Our comprehensive guide will teach you how to plant, grow, and care for your own stunning dahlias.
Dahlias are one of the most stunning and versatile flowers available today. A member of the Asteraceae family, they are celebrated for their incredible variety of vibrant colours, intricate petal shapes, and diverse sizes. From small pompoms to large dinner plate blooms, these magnificent flowers are a favourite for gardeners and florists alike.
At Westmount Florist, we’re crazy about dahlias, and we love sharing our knowledge of caring for them with our customers. We’ve put together this guide for all you dahlia lovers out there — whether you’re just trying to get freshly cut blooms to last in an arrangement or are first-time grower or a seasoned gardener looking to perfect your blooms.
How to Care for Cut Dahlias
Dahlias are just as stunning indoors as they are in the garden. With proper care, cut dahlias can last up to a week in a vase.
Here are some ways to extend their vase life:
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Harvest blooms early in the morning or late in the evening.
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Use sharp, clean scissors and cut stems at a 45-degree angle.
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Strip off any leaves that would sit below the water line.
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Place your cut dahlias immediately in lukewarm water with a floral preservative.
Change the vase water every other day to prevent the growth of bacteria.
Choosing Dahlias
The first step in learning how to care for dahlia plants is choosing the right variety. Dahlias come in countless forms, from small pompoms to giant dinner-plate blooms.
- Start by thinking about your growing space: tall dahlias are perfect for garden borders, while dwarf varieties thrive in containers.
Soil Preparation
If you want gorgeous dahlias, be sure to plant them in well-drained, fertile soil.
- Before planting dahlias, enrich your garden bed with compost or organic matter.
- A slightly acidic to neutral pH (6.5–7.0) will help your dahlias absorb nutrients effectively.
Planting and Spacing
If you’re searching for how to plant and care for dahlias, know that timing and spacing are key.
- Plant tubers in the late spring, once the soil has warmed and the risk of frost has passed.
- Space the tubers about 10–15 cm deep with the “eye” facing up.
- Leave 45–60 cm between plants for proper air circulation.
Caring for Dahlias Through the Season
Watering
Dahlias need consistent moisture, especially during hot weather.
- Water your dahlias deeply two to three times per week.
- Soak the soil around the roots – avoid overhead watering, which can encourage mildew on the foliage.
Fertilizing
Dahlias are nutrient-hungry plants. It takes a lot of energy to produce such huge, showy flowers!
- To encourage strong stems and abundant blooms, fertilize every three to four weeks with a low-nitrogen, high-potassium fertilizer.
- Avoid using too much nitrogen, which will result in leafy growth at the expense of flowers.
Staking and Support
Tall dahlias often need staking to prevent them from toppling over under the weight of their blossoms.
- Place the stakes when you plant your tubers; that way you won’t have to worry about damaging them later.
Pest and Disease Control
Dahlias are gorgeous, but they do have a bit of a reputation for attracting pests and being susceptible to disease.
- Watch for common pests like aphids, slugs, and earwigs. Hand-picking them off or using an organic insecticidal spray can help.
- To reduce the risk of disease, space plants properly, avoid wetting the foliage, and remove any yellowing leaves.
How to Care for Dahlias in Pots
Short on garden space? No need to fret. Dahlias also grow beautifully in containers.
- Choose a pot that’s at least 30 cm deep and wide, with drainage holes.
- Use a high-quality potting mix enriched with compost.
- Watering is especially important for potted dahlias, since soil dries out faster in containers.
Feed your container dahlias every two weeks to keep them happily blooming.
Winterizing Dahlias
Dahlias won’t survive the winter outdoors in our colder Canadian climate, but that doesn’t mean they’re a one-season flower. With the right care, you can encourage your dahlias to bloom for you year after year.
- After the first frost blackens the foliage, cut the plants down to 15 cm.
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Gently dig up the tubers, shake off the soil, and let them dry for a few days.
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Store the tubers in a cool, frost-free place packed in peat moss or vermiculite.
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Replant them in the spring for another dazzling display.
Pro Tips for Thriving Dahlias
Dahlias look exotic and dramatic, so many people assume they’re fussy. But with a few basics in place, they’re actually quite straightforward to grow and can reward you with spectacular blooms from summer through fall.
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Deadhead dahlias regularly to keep flowers coming.
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Add mulch around your dahlias to conserve moisture and suppress weeds.
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Rotate your planting locations each year to reduce the risk of disease.
Additional Resources for Caring for Dahlias
For even more on how to grow and care for dahlias, we recommend the Royal Horticultural Society’s Dahlia Care Guide.
And don’t forget to explore our other flower care guides, including peony care tips and our seasonal bouquet collection.
Find all your favourite flowers at Westmount Florist! Browse our online flower collections or visit us in person at our Westmount and Pointe-Claire boutiques.
