Starting seeds indoors is a rewarding way to get a jump on the growing season without requiring specialized, expensive equipment. Using a simple household item like an egg carton transforms refuse into a functional, miniature nursery for your plants. This accessible method offers a practical, low-cost solution for sprouting delicate seeds before the outdoor weather allows.
Gathering Your Supplies
Selecting the right container involves distinguishing between the two common types of egg cartons. Pressed paper or pulp cartons are the preferred choice, as their porous nature allows for air circulation and they are completely biodegradable. Plastic or Styrofoam cartons can be reused, but they require extra steps later since they cannot be planted directly into the ground. You will also need a soilless seed starting mix, which is distinct from regular potting soil because it has a finer, sterile texture to prevent compaction and disease. Finally, gather your seeds, scissors, a pen or marker for labeling, and a waterproof tray or the carton lid to serve as a saucer for watering.
Planting the Seeds
Before adding any growing medium, prepare the bottom of the carton to allow excess moisture to escape. Use a small tool, like a skewer or needle, to poke drainage holes into the base of each egg cup. Proper drainage is important because standing water can suffocate roots and lead to a fungal disease known as damping-off. Next, gently fill each cup with the seed starting mix, which should already be lightly moistened to the consistency of a wrung-out sponge.
Sow the seeds according to the packet instructions, generally planting them at a depth about twice their diameter. Place one or two seeds in each cell, lightly cover them with the mix, and tamp the surface gently. Immediately label each row or section with a small tag or marker to keep track of different varieties.
Nurturing the Seedlings
Once planted, seeds need a consistent environment to encourage germination and early growth. Initially, warmth and humidity are the most important factors, achieved by placing the carton in a plastic bag or covering it with clear plastic wrap to create a mini-greenhouse. Seeds germinate best when the temperature is maintained between 65 and 75°F. As soon as the seeds sprout, remove the plastic cover to increase airflow and prevent fungal issues.
Light then becomes the primary concern, as young seedlings require 12 to 16 hours of light per day to grow strong and stocky. A sunny, south-facing window is often insufficient, so supplemental lighting from a dedicated grow light positioned a few inches above the plants is necessary to avoid thin, stretched stems.
Watering is best accomplished from the bottom. Place the egg carton in the waterproof tray and fill the tray with about a half-inch of water. Allow the mix to absorb water through the drainage holes for 20 to 30 minutes, then drain any remaining excess water from the tray to ensure the soil remains moist but not saturated.
Moving Seedlings to the Garden
The final stage is transitioning the young plants from the controlled indoor environment to the unpredictable conditions outside, a process called “hardening off.” This involves gradually exposing the seedlings to direct sunlight, wind, and cooler temperatures over a one-to-two-week period to prevent shock. Begin with a few hours outdoors in a shaded spot, slowly increasing the duration and light intensity each day until they can handle a full day outside.
The method for planting the seedlings depends on the carton material chosen. If you used paper or pulp cartons, carefully cut or tear the carton into individual cups and plant the entire cup directly into the soil. The paper will naturally decompose, allowing roots to grow freely while minimizing root disturbance and reducing transplant shock. For seedlings grown in plastic or Styrofoam cartons, the plant must be gently removed from its cup before planting, taking care to handle the delicate roots and surrounding soil mass as little as possible.