In the Garden
Dahlias are relatively easy to grow, and many of them are seriously prolific bloomers, making for lots and lots of flowers to bring inside for bouquets. In my neck of the woods, where we rarely get freezes, they're hardy enough that you can leave the tubers in the ground and they'll crop back up every summer. In colder climes you'll have to dig them up when it gets cold and plant them again in the spring.
You'll want to plant your dahlias in a sunny spot, with nice loose soil for good drainage. Taller varieties will need to be staked, and all dahlias are delicious meals for slugs, so you'll want to use a non-toxic slug bait to try and keep the chompers away. If you don't have drip irrigation, water deeply about once a week (or more if it's really hot).
Dahlias do require some maintenance if you want them to produce lots of blooms: you'll need to cut off spent buds and flowers often to keep the plant healthy. But dead-heading is kind of fun and relaxing, especially when you reward yourself at the end by cutting some lovely still-fresh flowers to bring inside for your table.
In the Vase
Cut dahlias in the morning, and try to get them when they've first opened for maximum vase life. As always, you'll want to harvest your flowers by cutting precisely at a fork in the stem.
Certain varieties of dahlias last longer in water than others, and they do benefit from proper conditioning. After you bring them inside, give them a fresh, angled cut while holding the stem UNDER WATER, then transfer them to the clean water in your prepared vase. (This is a technique that never seems all that helpful to me when it comes to other flowers, but dahlias really need the extra step for hydration.)
Even a single dahlia stem can be gorgeous and dramatic in a vase or jar. Giant dinner-plate dahlias or the sculptural sphere-shaped varieties are especially stunning on their own. They're also amazing as focal flowers in mixed bouquets—you really can't go wrong! For a romantic, sophisticated monochrome look, mix dahlias with other flowers in a similar color palette but with different textures, then bring in branches and pods to give the bouquet some structure. (Check out the gorgeousness from Saipua in the second photo above.)
Can't get enough of dahlias, like me? Here's some more inspiration from our archives: