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Reusable Microgreen Grow Mediums: Sizes, Seeds, and Care

 

A reusable grow medium is a washable mesh sheet that replaces soil and coco coir in a microgreens tray. Ours are food-grade silicone, and the 1.2mm version is rated for 20 to 30+ grow cycles. We have grown on them for over 4 years and tested more than 70 seed varieties. Pick your tray size below to shop, or follow the learn more link under each one.

10x20 Reusable Silicone Grow Medium

1.2mm holes, pre-cut for standard 10x20 trays. Best for small seeds like broccoli, kale, and radish. Shop the 10x20 or learn how to grow in 10x20 trays.

10x10 Reusable Silicone Grow Medium

1.2mm holes, pre-cut for standard 10x10 trays. The same small-seeded crops in a smaller tray. Shop the 10x10 or read the complete silicone overview.

1.7mm Large Hole Silicone Grow Medium

Larger holes for large seeds such as sunflower, pea, melon, and wheatgrass, in 10x20 and 10x10. Shop the 1.7mm or learn how to grow sunflower.

7x14 Reusable Silicone Grow Medium

Pre-cut for the 7x14 OTG Tray Kit, a good fit for home growers and small spaces. Shop the 7x14 or read the 7x14 growing guide.

Small Sprouting Tray Silicone Grow Medium

Sized for the small sprouting tray. Shop the small size or learn the sprouting tray method.

Large Sprout Tray Silicone Grow Medium

Sized for the large sprouting tray. Shop the large size or learn the sprouting tray method.

We no longer sell the sprouting trays themselves, only the grow mediums sized for them. For trays, see our Sprouting Trays list on Amazon (affiliate link).

1.2mm vs. 1.7mm: Which Hole Size Do You Need?

The 1.7mm medium has holes 0.5mm larger than the standard 1.2mm. Use the 1.7mm for large seeds with aggressive roots, such as sunflower, pea, melon, and wheatgrass, because the larger openings let roots pass through more easily. Use the 1.2mm for small and medium seeds, because brassicas such as broccoli, cabbage, and kale will fall through 1.7mm holes.

The two are easy to tell apart by touch. The 1.2mm feels smooth and even, and the 1.7mm feels coarse and bumpy. One difference to know before you buy: the 1.2mm is LFGB tested and third-party tested for FDA compliance, while the 1.7mm is made differently and has not been LFGB tested.

Seed Compatibility

Our full guide covers more than 70 varieties tested on reusable silicone, plus the heat mat method for tiny seeds like amaranth. The short version:

  • Works well: sunflower, pea, radish, broccoli, kale, cabbage, arugula, basil, mustard greens, kohlrabi, and most brassicas
  • More challenging: amaranth can grow at 75F with a seedling heat mat during germination, and very fine seeds may need adjustments
  • Not recommended: Swiss chard, beets, and cilantro. These grow better on soil or coco coir, and the hard seed hulls on chard and beets stay attached without a layer of medium to push through
  • Best without a medium: some pea varieties with aggressive roots do best bare on a mesh tray

For soil and coco coir crops, see our guides to Swiss chard and cilantro. To buy seed, see our Microgreen Seeds page.

Best For and Not For

Reusable silicone is best for growers who want a clean, soil-free setup with less waste, who grow small-seeded crops such as brassicas and radish, or who run enough trays that buying coco coir every harvest adds up. It works for home and commercial growers.

It is not the right choice for Swiss chard, beets, or cilantro, and it does not carry nutrients, so growers who want a medium that feeds the plant should use soil. It is also not a no-maintenance option, because every sheet needs to be cleaned and sanitized after each grow.

Growing on a Reusable Medium

Because silicone is inert, you supply the nutrients. We feed with Ocean Solution 2-0-3 at 0.5 oz per gallon with pH balanced to 5.5 to 6.0, on coco coir or reusable silicone and not on soil. We no longer carry it, so that link is an affiliate recommendation. Our 10x20 guide walks through tray dimensions, bottom watering, and step-by-step instructions for each medium.

Cleaning and Care

Reusable only works if every sheet starts each grow clean. After harvest, remove root residue with our Microgreen Medium Scraper, then hand wash with warm water and a free-and-clear dish soap or another silicone-safe, food-safe soap. For deeper sanitation between grows, pour boiling water over the sheet or submerge it for 1 to 2 minutes, then let it air dry fully before reuse. Store it flat to prevent creases, ideally inside a spare tray.

Replace a sheet if you see tears, deep cuts, or significant wear, because those can expose the fiberglass core. Some seeds leave natural staining on the silicone, which does not affect how it grows. We buy the size that matches the tray and do not trim sheets to fit.

Stainless Steel Mediums

We moved to silicone and are phasing out stainless steel. We no longer sell a 10x20 stainless version, and the 316 grade 10x10 and small sprouting tray stainless mediums are the last remaining sizes. Our guide explains how stainless works and why we made the switch.

Videos: Silicone Reusable Grow Medium Playlist

Our YouTube playlist, Silicone Reusable Microgreen Grow Medium: How to Grow and Experiments, has 83 videos covering seeding, germination, harvest, cleanup, and side-by-side comparisons. Watch it here or open the full playlist on YouTube. More topics are in our Free Video Library.

Reusable Grow Medium Blogs

Every post we have tagged for reusable mediums, grouped by what you are trying to do. The full tagged list updates as we publish.

Start here

Crop and method guides

Experiments and comparisons

Growing basics and troubleshooting

Free Guides and Trays

Match the medium to a tray and a seeding rate. Our Free Tray-Specific Microgreen Seeding Guide lists seed amounts by tray type, and the Free Ultimate Microgreen Tray and Kit Guide covers every tray style. For trays, we carry the Bootstrap Farmer 10x20 Shallow Trays, the Bootstrap Farmer 10x10 Shallow Trays, and the 7x14 OTG Microgreen Tray Kit.

Microgreen Tracker

Running several trays on reusable sheets gets easier when you log each one. Microgreen Tracker records each tray from seeding day to harvest, including seed weight and notes, so you can write down which medium and hole size you used. It also includes an automatic seed density calculator, and it comes with a 7 day free trial. Try Microgreen Tracker Free.

Reusable Grow Medium FAQ

What is a reusable grow medium for microgreens?

A reusable grow medium is a washable mesh sheet that sits in a microgreens tray in place of soil or coco coir. Seeds rest on the mesh, roots grow through it, and after harvest you clean and sanitize the sheet and use it again.

How many times can I reuse a silicone grow medium?

The 1.2mm silicone medium is rated for 20 to 30+ grow cycles per sheet with proper cleaning and flat storage. Commercial use may need more frequent replacement. The 1.7mm version lasts months of continuous use with proper care.

Should I choose the 1.2mm or the 1.7mm medium?

Choose the 1.7mm for large seeds such as sunflower, pea, melon, and wheatgrass, and the 1.2mm for small and medium seeds such as broccoli, kale, cabbage, arugula, and radish. Small seeds fall through the 1.7mm holes.

Which seeds do not work on silicone?

Swiss chard, beets, and cilantro do not work well on silicone and grow better on soil or coco coir. The hard seed hulls on chard and beets stay attached without a top layer of medium to push through. Amaranth is more challenging and can work at 75F with a heat mat.

Do I still need fertilizer on a reusable medium?

Yes. Silicone is inert and adds no nutrients, so you feed with a liquid fertilizer the same way you would on coco coir. We use Ocean Solution 2-0-3 at 0.5 oz per gallon with pH 5.5 to 6.0.

How do I clean and sanitize a reusable grow medium?

Remove root residue with a scraper, hand wash with warm water and a silicone-safe, food-safe dish soap, then pour boiling water over the sheet or submerge it for 1 to 2 minutes. Let it air dry fully before the next grow.

Which size do I need?

Match the sheet to your tray. The 10x20 medium is pre-cut to 19.65" x 9.5" for standard 10x20 trays, and the 10x10 medium is 9.25" x 9.25" for standard 10x10 trays. The 7x14 medium is pre-cut for the 7x14 OTG Tray Kit, and there are separate sizes for small and large sprouting trays.

Is the silicone food safe?

The 1.2mm medium is food-grade platinum-cured silicone with a fiberglass core, third-party tested for FDA compliance and LFGB tested and compliant. The 1.7mm medium is made differently and has not been LFGB tested.

Is there a warranty on the grow mediums?

Yes. All silicone mesh grow mediums have a 1 year warranty covering manufacturing defects, material failures, and premature deterioration under normal use.

Do you still sell stainless steel grow mediums?

Only in two sizes. We are phasing out stainless steel in favor of silicone, and the 316 grade 10x10 and small sprouting tray sizes are the ones that remain. We no longer sell a 10x20 stainless version.

Is shipping free?

Shipping is free in the U.S. on orders over $65.

Not sure where to begin? Start with the 10x20 or 10x10 1.2mm medium and the compatible seeds guide. The Microgreen Masterclass is there when you want the full walkthrough.

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Affiliate disclosure: the Ocean Solution 2-0-3 and Sprouting Trays links on this page are Amazon affiliate links, and we may earn a commission at no extra cost to you. We only recommend products we use ourselves. Read our full Disclaimer and Affiliate Disclosure.

Product disclaimers: please review our Reusable Grow Medium Safety Disclaimer before purchasing. Reusable grow mediums are inert and do not add or remove nutrients, and we make no claims about the nutritional content of microgreens grown on them. Replace a sheet if you see tears, deep cuts, or significant wear. Trays, seeds, and other items shown in product photos are not included. Our results come from our own grow space, and your results may vary with your environment, seed, and setup.

Happy growing!