Regarding the use of newspaper and cardboard, both can be useful materials used in organic crop production to eliminate weeds, retain moisture, and add organic matter to your soil. There are two kinds of inks used to print paper and cardboard: vegetable dyes and colored inks. If you've recently moved, there's something fun you can do with all those cardboard boxes besides filling up your recycle bin. Reusing cardboard for the garden provides compostable material, kills annoying weeds and develops a bountiful harvest of earthworms.
Cardboard in the garden will also kill the lawn and help you prepare a new bed for vegetables, ornamentals or whatever you want to grow. Keep reading for more cardboard garden ideas. You can cover your paths with old cardboard, but definitely check if it's printed with ink. If it is, you should make sure it only has black ink.
Most black inks are made from soybean oil. Use the material only for the paths. Paper and cardboard printed with color ink is another matter, as this ink may contain some toxic heavy metals. Avoid using cardboard or paper as mulch if it contains colored ink.
Of course, if your cardboard is more than dirty and has absorbed oil or other chemicals, it probably shouldn't be distributed on the floor. Whether it's used as mulch to prevent weeds or use it around the stem of plants to keep pests out, cardboard can be very useful in a garden. Many gardeners build raised beds on their lawns and cover the bottoms with cardboard to suffocate the lawn, a technique that allows you to fill the beds and start working in the garden right away. Another idea for reusing cardboard for the garden is to place pieces of cardboard around plants in areas prone to weeds.
If you are going to make a layered or lasagna garden, make sure to moisten the cardboard first before covering it with organic material or mulch. According to the National Center for Appropriate Technology, “The building blocks of corrugated cardboard appear to be relatively benign. The most common use of cardboard in the garden is to use it to start a new bed, called leaf padding. If you are planning a layer or lasagna garden, make sure to moisten the cardboard first before covering it with any organic material or mulch.
Gardeners have different opinions about using cardboard in the garden, but certified organic growers can use what I call “clean” cardboard: smooth, unwaxed boxes with all tape and adhesive labels removed, with minimal printing on the outside. As long as you use organic plain brown cardboard without heavy color prints, it's safe to assume that yes, cardboard is safe for organic gardening. Moisture keeps the cardboard in place and is important for both gas exchange and microbial life in the soil. They mistake the box for a safe haven, they crawl inside and are easily shaken in a container of soapy water on cold mornings.
For a nice gift idea, ask the children to paint smaller cardboard boxes and fill them with dirt and colorful flowers.