Quote from Lee Garden Ninja on 25th June 2025, 11:24 am

Hi @kathysgreenishthumb27

Thanks for getting in touch from the USA! I'm sorry to hear your seedlings are struggling, and I know exactly what the problem is. It's a seedling disease called 'damping off'.

Damping off is a disease specifically found in greenhouses and window sills where plants are being grown in large quantifies closely together. It is this proximity mixed with humidity that can cause a series of pathogens and fungi to decimate your seedlings just as they are starting to find their feet.

The only cure is to thin out the seedlings, ensure better airflow and pot on as many as you can to separate them before the whole lot goes down with the illness. Probably not the news you want to hear, Kathy, but if not, you may lose the lot.

https://youtu.be/DICGT44SMSs

Damping Off: What It Is and How to Avoid It

Damping off is a common problem that affects seedlings, causing them to collapse and die soon after germination. It’s caused by soil-borne fungi such as Pythium, Fusarium, and Rhizoctonia, which thrive in damp, poorly ventilated conditions.

How to Spot It

Seedlings affected by damping off often look healthy at first but quickly wilt and collapse at the base. The stem may appear pinched, thin, or water-soaked at soil level. Sometimes seeds rot before they even sprout.

What Causes It

Damping off is encouraged by overwatering, poor air circulation, contaminated tools or trays, and overcrowded seedlings. Using old compost or garden soil can also introduce fungal spores.

How to Prevent It

Always use clean pots and fresh, sterile seed compost. Sow seeds thinly to improve airflow and avoid overcrowding. Water sparingly and ideally from below to keep the stem base dry. Remove propagator lids once seeds have germinated and ensure good ventilation. Let the compost surface dry slightly between waterings.

A light layer of vermiculite or horticultural sand on the surface can help reduce stem rot. Some gardeners use diluted chamomile tea or cinnamon as a natural anti-fungal rinse, though cleanliness is still the most effective measure.

If It Happens

Remove infected seedlings and compost immediately to stop the spread. Improve ventilation and review your watering habits. In severe cases, re-sow using clean containers and fresh compost.

Do let us know how you get on Kathy!

All the best

Lee Garden Ninja

 

Quote from kathysgreenishthumb27 on 25th June 2025, 4:46 pm

Thank you so much for responding. I don't think I added enough information. My petunias are outside over a foot tall. I planted them outside several weeks ago. They were amazing inside. All my seeds germinated and even flowered in the house. They were perfect when I planted them outside. Large plants covered in beautiful flowers. They are planted among snapdragons, cosmos, ageratum and dahlias. Everything else is fine. Just the petunias are dying. One will wilt and die and then the one beside it does the same thing and so on. It just looks like a disease spreading over my flower bed. Soon I won't have any petunias. I've been gardening for years and this has never happened. It breaks my heart because they are gorgeous, sturdy plants. I thought that maybe it was slugs or earwigs so I got some sluggo plus. I'm hoping it helps. I have also been using neem oil for fungus. OH! And I just ordered 1,500 ladybugs to release in my garden to help with aphids. I'm excited about that. I love ladybugs! Any other ideas from these added details?