Growing Hydroponic Microgreens | A Step-By-Step Guide

Microgreens are easy to grow, taste great, and yield incredibly quickly. They are a favorite of chefs, foodies, hobbyists, and serious commercial farmers alike.

The most popular way to grow microgreens is in soil. 

Soil is easy to work with, retains water well, and naturally contains nutrients that help microgreens grow. There are dozens of companies that make seed-starting soils ideal for growing microgreens. 

These work great, but they have some downsides. 

Lugging around huge bags of soil is a pain. And it’s a hassle to clean up. Worst of all, the grit and contamination left behind by soil should be washed off before eating microgreens. Washing microgreens reduces their shelf-life and makes them vulnerable to mold. 

These undesirable traits cause many growers to seek an alternative. 

Luckily, there is a solution—hydroponic microgreens.

While hydroponics is a bit new to the microgreens scene, it is a capable contender that gives soil a run for its money. 

In this guide, I will show you everything you need to know about growing microgreens hydroponically—the pros and cons, what growing medium to use, a step-by-step guide on growing microgreens hydroponically at home, and more.

Can you grow microgreens hydroponically?

Yes. Microgreens grow just as well hydroponically as they do in soil. Growing hydroponically takes practice, but has several advantages and is great for first-time growers and veterans alike. It’s convenient, makes harvesting easy, and eliminates the risk of soil-borne contaminants.

Is it better to grow microgreens in soil or water?

Despite what you may hear from growers on each side of the fence, there is no “better” way to grow microgreens. Microgreens grow incredibly well hydroponically and in soil. Each method has its pros and cons.

No matter where you grow them, your microgreens will have more or less the same flavor, color, and yield.

Whether you choose soil or soil-free depends on your personal needs and limitations.

In short, hydroponic microgreens offer greater convenience but can be trickier to get right. Let me explain…

What are the pros and cons of growing microgreens hydroponically?

Microgreens grown in soil almost always have some soil on them post-harvest. This soil will either end up ruining someone’s meal with an unpleasant grittiness and dirt flavor or even make them sick.

And washing the plants may not sound like a big deal, but fungus and mold are a big issue for microgreens. Wet microgreens are very susceptible to mold.

Mold can creep up in a matter of hours. Even if done carefully, washing will inevitably reduce the shelflife of microgreens.

With hydroponic microgreens, you don’t need to harvest as carefully, as you run zero risk of contaminating your plants with dirt. And post-harvest, you don’t need to wash them.

On a similar note, using soil can be messy, especially for indoor growers. By using a soilless growing medium (like what is used in hydroponics) you can skip the hassle and cleanup. 

Compared to soil, hydroponic mediums are easier to ship, handle, fill trays with, and dispose of post-harvest.

On the flip side, hydroponics does have a downside.

Compared to soil, it can be more difficult to optimize.

For experienced growers, yields of microgreens grown in soil and hydroponic systems are comparable. You do not need to sacrifice yield weight with hydroponics.

But for beginner growers, it can take a few tries to get things right. You will likely need to tweak your seeding, watering, nutrition, and lighting a few times before hydro-yields get up to par with soil ones. 

Because soil growing is less complicated and the plant’s nutrition is built right into the medium, it’s harder to mess up.

Hydroponics, on the other hand, requires you to add the right balance of nutrients.

Also, not every plant type or variety is suited for hydroponics. Some do extremely well without soil, and others just do alright. More on the best microgreens for hydroponics below.

What is the best growing medium for hydroponic microgreens?

The best and most popular growing media for hydroponic microgreens are BioStrate, hemp mats, jute mats (burlap), coconut coir, and vermiculite.

BioStrate Felt is a proprietary growing medium made by Grow-Tech. This is a flat, soilless pad made of biopolymers and natural fibers, specially designed for hydroponics. It holds water well and gives roots plenty of space to grow.

Check Price on Amazon

Hemp mats are another pad-type growing medium. These are made of 100% natural hemp fibers. These also have great absorption properties and give a good structure from which your microgreens can grow. Hemp mats are biodegradable and compostable.

Check Price on Amazon

Jute pads are yet another growing mat. Also known as burlap, Jute fiber is sustainable and cheap but unfortunately doesn’t hold as much water as the other pads.

Check Price on Amazon 

Coconut coir may look like soil, but it is totally soil-free. Made from a byproduct of coconut production, coco coir has impressive absorption, aeration, and drainage properties. This is an organic and sustainable growing medium. The only downside is that it can be messy to work with.

Check Price on Amazon 

Vermiculite is made when a naturally-occurring mineral is heated until it expands. The resulting product is vermiculite, an incredibly absorbent growing medium. These tiny pebbles are versatile and popular, being used in potting soils, hydroponics, seed starting, and more.

Check Price on Amazon 

Each of these is a great growing medium in its own right. The difference mostly comes down to price and whether you prefer a pad-type medium or a loose product.

Do hydroponic microgreens need fertilizer?

Hydroponic microgreens don’t need fertilizer, but in general, they do better with it.

This is because hydroponic growing media don’t contain any nutrients. By adding nutrients to the water, microgreens will grow taller and fuller and be healthier. 

Having said that, you can certainly throw some seeds into your tray onto a piece of Biostrate, hemp mat, or coco coir, add nothing but pure water and watch an impressive crop of veggies sprout up. This is by far the easiest and cheapest way to grow microgreens.

However, to increase your yields and get more consistency in your system, nutrients should be added to the water. 

Some of the best nutrients to use for hydroponic microgreens are MaxiGro, FloraGro, Liquid Kelp, and OceanSolution.

These are high-quality fertilizers that contain the essential nutrients that help microgreens grow. They are also incredibly easy to use. Here is how to prepare them:

  • MaxiGro – Mix 1-2 teaspoons of MaxiGro with 1 gallon of pure water. 
  • FloraGro – Mix 3 teaspoons of FloraGro with 1 gallon of pure water.
  • Liquid Kelp – Mix 1-2 ounces with 1 gallon of pure water.
  • OceanSolution – Mix 1 ounce with 1 gallon of pure water.

After diluting and mixing the fertilizer, you can use it to water your microgreens or as a spray to moisten growing media and seeds. 

In general, seeds are germinated with pure water. Only after the seeds have sprouted and the tray goes under lights do you need to use fertilizer. The kick of nutrients at this stage helps to get boost height, thickness, and cotyledon size. 

What microgreens grow best hydroponically?

Most types and varieties of microgreens can do well in a hydroponic system. However, some do better than others. 

For the best success rates and yield sizes, try growing wheatgrass, broccoli, amaranth, cabbage, clover, kohlrabi, kale, mustard, radish, pea, sunflower, and mixed microgreens.

Check below to see a full guide on how to grow broccoli microgreens hydroponically.

The Basics of Growing Hydroponic Microgreens

Getting started with hydroponic microgreens is surprisingly simple. If you have previously grown microgreens in soil, you probably already have most of the equipment and expertise you’ll need.

To grow hydroponic microgreens, you will need:

Step 1: Take one of the trays with holes and place it inside a tray with no holes. The top tray will hold the growing medium and seeds and the bottom one will be used to hold water after the seeds germinate.

Step 2: Balance the pH of the water you will be using. Use your pH tester to test the water and then use pH-Up or pH-Down solution (all included in the kid) to bring the water as close to 6 as possible.

Step 3: Soak your BioStrate growing pad in plain water until it is completely saturated. Let it drip for a few seconds before placing it into the top tray (the one with holes).

Step 4: Measure 30g of Purple Sprouting Broccoli seeds (or another microgreen seed of your liking) and sprinkle them evenly across the growing pad. If you don’t have a scale, you can use about 2 tablespoons of seeds. These seeds do not need to be pre-soaked.

Step 5: Give the seeds a few sprays of pH-balance water, just enough to get them all coated.

Step 6: Now, take another holeless tray, flip it upside down, and place it on top of your growing tray. We do this just to cover the seeds and keep them out of the light. Microgreen seeds need a dark, moist environment to germinate. Place your covered tray somewhere safe. It’s best to keep it away from extreme temperatures.

Step 7: Water your seeds twice a day for the next few days by lightly spraying them with plain water until the seeds and growing pad look moist. You can gently lift the tray with the seeds in it and check the bottom for roots. Once you see roots poking through the holes, you can begin to water the bottom tray as well as the sprouts and pad. Just spray some plain water into the bottom tray until there is a very thin layer. Re-cover after each watering.

Step 8: By the fourth day of watering and darkness, your seeds should have germinated and should be looking great. Now we can remove the cover tray, place the tray under grow lights, and begin bottom-watering.

Step 9: Mix one ounce of OceanSolution fertilizer with one gallon of pH-balanced water. Then take a half cup of that diluted solution and pour it into the bottom tray. Place the tray, uncovered, under grow lights (if you don’t have any grow lights, you can use a very sunny windowsill).

Step 10: Continue bottom-watering like this with the fertilizer solution twice a day for another seven days. 

Step 11: On the seventh day, the microgreens should be ready to harvest! Use scissors to cut the microgreens free. Hold the canopy of the microgreens and cut as close to the pad as possible. 

Your wonderful harvest of microgreens is ready to eat and doesn’t need to be washed. You can harvest the whole thing and store it in an airtight bag in the fridge.

Alternatively, you can begin harvesting as much as you need bit by bit, keeping the rest of the tray alive. This way, your product will last longer. 

You can have a fresh microgreen salad each day for a week or more. Just be sure to keep the tray under light and continue watering it with plain water to keep the plants fresh and prevent wilting.

If you want to wash the microgreens, you can harvest the entire tray and store it, unwashed, in an airtight bag with a paper towel or two inside of it (to absorb moisture and prevent mold). When you are ready to eat, take out the amount you desire and wash it right before eating. 

Microgreens stored unwashed this way will keep fresh in the fridge for at least a week, if not more.