Growing your own transplants from seeds is a very satisfying experience and can save you money too. However it is not without it’s problems. Just about every gardener who has started plants from seed has a story to tell of watching a crop of seedlings just starting to make good growth then all of a sudden the plants shrivel at the soil line, fall over and finally die.
That is a symptom of a condition known as “damping off”. It also kills newly sprouting seeds under the soil giving the impression of a low germination percentage. The gardener gets the wrong impression that he’s planted a batch of bad seed when in reality it’s damping off.
Damping off is most commonly caused by a soil based fungus called Phythium, but Rhyzoctonia and other species of fungi can cause similar problems. Whatever the case, it is not curable.
It’s an insidious disorder. The seedlings can look sturdy and strong then suddenly,bam! overnight an entire tray of seedlings will be lost.
Most of the time you can avoid damping off by purchasing a fresh bag of sterilized soil-less seed starting mix. Sometimes however, even a new bag of starting mix can harbor the fungus, although that is pretty rare.
When Pythium shows up, it’s probably the gardener who contaminated the mix by using dirty tools, pots, or even the potting bench. All tools and containers need to be scrubbed clean with a detergent. To be doubly sure, the items can be dipped into a 10 percent solution of household bleach.
While all plants can be infected, some species of plants are more susceptible to damping off than others. For example, petunias are quite prone to the infection.
Whenever I start a batch of expensive or hard to find seeds and don’t want to take any chances of losing those precious seedlings, I take the extra step of re-sterilizing the starting mix. Some might say I’m being extra cautious but sometimes seeds are irreplaceable and need all the protection we can give them.
For small amounts of soil, I pour boiling water through a pot of starting mix — then go back and do two additional pours. If you decide to try it yourself, be sure to place the pot in a spot where the water can drain through easily. I like to do this outside on a wire rack rather than in the sink.
This boiling water method has been used by gardeners for a long time and has shown to be pretty effective. Since the entire volume of the soil mix will not reach 212 degrees Fahrenheit — the temperature at which it would be considered sterile — this could be considered more of a pasteurization method rather than an actual sterilization technique.