I planted my dahlia in pot in late May. Have used liquid fertilizer 15-30-15 every 3 weeks. It is grown in sunny spot for + 7 hours of sun. Been moving the pot to sunny area . However, it has failed to have any flowering buds. I have pinched and pruned it. Looks like a healthy plant, without any pests or slugs. Any suggestions for blooming will be greatly appreciated.
Thank you for contacting the Toronto Master Gardeners regarding your potted dahlia
There are a number of reasons why dahlias do not bloom. The first is sunlight: dahlias bloom best in full sun, meaning 6-8 hrs of direct sunlight every day. You mention that your pot was in direct sunlight so it appears that this is not the issue.
Water is another major cause of dahlias not flowering. If they don’t get enough water, dahlias do not bloom. If the soil around your dahlia is dry, moisten it to a depth of 1 inch (2.5 cm).
Lastly, over fertilization is another reason why dahlias will not flower. Dahlias do not require nutrient-rich soil to grow, however if you are fertilizing already rich soil then what you end up with is an over abundance of leaves.
No fertilization is required at the time of planting but your dahlias will benefit from an application of liquid, organic fertilizer 30 days after planting and then monthly during the blooming season. Be sure to avoid a high nitrogen fertilizer which will give you lots of leaves at the expense of fewer blooms. something on the order of 5-10-10 would be best.