How To Fertilize Microgreens: Everything You Need To Know

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Microgreens are relatively easy to grow either indoors or outdoors, but providing them with the best nutrients can be the tricky part, especially the use of fertilizer.

How do you fertilize microgreens? The process for fertilizing microgreens does not differ much from that of any other garden plant. When it comes to fertilizing microgreens, the most important step is choosing the right type of fertilizer that will work best to provide the nutrients your microgreens need. Depending on the growing medium you use, you’ll mix your fertilizer with your soil, add it to water or use it as topdressing.

Fertilizing, in general, is a fairly simple process, but it can be a bit confusing when it concerns microgreens. When there are any conversations about the best fertilizers and how to use them, they rarely involve microgreens and instead focus more on common garden plants such as vegetables, fruits, herbs, and flowers. Depending on the type of medium you will use to grow your microgreens, you may or may not benefit from using fertilizer. 

Deciding What Growing Medium To Use

What fertilizer to use and how to apply it to your microgreens depends, as mentioned, heavily on what growing medium you are using to grow your microgreens. The growing medium refers to the materials that they grow in and not the type of container or gardening platform the microgreens will grow in.

There are different ways of growing microgreens and depending on which one you’ll choose, different mediums are used.

The different methods for growing are:

  • Soil growing – growing microgreens in soil is a common method. It involves simply the microgreens being planted in soil, ideally organic, and sterile potting soil. Depending on the quality of your soil, additional fertilizer is not required. 
  • Soilless growing – this implies growing microgreens using a mix of soilless mediums composed of a variety of organic and inorganic materials. The mediums can look like soil but they don’t provide the same high nutrition value. Adding fertilizers may be beneficial depending on the medium’s ability to provide nutrition.
  • Hydroponic growing – hydroponics is a type of soilless method. It involves growing your microgreens without the presence of soil, and instead, they will be grown in a nutrient-rich water-based solution. Using fertilizers is valuable if the medium used is not providing enough necessary nutrients.

Some microgreens grow best in specific mediums so take note of which microgreens you would like to grow and what medium works best for them. Seeds that require to be covered with a layer of soil doesn’t work well growing with a hydroponic medium. 

Soil

Soil is one of the most used mediums for growing microgreens for many reasons including its ease to work with and the fact that it comes already packed with nutrients and minerals. Soil mediums can include compost, potting soil, and other commercial soils such as MiracleGro for example. 

Organic soils work the best because they are free from any harmful pesticide, insecticides, and harsh chemicals that can damage your microgreens. Beware of the brand and ingredients, however as some may not provide as many nutrients as they claim to. 

It’s also important to sterilize any forms of soil you use before planting your microgreens. Check that the soil you use is sterilized or you can do it yourself, but it will take time. This can be done by baking the soil in the oven in small batches or for larger amounts, evenly spreading it out on a plastic sheet and laying it in the sun. 

Once it’s laid out, moisten it and cover the soil with another layer of plastic. Leave the soil out for 3 to 4 weeks and allow the heat from the sun to naturally sterilize it. 

Soilless

Soilless mediums are exactly what you would’ve guessed, soilless! Instead of soil, the microgreens are planted in natural or man-made materials similar to soil, but not with the same level of nutrients. Soilless mixes have little natural fertility, so they may need fertilizer. 

When using soilless mediums a great way is to mix them with other mediums that can support the retention of nutrients. An example is mixing peat moss with Vermiculture.

It may sound a bit strange at first, but it’s absolutely possible to grow plants without soil and even less costly depending on which one you use.

Some examples of organic soilless mediums are:

  • Peat Moss – This is an ideal base for soilless mixes. It can hold both water and air. It holds nutrients well but will benefit from using additional fertilizer. The texture of the peat moss is light and fibrous.
  • Pine Bark – you can use composted pine bark as a growing medium. They don’t have the same moisture-holding capacity as peat moss but they help to increase the porosity of a soilless medium mix. Use it with peat moss and you can get a good mix.
  • Coconut Coir – this organic material is derived from coconut hulls. This medium is exceptionally good for holding water. You can mix this with pine bark to get a good soilless medium mix.

The above organic soilless mediums can as well be mixed with in-organic ingredients such as vermiculite and perlite.

  • Vermiculite – this medium is a type of mineral that is mined from the ground and is great for preventing mold from ruining your precious microgreens. Vermiculite can do this thanks to its natural pH balance that is resistant to mold. Some regular soils list vermiculite as a component because it provides small amounts of minerals and nutrients. Adding this to your soilless medium increases water and nutrient retention.
  • Perlite – this is as well a mineral, an amorphous volcanic glass. You may have noticed tiny white roundish objects in soil and they are called perlite. Mixing these minerals with soilless mediums will be giving extra nutrition, support moisture retention, and have a beneficial effect on your microgreens. 

Hydroponics

When growing microgreens hydroponically you use a water-based solution. Hydroponically grown plants dip their roots directly into nutrient-rich solutions. This means that microgreens need much smaller root systems and can divert more energy into leaf and stem growth. 

In theory, the word “hydroponics” means growing plants in water (from two Greek words meaning “water” and “toil”), but because you can grow plants without actually standing them in water, most people define the word to mean growing plants without using soil. 

Source: What is hydroponics?

When you grow hydroponically there are different mediums you can use. The following different nutrient-enriched mediums will allow the roots to be supported. These will act as a sterile substitute for soil.

You can grow microgreens with their roots supported by a nutrient-enriched medium such as Burlap fabric, Coconut coir bricks, Hemp mats, Rockwool plugs, and biostrate mats, which all acts as a sterile substitute for soil.

  • Burlap – burlap is most commonly used to make clothing, baskets, ropes, and other everyday objects. It is a type of fabric that is made from jute plants and is woven together. Burlap can also be used as a hydroponic medium. It is a lot harder to work with compared to other soilless mediums, given that it must be used in combination with either fertilizer or water to get a substantial amount of crops. 
  • Coconut Coir – this is made from coconut fiber and is great for retaining and over absorbing moisture. Coconut coir can either be purchased in the form of dehydrated blocks or sheets. Once you ready to plant your microgreens, just add water to it and it will expand. Much like soil, tiny coconut fibers can be a bit of a mess if you’re not careful! Also, coconut coir does not contain as many nutrients as soil. 
  • Hemp Mats – these are mats made from hemp fiber and are also great hydroponic mediums as well given they can evenly distribute water to your microgreens. You also don’t have to worry about having to water your plants as much because they retain water well. Hemp mats can be hard to use because they are fragile and become flimsy when moistened. 
  • Rockwool – this medium is made from man-made material using chalk and basalt rock. Rockwool is used as an insulation material as well. This is medium is not the most recommended however, due to its ability to cause mild skin irritation from the thin fibers it’s made out of. 
  • Biostrate – One particular material that can be used as a hydroponic medium is biostrate. Biostrate is the brand name for a type of felt textile. It is very much similar to vermiculite or burlap in that it is pH balanced and generally lightweight, making it a great choice for preventing mold build-up on your microgreens. Like burlap, however, it is harder to work with because it doesn’t retain and absorb water as easily and can be hard to maneuver. 

Because many soilless mediums don’t provide essential nutrients on their own, it can help to use fertilizer to sustain the growth of the microgreens. 

If you do decide to use a hydroponic medium to grow microgreens, make sure you have the proper set-up so that your plants are receiving moisture and nutrients, but no so much that they are drowning. The best set up for a hydroponic medium is to use a tray or materials like biostrate or hemp mats in addition to a nutrient-rich water-based solution. 

RELATED: How To Grow Microgreens in Water: The Ultimate Guide

Do Microgreens Need Fertilizer?

As you have learned, microgreens don’t necessarily require fertilizer, but it certainly can’t hurt to use some, depending on the medium they grow in. For example, if the soil they are in doesn’t already provide enough nutrients.

If you have new high-quality soil, they should already provide the essentials for your plants on its own however, this depends on how much of the essential nutrients the soil already possesses. 

While it is not necessary for growing microgreens, some mediums will benefit from the use of fertilizers to provide extra nutrients. Essential minerals and nutrients such as potassium, phosphorous, and nitrogen helps in producing strong healthy plants. 

“The nutrient solution is the most important factor in the success or failure of a hydroponic system. Most fertilizers commonly available in garden centers do not contain all of the 13 elements necessary for plant growth because the growing media usually provides many of them. Hydroponic plants receive nutrients from a different source; so it is necessary to use a fertilizer formulated for hydroponic systems.” 

Source: Home Hydroponics

Fertilizers also give plants the boost that they need to sustain their growth period and you may even end up with a bigger harvest by using fertilizer. It may not necessarily make a difference in whether your microgreens grow or not, but it will certainly improve the chances of them thriving longer throughout the whole growth period. 

It’s always up to your personal preference whether or not to use fertilizer on your microgreens and if you’re not sure, consult the advice of an experienced gardener or local expert. 

When Is Fertilizer Necessary?

If you notice that your microgreens are starting to wilt or appear to be lacking sufficient nutrients, then you can consider using fertilizer in addition to the growing medium that is currently being used. 

Sometimes soils and compost don’t always provide enough nutrients on their own or they lack a specific nutrient or mineral. If that is the case with your microgreens, simply incorporate a small amount of fertilizer and you should start to notice a difference. If you are using a soil that contains 50% compost, you can reduce the fertilizer amount by ½.

With hydroponic mediums, you may get through the whole growing and harvesting process without having to use fertilizer, because some water-based solution makes up for the nutrients that soil would provide. Check which mediums benefit from the extra fertilizer. 

Microgreens grow faster in a hydroponic medium and thus may be able to avoid becoming nutrient deficient as fast. 

If you do find that there is a problem to get your microgreens to grow, you can apply fertilizer. The solution remains the same for this issue and that is that you should use fertilizer in addition to whatever soilless material you are using. 

What Fertilizers Work Best For Microgreens?

Deciding what fertilizer to use for your microgreens ultimately depends on the type of medium you are using and what plant needs need to be addressed. For hydroponic mediums, try using water-soluble fertilizers that will easily be absorbed by the microgreens and the water-based solution. 

Try to steer clear of some of the more popular commercial fertilizers unless they are labeled organic non-GMO. Many of the commercial fertilizers provide nutrients and such, but not without a cost. Many contain synthetic ingredients that could be harmful to your microgreens and soil mediums. 

There are many fertilizer options available, both commercial and man-made. 

Some common fertilizers include:

Liquid kelp – this fertilizer has more than 70 varieties of minerals in addition to plant growth hormones such as cytokinin and auxins. This fertilizer is best for microgreens grown using soilless and hydroponic mediums because they don’t already provide many nutrients on their own. Liquid kelp provides a high amount of nutrients and using nutrient-deficient mediums will prevent the microgreens from becoming over-nourished. 

How to use it? You mix this fertilizer with water and then you can use the mix to spray directly onto your microgreens. Always read the instructions on the measurements to apply.

Buy Liquid Kelp on Amazon

Azomite – this fertilizer consists of a powder made from volcanic ash containing numerous earth elements and minerals. Azomite trace minerals are meant to improving mineral contents of the nutrient-depleted soils. It has been proven to generally improve root systems, plant vigor in garden vegetables, and field crops. Azomite is best applied to the growing medium before planting. 

How to use it? You can mix Azomite directly with the soil. Blend in the ultrafine version of their products. If you use composted soil you can add it at the beginning of the composting cycle. Always read the instructions on the measurements to apply.

Buy Azomite on Amazon

Cottonseed Meal – this fertilizer is made from cottonseed hulls that have had all seed oil removed and then further processed into meal. It contains nitrogen, potash, and phosphate and helps to reduce high pH levels in the soil. It also improves the texture of soil mediums and should be placed on the soil and all other mediums before planting. 

How to use it? You can apply it before planting your microgreens. Mix it with the soil and it will ensure that you have good soil. You can also use it as topdressing and then you work it into the soil and water. Regardless of how you’re using it, be sure to water it in generously once applied. Always read the instructions on the measurements to apply.

Buy Cottonseed Meal on Amazon

Osmocote – Osmocote is a brand of fertilizer that comes in several different forms to treat different plant needs. This fertilizer consists of capsules that contain nutrients that are released when moistened.

How to use it?  You can use this product by applying dibbling, mixing, or top dressing. For microgreens, you can mix it with your soil. A mixture of Osmocote and growing media ensures nutrients are present as soon as the plant’s roots can absorb them. You can also spread the granules over your microgreen seedlings. Always read the instructions on the measurements to apply.

Buy Osmocote on Amazon

MiracleGro – MiracleGro is a popular commercial fertilizer that contains certain percentages of nitrogen, phosphorous, and nitrogen, all essential nutrients that plants need to survive and grow. This fertilizer is more of a synthetic type of fertilizer and should be used in small amounts. For this reason, it also begins to work immediately.

How to use it? You mix MiracleGro (liquid form) with water and then you use the blend to water your microgreens. It’s important to mix the MiracleGro according to package directions because overfertilizing can burn the microgreens. Always read the instructions on the measurements to apply.

Buy MiracleGro on Amazon

FloraGro – this water-soluble fertilizer is great to use in hydroponic mediums. It contains lots of nutrients that support plant growth and structure. This fertilizer shouldn’t be applied until the microgreens have begun to come out of the soil. 

How to use it? You can apply this after you see that your microgreens are starting to germinate. You add this fertilizer to the water, blend it, and then water your microgreens. Always read the instructions on the measurements to apply.

Buy FloraGro on Amazon

True Leaf Market Seed Company, a reputable retailer for gardening resources and products, suggests using Azomite or FloraGro for treating your microgreens.

“We suggest using either Azomite, a trace mineral fertilizer, or a water-soluble fertilizer such as FloraGro. Both provide essential nutrients to your seedlings – and in this case, your microgreens – but they are applied using different methods.”

Source: Fertilizing Microgreens

In addition to fertilizer, compost is also a great source of natural plant nutrients. This can be used as either a soil medium or a fertilizer or both! The great thing about using compost is that you can make it on your own and even get creative with popular ingredients such as eggshells and coffee grounds. 

For more information on whether to use fertilizer or compost, visit an article outlining the pros and cons of both sources of plant nutrients here. 

D.I.Y Compost Ideas

Finding the right fertilizer and compost materials for your microgreen garden doesn’t have to be expensive, especially when you make them all on your own! Making your own compost fertilizer not only saves you money, but you also know all components and can be sure of their quality and safety for the environment. Compost fertilizer can provide your microgreens with organic nutrients and keep them looking strong and healthy.

Compost is a great fertilizer because it can be made from any type of organic scraps including vegetables, eggshells, coffee grounds, decomposed leaves, and more!

“Compost is what’s left when the bacteria in dirt break down a meal of leaves, grass clippings, and table scraps. The end product contains plant-sustaining nutrients such as phosphorus, potassium, calcium, and iron. 

But it’s more than mere fertilizer; compost also regulates soil pH, improves soil texture, and helps retain moisture and microbes – all essential for healthy plants.”

Source: How To Make Compost: Homemade Fertilizer Made Easy

Think of compost as a mixture of all organic material nature provides. All the ingredients used can be to your preference and after you’ve found the right compost container, you’re all set. Compost bins generally retail for around $30 and even upwards of $100 if you’re an expert of all things compost. 

Summary

In general, you have learned that it’s not necessary to add fertilizer to your microgreens but it is beneficial. 

Since you’ll be harvesting the greens so young, you won’t need to fertilize them while they’re growing in soil. However, if you find that you haven’t invested in high quality and nutrient-rich soil, or if you have planned to reuse soil, then it’s definitely beneficial to add fertilizer.

If you are growing your microgreens in soilless mediums that don’t provide nutrients, you will also benefit from adding fertilizers. That will help your microgreens to improve the growth of your crops.

Microgreens Corner
Microgreens Corner
We are Janette & Jesper, and we love microgreens.

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