When talking about dahlias, I have some pros and some contras too. They are certainly beautiful plants, and have a long blooming period. Mine have started in June and are still flowering. I do not really like the fact they need to be dug up after the first frost and stored inside during the winter. Tall varieties need also lots of place and need staking. Young shoots are easily eaten by slugs in Spring. Despite of all these I love them. They are in fact easy to grow. There are many cultivars for every garden, tall, medium, small. They are grouped according to the type of flowers: cactus, ball, pompom, paeony, collerette etc.
Dahlia is native to Mexico. The Aztecs used to grow them for food and ceremonies.
After a few frosts the plant will turn black but, there are tubers in the ground that need to be dug out and stored for the next planting season. The clumps of tubers can be carefully divided and left to dry laying upside down for a few days. When separating the tubers make sure that each of them has at least an eye.
I place the tubers into boxes filled with sawdust. I keep them in the cellar because they must not be left to freeze. During the winter check them now and then to keep them moderately moist and prevent possible fungal diseases.
The one with tubular flowers...
Dahlia flowers come in pink, white, red, orange and yellow colour and all of their shades. There colour may be solid or mixed. The size of the inflorescence (what we call flower are in fact many flowers clustered together) may be really big, more than 25 cm in size or rather small, less than 5 cm.
Dahlia needs sunny spot and rich soil, but more about planting Dahlias in Spring.
My Dahlias are still full of flower buds.
The American Dahlia Society
Dahlia Society of Quebec French language Dahlia