Introduction

I’ve written at least 60 blogs and only now realized I never defined a microgreen. Before we jump in, I want to note that there isn't a single, universally accepted definition for microgreens. There will be a technical definition, a purist’s definition, my definition, and a broader description. More important than a strict definition is understanding the basic structure of a young seedling - the roots, radical, hypocotyl, and cotyledons. Only when you know a bit of plant physiology and anatomy can you create your definition of a microgreen.

Microgreen Definitions

My Definition - The youngest stage in the life of normal vegetable and herb crops.

I usually go on to say that microgreens are the stage between a dormant seed and a baby green. Not to be confused with sprouts, microgreens are grown in soil with lights and proper airflow. We only eat the stem and leaves of microgreens, but we eat the whole plant with sprouts. Microgreens are beautiful, packed with nutrients, and bursting with flavor.

The Technical Definition - A young seedling of an edible vegetable or herb, harvested at a specific stage of growth.

Depending on the source, there will be a list of characteristics that define a microgreen. For example, the plant’s age, size, and the present structures.

The Purist’s Definition - A vegetable crop with developed cotyledons, but no presence of true leaves.

I’ve seen many purists say that only vegetable crops can be a microgreens. If you grow young herbs, like cilantro, dill, fennel, or basil, you should call them microherbs, not microgreens. Also, when the first true leaves emerge, the plant is no longer a microgreen. It is now a baby green or something else.

A General Microgreen Description - A microgreen can loosely be described as an edible plant in the first few weeks of life. A harvested microgreen includes the stem and leaves, but not the seed or roots, like with a sprout. Microgreens can be annuals or perennials, vegetables or herbs.

You’ll notice I didn’t mention anything about the number or type of leaves. I think the litmus test for that parameter should be to compare it to supermarket baby greens. For example, if the leaves of your arugula microgreens are similar in shape and size to baby arugula greens, you’re now growing a different type of crop.

Plant Anatomy

Most annual crops are angiosperms or flowering plants. Angiosperms are the dominant source of food for humans. The diagram below outlines the basic structures of an angiosperm seed and seedling. Let’s review the germination process and the associated structures.

• Water is the primary trigger for germination in angiosperms. When water contacts a seed, the seed absorbs the water, causing the seed to swell and the seed coat to soften.
• The water activates hydrolytic enzymes, which break down food stores and initiate the seed’s metabolism.
• The new metabolic activity causes the embryo to begin growing. The cell growth and softening of the seed coating allow the embryo to emerge.
• The embryo continues metabolizing its food store, called the endosperm. The endosperm is what people refer to when they say microgreens can grow on their own. The endosperm supplies nutrients to the plant. It does this before the plant can use photosynthesis to produce energy.
• The embryonic root, the radicle, emerges and anchors the seed in the ground. Before the radicle is well developed and rooted, you'll see thousands of small root hairs emerging from it. With the radicle in the ground, the plant can absorb water and nutrients from its environment.
• After the radicle emerges, the embryonic shoot or stem will emerge, called the hypocotyl. As your microgreens push up in germination, you’ll see a distinct bend at the top, before the cotyledons. This is called the hypocotyl arch.
• The first tiny leaves to appear are called the cotyledons. These embryonic leaves are commonly called the “seed leaves.” The cotyledons will photosynthesize until the plant grows its first "true leaves." The true leaves are the first leaves the plant grows itself, rather than those it’s born with. Most annual plants are called “dicots,” di- comes from the Greek word “dis” meaning two or double. “-cot” is short for cotyledon. Most microgreens you grow are cotyledons because they have two seed leaves. A few, though, are “monocots,” meaning they only have one cotyledon. Onions, leeks, chives, and the rest of the Allium family are monocots, as well as wheatgrass.
• As the plant grows more true leaves for itself, the cotyledons will wither and fall off.

Around steps #7 or #8, growers will draw the line between a microgreen and a baby green.

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