Did you know that in New Orleans, the average annual humidity percentage is a whopping 73 percent? Let's hope your humidity dome is keeping your plants just as moist - but on a much, much smaller scale.

Here are two reasonably common scenarios. Two weeks after planting, your sprouts didn't come in. Maybe a few days of trying to clone your plants yielded nothing but dry soil and no roots. If you're wondering why they are not growing, you may need a humidity dome to make cloning and germination successful.

This small part is a crucial component to ensuring your plants grow quickly without emptying your bank account. If you're not sure what a humidity dome is, fret not -- we're here to walk you through every step of the way.

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What Is a Humidity Dome?

What Is a Humidity Dome

In layman's terms, a humidity dome is a piece of plastic which sits atop propagators and seed trays. It is domed to allow seedlings to grow tall. It is plastic, due to the low cost and flexibility. The dome is meant to raise the humidity and temperature levels inside. The ideal temperature for successful germination is between 50 to 65 degrees Fahrenheit.  Humidity domes are mostly for indoor use because most homes are not this warm. Having a humidity dome will control and stabilize the temperature and humidity for maximum growing.

Introduction to Cloning

Introduction to Cloning

Propagators are a little different from seed trays. The purpose of propagators is to generate roots while a seed tray is to start growing small seeds into plants (i.e., tomatoes). Cloning involves cutting a branch from the "mother plant" and planting it. There are a few planting options such as deep water cloning, aeroponic cloning and propagator cloning using Rockwool. Basic propagator kits have a deep base, a tray to hold the cutting, and a humidity dome to regulate humidity levels and temperature.

Add-ons for Your Propagator or Seed Tray

Add-ons for Your Propagator or Seed Tray

While there are plenty of propagator and seed tray kits, you may wish to purchase other products to speed up the process. A lamp is one extra in which you may choose to invest. This external lamp will do two things: stabilize temperature and give the plant the red and blue waves it needs to grow. These lamps are particularly useful if temperatures fluctuate in your home and your plants require a particular (and stable) temperature to develop. Additionally, they provide the correct kind of light for your plants to grow should you be unable to place them near sunlight.

Another item you may consider investing in is a heat mat. Not unlike heat mats for reptiles to regulate temperature, heat mats also benefit your plants for the same reason. 

Makes and Models

Many manufacturers make propagators and seed trays. We’ll be showing just a couple of seed trays and propagators and exploring their pros and cons.

EarlyGrow 70771 Large Domed Propagator, 16" X 7" X 23.5", Black/Dark...
  • 16 x 7 x 23.5
  • Our largest sized propagator
  • Includes 2 vents in dome lid to control humidity for seedlings

Early Grow has quite a few propagator kits available such as the large 16 inches by 7 inches by 23.5-inch domed propagator, the 24 inches by 15 inch by 12.75-inch propagator, and the three-in-one 9 inches by 21 inch by 6 inches. These three models (as well as many other models from EarlyGrow) are available for purchase at Amazon or in-store retailers including Walmart. Their prices range from high to low depending on the product. For now, we will be looking at the former propagator mentioned: the standard 16 inches by 7 inches by 23.5-inch propagator.

This model is one of EarlyGrow’s larger trays and comes with a dark green or black plastic bottom. It also contains a humidity dome with two vents to control humidity levels. 

Buyers can choose between planting directly inside the tray or purchasing a separate, lighter tray inside. 

Garland 3 x Mini High-Dome Propagators, Green, 13x17x13 cm
  • Quarter-sized, high-domed propagator
  • Shatter-resistant, Crystal clear, high lid
  • Measurements: 13cm high with lid (5cm high without) x 17cm long x 10cm wide.

Garland is a large company which sells everything from wire plant support to weed protection fabric. Within Garland's arsenal are also several propagator models, one of which is the triple mini high-dome seed propagators. They measure 30 inches long, 7.25 inches wide, and 8 inches high. Having three smaller propagators is ideal if you’re trying to clone several plants at once.

The base is sturdy, injection-molded plastic and the humidity done boasts an adjustable vent control. The tall humidity dome allows gardeners to clone plants that require more headroom. Additionally, its slim size means even apartment dwellers can clone plants so long as they have a narrow windowsill.

While Garland does sell products worldwide, obtaining their products may prove a little tricky. Garland is based out of the United Kingdom and lists websites where their non-UK customers can purchase their items. 

National Garden Wholesale Super Sprouter Ultra Clear Vented Humidity...
  • These Excellent Quality 4 And 7 Inch Ultra Clear Humidity Domes Now Have Built In Light Tracks That Accommodate The 18...
  • The Light Tracks Are Directional To Allow The Light To Run The Length Of The Domes Or The Width Of The Domes, Allowing...
  • Vertical Sides Allow The Use Of All Plant Sites In A Propagation Tray

Humidity domes are also used extensively in conjunction with seed trays to raise the internal temperature and regulate humidity. Super Sprouter has a long list of humidity domes and seedling trays. While Super Sprouter sells propagation kits, they do not have complete seedling kits. Instead, the company sells all the pieces separately. This vented humidity dome with a light track, for instance, would work with their 24 cell tray.

With Super Sprouter, every item is available separately. Because you’re only buying what you need, making your own kit with Super Sprouter parts will be significantly cheaper. 

Jump Start CK64050 Germination Station w/Heat Mat Tray, 72-Cell Pack,...
  • UL-listed waterproof heat mat, 17 Watts, 120 Volt, 8.875" x 19.5"
  • 2" humidity dome
  • 11" x 22" watertight base tray

Available both on Hydrofarm’s website as well as online retailers such as Amazon, the germination station has everything you need to start growing your seeds. Included in the kit is a 17-watt heat mat, a 72 cell seedling insert, a watertight base tray, and a 2-inch vented humidity dome.


Humidity domes are a vital part of germination and cloning for any serious gardener. They provide a haven for plants to grow under the right amount of humidity and keep temperatures stable. Without them, your seedlings may not grow, and roots may not develop for when cloning. Whether you’re using a propagator for cloning or a seedling kit to germinate, make sure always to purchase an adequately sized humidity dome as well.

We can't tell you adequately which is best for your situation. But after examining the specifications for yourself, you should have no problem deciding which is right for you.

Last update on 2021-08-04 at 14:25 / Affiliate links / Images from Amazon Product Advertising API


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