New gardeners often experience an unfortunate phenomenon called “damping-off,” a fungal disease that is ironically caused by the same warm and humid conditions that promote germination and seedling growth. With damping-off, however, seeds fail to germinate at all or germinate but die shortly afterwards, sometimes even within a matter of hours. If you look closely, you’ll see the roots of the small seedling are dark and rotted and the stems may be dark and shrunken. This is damping-off and it can be both heartbreaking and costly.
Damping-off can occur if the seeds, soil, tools or containers are contaminated with fungal spores. All vegetable and flower seeds and seedlings can be affected, but lettuce, snapdragons and zinnias seem most susceptible. If seedlings are over-watered, overcrowded or too warm or cold, conditions may be ripe for damping-off.
Fungal Control for Damping Off
While there is no cure for damping-off, there are certainly a number of measures you can take to prevent it. One measure is through the use of commercial fungicides. Without going too heavily into the science of it, damping-off is generally caused by one of three types of fungi that live at or just below the soil surface: Phytophthora, Pythium and Rhizoctonia.
To be effective, fungicides must be targeted to the specific fungi, so it’s essential you know which one you’re dealing with. You can often have the seedling tested at your university extension service. Other things to consider about fungicides are that there are many on the market and they often come and go quickly because they’re deemed unsafe or ineffective, and some are just not recommended for home use.
It’s possible to purchase seeds that come pre-treated with a fungicide to prevent damping-off. This is not necessarily foolproof, because damping-off can also be caused by contaminated tools, containers or soil.
Homemade Remedies for Damping Off
Obviously, not everyone feels comfortable about the idea of using fungicide on their seeds or seedlings, so more earth-friendly remedies can be utilized as well, often with ingredients found right in your home kitchen. Some of those remedies include:
- Chamomile: Make an infusion with three chamomile teabags, steep for 20 minutes and then mist your seedlings.
- Cinnamon: A natural fungicide, cinnamon is sprinkled directly on soil to attack soil-based fungi.
- Garlic: Mash several cloves, boil in a little bit of water, cool, and use to water the seedlings.
- Hydrogen peroxide: Use a 3% solution to mist seedlings.
Other Tips to Prevent Damping Off
- Use a sterile potting mix for germination, rather than soil from your garden, which can be infected. You can sterilize your own soil by heating small amounts in an oven or a microwave.
- Use clean tools and containers. These can be sterilized by cleaning them with one part bleach to 10 parts of water.
- Purchase seeds and seedlings from a reputable source.
- Don’t overcrowd your seedlings — leave plenty of room for air circulation.
- To increase circulation around the plants, direct a breeze at them with a small fan, being careful not to blast them.
- Top your potting soil with a thin layer of sand to keep the surface dry.
- Don’t over water your seedlings or leave them sitting in water; wait until the soil is dry or water them from the bottom so they can absorb water as needed.
- Don’t use tray covers, as they increase the humidity level around the plants and encourage disease.
- Give your seedlings plenty of heat and light, so that they quickly outgrow the danger of damping-off.
- Remove any plants or trays of plants immediately if they appear to be infected.