How to Grow Microgreens in Potting Soil

At Farmers Markets, visitors often ask me how I grow my microgreens, and how they can grow their own. Sometimes, people even ask me how to grow microgreens out in their yard. Read on and I'll get into all the details!

 

Intro

When you plant microgreens, you densely seed your chosen crop and harvest using scissors or a knife when they are a few inches tall. It's not complicated, but if you are new to growing plants, there is a learning curve. To keep things simple, I'm going to assume you want to grow broccoli, alfalfa, kale, radish, clover, or similar microgreens that don't require soaking the seeds and don't produce a gelatinous coating on the seeds. Peas and sunflowers do best with soaking, so that will be a separate blog post. 

Step One: Choosing a Container for Microgreens

To grow microgreens, you will need a container, preferably with a drainage hole. A small container is fine, and it doesn't even need to be made for plants. You can use a plastic take-out container, or anything that is about 4"-8" across and 1"-4" deep. Shallow is fine, since you will be eating the microgreens before they need more room for their roots. A nursery pot is great too. 

If you are good at avoiding over-watering, a container without a drainage hole will work. But it's easier if you find a container with a hole, or make a hole if it doesn't have one. You can use a nail and a hammer to make a hole, or else a knife or maybe a screw driver, depending on the container. If your container has a hole, you'll also want something to catch the water. 

Step Two: Choosing Soil for Microgreens

You can use just about any potting soil for your microgreens. Microgreens don't need a lot of nutrients because they get most of their nutrients from the seed. A potting mix meant for seedlings is ideal because it will be finer, but other mixes will work too. I like Happy Frog potting soil, an organic soil from Foxfarm. Organic or non-organic soil is your choice as well.

While it is also possible to use other growing mediums such as coconut coir, grow mats, or even silicone mats, these methods are more difficult to perfect, so I'll just be talking about soil here. 

Step Three: Finding Microgreen Seeds

Microgreens seeds are basically the same as normal seeds, but they will be chosen with germination rate in mind as well. When you are seeding densely, you want most of your seeds to grow, because the ones that don't germinate can mold. Also, seeds labeled as microgreen seeds will be cheaper because the seller knows that you need a lot of them. Buying those small packets you see at garden centers will not get you very far.

Most likely, you'll find the best options online. I like True Leaf Market and Everwilde Farms for microgreen seeds. You can start with a smaller size like 4 oz. If you like some of the mixes offered, you can buy a pre-mixed bag of seeds. But you can also mix them yourself in the tray or grow single varieties. If you're not sure where to start seed-wise, any variety of broccoli is a good option, as is any variety of radish. If you are looking for a mix, you will usually see spicy and mild options and can choose based on that. 

What about seeds that you already have? Maybe you have seeds left over from starting broccoli seedlings or other vegetables. If you want to try those seeds, go ahead! If they don't grow, you can try again. That's the nice thing about gardening - you can try things out, and if they don't work, you can try something else!

Step Four: Seeding your Microgreens

Fill your container with soil and tamp it down with your hand or the bottom of another tray. An even surface will help the seeds spread out more evenly. Don't water yet, since the seeds will stick to damp soil. You want the seeds to bounce and spread out. But don't worry if you did already water, it'll still work!

Grab a few seeds with your fingers and sprinkle them over the soil. The seeds will bounce around and spread out a bit. As for density, meaning the amount of seeds you should use for the size of your container, for small containers it is easiest just to eyeball it. When I seed my 10" by 20" trays I do weigh 

the seeds so that I use the ideal amount, but when you are growing for yourself or your family it really isn't necessary. You can look at the photos here as an example of how close together the seeds should be.

The first tray with the smaller seeds is alfalfa and broccoli. The second tray with the slightly larger seeds is radish. These trays are about 4 by 6 inches. As you do more plantings, you'll learn what density is best for your container size. 

Step Five: Watering your Microgreens

If you have a spray bottle, you can spray the top of the soil now. You want it to be pretty well soaked. If water is coming out of the drainage hole, assuming your container has one, that is a good amount. If you don't have a spray bottle, you can use a small watering can, a measuring cup with a spout, or something similar. To avoid disturbing the seeds, I find it works well to water all along the edges of the container and then wait until the water spreads and the soil is fully moist. 

At this point, you'll want to keep your seeds from drying out so that they can germinate. Notice we did not cover the seeds with soil, although you can if you want to. However, when you don't cover the seeds, you end up with less soil on your microgreens when you want to eat them.

To keep the soil damp, you can choose from a few options. If you have another container of the same size, you can stack it on top of the seeded container so that it is directly touching the seeds. This will keep the soil damp and provide darkness as well. You can use a small rock to provide some weight, which will help the seeds know which direction is down. Don't worry, seedlings are strong and they will lift up the tray as they grow, at which point you can remove it. Alternatively, you can cover your seeds with seran wrap until they are tall enough to push against it. At that point, you can remove the wrap.

Step Six: Giving you Microgreens Light and Water

Once your seedlings have sprouted and you have removed their cover, you'll want to give them some light. A windowsill works for this, as does a plant light if you have one. Then, make sure you water often, and once they have gained some color, you can start tasting them! You'll notice that their flavor changes as they grow. Generally, at a few inches tall they are ready to use. Just use a knife or scissors to cut what you need just above the soil!

Most microgreens are ready to harvest in about 7 days, but there are no hard rules! Generally, you can eat them when their first 2 leaves appear, until right after their first adult leaves appear. But harvest when they look good to you! And taste to see when the flavor changes. 

*Important: Not every vegetable can be grown as a microgreen. Most vegetables that are grown for their leaves are good as microgreens. But don't grow nightshades, such as tomatoes, as microgreens since those leaves are toxic. 

 

Common Questions

Will microgreens re-grow after being cut?

Most will not regrow. Peas can regrow, but they are the exception. Think of microgreens like small seedlings. If you cut off a vegetable seedling, it will not grow back. But, since microgreens grow so fast, you can have more in a week!

Can I grow microgreens in my yard?

Microgreens need to be kept moist so that the seeds can germinate. This is hard to do when you plant them directly into your garden. They would most likely dry out in the sun and not grow. If they did grow, they would be difficult to harvest because they are so low to the ground. Also, pests could be an issue since most pests love soft, new growth. But I would never tell you not to try! Just be aware that growing in your garden may not work. 

However, growing microgreens in containers on a covered porch or patio is something that would be more likely to go well. 

Why did my microgreens mold?

There are a few possibilities here. First, check the seed packet and make sure that they have not expired. For microgreens, you want very fresh seeds so that they grow quickly and don't mold even when crowded together. Sometimes, companies can also have batches that don't do as well. But if your seeds seem fine, you may have sown too densely or overwatered. Just try again using fewer seeds and watering a little less! If the mold is on the seedling leaves, rather than at soil level, it could also be an issue with air circulation. Both airflow, such as from a fan, and reducing the seeding density will help. Mold at soil level on the seeds themselves is more likely to be due to un-germinated seeds. Mold on the soil could be due to bad soil, especially if the mold is wide-spread and occurs every time you grow.

Why are some germinated seeds getting stuck to my other seedlings?

If your microgreens are growing well but you see a few barely germinated, shriveled seedling stuck to larger ones, this is not a big deal! It is a natural result of growing a lot of seedlings close together, as you do when growing microgreens. A few of your seedlings are getting tangled up with each other and then getting raised up into the air and away from the soil, causing them to dry up. Just remove those and enjoy your greens. With future trays, you can try using fewer seeds.

Is it ok for pets to eat microgreens?

Yes! Most microgreens are safe for both cats and dogs, and are even healthy for them to eat! In fact, my dog loves eating microgreens!