If you’re looking for flowers that turn heads and make your garden remarkable, growing dahlias are the ticket. These firework-shaped flowers offer an explosion of color in an old-fashioned package. Your great-grandmothers probably featured these beauties in their gardens.
Blooms can range from tiny 2-inch size to dinner plate proportions, and they can reach heights of up to 5 feet tall, so give them plenty of space.
Dahlias were first described in the Western world by Spaniards who observed them in Mexico around 1570. Native people there harvested and cultivated them as a food source and for medicinal use. They are part of the Asteraceae family, related to sunflowers, daisies, chrysanthemums and zinnias.
Tip: To keep these blooms going all summer long, deadhead spent blooms and pinch back tips to encourage a branching, bushy habit.
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Quick Guide: Planting, Growing & Caring for Dahlias
- Choose a size that fits your space and color scheme
- Blooms can range from 2-10 inches across and bloom throughout the summer
- Propagate from seed or from tubers
- Plant in rich soil; offer morning sun and protection from wind
- In US Hardiness zones 3-7, dahlia tubers must be dug up and brought inside each winter
Sunlight: Full sun
Maturity: 8 weeks from planting to bloom
Height: 3-5 feet
Spacing: 9-12 inches for smaller varieties
To fully develop the huge, technicolor blooms that dahlias are known for, they need to be planted in rich, well-drained soil that has been amended with compost, peat moss or well-aged manure to provide nutrients and moisture, retaining capacity.
A wind-protected site in full sun is best, with morning sun preferred.
Tip: To keep dahlias fresh as cut flowers, cut them in the morning and immediately plunge stems into hot (not boiling) water. Then let them rest for a few hours before placing in a flower arrangement.
How to Plant
Dahlias grow best from tubers, which should be planted 9-12 inches apart for smaller varieties and 2-3 feet apart for the larger ones.
Plant in the spring after the danger of frost is gone. Dig a hole slightly larger than the root ball and add compost and a handful of bonemeal. Then plant whole, healthy tubers about 6-8 inches deep. Do not cut tubers into pieces as you would potatoes. When planted, the tuber crowns should just break the soil level.
Do not water until you see new growth emerge or you increase the risk of tubers rotting. Once the plants are established, water deeply a couple of times a week so the tubers have the chance to dry out between waterings.
Large plants may need staking, especially in windy or unprotected areas.
Note: Dahlias can be grown from seed, but the germination rate is so low even under ideal conditions that we recommend using tubers.
In zones 8-10, leave dahlia tubers in the ground because digging them up can increase the risk of damage.
Gardeners in colder areas can dig up the tubers each year and store them in loose material like sand, vermiculite or even packing peanuts. Before storing, make sure foliage is cut back to 2-4 inches long and soil has been shaken off the the tubers. Store in an area that stays about 40-45 ℉.
If you don’t have an adequate storage area, just plant new tubers each year.
Insect & Disease Problems
These knockout flowers are a target for all sorts of pests, including slugs and snails, spider mites, aphids and cucumber beetles. Control these using organic solutions that are safe around wildlife, your pets and your family.
Powdery mildew is a problem on dahlia when weather turns more damp and cool, so provide adequate air circulation and water in the mornings, so plants have the chance to dry out throughout the day.
Deer find these plants especially tasty, so choose a powerful deer repellent and select deer-resistant plants for your area. Contact your local nursery or for a list of plants.
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