I grew my lemons from seed and I keep them year round in a humidor inside my house. I also am growing roses from seed in an unsealed humidor made of plastic bottles.
Less watering. I water my lemon seedling when I change the size of the humidor which is about every 3 months.
Less plant stress. Hot air either from heating in the winter or an open window in the summer can cause severe evaporation.
No need to wipe dust off leaves.
Why: I live in an area that is 5,000 feet above sea level in a desert where summers reach 100 degrees F and winters dip to -20 F. In the summer humidity hovers between 5 to 10% which is too dry climate. Indoors in the winter heating the house can cause stress to some plants along the hot air's path. For delicate plants like dill I surround them with taller more bushy plants.
How Long? I keep my lemon seedlings in their humidor year round. In the summer I keep them on the floor and out of direct sunlight. In the winter I place them on a table near the window and cover with a garden cover on sunny days to shield for too much sun or surround them with other plants.
Step 1: Let's Begin!
I collect some lemon seeds because I find the fruit so delicious. I placed all of my seeds in a sprouter on the kitchen table because the container is clear and when they sprout I can plant them. If there is trouble like mold growing I can do something about it. If you have other seeds that need chilling time like apple seeds you can keep your apple seeds in the refrigerator in in a zipped plastic bag with moist dirt and in a month or three months later they might sprout.
Step 2: The Plan
A carefully designed indoor garden is what can make it almost carefree. The humidor shields some of the other plants from the indoor winter heating. Place taller, bushier and more heat tolerant plants closer to the window to create filtered shade for other more delicate plants. Place deep lids under plants that don't have a humidor.
I have drawn a plan of a window facing the south side with Danger Zone that is an area that touches the window to about 4 to six inches deep. I have found that carnation with tough leaves seems grow well in the danger zone. A little bit farther is the okay zone, it is sunny and warm if the sun shines. Lemon grass is thriving here. Passion flower seems to do well in both danger zone and the okay area. Lemon seedlings and dill like the Best area which could get morning or evening sun. Even though I carefully chose the location of my humidor some times I toss a garden cover on to shield it from too much sun to prevent the plant from leaf curling.
Step 3: The Humidor
You need to plan for growth. How will you cocoon your seedling in plastic and extend it's size once it out grows the humidor. Kind of like a nesting doll, I choose a 1 liter plastic bottle and a 2 liter plastic bottle. I sliced the smaller bottle in 1/2, drilled a few holes for drainage. I planted my seedling in the 1 liter bottle. I sliced the 2 liter bottle in half. I placed the plant in the larger bottle and sealed the top and bottom of the bottle with tape. You need to seal the bottle so that condensation forms inside the bottle and the high humidity helps your plant grow. Eventually your plant out grows its bottle. If you want to extend the height of the humidor you will need another 2 liter plastic bottle, cut both top and bottom. Cut about 4 to 8 slits about 1/2 deep from where you want to connect. Give your seedling some water, grooming if there any dead leaves. Slide the pieces of plastic together. Stick your plant in it and seal it. If your plant needs a wider container you will need to get crafty and see the container in unexpected places. I bought some plastic Christmas ornaments to add to my collection and kept the container for the plant! I chose a coffee creamer for bottom because it fits inside the container.