The Q&A Archives: Indoor Seedlings Die

Question: Every spring I start hundreds of seeds indoors, and every year a percentage of them die when they are still very small. The seem fine one day, then the next day they topple over. What am I doing wrong?

Answer: Generally the biggest problems in starting seeds are either too little or too much moisture. As seeds germinate, they need lots of attention. If the soil is allowed to dry out the little roots shrivel and die. On the other hand, high temperatures, poor lighting and excess moisture can all encourage the fungal disease called damping off, which causes the stems to constrict at the soil line.

Since the damping-off fungus enters the plant at the soil line, you can try this method: Once the seeds are planted, but before they germinate, cover the soil surface with a fine layer of "play sand" (this is sand that has been sterilized; you should be able to find it at a hardware store or lumberyard). This provides a sterile, dry -- and therefore unfavorable to the fungus -- surface at the point the fungus usually enters the stem.

In general, to have better seed starting success, begin with clean containers (disinfect with 1 part bleach in 9 parts water). Use loose, well draining, fine-textured planting medium, preferably a commercial sterile seed-starting mix. Fill the container, sow the seeds thinly, sprinkle just enough potting soil to cover seeds and then mist to moisten. Place the container in a plastic bag and put it in a warm location until the seeds germinate. Then remove the plastic, move into bright light and keep the soil moist but not soggy. Don't crowd plants, and provide good air circulation to minimize disease problems. A small fan blowing in the room, but not directly on plants, will help keep air moving.

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