Soda bottles excel as mini greenhouses to counter cool spring temperatures and autumn frosts. Seeds and seedlings go out in garden beds and planters as normal. Bottles with the bottoms removed are placed over the plants neck-up, nestled just slightly into the ground or pressed in a couple of inches if wind is an issue. If manpower is available and inclined, the lids can stay on overnight and be removed in the morning. Otherwise, small holes can be punched or drilled around the middle of the bottle to allow for airflow.
With the bottles over the plants, not as much rain will get through. Also, baby plants may very well be shooting roots out to the sides near the surface. The most vital part of roots are on the extreme tips, so caution should be used in placing jugs. If plants are going out with the intention of extending the season with mini greenhouses for more than the first couple of weeks, consider “planting” a ring of cardboard, thick fold of paper, or even rings of other soda bottles right at the surface. Plants will be inclined to grow downward once they hit those and the soda bottle cloches can go outside the rings, eliminating the risk of root damage. Milk jugs can also work but due to the darker plastic, more light will be filtered out so they’re better for overnight.
The effectiveness of the mini greenhouses can be increased by reusing a few other items. Black plastic trash bags or garden liner, old ratty green military blankets, dark tarps that have been ripped, and any other dark material laid out beside and around the plants and jugs will absorb solar energy. They will help warm the soil faster and help hold heat through the first part of the night.
Bottles filled with water will absorb the sun’s rays. Water’s properties means it will hold onto the heat it collects, releasing it slowly through the night. Painted a dark color they will absorb even more heat. If left clear, light will be able to pass through them. It’s most effective when water-filled bottles are under a cover with the plants – a white sheet or clear shower curtain propped up with dowels or even clear and white plastic trash bags with old wire hangers bent to prop them up off the plants. The outer shell helps insulate the plant and warmed bottle from the chillier outside temperatures. Any container can be used this way: milk jugs, cans, even old jars with chipped threads or rims. Just leave enough room for water expansion in the heat of the day and during hard freezes.
Floating row covers have multiple uses. They can prevent cross pollination if trying to avoid hybridization and they can limit insect infestations. The same can help protect delicate flowers from heavy storms if plants are small enough. Tents can be constructed over plants to avoid setting back harvests because fruit hasn’t yet set as well.
One of the greatest benefits of row covers is frost protection. Clear painting drop cloths, white sheets, transparent one-use ponchos with a hole that was repaired, white trash bags, old curtains, and even discarded mesh from storm doors and windows can be used to create a row cover. Plastics create the most effective mini greenhouses. All of them can be propped up with any spare lumber, old baseball bats, spare tool handles, faulty umbrella handles, or canes from around the house, plus antennas and chunks of automotive parts from the local junkyard. Pallets collected from Craigslist and pruned tree limbs can also be hacked apart and used as framework and supports.
They are made even more effective against frost protection by using them with bottles of water that have been sitting in the sun. Bottles also mean pinning isn’t absolutely necessary for the row covers – the bottles sit on the edges during the day, then are tucked inside under the edges in the evening. Moving the bottles isn’t necessary for clear plastics, but true cloth row covers will limit the amount of sunlight that reaches those bottles even though they don’t overly bother the plants’ abilities to photosynthesize.
White shirts and pillowcases can also be used in conjunction with black-painted bottles, with the heat sink placed near the stem and roots of the plants, some sticks, dowels, stakes, or bent wire hangers used as supports, and the cloth draped over them.
Jugs, bottles or jars can be used to turn any section of yard or raised bed into a cold frame. Clear or pale green bottles are most effective because they allow light to penetrate through the sides. A mix of bottles where every-third or every-fifth bottle is painted a dark color or covered with dark material will increase the amount of heat absorbed through the day while leaving areas for light at low angles to penetrate and give young plants a boost. Thick layers of mulch can also help insulate the ground and roots from light freezes, but bottles have to be placed so at least half of them stays exposed to absorb solar energy.
If one side of the frame is somewhere it wouldn’t block much light, anyway, such as near a building or under a shrub, darker bottles can line that side, absorbing light from the other side and heating the water inside the bottles more, which provides more warmth to disburse later.
Tall juice jugs and 2-liter soda bottles tend to be most effective because they’re taller. They trap more air inside and can be used longer and for more plants as seedlings grow, and are tall enough to keep lettuces and small cabbages going throughout winter in some of the milder regions of the country.
The frames are easy to construct. Select a section of yard or garden bed, fill jugs with water, and “plant” them neck-down to form a level wall. The bottles will need to stick up at least six or eight inches for most seedlings. Small spaces – three and four-foot squares or 2x6-foot rectangles – tend to be easier to work with. Once the bottles are level, the cold frame cover is constructed.
For ease of managing plants and watering, it should be maneuverable. Dowels, yard sticks, or pruned tree limbs can be tied or screwed into a square with an X cross section, then covered with an old, translucent shower curtain (try to avoid blue and red because they’ll reflect away more of the light wavelengths that plants make the most use of; green is fine as long as some light will pass through).
Clear plastic or re-purposed glass or windows are most effective, but floating row covers are regularly used to extend growing seasons and are lightweight, puckered cloth. It’s most important that plant leaves not touch the cloth, because they’ll be exposed to frosts and also susceptible to water damage. Once the top is constructed, it can be laid so it sits on the soda bottle “ledge” that was formed, then braced down with a couple of bricks, another few water-filled soda bottles, or simply tied in place.
Plants under cold frames constructed of plastic won’t be getting much water and plants under row covers aren’t available for pollination, so they’ll require checking on.
Non-bottle material sources
Shower curtains, painter’s drop cloths, and other material can be found at low or no cost at websites like Freeecycle and Craigslist, and at Goodwill or Salvation Army. If there is a sorting depot nearby, stop in and introduce yourself. Most thrift stores poke through donations and discard items that are in poor condition, so white dress shirts with stains on the collars and sleeves, white sheets and white pillow cases with holes, and mildew shower curtains may be available for free. If they have your name and number, most would be willing to pass them along since they would just be discarded, but it takes some regular checking and friendliness to make the contacts.
Thrift stores, flea markets, and websites like Craigslist or trader sites can also be good places to score aquariums that can be hacked apart for cold frame panels, cribs and playpens that can have the bottoms removed and be flipped over as framing, and for old shelving that can also be used in constructing the cold frame cover.
Local window repair shops will either have or know where chipped, cracked and imperfect pieces of glass can be obtained, usually for less than purchasing them new. Also stay aware of the neighborhood and rehabilitation of downtown homes. Renovations commonly mean newer, more efficient windows, which means somebody is getting rid of the old ones. Sliding glass doors and storm doors can also make good cold frames – and be stacked up to eventually build a “real” greenhouse. Construction and renovation companies can also be good sources for clear plastic and white drop cloths and painting drapes.
Plastic bottles in the garden and elsewhere
Soda bottles are pretty useful, sadly. Since they’re safe for storing grains and beans in reasonable portion sizes, diverting them to the garden may not be a top priority. Tall, clear plastic bottles are best for the cold frames, but milk jugs will also work. Some light will penetrate the slightly transparent versions. The opaque jugs will block more light at the low angles the sun travels in winter, leaving the frame only receiving strong light in the midday hours. Tall “Arizona Tea” type jugs can also work.
Water bottles with short caps that aren’t appropriate for food storage can be used as heat sinks around plants, but will work best if set up in trios and foursomes – the skinny bottles will lose heat faster and be less effective than larger bottles, something that holds true for peanut butter jars and jelly jars as well. Water from the bottles that were used as heat sinks can be doled out to the garden during warmer, dryer seasons, but water from milk jugs should not be consumed by humans or animals because of leeching potential.
As we all try to be a little more self-sufficient, growing becomes a major focus. We can grow more by extending our growing seasons a little. Reusing items that would otherwise be thrown away can be a great way to accomplish that goal without also extending the costs of preparedness. We just have to look at things in a new light.
The PL forum has an entire topic thread on re-purposing items. “Reusing things for prepping” can be found under the “General Preparedness Discussion” category. Additional garden tips are available there, as well as other ways to make use of everyday household goods and “trash” in new and creative ways. Pop over to share in the collective knowledge and share your own tips.