Dahlia bud not coming out

andre_1990

I started growing dahlias in pots last year in the Netherlands (roughly zone 8a). I grew about 30 varieties in terracotta pots of different sizes. The biggest pot was 27cm in diameter, so I imagine some commenters would suggest using larger pots. I started the season relatively late and we had a wet spring in the Netherlands last year. I regularly supplied my dahlias with liquid fertilisers. Some tubers rotted, probably due to the wet spring. Quite some varieties didn't flower at all, or really late. However, some varieties formed a bud relatively early (American Spring, Bilbao, some unnamed varieties that were part of a mix) and the buds even already gave away the color of the flowers. But those buds never came to flower. I have seen avids being farmed by ants on some plants, but not necessarily the plants with the buds that did not come to flower. Any thoughts?

SteveM

andre_1990 Any thoughts?

The only time I have ever seen buds abort was when the plants were burned by extremely hot and dry weather. If the plants looked healthy I have no idea what it might be. If the buds turned brown or the plants were sickly looking (wilted, yellowed, etc.) then I would guess it is some sort of stress causing the problem. Very dry pots, insect damage (broad mites), spray damage, low light levels, or fertilizer deficiencies are a few stresses i would consider but it would take quite an extreme to cause a fully formed bud to abort.

blown_dry

andre_1990 I'm sorry that your plants didn't work out. You say some rotted and perished, but maybe the others also suffered from rot or other stress issues but managed to go on longer. They got as far as forming blooms before growth ceased due to rot or other issues. Better luck next time.

Bessie

andre_1990 Hi Andre, it's sad to have your first attempt at growing dahlias fail. Dahlias grow to different sizes, with some varieties getting as tall as 5-6 feet or more( around 1.8 meters or more!) Using terracotta pots is a good strategy to help with overwatering, however most recommendations for growing dahlias in pots recommend much, much larger containers( 10 liters or more), depending on the mature size of the dahlia. If you want to grow dahlias in smaller pots, it would be best to chose varieties that are low growing(less than 1 meter). It's hard to tell how much gardening experience you have, so please forgive me if some of this information you already know. To give you a complete list to consider the complexities of growing dahlias, I used Google to get a summary of how to grow dahlias in pots. If you search on YouTube for growing Dahlias in Pots you will find some videos that will give more information.
Below is the very basic growing info from the google search. ( 1" = 2.54 cm):

Search Labs | AI Overview
To grow dahlias in pots, choose a large container with good drainage, plant one dahlia tuber per pot in a well-draining potting mix, position the "eyes" of the tuber facing upwards, and place the pot in a sunny spot; wait to water until you see green growth, then water regularly to keep the soil moist, and remember to stake taller dahlia varieties for support; ensure the pot is at least 12 inches deep and 15 inches wide to accommodate the root system properly.
Key points to remember when growing dahlias in pots:
Pot size: Select a pot that is at least 12 inches deep and 15 inches wide to provide enough space for the dahlia roots to grow.
Drainage: Ensure the pot has adequate drainage holes to prevent waterlogging, which can rot the tubers.
Soil: Use a well-draining potting mix amended with compost.
Tuber placement: Plant one dahlia tuber per pot with the "eyes" (growth points) facing upwards.
Watering: Wait to water until you see green growth, then water regularly to maintain moist soil.
Sunlight: Place the pot in a sunny location.
Staking: For taller dahlia varieties, provide support with stakes to prevent them from falling over.
Deadheading: Regularly remove spent blooms to encourage continuous flowering.

Teddahlia

We use 56 liter pots and three plants per pot. We use Haifa Multicote time release fertilizer. Even 6 foot tall varieties did well here and we hand water the pots. We used good potting soil that is peat moss based and most of it was 2 or more years old.

andre_1990

Thanks for your replies! Just to be clear: I had some luck with several varieties (Fleurel, red pigmy, sylvia and also some unnamed varieties), but I guess those are more resilient.

I hear you guys say the lack of flower development from buds is more a sign of general failure to thrive than of any specific disease or malnutrition. I already bought some bigger pots (35cm in diameter, about 17L as compared to only 7L in the 27cm pots) and intend to buy more. I’m still contemplating mixing my general purpose potting soil with vermiculite, coconut coir of sand to improve drainage. I am also intending on using less liquid fertiliser en more slow release fertiliser.

Thanks agains for your tips!

blown_dry

andre_1990 It's true that the size of the pot needed for success depends on the variety. Some varieties do not form large plants and are promoted for growing in pots.

Teddahlia

"...on using less liquid fertiliser en more slow release fertiliser." Fertiliser is how they spell fertilizer in the UK. Time release is the main fertilizer and liquid fertilizer is what you apply if the plants needs to do a little bit better. Potting soil is something we re-cycle from year to year. Vermiculite breaks down into clay. Coir is a good all around product. Sand is too heavy for pots. Sand weighs more than garden soil and that is too heavy for pots too. Sand is what lots of people say they want in their garden but actually when you ask a person who has sandy soil they invariably say they do not like sandy soil.