Your plants are under insect attack.. Try Neem oil, Soap cooking oil and water.

Thank you for your reply and I will certainly try your suggested remedy. I was wondering, however, why the dandelions would so easily succumb to attack. Could it be that I put too many seeds in the pot? (I mean, I know that I put way too many seeds in, but could that be the cause of their weekness?)

Thanks again.

I wish you could forage in our lawns, where they are florishingly healthy :)

The dandelion are that insects favorite food of your group of plants. I grow weeds in my garden with other plants.
Wild amaranth-------- for striped and spotted cucumber Beatles, the beetles don't touch my melons or squash.

Smart weed -------for Japanese beetles. the beetle pack on the smart weed so thick you have to bag and drown them to save your smart weeds plants.

Be happy you have found a trap plant to protect your other plants and pick your neighbors dandelions.

This is how I found what works.

Grow what grows well and let the farmer grow what doe'st

Saleve,

It wasn't clear to me if you were sowing seeds in a garden or in a pot? This could be white fly, aphids, or just about any insect that likes them. If the remedies suggested by poncirusguy don't work, then you might try some commercial insecticide to get it under control. You may have to forgo using the current leaves and flowers, but at least you'll get it under control. Alternately there are nematodes you can use on it, they'll control the growth of most bugs in the soil leading to less likelihood of insects attacking your plants. This would help you in the next growing season.

I don't know if you're in Geneva, Switzerland or New York, however-

Steinernema Faltiae are the most common type of nematodes to use. Amazon sells them as do other sites. That's US wide.

May I ask how you use the plants? We have an abundance of them all spring and summer here. If I could find a good use for them, I'd be less likely to kill them off. They're very invasive here.

Best regards,
Judy

Looks like foliar thrips? (judging by the damage and black poop all over the leaves.) They can be quite damaging. I'm not sure what will work for them and help keep the plant still edible. You can try neem oil and coating all of the leaves. You'll have to wash it off before harvest though. Systemic pesticides might help, but you won't be able to eat the leaves safely. In the short term you can try submerging the plant in water or neem oil/ water, but again, this might either kill it or render it less edible.

You might be better off tossing and restarting fresh if growing for edible plants.

Personally, I am amazed people buy seeds and cultivate this plant. When I see those seed packets in the garden centers, I always wonder if such varieties are different in some way than the thousands I see growing wild in our area. Are they hybridized to taste better? Do they bolt at a slower rate? Are they less likely to self propagate/ take over a garden? Just wondering what makes it worth buying such seeds vs, harvesting some wild dandelion seeds from outside and growing those. Just curiosity.

Hello fieldofflowers,
Thank you for your reply. Yuck! I didn't realize that that black stuff was poop.

I agree that purchasing dandelion seeds would be silly. My downstairs neighbor maintains an organic lawn and I have always harvested my dandelions there. But this year I thought it would be more convenient to have some pots on my terrace so I planted seeds from her supply of plants. Unfortunately, my plants did not do well. She recently replanted her whole lawn so, for the moment, there's nothing but lush grass...

I suppose I should try to find a plant that is even more attractive to pests than dandelions as I really like them for salad.