponic nutrient solution. I find a one part solution like the one sold by Aerogarden on Amazon is easiest for beginners.
  • Optional: A PH testing kit. You can get this from the pool or aquarium section of your local supermarket for cheap. If you need to lower the PH of your water, a few drops of vinegar or lemon juice should do.
  • Optional: A LED light to grow your plants under. Herbs don’t use much light, so it doesn’t much matter which one you get. I’ve seen the absolute cheapest models go for around $5. If you want to grow multiple plants or grow other plants you’ll probably spend more. If you don’t use an LED light, grow in a very sunny window.

As you can see, the items you’ll need for a Kratky setup should mostly be ones you already have. The only things you should need to buy are the nutrients and net pots.

Ideally, you’ll be able to get started for under $20.

Ironically, the cheapest way to get started with Kratky if you don’t already have the net pots and nutrients may just be to buy an aerogarden herb seed pot kit (or the grow anything kit) and stuff the pods into old gallon jugs you have, filled with water.

These kits contain everything you need for the price you’d usually pay just for a bottle of nutrient solution.

Step 1 – Filling Your Bottle & Adding a Net Pot

Just get a net cup that fits into a plastic bottle or mason jar you have handy and put the net cup into the bottle.

If you have a bottle with a very small lid, like a gallon water jug, you can use an Aerogarden seed pod instead of a net pot.

For large herbs, like rosemary, you can use a 5 gallon bucket with a net pot lid for your kratky setup.

Fill the bottle up with plain water (PH adjusted to your herb’s needs) to where it’s just covering the bottom of the net cup. Here are the PH levels for some of the most common herbs:

  • Basil = 5.8 to 6.2
  • Oregano = 6.0 to 8.0
  • Sage = 5.5 to 6.0
  • Chives = 6.1 to 6.8

Put your rockwool or rapid rooter with seeds (as we discussed in the previous section) into the net cup.

Tip: Cover the bottle with aluminum foil or duct tape to prevent light from getting to the water. (Alternatively, you can spray your container with plastidip.)

Step 2 – Keep the Water Topped Up Until Germination Happens

Note: If you’re starting with pre-germinated seedlings, you can skip this step.

Make sure the water stays around the bottom of your plug until the plant germinates and starts growing roots down into the water.

This is essential to keep your grow medium moist so that your seed will successfully germinate.

Optionally, you can cover your container with plastic wrap to keep the moisture in and increase the humidity. Remove this as soon as your plant germinates.

Step 3 – Add Your Hydroponic Nutrients & Set Up Your Grow Light

Once this your plant has germinated, remove your net pot from the bottle of water it’s sitting in long enough to add nutrient solution into the water.

Note: Follow the instructions on the bottle of nutrients for how much to add.

Now that your plant has sprouted, it’s time to set up your grow light.

Ideally you’ll want to use an LED grow light and keep it between 6 to 12 inches above the top of your seedlings. As they grow taller, keep your light about the same height above the top of your plant.

Step 4 – Wait & Harvest

This is literally all you have to do. Kratky is passive, so you shouldn’t need to do anything else for the life of your plant. As it grows it will uptake water and nutrients.

You can harvest it a little at a time along the way, and when it runs out of water it’s ready to be fully harvested.

If the plant gets to the bottom of the water and hasn’t finished its lifecycle, you can refill the container with a little bit of water to keep it growing.

Tips for Growing Herbs in Hydroponic Systems

Here are a few tips for getting the most out of your hydroponic setup, regardless of which method you choose for your setup:

  • You should avoid planting slow-growing herbs with fast-growing herbs that could outgrow them and shade them out. With Kratky systems, you can move your plants around, but if they’re all planted into a single setup, you’ll be stuck with how you planted them.
  • When growing plants hydroponically, air flow over your plants is important for preventing mold growth. Because of this, it can be a good idea to point a fan at your plants so they get air through their canopy.
  • If humidity levels get too high for comfort (or for the health of your herbs), try using a dehumidifier to bring things down to an acceptable level.
  • You’ll also need to adjust the water in their system as needed so it has a pH that works well with whatever type of herb you’re growing—this will vary by species. Basil, for example, likes a PH around 6.

How to Harvest Your Herbs Without Damaging the Roots

When harvesting your herbs, it’s important to cut from the top of the plant, rather than the bottom. This is especially true for basil, oregano and parsley.

Cutting from the top will encourage your plants to grow more shoots and become bushier. When cutting from the top of your hydroponic herbs, it is ideal to use a sharp blade—avoid serrated knives or dull scissors that will crush stems.

Just select the parts of the plants you want to harvest and cut them above a leaf node. Never harvest more than 1/3 of your plant at one time. (For chives, cut them just above the bottom of the plant since there are no leaf nodes.)

Ideally, you want to harvest herbs in the morning, as this is when they have their highest concentration of oils.

The best way to preserve freshly harvested herbs is by drying them: Cut long stems and hang them upside-down in a dark room or the trunk of your car for about three weeks until thoroughly dried out.

Alternatively, you can drop them into a dehydrator overnight or into an air fryer at its lowest setting for 15 minutes.

Enjoy Fresh Hydroponic Herbs Year Round

It doesn’t matter if you have a large house or apartment, with hydroponic herbs you can enjoy fresh herbs year round and keep your kitchen stocked with nutritious greens.

Hydroponic systems can be super simple to use, and as an added benefit you’ll get larger harvests in less time compared to growing in dirt.

Best of all:

No more starting a recipe only to realize you’re out of the seasonings you need and have to run down to the store!

I’m positive that once you get started with growing herbs hydroponically you’ll never look back.

Good luck!

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