I have had an issue this year with several of my dahlia flowers being abnormal. These are on plants that grew from tubers that I overwintered from plants I grew last year, and have grown these varieties for several years with regular looking flowers on them. This year I used fresh potting medium in my containers, and have been growing in these types of containers successfully for at least a decade.

It's not every flower on each plant, but it does seem to be that majority. Specifically, my collarettes have a double row of petals. 'Appleblossom' is super yellow, with very little of the pink. 'EZ Duzzit' is very red and yellow instead of orange and gold. 'Giraffe' has very little horizontal barring on the backside of the petals, with lots of vertical striping instead. 'Steve Meggos' and 'Vassio Meggos' aren't creating the nice globe shape with the petals folded back to the stem, while 'Louis Meggos' is.

In contrast, I have varieties that are just rockin' it. All my waterlily and formal decorative types, as well as my only single.

Anyone have any suggestions for what could be causing these odd flowers? My guess is some kind of stress, but not sure which (chemical, heat, fungal, etc.), so I don't know how to prevent it in the future. Thanks for the help!

I love growing dahlias but they can seem very temperamental at times. Odd shaped blooms or lack of blooms can be caused by many things with weather related issues often being right at the top. Heat can be a huge factor as can the lack of rain. Insects can cause unseen problems. Last year I had one bed that was my worst producer ever. I wouldn't have known it was infested with thrips and aphids if I hadn't put out some yellow sticky strips among the plants. In a short period of time the strips were literally covered with bugs. These insects can sap the life out of a plant.

You might also want to have a soil test done. Sometime certain minerals can become depleted from the soil. Some can be trace minerals that we don't often consider. Tests are worth the cost if done by a quality lab.

This time of year, I always get some odd shaped blooms. I think most of that is caused by the sudden change to cooler fall temps and less sunlight. Many blooms are also smaller now.