How to Use Humidity Domes When Starting Seeds

May 09, 2020 3 min read 0 Comments

Microgreen tray with humidity dome

This article is included in our brand new microgreen resource page.

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Are Humidity Domes Necessary?

Starting up seeds for this year's garden? Here is the lowdown on the humidity dome debate when starting seeds in cell trays or starting a tray of microgreens. Humidity domes are a useful tool to use during germination, often used in conjunction with heat mats.  They help protect the seeds, maintain moisture levels, and create the perfect environment for those seeds to get a great start. While, your seeds will germinate without the help of a humidity dome, using one will increase your germination rates. 

This cuts down on wasted seed and time. Humidity domes are meant to stay on the tray until the first sign of germination, basically once you begin to see the sprout.  After this, remove the dome and start your trays under light, with proper air circulation.  If brought under light too late, seedlings can get leggy. It is important to keep an eye on your emerging seeds during this step.

How Long Do You Keep Seedlings Under Humidity Domes?

While the seeds are in the germination process they require constant moisture.  This is where a humidity dome can save you a bunch of time.  Having to mist trays less often is huge!  Once sprouted, this same humidity can lead to dry off mold, so be sure to get them uncovered once the sprouting begins. Some growers like to wean their seedlings off of the humidity domes by propping them up to allow airflow before fully acclimating them into the outside air.  Sprouted seeds need light and air circulation to thrive at this point. Check out our Microgreens Ultimate Growing Cheatsheet for more information on microgreen germination times.

How Do You Prevent Mold When Starting Seeds using Humidity Domes?

Using domes that have an adjustable vent helps to combat this issue.  You will typically see mold issues if you leave the humidity tray on for longer than the recommended time (germination phase). If any mold occurs during the germination process, it will often disappear once the tray has been exposed to proper airflow and light. It is also very important to clean your humidity domes between uses and only plant seedlings together with similar germination times, ideally the same length as to prevent molding on the first emerging sprouts. Cleaning trays can be done with a basic detergent, a good rinse, and a quick spritz of h202 water.

Try to keep your growing space's humidity levels under 70% and temperatures below 75.  For more on maintaining ideal temperatures and humidity in your germination room, check out this video where Nick & Nathan from On the Acre in Houston, TX discuss the topic at length.

Other Benefits to Using Humidity Domes 

Humidity domes provide protection for your seeds during the germination process.  Have you ever had mice or bugs destroy a newly planted flat? Humidity domes seal up at the edges of the tray to help prevent pests from wreaking havoc on your new seedlings.  Another huge benefit to using humidity domes is for transport of fresh microgreens. In a time of contact free sales, customers welcome live trays of microgreens delivered with a cover and the reassurance that it has been protected during transport. From seed to sale, humidity domes can help ensure better germination, proper protection, and contact free transport.

Lastly, humidity domes can be converted into blackout domes using a non-flaking spray paint.  Blackout domes help germinate certain types of seed, but it also lets you do wildly creative things you probably never thought possible.  

To learn more about that, watch the video below or read our next post, When to Use a Blackout Dome.




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