The last time I wrote about microgreens, I described how to grow them in potting soil. What you didn’t see was me making a huge mess in my kitchen. I accidentally bumped my container, which sent the mix flying across the table. (And FYI, wiping it with a sponge just makes it worse. Ugh!)
Potting mix is wonderful for producing healthy plants. If you’re accident-prone like me, however, you might wonder can you grow microgreens without soil?
Fortunately, the answer is yes. Microgreens are harvested so early in their development that they don’t need soil or even nutrient solution. This makes them ideal if you don’t have the space for bags of potting mix and prefer not to deal with the cleanups.
So now that you know you can grow soilless microgreens, what type of growing media (growing medium) should you use? (By the way, “growing media” or “growing medium” is the material that your plants grow in.) Some types of media work better than others, depending on the microgreen you’re growing.
In a simple setup, you can grow hydroponic microgreens using a grow pad or growing mat. These types of media are made of soilless materials, such as jute or wood fibers, and they’re designed to hold moisture as the microgreens grow on them.
Which Microgreens Grow Best Hydroponically?
Many microgreen varieties work well in a hydroponic growing environment. Here are some examples:
- Curly Cress
- Salad Mix
(You can download these microgreen cheat sheets for more examples and growing tips.)
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Growing Microgreens Without Soil Step By Step
Here’s an example of how you can grow microgreens without soil using hydroponic grow pads.
- Microgreen seeds that can grow hydroponically (certified organic, non-GMO)
- 2 Plant trays (one holds the growing tray and the other acts as a blackout cover)
- Growing tray (has holes in bottom and contains your microgreens)
- Hydroponic grow pads
- Spray mist bottle
- Optional: Grow light like T5 fluorescent or LED (if you don’t have a sunny, indoor area)
- Alternative: This hydroponic microgreen kit has everything you need (except the grow light) so you don’t have to buy all your supplies separately.
Pour water into your plant tray (the solid one). As a reference, I poured 1 cup of water in this 10×20 tray.
Put your grow tray (the one with the holes in the bottom) inside the solid tray.
Add a grow pad to your tray. Wait a few minutes as the water starts wicking up from the bottom and dampening the pad. The whole surface area of the pad will be wet when it’s ready.
Densely plant your seeds so that they cover the surface area of the pad, but don’t overlap each other. Use a spray bottle to spray your seeds with water and help them settle in.
Add your remaining tray to the top so that it covers the seeds. This extra tray helps keep the humidity in and creates a blackout environment that seeds need to germinate.
Going forward, mist the tops of your seeds every 12 hours. In general, microgreen seeds germinate in about 3 to 5 days.
After Seeds Sprout:
Give your microgreens at least 8 hours of light each day. This light can be from a sunny windowsill (if you have one) or use a plant grow light.
Continue to water your plants only if the pads are no longer damp. To do this, pour water in the bottom tray and then swirl it around so the moisture distributes evenly. Be sure to pour out any leftover water after the pads are wet.
Microgreens are typically ready to harvest around 10 days. Use clean scissors to cut them off the grow mat. You can compost the used mat.
Growing Microgreens On Paper Towels
In the event that you don’t have grow pads, you can use paper towels instead. Using towels is effective if you’re growing in small containers and plan to grow microgreen varieties with shallow roots like lettuce and arugula microgreens.
Here are some things to keep in mind:
- It’s best to use paper towels without chemicals like dyes and fragrances.
- Don’t let your towels get sopping wet because too much water encourages mold. You can dunk the paper towels in a bowl of water, then squeeze them so that they are damp and not dripping wet.
- Use a few layers of paper towel to line the bottom of the growing container.
The growing process is the same as when using grow pads. Again, be sure to check daily that your towel doesn’t dry out.
Around the 3rd day, you should see germination. Somewhere around the 5th day is when you can remove the cover and start giving your microgreens light.
If your growing container doesn’t have holes so that you can water from the bottom, use a watering can to pour water into the tray. Alternatively, you can gently mist the towel with a spray bottle.
Generally, you can harvest your microgreens around day 10. Gently pull them off the paper towel or cut them off with scissors.
Can You Grow Sunflower Microgreens Without Soil?
You sure can. In my experience, sunflower microgreens grow really well in coconut fiber (coco coir) because it gives the roots plenty of room to grow.
Coconut coir is a natural, organic fiber that comes from coconut shells. I really like using it for microgreens because coir has good water retention and airflow and it works just like soil. You can get coconut coir in solid puck form and then soak the disc in water to expand it.
Before planting, you’ll want to soak your sunflower seeds anywhere from 8 to 24 hours. This helps soften the seed shells so that germination is easier.
When growing sunflower microgreens without soil, it helps to put a weight on top of the blackout cover (the container that goes on top to block out light). This helps knock off sunflower shells as they grow, and makes it so the roots anchor into the coir better.
In general, sunflower microgreens germinate in about 2 to 3 days. You can expect to harvest them between 12 to 14 days.
Growing Microgreens Without Media
So what if you don’t have hydroponic grow pads, paper towels or coco coir? As we saw in 2020, many of these items became a precious resource.
Turns out you can grow micro greens without any media. I came across this Reddit thread where the poster uses an inner mesh tray for larger seed microgreens like pea shoots, wheatgrass and mung beans.
The idea is to use seeds that are bigger than the mesh holes so they don’t fall through to the bottom tray.
I haven’t tried this method yet, but I plan to. It’s good to have a variety of growing methods on hand if supplies run out!
As you can see, there are many different ways that you can grow microgreens without soil. You just need to pick a growing medium that can support the varieties you want.
Some may question whether it’s better to grow microgreens in soil or water, but I say do what works best for you. I’ve grown microgreens in soil, using hydroponic grow media and in growing kits. Soil typically produces a better harvest, but I still get plenty of microgreen herbs, vegetables and even edible flowers by growing them hydroponically.
If you ever decide you want to try soil, here’s a step-by-step tutorial on growing microgreens indoors. You’ll have a very nutritionally-dense vegetable and herb harvest no matter the method you choose. Happy growing! 🙂
- Pour water into your plant tray (the solid one). As a reference, start with 1 cup of water in a 10x20 tray.
- Put your grow trays (the one with holes in the bottom) inside the solid tray.
- Add grow pads to your trays. Wait a few minutes as the water starts wicking up from the bottom and dampening the pads. (The whole surface area of the pad will be wet when ready.)
- Plant your seeds -- densely --so that they cover the surface area of the pad, but don't overlap each other. Use a spray bottle to spray your seeds and help them settle in.
- Add the remaining tray to the top so it covers the seeds. This top tray acts as a blackout cover and helps keep the humidity in.
- Mist the tops of your seeds every 12 hours. Germination usually occurs in 3 to 5 days.
- Continue to water your plants (after germination) only when the pads are no longer damp. Further, give them light (either from a sunny windowsill or a plant light) after they sprout.
- Harvest your microgreens between days 10 to 14. Use clean scissors to cut them off of the grow mat. (You can compost the used mat.)
- Some microgreens with hard shells, such as sunflower seeds, need to be presoaked before planting. You can find this information on the seed packet, or download these cheatsheets for more help.
- Never let the hydroponic grow pads get dry. Before germination, mist about every 12 hours. After the seeds sprout, continue to mist whenever necessary.
- Microgreens need at least 8 hours of light a day after they germinate. If you have a plant light, you can increase this time, such as 12 hours, for even better growth.
- If using a plant light, be sure to check the manufacturer's recommendation for height. A T5 fluorescent can usually sit a few inches above the tops of your microgreens, while an LED may need to be higher.
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