Geranium Guide

How to Prevent Damping Off in Geranium Seedlings


Planting geranium seeds can be an exciting event, but damping off in geranium seedlings can really put a dent in the whole process. For those who have never heard about this, damping off in geranium seedlings is a condition that causes young seedlings to becomes diseased and die. What is hard to accept for many geranium lovers is that there is really nothing that can be done once the seedlings are affected by damping off.  The death comes quick with little time for intervention. However, the good news is that knowledge is power and you can take several steps to prevent your geranium seedlings from being affected by this devastating condition.

Causes of Damping Off

Damping off is caused by several varieties of fungi-like organisms. As in geranium root rot, the fungi-like organisms are attracted by moisture.

On top of moisture, fungi are attracted to cool, wet weather, and therefore seedlings planted directly in the garden are susceptible to damping off if the seeds happen to be planted when the soil is cooler than their optimal germination temperature (in geranium seeds, optimal soil temperature for germination is 70-75 degrees).

Generally, it’s impossible to avoid fungal spores altogether. Unless you work in a vacuum, fungal spores are everywhere. Even when you think you are operating in sterile conditions, a spore may manage to make its way through.

The bright side of things though is that spores tend to lie dormant until they are provided the right conditions for them to thrive. So the secret to preventing damping off in geranium seedlings is denying the fungal spores the ideal habitat that allows them to take over and thrive.

Symptoms of Damping Off in Geranium Seedlings 

Damping off effects of geranium seedlings may manifest in their leaves, stems and roots. Symptoms include seedlings that never manage to emerge from the soil or in growing seedlings, wilting and the presence of mushy leaves that may be discolored or brown.

Stems may appear thread-like causing the seedlings to fall over (keeling over). Sometimes a cob-web like growth may be seen on certain parts of the seedling. In any case, the end result is always the seedlings falling to the ground and never growing back up. Sadly, it is very difficult to get the seedlings to recuperate past this stage, and as mentioned, prevention is worth a pound of cure when it comes to damping off of geranium seedlings.

Preventing Damping Off in Geranium SeedlingsHeat Mat for Geranium Seedlings

There are several precautions you can take to prevent your young geranium seedlings from being affected by damping off. One important step is using sterilized growing medium; however, as mentioned, consider that even though sterilized, fungal spores can  still make their way to the growing medium either from the seeds themselves or the tools you are using (pots,trays etc.).

Fungal spores may also introduce themselves through water and wind or the presence of diseased plants nearby.

Fungal gnats have been reported to be capable of also transferring disease-causing fungal spores.  So it’s best to sterilize pots, tools and trays with a solution of 10 percent household bleach to at least reduce the chances for contamination.

The use of a heating mat for geranium seedlings can also come handy as it can help maintain the temperature of the soil warm enough to prevent the coolness that attracts fungi. Ideally, the mat should be kept at 70 -75 degrees. A thermostat can help in maintaining these ideal temperatures.

It’s also a good idea to ensure the soil stays moist, but not soggy. Once sprouted, seedlings should be placed off the warming mat and out of the dome if using one. When watering, it’s best to use warm water (around 68 to 77 degrees). Fertilizers should not be used at least until the seedlings have grown to have several true leaves.

Seedlings do best when they receive about 12 to 16 hours of light, ideally from a grow light as the light from a window is often not enough. A fan may help increase circulation of air and bottom watering may be helpful. And when using pots, don’t forget that they should have sufficient drainage holes!

For how long are seedlings vulnerable to the effects of damping off? According to the University of Minnesota, once the plants are equipped with mature leaves and a well-developed root system, they should be strong enough to survive the pathogens associated with damping off.

Did you know? Some gardeners use a solution of chamomile tea or diluted three percent hydrogen peroxide to prevent damping off. Generally, 1 teaspoon of 3 percent hydrogen peroxide to two cups of water is sufficient. A too concentrated solution may kill the seedlings. For the chamomile tea, a weak solution should be used to bottom water. Some gardeners like to sprinkle the soil with powdered cinnamon or turmeric. In a study, cinnamon was found to have antifungal properties.  And some others will whirl a garlic head in a blender and add a bit of water to obtain a mush. Then a quart of water is added and the solution is kept in a jar for about two days. Then the water is separated from the garlic and used to spray the plants.

” The antifungal effect of twenty powdered spice plants and their extracts at concentrations of 2, 4, 8 and 1, 3, 6%, respectively was evaluated in relation to the radial mycelial growth of various soilborne fungi causing damping-off disease. High significant inhibitory effect on radial fungal growth was observed for different concentrations of carnation (Dianthus caryophyllus), cinnamon (Cinnamomum burmannil), garlic (Allium sativum) and thyme (Thymus vulgaris).”~ Journal of Plant Protection Research


  • University of Minnesota Extension, How to Prevent Seedling Damping Off

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