A beautiful array of flowers is one of the real joys of gardening, and one of the real tricks in ornamental gardening is keeping something flowering in your garden throughout the year. While spring is the season most commonly associated with flowers, the fact is that with a little planning you can have blooms in your garden (almost) all year long. Dahlias are a popular garden flower, a unique and striking feature in the garden, and a late-season bloomer that can bring color and delight to your garden as summer turns into autumn. While Dahlias are relatively easy to grow, they do have some special considerations. So let’s dig in!
We’ll start with a safety note: Dahlias are toxic to dogs and cats, and should only be grown in places that animals can’t access. We realize this places a bit of a burden on many gardeners, but it’s best to be on the safe side. Please remember that the world is full of stray and feral animals, so take all reasonable precautions to grown dahlias in a safe place. And check out our blog on pet-safe gardens for more information on how to keep your space animal-friendly.
Native to North and Central America, Dahlias are a perennial in warmer climates, and thrive in USDA zones 8-10. A tall plant, dahlias can reach heights of 6 feet or more. This makes them perfect as a vertical feature in many gardens, but they may require staking to reach and maintain their full height. They prefer a loamy and well-drained soil with a neutral pH. It’s important to remember that dahlias are heavy feeders, and that regular application of fertilizer is required to get the most and best blooms. However, read the labels on your fertilizer with care: dahlias require a relatively high phosphorus fertilizer (10-20-10 or 10-30-20 for example) in order to thrive. Too much nitrogen in the fertilizer will lead to lush, green plants with few blooms, so read those labels and follow the manufacturer’s instructions carefully.
Dahlias come in a huge number of varietals and colors, but reds, yellows, purples and whites seem to be the most common. This is another time when consulting with your local extension office or garden club might be helpful—they can identify the best varietals of dahlias for your area. Typically dahlias are started from tubers, which are planted outdoors when the soil has warmed up and there’s no longer a chance of frost. A quick tip from the American Dahlia Society is to plant your dahlias at the same time you would plant your tomatoes—both plants like similar temperature and weather conditions. If you would like your dahlias to bloom sooner, you can start them indoors in containers. Generally speaking you should plant dahlias two or three inches below the surface and leave them undisturbed as they grow.
Spacing is important with dahlias, so you should plant them about two feet/60cm apart to give them room to grow. This makes dahlias an ideal backdrop for more low lying flowers, so let your creativity run wild when designing your garden! Good spacing also allows for air flow, which helps avoid some of the pests that may trouble your flowers. Just make sure to give them enough water—they are heavy feeders and big drinkers. When the plant starts to bloom, you should deadhead fading flowers to encourage the plant to create more blossoms. With a little care you can extend the flowering season for your dahlias and get them to create a larger number of blooms!
Many of our readers are container gardeners, so we did some research and yes—you can grow dahlias in containers! A well draining container made out of a breathable material is best; container dahlias need the same soil conditions and ventilation that in-ground dahlias do. An important consideration in growing dahlias in containers is the size of both the varietal of dahlia and the container in question. Dahlia vareitals can range in height from 10 inches to six feet or more, so a small or medium sized varietal in a large-ish container is best. By giving them plenty of space, you’ll be creating healthier plants with more flowers.
Dahlias add a touch of joy and whimsy to any garden, and they may be the right plant for your space. Just remember to give them the space and food they need to thrive, and to keep them away from dogs and cats! With so many colors, dahlias are a gift that keeps on giving as the plant returns year after year. If you have dahlias in your garden, we’d love to see them, so please send us photos either by email or via social media. Gardzen is all about community, and we love to hear from you!