Love baby greens but hate when the frost and deer kill them? We found a simple solution that can be done anywhere. Here’s how to grow lettuce in a mini green house!
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Grow Lettuce in a Mini Green House
The Inspiration
The idea to grow lettuce in a mini green house comes from the Roots & Refuge YouTube channel where Jess teaches viewers how to grow lettuce directly in potting soil bags under a clear tote. It is a fantastic video that is incredibly useful! No matter how new or old you are to gardening, it’s a great way to grow greens all winter.
But if you’re like me and must battle droves of hungry raccoons who could easily yank a plastic tote off your bag of delicious baby greens, here’s a long-term solution. We upcycled an old glass window, utilized some pressure treated 2×4’s (sawed in half long ways to make 1×2’s) and some scrap pressure treated fence planks to create a miniature green house perfect for growing winter greens! Even better, the window lid is heavy enough that raccoons can’t lift it.
Our Upcycled Window Cold Frame
We began with an old window with all 6 panes of glass still in place (albeit one was cracked) for the top. This determined the size of our mini green house. I knew I wanted to grow greens in a bag of potting soil so we had to use a window that was a minimum of 24 inches on one side so a standard size bag of soil would fit. Our 31 x 28 window ended up fitting two bags of soil side by side, with room to spare.
Building the mini green house, properly called a cold frame, took my talented hubby one Saturday and then a second day for me to paint it. He added all the hardware once the paint was dry. To attach the frame pieces at the corners, he uses this Kreg pocket hole jig kit. (It is well worth the investment as it gets a ton of use! Making clean, square corners has never been so easy.)
Use Any Potting Soil in a Bag that Fits Your Cold Frame
Most potting soil comes in bags that are roughly 15-16 inches wide by 22-24 inches long, not including the top flap. They contain 1 cubic foot of soil. This is all you need to grow baby greens for a family of 3 to have a salad every ten days or so if you harvest the outer leaves in cut-and-come-again fashion. You’ll also enjoy a steady stream of sandwich lettuce picked here and there as needed each week.
Getting Ready for Planting
When you’re ready to plant, use a Phillips head screw driver to punch holes in what will be the bottom side of the bag so water drains and doesn’t drown your lettuce seedlings. I tend to punch holes in the decorative front of the bag because the back of most soil bags have centered graphics inside of a border. That border can serve as a cutting guide for making a nice rectangular cut later.
After you’ve punched drainage holes in the bags, place them drainage holes down inside the cold frame. Press and wiggle the bags into place so they lie flat and smooth.
My cold frame is on our deck for a few reasons. 1) Our grass will continue growing in Texas through December and I don’t want to have to move the frame to weed eat the grass under it. 2) Lettuce needs good drainage and we are entering our rainy season where soggy ground might not let the bags drain. 3) Fire Ants would love to turn the entire thing – bags of soil and all – into a giant mound of misery. 4) The deer. I never know what those hungry brats are going to figure out how to get into but they avoid the deck. The deck slats that allow for drainage, the deck height and lack of ants makes this the safest spot.
Cut a Rectangular Planting Area
This is the trickiest step. You need to cut out a rectangular section of the bag plastic in which you can plant. Cut too much and the sides of the bags will collapse, spilling soil which will wash away with each watering. Cut too little and you won’t be able to grow as many greens. Again, the centered back graphics are generally helpful. I began my cuts with a box cutter then used scissors to make them as straight as I could.
Ready the Soil
After removing the plastic, you’ll see the soil is pretty compact. Simply use a hand rake or hoe – &- cultivator to very gently loosen the top surface of the soil. This will help the tiny lettuce seeds get the foothold they need.
Select Your Seeds
Now it is time to select the seeds for what you want to grow! I’m using up some lettuce seeds and salad seed mixes I already had by blending them into one huge mix that I’ll sow for baby greens.
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Tatsoi (sweet Asian green)
Sow Your Seeds!
I sowed about 1 tsp of lettuce seeds in the right hand garden soil bag. This was a generous covering and I’m wanting very closely packed seedlings that I can use for baby greens. For the Tatsoi I used 1/4 tsp for the entire left bag, evenly scattered, to allow the plants a bit more room.
Water in your tiny lettuce seeds very, very carefully using a seedling watering can with smaller rosette holes. The gentle watering will shift the seeds into the soil. It is not necessary to cover them – lettuce seeds actually need light to germinate.
Now We Wait!
After watering, wait 7 to 14 days for your seeds to germinate. Keep the soil moist by watering a little bit every 2-3 days as needed but do so lightly as lettuce seeds don’t like a lot of moisture.
Since I planted my seeds on a hot, late September day, I had to use a block of wood to prop the cold frame open to encourage airflow. Otherwise the greenhouse can act as a sun oven and roast your seeds. The frame can remain propped open until seedlings are growing and the temperatures drop.
If you’ve wanted to try growing baby greens, hopefully this post helps you to grow lettuce in a mini green house of your own. You can typically grow an entire season’s worth for the price of 4 bagged salads – a real bargain if you end up getting 6 months of harvest (November through April) from your cold frame!
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