We have all seen the mini greenhouses in the garden centers – seed trays with a clear, plastic cover that is often so flimsy it doesn’t last much past the essential time period needed to get those seeds off to a good start. The seed trays often have a longer lifespan than the cover, and this is ok, to a point, because there are other ways we can recreate the greenhouse effect. I have found some success in storing the clear cover inverted underneath the seed tray as the tray is still in use (as they are often purchased), which prevents it from being in the way, however it doesn’t last very long even when stored that way because it is such thin plastic.
First let’s discuss why a cover is necessary for starting your seeds: A clear cover over the top of seeds just started helps retain moisture and heat that will keep the top layer of the seed starting medium favorable for new seedlings to emerge, and provide a beneficial atmosphere for the new seedling to grow. Without that cover, the seed starting medium can develop a crust, making it hard for new seedlings to emerge, and the environment that it sprouts into can be cold and unwelcoming. Some seedlings are more sensitive than others, but it’s generally a good idea to provide some sort of a cover until the seedlings have sprouted, especially if you are starting the seeds somewhere in your home that has varying temperatures and/or dry air.
If you are in need of a makeshift cover, in years past I have put the seedling trays or containers in plastic bags and tucked the ends under the tray, and I have also laid plastic wrap over the top of the containers and it is lifted as soon as I notice seedlings starting to sprout. Poke some small holes in the cover so developing seedlings can still breathe. After seedlings have begun to sprout, I often remove the cover all together, however some seedlings will benefit from continued covering until they have grown a little more. For plastic coverings that need to be raised off the surface of sprouting seedlings, I have inserted popsicle sticks or similar materials around the corners and some supports on the inside to lift the plastic off the surface of the seed starting medium.
Are seed starting trays with the plastic domes necessary? While they are helpful, they are not vitally necessary. There are other containers that will offer the same benefit, that you may already have laying around your home.
Salad trays, rotisserie chicken trays, berry containers, and other takeout containers that have a solid-bottomed container with a clear top will work perfectly. You may need to add some holes at the bottom to allow drainage and in the top if it is not already vented. You can also use a milk jug or plastic pop container with the label removed. Cut the containers in half leaving them connected on one side so you can insert your seed starting medium and seeds, then close the container again. You may want to tape the container together on the opposite end to keep the top end from lifting.
Another way I have made mini greenhouses is by buying the $1 plastic shoe boxes at the dollar store and drill a few air holes in the box, then use the lid as the tray that holds the seed starting containers and set the box over the lid.
In what ways have you made an “unconventional” mini greenhouse? Feel free to share what has worked for you!