How to Grow Red Garnet Amaranth Microgreens: Soil, Coco Coir and Silicone

Red garnet amaranth is the crop that turns a tray into a mass of magenta, and it is also one of the more delicate crops we grow. We have been growing microgreens since 2018, and we have grown amaranth on soil, coco coir, and several hydroponic mediums, with plenty of good harvests and a few trays lost to damping off. This guide covers how we grow red garnet amaranth on soil, coco coir, and our reusable silicone grow medium, what changes on each, and how we avoid the problems this crop is known for.

Quick Answer: How to Grow Red Garnet Amaranth Microgreens

Seed a 10x20 tray with about 15 grams of red garnet amaranth seed and do not presoak it. Cover the tray with an empty tray for about 3 days, flip that tray into a blackout dome for 1 to 2 more days, then move the tray into light and bottom water it lightly. Most of our trays are ready to harvest 10 to 14 days after seeding, and we have grown it out to 15 to 20 days when we wanted a fuller look. Amaranth does not like soggy medium, big temperature swings, or dirty trays, and damping off is how we lose it when something slips.

• Seed: about 15 grams per 10x20 tray, no presoak
• Germination: about 3 days under an empty tray, no heavy weight needed
• Blackout: 1 to 2 days under an upside-down empty tray
• Light: 16 to 17 hours a day, lights 8 to 12 inches above the canopy
• Harvest: usually day 10 to 14 in our grow space, up to day 15 to 20 if you want pronounced true leaves for chefs
• Value: a premium garnish crop, but one of the faster to perish after harvest, so grow to order
• Soil: no fertilizer. Coco coir and reusable silicone: feed through the bottom water
• Silicone: a heat mat set to 75F during germination

Why Red Garnet Amaranth Is Worth Growing

Red garnet amaranth has bright magenta and fuchsia stems and a light, delicate texture, and nothing else on our shelves looks quite like it. The flavor is mild and earthy. We describe it as tasting like red, since most of the red crops land in the same beet-like neighborhood. Amaranth was also a staple crop of the Aztecs, which is a fun fact to share when you hand someone a garnish.

It is a light crop. Our coco coir walk-through grow came in at 108 grams from a 10x20 tray, which is a good weight for amaranth since it will never weigh in like broccoli or sunflower. The point of this crop is color. A small pinch on a salad, a pizza, or a dessert does a lot of work.

It is also more particular than our beginner crops. If you are new to growing, start with a more forgiving crop like radish and come back to amaranth once your watering and sanitation habits are steady.

Why Red Garnet Amaranth Is a High Value Crop

Amaranth is a good example of a crop that earns its tray space by value and not by weight. A 10x20 tray will not out-weigh sunflower or pea, but the magenta color is something green crops cannot offer, and color is what chefs and buyers pay for. Specialty crops like amaranth tend to sell at a premium over everyday brassicas, commonly cited at two to three times more, though what you actually earn depends on your market, your buyers, and how you package it.

Three things drive that value:

• Color. It is one of the few microgreens with true magenta and fuchsia stems, so it stands out on a plate and in a mixed clamshell.
• Small portions. It is used as a garnish, so a small amount does a lot of work, and a light tray still fills a lot of orders.
• Difficulty. It is more particular than radish or broccoli, with damping off risk and a need for steady conditions, so fewer growers offer it consistently. That scarcity is part of the premium.

The other side of the value equation is shelf life. Amaranth is one of the faster-perishing crops we harvest, and it does not hold as long in the fridge as sturdier crops like radish or sunflower. That changes how we treat it commercially:

• Grow it to order. Plant against orders instead of growing extra trays to hope they sell.
• Harvest as close to delivery as you can, ideally the day of or the day before.
• Pack it loosely and dry, keep it cold, and do not wash it until it is going to be used.
• Sell it as a premium garnish in small containers, and do not stockpile it.

If you are thinking about selling, our guide to selling microgreens covers pricing, restaurants, and markets, our complete guide to starting a microgreens business goes deeper on permits and pricing, and the storage section below covers how we pack amaranth after harvest.

Choosing Red Garnet Amaranth Seed

We buy organic red garnet amaranth seed from True Leaf Market, and it has done well for us across soil, coco coir, and hydroponic grows. We also buy microgreen seed from Johnny's Selected Seeds and, at times, Amazon, so if one supplier is out of stock, the others are worth checking. Our microgreen seed page covers where we buy seed, germination help, and seeding rates for other crops, and our bulk seed buying guide is useful once you are growing amaranth regularly.

Amaranth is also sold as a grain and in bird seed mixes. Buy seed sold specifically for microgreens or sprouting from a reputable supplier, never bird seed or bulk feed, because those are not handled to food safety standards. Our seed quality guide explains why this matters.

Stick with red garnet. We have never gotten the green amaranth variety to harvest day, so we do not recommend it.

Seeding Rates by Tray Size

We seed 15 grams per 10x20 tray. That is roughly 1 to 1.5 tablespoons depending on how heaped the spoon is, so weigh it if you can. Do not presoak amaranth seed. It is very small and will clump.

• 10x20 tray: about 15 grams
• 10x10 tray: about half of that, so 7 to 8 grams. Browse our 10x10 trays and flats
• 7x14 tray: roughly one third to one half of the 10x20 rate, so about 5 to 7 grams. Our 7x14 Microgreen Tray Kit is the easy way to start small

These are starting points from our grow space. Some seed suppliers list a lighter rate, closer to 8 grams per 10x20, and that can work too. We seed denser because we like a full canopy, so try both in your own space and see which you prefer. Our free tray-specific seeding guide has rates by tray size for other crops.

What You Need

• Three 10x20 trays for the three-tray method: a no-hole tray for water, a mesh or slotted tray that holds the medium, and a second no-hole tray on top. We use Bootstrap Farmer 10x20 shallow trays. For other sizes, see our tray and kit hub
• Red garnet amaranth seed and a small digital scale from our Harvesting Tools We Use list
• Your medium: seed-starting soil, the coco coir we use, or a 10x20 reusable silicone grow medium
• A fine mister. We like this misting tool from Home Depot
• LED grow lights from our Grow Lights We Love list, and a shelf from our Grow Racks We Love list if you do not have one yet
• For coco coir and silicone: the fertilizer we use, Ocean Solution 2-0-3
• For silicone: a seedling heat mat with a thermostat
• A sharp harvest knife, such as the Mercer bread knife we use

Soil vs. Coco Coir vs. Reusable Silicone for Amaranth

All three work for red garnet amaranth, and they ask different things of you. In our side-by-side test we grew 15 grams of seed per 10x20 tray, bottom watered, and harvested at day 8. The soil tray weighed 143 grams and the coco coir tray weighed 114 grams, so the soil was heavier by 29 grams. Coco coir was noticeably easier to work with and clean up, and the soil we used was sandy, which made us think about grit in a crop we do not wash before it goes in the jar.

Soil or coco coir is where we would start with amaranth. If you already grow on silicone and want to try it, the silicone section below covers what we do differently. Our coco coir vs. reusable medium case study and our hydroponic grow medium rankings show how other crops behave on each.

A note on older testing: in our earlier hydroponic mat tests, a tightly woven mat gave amaranth poor germination because the tiny seed hulls could not push through. On another mat, trays were not tall enough to harvest at day 8 while the soil and coco trays were. Those were older grows in our space, so treat them as one data point and not a verdict on any product.

How to Grow Red Garnet Amaranth: Step by Step

This is the method we use on a 10x20 tray, whichever medium you pick. We cover medium-specific details in the sections after it. Our 10x20 tray guide walks through the same framework for any crop, and our free tray and kit guide covers the tray stacking in more detail.

Step 1: Prep the Tray and Medium

Stack your trays in the three-tray order: a no-hole tray on the bottom for water, the mesh or slotted tray holding your medium above it, and a no-hole tray reserved for the top. For soil or coco coir, use about 6 cups per 10x20, pre-moistened, spread evenly. Break up clumps and pull out any large sticks. For silicone, place the medium flat in the mesh tray and give it a light mist so seed sticks to it.

Step 2: Seed the Tray

Weigh out about 15 grams. Seed with a pinch and keep your hand moving, since the seed is tiny and slips through your fingers fast. Spread it as evenly as you can and avoid clumping, because disease starts in clumps and spreads from there. Wash your hands first and keep your trays and space clean.

Mist the seeded tray gently with plain water. Start with the mister held high so the first pass does not scatter the seed, then work closer as the seed settles. The goal is wet but not saturated, with a little extra on the corners and edges since they dry out first.

Step 3: Germinate Under an Empty Tray

Set the empty tray on top and press down lightly so it touches the medium. Amaranth is delicate, so it needs very little weight and often none. We use an empty tray for about 3 days. We have also used a 5 pound brick on a coco grow without a problem, but the empty tray is our standard.

During germination we mist as needed to keep the surface lightly moist, and plain water works fine. If you want to be proactive about disease, you can mist with a mix of about 2 tablespoons of 3% food-grade hydrogen peroxide per liter of water, or even better, the prophylactic spray from our DIY organic pest and disease control spray guide. Neither is required.

Around day 2 you will see a small white ring around each seed, which is the radicle getting ready to push out. By day 3, wipe or tap off any seed hulls stuck to the underside of the top tray and any hulls sitting in the canopy, then vacuum them up. A hull that stays on the tray can decay and cause trouble later. Our post on when to move from weight to blackout explains the transition in more detail.

Step 4: Blackout for 1 to 2 Days

Flip the empty top tray into a dome over the seedlings and leave it for 1 to 2 days. This stretches the stems a little so the tray is easier to harvest. Amaranth is a shorter crop and tends to hold roughly the height it has when it first goes into light, so do not skip this step.

Step 5: Move to Light and Bottom Water

Remove the dome and put the tray under light for 16 to 17 hours a day with lights 8 to 12 inches above the canopy. Our microgreen lighting guide covers the lights we use, and our grow lights and setup hub covers shelves and spacing. Switch to bottom watering now. Start with about half a cup to one cup in the bottom tray of a 10x20 per watering, and only add more once the last water has been absorbed. Our full watering guide goes deeper on volumes.

Amaranth likes to dry out a little between waterings. Some days it needs less water than your other crops. If you over-water, do not add more water. Let the tray drink what is already there, or drain the tray and add fresh water.

Step 6: Feed Coco Coir and Silicone Trays

Coco coir and silicone carry no nutrients of their own, so we feed them through the bottom water with Ocean Solution 2-0-3 at 0.5 oz per gallon, pH balanced to 5.5 to 6.0. Wait until the tray is in light before you feed. In one of our hydroponic grows we added nutrient while the tray was still in blackout, and the roots browned soon after. We think the extra moisture did not help. Soil grows do not need fertilizer. We personally do not suggest most liquid fertilizers with soil since quality soil mixes are already nutrient rich, though every soil is different and you are welcome to experiment. Our fertilizer guide compares options, and our free fertilizer ratio guide has the dilution and pH numbers.

Step 7: Harvest

Harvest when the tray has a full canopy. You can harvest early for a baby look, or wait for true leaves if your buyers want them (more on that in the timing section below). Use a clean, sharp knife, like the Mercer bread knife we use, and harvest just above the medium line. Go low enough to get the stems but not so low that you pick up medium. If you do, trim the wet bottoms off the bunch. Wipe the knife on a clean towel as you go. Our post on harvesting tools and methods covers knives, scissors, and trimmers.

Growing Red Garnet Amaranth on Soil

Soil is the most forgiving option on feeding, because you skip fertilizer entirely. Moisten a seed-starting mix, level it in the mesh tray, sow the seed on the surface, and follow the steps above. Bottom water from the day the tray goes into light.

The one thing to watch is the soil itself. The sandy soil we used in our test produced the heaviest tray, and we also worried about grit in the harvest, since amaranth is not a crop we rinse before packing. Pick a fine, clean seed-starting mix and pull out large sticks and clumps before you seed.

After harvest, the soil and root mat go into compost. We do not reuse medium, and we do not bring composted material back into our grow space. Our guide on what to do with used grow medium has more.

Growing Red Garnet Amaranth on Coco Coir

Coco coir is the medium in our on-camera amaranth walk-through, and it is our everyday pick for this crop. Six cups of coir pre-moistened and leveled in the mesh tray is the amount we use for a 10x20. It is clean, easy to work with, and cheap per tray. The coco coir tray in our side-by-side test weighed 114 grams, and the walk-through tray weighed 108 grams.

Because coir has no nutrients of its own, feed it with the bottom water once the tray is in light (Step 6). The first bottom watering in our coco grow was about a cup. When the roots drank that down we added a second smaller watering later the same day, and we adjusted from there based on how the coir looked.

Watch the full grow from seed to harvest in our amaranth walk-through video:

If you want to keep your amaranth batches straight, our tray clip labelers make it easy to keep sow dates in view, and you can read how they work in our tray clip labeler guide.

Growing Red Garnet Amaranth on Reusable Silicone Grow Medium

Amaranth is one of the more challenging seeds on our reusable silicone grow medium. The seed is small enough to slip through the 1.2mm holes, so it needs a little help. We have confirmed it grows on the 1.2mm version when the tray sits on a heat mat set to 75F during germination. The 1.7mm large hole version is not the right choice, since small seeds fall through its holes.

How We Adjust for Silicone

• Buy the size that matches your tray: 7x14, 10x10, or 10x20.
• Place the medium flat in the mesh tray and mist it lightly before seeding, so the seed sticks instead of bouncing and falling through.
• Seed evenly at the same 15 grams per 10x20. Do not presoak.
• Put the tray on a seedling heat mat set to 75F for germination. Keep the empty top tray on, and mist with water as needed to keep the surface lightly moist.
• Once the tray is in light, feed through the bottom water with Ocean Solution 2-0-3. Silicone is inert, so the water is the only nutrition the tray gets.
• Natural seed staining can show up on silicone from red pigmented seed. It does not affect how the medium grows.

Why a heat mat? In our heat mat test, we seeded 15 grams of amaranth per tray on a hydroponic hemp mat. Two trays sat on a heat mat set to 78F and two sat on a shelf at our ambient temperature of about 70F, so the heated trays ran about 8 degrees warmer. By day 3 the heated trays were clearly ahead. By day 4 the amaranth on the heat mat was reaching the edge of the tray, while the unheated trays were still below the rim with smaller cotyledons. We ran that test on hemp and not silicone, but it is the reason we reach for a heat mat with this crop on any medium. You can watch the whole test here:

After harvest, use our Microgreen Medium Scraper to clear the roots, then hand wash with mild food-safe dish soap and warm water, and deep sanitize between crops. Amaranth is prone to disease, so we do not skip sanitizing. Our cleaning and sanitizing guide walks through it. The reusable grow medium guide covers sizes, care, and the 1.2mm vs. 1.7mm difference, and our seed compatibility guide lists which seeds work on it.

Temperature, Humidity, and Watering

Amaranth likes warmth, but not too much, and it wants steady conditions. Our grow space runs roughly 75 to 80F with humidity at or below about 35%, and that has been a good match. Our humidity guide covers how to manage that range.

Water is the other half. Keep the medium lightly moist during germination and then keep bottom watering modest. A tray that stays wet invites root problems, and over-watering is the quickest way to invite damping off. Check the bottom tray before you water, and skip the watering if water is still there.

Damping Off: The Main Way We Lose Amaranth

Damping off is a group of pathogens that attack seedlings at the roots and stems, usually in humid, moist conditions. It can create large patches of die-off very quickly, and once it starts it cannot be stopped. Amaranth is more prone to it than most crops.

It has happened to us. In a four-medium amaranth test, one tray was well ahead of the others on growth when a small circle of damping off appeared and spread across the whole tray. We pulled it out of the space as soon as we could. Our best guesses were temperature spikes, since we had random 80 to 93F days in the middle of winter after weeks near 30F, and our habit of drying trays outdoors, which can carry pathogens back into the grow space.

Here is what we do to lower the risk:

• Keep temperature steady, and do not let the space swing between hot and cold days
• Mist lightly during germination, and do not let the surface turn soggy
• Seed evenly and avoid clumps
• Wipe off or vacuum up stuck seed hulls before they decay
• Water lightly, and never add more water to a tray that is already wet
• Clean and sanitize trays and reusable mediums between every crop
• Give the tray airflow above the canopy
• Optionally, mist with the prophylactic spray from our DIY spray guide, though it is not required

If you see a patch, remove the tray from the space. Our full guide on damping off explains how to identify and prevent it, and our mold guide helps you tell mold from healthy root hairs. For other issues, see our troubleshooting hub.

Common Problems With Red Garnet Amaranth

Seed hulls stuck to the canopy

A few stuck hulls are normal. Wipe them off the underside of the top tray on day 3 and vacuum what falls. By harvest we were seeing about 1% or less still on the tray in one of our best grows, and the hulls were so small they were easy to chew without noticing.

Roots look tan or yellow

We want white roots. In our hydroponic grows, roots that turned tan or yellow were a sign that the medium was holding too much water. If it starts early, cut back on watering. If it shows up late in the grow, as it did on day 12 in one of ours, the tray finished fine.

The tray stays short

Amaranth is naturally a shorter crop. Blackout helps it stretch a little, but it will not reach radish height. If it still seems stunted, check light timing, temperature, water quality, and fertilizer on coco or silicone. Our post on why microgreens stay short has the full list.

How Long Red Garnet Amaranth Takes, and How to Track It

Amaranth does not have one finish line for us. Our soil vs. coco test was harvested at day 8. Our usual window is 10 to 14 days, and we have grown it for 15 to 20 days when we wanted true leaves and a fuller look. It moves with temperature, medium, and the look you are after.

Growing Amaranth Out to True Leaves

Some growers let amaranth grow past the seed leaf stage until the first true leaves show up. The true leaves are more pronounced in shape and color than the small seed leaves, and chefs love to see them because the garnish looks closer to a mature leaf and reads as more dramatic on the plate. If a chef or restaurant buyer asks for it, this is the look to grow toward. Our guide to the best microgreens for restaurants covers what chefs tend to look for.

There are trade-offs. A longer grow means more days of careful bottom watering, steady temperature, and clean conditions, and that is more time for damping off to show up in a crop that is already prone to it. The canopy also gets taller and fuller, so you will want to keep airflow above it. Ask your buyer which stage they prefer before you plan the tray, because a baby-leaf tray and a true leaf tray are on different calendars. Logging each tray's harvest day, as described below, tells you which stage your space delivers at what day.

Because of all that, we log every amaranth tray with its sow date, medium, seed weight, and harvest weight. Microgreen Tracker, our grow-tracking web app, keeps a day count and estimated harvest date for each tray, lets you add notes along the way, and records the harvest weight against the seed you sowed. After a few trays you will know your own amaranth window in your own space. It works in any phone or desktop browser, and every new grower starts with a 7-day free trial of the whole app. Our post on tracking microgreen grow data explains why the records are worth keeping.

Harvest, Storage, and Staining

Amaranth is one of the faster-perishing crops we harvest and does not keep long, so plan to use it or deliver it soon. We pack it loosely in a wide-mouth jar and do not press it down. About 70 grams fit in one 32 ounce jar in our grow. Do not wash it until you are ready to eat it. Our microgreen storage guide covers containers and fridge tips.

Fair warning: amaranth can stain your hands and clothes, so wear an apron and expect pink fingertips.

Roots and medium go to compost. We do not eat microgreen roots, and our post on why we do not eat microgreen roots explains the food safety reasoning.

How to Use Red Garnet Amaranth Microgreens

The earthy, beet-like flavor is gentle, so amaranth works as a garnish more than a base. We use it on salads, pizzas, soups, and smoothies, and it adds color to nearly everything. Add it at the end so it keeps its shape.

It also pairs surprisingly well with chocolate. We have put it on brownies with almond whipped cream and raspberries, and the magenta color looks great against the dark chocolate.

For more ideas, see our microgreen recipes page.

Frequently Asked Questions

How long do red garnet amaranth microgreens take to grow?

Most of our trays are ready 10 to 14 days after seeding. A soil and coco coir test we ran was harvested on day 8, and we have grown it out to 15 to 20 days when we wanted true leaves and a fuller look.

Is red garnet amaranth a high value microgreen?

It is a premium garnish crop. The magenta color is hard to match, and specialty crops like amaranth tend to sell for more than everyday brassicas. It is also harder to grow and perishes faster after harvest, so the best approach is to grow it to order and harvest close to delivery.

How long does amaranth last after harvest?

Not long. It is one of the faster crops to perish, so we pack it loosely and dry, keep it cold, skip washing until it is used, and use or deliver it quickly.

Why do chefs like amaranth with true leaves?

True leaves are more pronounced in shape and color than the small seed leaves, so the garnish looks fuller and more dramatic on a plate. We grow it out to about day 15 to 20 for that look, and it takes more careful watering and cleanliness than a baby-leaf harvest.

Do you soak amaranth seeds before planting?

No. The seed is very small and clumps when it gets wet, so we spread it dry and mist it afterward.

How much seed do you need for a 10x20 tray?

About 15 grams, which is roughly 1 to 1.5 tablespoons. Use about half that for a 10x10 tray. Some suppliers list a lighter rate, so feel free to test a lower rate in your own space.

Can you grow amaranth microgreens on silicone?

Yes, with adjustments. Use the 1.2mm reusable silicone grow medium, pre-mist it so the seed sticks, and put the tray on a heat mat set to 75F during germination. It is one of the more challenging seeds on silicone, so soil or coco coir is the easier place to start.

Why are my amaranth microgreens falling over or dying in patches?

That is usually damping off, which is more common with amaranth than with most crops. It is linked to excess moisture, temperature swings, and dirty trays. Remove the affected tray from your space and sanitize everything before the next grow.

Does red garnet amaranth need fertilizer?

On coco coir and reusable silicone, yes, because neither carries nutrients of its own. We feed with Ocean Solution 2-0-3 once the tray is in light. Soil grows do not need it.

Do I need hydrogen peroxide or a special spray when germinating amaranth?

No. Plain water works. A diluted hydrogen peroxide mix or the prophylactic spray from our DIY spray guide is an optional extra if you want to be proactive about disease.

Why did my hands turn red after harvesting?

Amaranth stems carry a strong pigment, and it can stain hands and clothes. It washes off skin, and an apron helps.

Final Thoughts

Red garnet amaranth takes a little more care than radish or broccoli, and the color is worth it. Keep your seeding even, your watering light, your temperature steady, and your trays clean, and you will get a bright, delicate tray that makes everything it lands on look better. If you want to see more full grows, our Video Library has our grow videos.

Just curious and want to learn for free:

• Browse the Learn page for our free guides and hubs
• Follow us on Instagram at @onthegrowfarms

Ready to start growing:

• Pick up the Beginner's Guide to Growing Microgreens PDF ($3.99)
• Grab a 7x14 Microgreen Tray Kit to start small, or Bootstrap Farmer 10x20 trays for full-size grows
• Browse our reusable silicone grow mediums for a no-mess grow
• Keep every tray on track with Microgreen Tracker: Start My Free 7-Day Trial

Ready to take it seriously:

• Enroll in the Microgreen Masterclass for the complete training

Related Blogs You Might Enjoy

• How to Grow Microgreens: A Complete Step-by-Step Guide From Microgreen Experts
• How to Grow Celosia Microgreens: Soil and Reusable Silicone Methods
• How to Grow Cilantro Microgreens: A Complete Step-by-Step Guide
• How to Grow Swiss Chard Microgreens
• How to Grow Radish Microgreens: The Fastest Beginner Crop
• How to Grow Broccoli Microgreens: A Complete Step-by-Step Guide
• Types of Microgreens: A Complete Guide to Popular Varieties
• How Many Types of Microgreens Are There? What You Can Grow
• Top Microgreen Growing Mistakes and How to Avoid Them
• Growing Microgreens in Winter

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The results and opinions shared in this post are based on our own first-hand testing in our specific, controlled grow space. Any mention of a brand or product reflects our own experience, not a sponsored or definitive review. Your climate, water, seed, and setup are different from ours, so your results can vary. We always encourage you to run your own experiments and see what works best for you.

Pricing, demand, and earnings vary widely by market and buyer, and nothing in this post is a guarantee of income or business advice. Always check your local food safety and licensing requirements before selling.

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Happy growing!