Microgreen Fertilizer

<a href='https://typesofmicrogreens.com/author/admin/'>Jon Smith</a>Jon Smith
June 2, 2021

You can use fertilizer when growing microgreens but it is recommended that you use safe microgreen fertilizer to ensure that your microgreen crop is as healthy as possible for your consumption.

Do not use plant fertilizer as that is not the best solution. Continue reading to learn more about various organic products that you can use to help your microgreen crop yield.

Best Fertilizer For Microgreens

Before we dive in and learn about fertilizers for microgreens I wanted to share with you the product that I prefer and use for my own personal microgreen crops.

OceanSolution 2-0-3 - Plant Food - Liquid Organic Fertilizer for Gardens, Landscapes, Hydroponics (Organic Ocean Mineral Fertilizer Concentrate 32 Ounces)
  • OMRI listed for Organic use
  • Complete Plant Nutrition - All 90 macro, micro, trace, and ultra-trace mineral nutrients
  • More Blooms, Greener Lawns, Bigger Yeilds, and Better Tasting Plants
  • Restores Depleted Minerals In Soils and Plants
  • Non-Toxic - Safe for Children and Pets

This is by far the best concentrated microgreen fertilizer you can buy. It is a bit pricy but the product is diluted and will last a very long time.

It is also easy to use. You mix the solution into a gallon of water and feed it when bottom watering your microgreens.

How And When To Use Fertilizer On Microgreens

Microgreens are not full-grown plants. Rather, they are the first cotyledons that come out of the seed right after germination and are harvested in a period of one to two weeks. As such, some of the reasons why people may use fertilizers may not be as relevant in the case of microgreens.

That being said, and as we discuss below, there are definitely good reasons to use fertilizers in certain situations when growing microgreens. We must be careful, though, in balancing the value-added against the possible negative effects that could impact the health and taste of the microgreens. Being delicate, anomalies in taste will become more apparent – especially when eaten raw in salads or used as a garnish.

Let’s first see why fertilizers are used to grow plants.

Why Use Fertilizer?

Fertilizers are a source of nutrition that allows the plant to grow greener, tastier and taller, given that they can provide nutrition above and beyond what soils or growing media can provide without fertilizer. For understanding this further, let’s probe a very basic Nutrition 101 question.

Basic Question: Where do Plants get Nutrition?

When we think of growing microgreens, shoots, or fully-grown plants, the first thing we often picture is the soil bed the greens come out of. While accurate in many cases, this is misleading.

Plants grow through photosynthesis, a natural process involving the following chemical reaction:

6CO2 + 6H2O → C6H12O6 + 6O2

Take a close look at the equation above. On the left-hand side (the inputs) are six molecules of carbon dioxide with six molecules of water. We know that light is needed to trigger photosynthesis, but notice anything missing?

That’s right, there’s no need for soil per se to grow plants. The function of soil is to provide a medium that has the 13 essential nutrients (the Nitrogen-Phosphorus-Potassium or N-K-P combo being the biggest need) that add to the health, taste, and other attributes of the plant. The base also provides a place where the plant roots can anchor and draw water and other nutrients from below.

The Key Ingredients Needed for Plant Growth

Bottom line – we don’t need soil to grow plants, certainly not ones that can germinate and get ready for harvesting as quickly as the average microgreen.

We do, however, need a base – which could be soil, a growing medium (like coco coir), water, and light. We can also deliver nutrients to the growing base using composts and/or fertilizers.

Compost vs. Fertilizers – Is There a Difference?

Composts and fertilizers are often used interchangeably by amateur gardeners, but they are not the same thing. Composts are decomposed organic material that adds to soil quality – the so-called “soil food web”. Fertilizers, while they may be applied to the soil at times, are specifically aimed at providing nutrition directly to the plant.

As we will see below, this distinction makes a difference when growing microgreens in particular, when the soil is not often reused and therefore does not need to be replenished and refreshed through composting or the use of gentler (organic) fertilizers.

Comparing Organic vs. Inorganic Fertilizers

For the rest of this discussion, we will not be talking about various types of composts (e.g., cow, sheep, or chicken manure, vermicompost, or what you can create out of decomposing your organic kitchen discards). Instead, we will be focused on fertilizers, specifically.

Fertilizers can be two types: (a) organic, or (b) inorganic or chemical.

  • Organic fertilizers are those made from natural (animal, plant, or mineral ore) ingredients, with very little done in terms of processing to alter the underlying characteristics, texture, or chemical balance of the ingredients. Examples include seaweed, worm castings, rock phosphate, and bone meal.
  • Chemical fertilizers are synthetically created by mixing parts of different essential minerals to produce a balanced solution with the desired N-P-K, added calcium, etc. The prime example is Miracle-Gro. Other common ones are Ammonium Nitrate, Ammonium Phosphate, and Potassium Sulfate.

The table below captures some differences produced by organic vs. inorganic fertilizers:

AttributeOrganicInorganic/Chemical Fertilizer
ProducedNaturally, with minimal change in underlying ingredients.Mixed and treated to produce desired nutrient balance synthetically.
Nutrient ValueGood, but content and release time could vary from batch to batch and is not predictable. Does contain micronutrients.Precisely proportioned for a specific use, predictable in terms of main nutrients. Often lacks micronutrients.
Impact on Plant GrowthIt will tend to make plants grow faster, be taller, and greener – however, effects will vary based on specific plant and type of organic fertilizer used.Same as organic in the basic scenario but will tend to act faster due to a specific mix of nutrients being applied.
Impact on SoilGentle on the soil, support microbiological life in the soil.Can be rough on the soil, especially when used in larger quantities and over several crop cycles.
CostHigher, both per unit and also due to higher amounts that may need to be boughtLower, both per unit and in terms of being specific in the amount required.

How To Change Your Pros/Cons When Growing Microgreens

Growing microgreens is different than growing normal plants indoors and outdoors. Below are some of the adjustments in thinking you need to make when considering whether to use organic or chemical fertilizers to grow microgreens specifically.

  1. The soil used in growing microgreens is usually not reused, especially beyond the second use. As such, there is no need to fear using organic fertilizers.
    • If microgreens are grown without soil (see below), the concern is nonexistent.
  2. However, synthetic fertilizers have been known to act faster than organic, which is a cause for concern with microgreens. In many cases, the young microgreens will pick up more harmful substances and lose taste when they become a sprout and certainly if they approach being a full-grown plant. So the use of fertilizers must be optimal.
  3. Chemical fertilizers often leach and/or release quickly, causing the tops to grow quickly before the roots fully develop. This is likely to be less of a problem with microgreens given that we are not waiting for the plant to fully develop anyway. Fast-acting fertilizers are better for microgreens.
  4. Due to the delicate nature of the microgreens, the taste of fertilizers (both chemical and certain types of organic ones) makes a big difference – so caution is needed. Excessive use of fertilizers can burn microgreens.

All in all, both organic and synthetic fertilizers can be used, but their use must be targeted in terms of suitability (type of microgreen, taste factor) and controlled.

When To Use Fertilizer To Grow Microgreens

Growing microgreens can be effectively done in one of three media: (a) soil, (b) a different growing medium, and (c) water. We will discuss each of the options below.

Growing Microgreens In Soil

When growing in soil, the need for fertilizers is diminished, though compost or fertilizer could be added in smaller quantities. Good, porous, organic soil mixes may well be sufficient. Many growers, however, prefer not using soil due to fear of mold, rot, and associated problems.

Growing Microgreens In Soil-Free, Solid Growing Mediums

There has been a growing move towards using a soil-free medium such as coconut coir, hemp pads, Rockwool, burlap, or coco-fiber pads. These substantially reduce the fear of waterlogging or mold. However, you may well need to add some fertilizer, since the base does not naturally possess the key nutrients that soil would have.

Growing Microgreens Hydroponically

Many microgreens can be sprouted hydroponically – simply in jars of water at home or with commercial operations with some soil but lots of water. In these cases, fertilizer use is again necessary since nutrients must be added to aid growth. This is important since there are certain microgreens such as alfalfa or kale sprouts that actually do better in water.

Hydroponically grown microgreens are less messy (little or no soil, no compost), can be controlled better, and yield great products when proper nutrients are added.

Seed Size Is A Consideration

Microgreens grow fast, and some scoff at the idea of fertilizers, positing that the seed itself has enough nutrients to sustain the early germination and harvesting of sprouts. However, the results are clear – with strategic use of fertilizers, you get better taste, a greener color, and a bigger crop (that is, higher yield).

If you have large seeds, you may want to reduce the amount of fertilizer when growing in soil-less mediums or in water. But even so, it does help unless you overdo it.

Some Recommendations On Organic Fertilizers

We first discuss the fertilizers that work best, specifying the type of use where relevant. We use suggestions from industry experts such as True Leaf Market:

  • Azomite – Trace Mineral Organic Fertilizer: This is True Leaf Market’s #1 recommended microgreen fertilizer. Made out of crushed Montmorillonite and containing over 60 trace minerals, this can be used for any type of growth but especially when growing on a solid medium. Follow the instructions here:

Purchase Azomite Trace Mineral Here

  • Organic Liquid Seaweed and Kelp Supplement: This is one of the highest quality fertilizers for both non-soil-based and hydroponic microgreen growth. The mix contains 70+ nutrients, among which are cytokinin and auxin. They can be sprayed on after mixing with water. Using Liquid Kelp with organic soil may overfeed the microgreens.
Organic Liquid Seaweed and Kelp Fertilizer Supplement by Bloom City, Quart (32 oz) Concentrated Makes 180 Gallons
  • FULLY ORGANIC SEAWEED AND KELP: A seven species blend of Ascophyllum Nodosum, Palmaria Palmata, Ecklonia Maxima, Laminaria Saccharina, Chlorella Vulgaris, Arthrospira Platensis, and Chondrus Crispus.
  • EXTRACTED TO PROTECT NATURAL ENZYMES: Clean Kelp’s unique processing techniques give the cleanest possible kelp extract.  Get all the benefits of natural kelp enzymes and hormones without the non-nutritious fibrous pulp that gives other kelps their thick, brackish appearance.  You can see the difference.
  • SIMPLE AND SAFE TO USE FOR ALL PLANTS: Add to every watering, it’s that easy. No risk of over application, plants love kelp. Clean Kelp aids in every stage of growth for root and stem health.
  • FOR BOTH PLANTS AND LAWNS: Add Clean Kelp to all of your houseplants, vegetable garden, and your lawn for healthy green plants.
  • FORMULATED AND MADE IN THE USA: Designed by botanists and plant chemists. Bloom City chooses only the highest quality ingredient sources and manufacturing methods to create the world’s best craft growing nutrient systems
  • Worm Castings: Another strong recommendation, worm castings – manure from redworms – is amazingly rich in nitrogen, phosphates, and other essential minerals. They are very appropriate for microgreens grown in soil.

Get Worm Castings Here

  • Organic Bone Meal Fertilizer: This works well with soil but the taste/smell may not be suited for hydroponic microgreens.
Burpee Organic Bone Meal Fertilizer, 3 lb (1 Pack)
  • Why bone meal? - provides vital Organic nitrogen, phosphorus and calcium
  • Strong roots, vibrant blooms - promotes strong roots, vibrant blooms and more delicious vegetables
  • When TO treat - early-season addition of phosphorus to soil will promote strong root development, enhance early growth, and superior blossoms and fruit at harvest time. May be added at to soil any time prior to harvesting to enhance plant growth
  • The earlier the better - Boosts young plants and helps them stay strong throughout the growing season
  • Ideal for fall bulb planting - promotes healthy growth of root crops and other vegetables
  • Rock Phosphate: Mined from phosphate rocks, these high phosphorous fertilizers work very well outdoors, but can also be used in smaller quantities on microgreens.
Espoma RP7 Rock Phosphate, 7.25-Pound
  • Pure mined phosphate rock containing 32% total phosphate
  • All natural source of phosphorus for all flowering plants
  • Promotes root growth
  • Made in the USA
  • Organic rock phosphate provides phosphorous for all flowering plants
  • Bat Guano: Despite the origin, Bat Guano has surprisingly little odor. It can be useful in microgreen growth, especially in soil, due to its fast-release properties.
Down to Earth Organic Bat Guano Fertilizer Mix 7-3-1, 2 lb
  • Down To Earth Bat Guano Mix is an all natural fertilizer with 7-3-1 formula and is listed by the Organic Materials Review Institute (OMRI) for use in organic production
  • Rich in readily available nitrogen, phosphorus and micronutrients and nearly the third of the nitrogen is water soluble, making it readily available to plants
  • Provides essential plant nutrition for vigorous vegetative growth and early fruit and flower development
  • Fast acting and highly effective when mixed into potting mediums, applied as a side dress or steeped to make a potent guano tea or foliar spray
  • A good fertilizer for both early and mid-season booster applications and is the undisputed champion of all-natural fertilizers

Some Organic Fertilizers that May Not Work Well

Here are some organic fertilizers that do not work as well with microgreens (reasons listed):

  • Alfalfa Meal: This fertilizer contains sugars and starches along with essential nutrients. Used indoors on microgreens, there is a significant chance of mold and bacteria developing, plus insects will be drawn to it.
  • Cottonseed Meal: Though 6-2-1 in N-P-K and a source of a number of other micronutrients, this has a smell (with fish, feather, bones, etc. mixed in) that may be bothersome.
  • Fish Emulsion: This is a no for indoor plants, and definitely for microgreens, due to the strong odor it will produce.
  • Blood meal: This product is exactly what it sounds like – nutrient-rich, dried, and sterilized blood from slaughterhouses. Good for outdoor use, there are multiple reasons this isn’t the best product for growing microgreens, especially indoors.
  • Feather Meal: Made from hydrolyzed chicken feathers, this non-vegan fertilizer is not considered to be a good option for microgreens due to odor and taste.
  • Mushroom Fertilizer: This is better used outdoors, in soil for longer cycle crops. Its slow-release property makes it less suitable for microgreen cultivation.

Some Recommendations on Chemical Fertilizers

Below are three inorganic fertilizers that can be used. The first two, Miracle-Gro and FloraGro are recommended by True Leaf Market:

  • Miracle-Gro Water-Soluble All Purpose Plant Food: This commercial fertilizer has sufficient N-P-K to help microgreen growth. It should be mixed in with water but added in small quantities to avoid the possibility of burning the microgreens. We do not suggest using this product with food.
  • FloraGro Hydroponics Microgreen Nutrient: This pH-neutral fertilizer is recommended by True Leaf Market as ideal use for hydroponic growth, though it can also be used in small quantities with soil bases.

Purchase FloraGrow Nutrient Here

  • Osmocote Smart-Release Plant Food Flower; Vegetable: Though on the expensive side, this is a great inorganic fertilizer to use, especially if mixed in with the soil or growing medium. It can also be spread on top of the seeds after germination.
Osmocote Smart-Release Plant Food Flower & Vegetable, 8 lb
  • Promotes vigorous top-growth, strong root development
  • A must-have for vegetable gardeners
  • Ideal for perennials
  • Formulated for flavorful vegetables and colorful blooms
  • Feeds up to 4 full months

Chemical Fertilizers to Avoid

Without getting into specific details, think back to the fact that chemical fertilizers tend to make the plant grow too fast and can oversupply nutrients. Certain types are not suited to certain microgreens, but more importantly, the user should be controlled to avoid burning the product.

Final Thoughts

Adding the right types of fertilizers, in controlled amounts, to hydroponic and non-soil-based growth mediums can produce dramatic effects on your microgreen crop in terms of both quality and quantity.

The main goal is to use in the properly specified amount and get comfortable with the results. The end product is sure to be delicious!

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About The Author
I have been growing microgreens for myself and others for quite some time now and I absolutely love the process.

Even more I love spreading awareness of an amazing crop that has so many nutritional benefits for our bodies which improve our overall health and wellbeing.

Jon Smith

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As an Amazon Associate I earn from qualifying purchases.