The dahlia is a flower that has grown in popularity in recent years and there are a number of reasons for that. The primary reason is that there is a huge variety of colours and sizes available, in fact there are dahlia's in virtually every colour. They also have the advantage of being easy to grow which certainly adds to their popularity.
The larger dahlia's tend to be the most popular varieties for growing outdoors, where they can be planted in flower beds. They are ideally grown in temperate climates where they will start to bloom in July and continue to do so until the first frost. They can be grown in cooler areas as well but in order to do so you will need to start them off inside or in a greenhouse and then move them out side.
The smaller types of Dahlia's tend to be more popular for growing indoors as well as on patios or in small gardens where space is limited. Care is basically what you would expect for an indoor flower, make sure that it is in an area where it gets lots of sunlight, and water it regularly. Consistent pruning will help to increase the frequency of blooms.
There was a period of about twenty years during which dahlia's were not particularly popular, although the reason for this is hard to understand. However in recent years the variety of colours and sizes combined with the ease which they can be grown has seen them return to popularity.