Growing Dahlias: Your Complete Guide to Planting, Care, and Blooms
Dahlias are some of the most rewarding flowers to grow, offering spectacular blooms for cutting gardens, bouquets, and landscapes. But if you’re in Colorado, growing them successfully requires a little local know-how. From frost dates to clay soil, hot summer afternoons, and Colorado winds, there are specific strategies that ensure your tubers thrive.
This guide covers everything you need to know to start growing dahlias — plus links to our Colorado Dahlia Growing Guide and our Beginner Dahlia Grower Email Course → for step-by-step monthly guidance via email with short how to video’s to support you through the season.
1. Planting Dahlias
• Timing: Plant your tubers after the last frost as temperatures below freezing are damaging to dahlias.
• Sun Exposure: Full sun is ideal as dahlias need a good 6-8 hours of sunlight per day. But hot summer afternoons above 90 degrees can stress your plants. Consider afternoon shade or shade cloth to protect leaves and blooms if hot summer days are normal in your area.
• Soil: Dahlias grow best in loamy well drained soil. Gardens that have heavy clay soil should be amended with compost or plant in raised beds for better drainage to insure the best growing conditions for your dahlias. See our blog post Protect your garden & prepare for spring with winter strategies! for more information on soil preparation.
2. Watering Your Dahlias
• Drip System: Water deeply 2–3 times per week, depending on temperature and soil type. Deep watering encourages strong root systems.
• Soil Moisture: Keep soil moist but not soggy; overwatering in clay soils can rot tubers especially early in the season before the tubers have sprouted green growth above the soil.
• Monitoring: Afternoon heat on hot summer days can dry out soil quickly, so check moisture regularly. New growers often notice there dahlias wilting and growth slowing during these hot times and often find out they aren’t watering enough on these hot days. We water a minimum of 45 minutes a time with our drip system design. We aim to water deeply - 12” deep so the roots go deeper to cooler soil from hot soil temperatures during summer heat.
3. Supporting and Staking Dahlias
• Many dahlias grow 4 ft or taller and Colorado winds can topple them and damage the plants and impact the blooms.
• Stake early with bamboo stakes, cages, or trellis systems as each plant will need to be supported. If you are planting many dahlias you can support many plants easily with tposts and hortonova netting.
• Tie stems loosely with soft garden twine to avoid damage to the dahlia stem.
4. Managing Pests
• Common Colorado pests include Japanese beetles, earwigs, and grasshoppers and they are attracted to and damage your blooms.
• Inspect plants regularly and remove pests by hand or use organza bags to protect the blooms from the pests.
• Healthy, well-watered plants resist stress and damage better.
To learn more about pest management please read our blog How to have pristine dahlia blooms during the dog days of summer and peak pest pressure.
5. Cutting, Disbudding, and Long Stems
• Disbudding: Remove smaller side buds to focus energy on the largest central bloom — results in bigger, more impressive flowers and longer flower stems.
• Cutting Blooms: Cut stems deeply in the morning for long stems and to insure long stems for the next set of blooms as the dahlia plant will send up more shoots right below the cut a the next leaf node. So, cut just above a leaf node 18”-24” deep.
• Frequency: Regular cutting encourages continuous blooming through the season as dahlias are a cut and come again plant. The more you cut them the more new, fresh blooms you will have throughout the summer! It is one of the wonderful traits of a dahlia!
6. Dividing and Storing Dahlia Tubers
• Dig, wash, and divide your dahlias within 1–3 days to prevent desiccating the tubers as they don’t store as well.
• Store tubers in lightly moistened vermiculite or peat moss in plastic totes at 45°F. Too much moisture and too warm of temperatures will impact your storage yields due to rot. Too dry and the tubers will desiccate. A little moisture is better than too much moisture.
• Monitor monthly - check for rot or excess moisture monthly while in storage. Remove any rotten tubers so they don’t spoil the remaining tubers. If too much moisture simply pull the lid ajar for a day or two to let the moisture escape.
For a more detailed review of how to dig, divide, and store dahlia tubers please read our blog From soil to spring: How to save your dahlia tubers for next season’s bold blooms.
7. Popular Dahlia Forms and Varieties
Different forms of dahlias offer unique blooms for cutting gardens:
• Ball Dahlias: Round, tightly-packed petals; great for uniform bouquets and longer vase life. Examples: Maarn, Cornel bronze, KA’s® Honeycomb.
• Formal Decorative: Large, classic blooms with pointed petals; ideal for showy garden beds. Examples: Lark’s Ebbe, Blizzard, Diva, KA’s® Mocha Katie.
• Dinnerplate: Huge blooms that make a statement; excellent for single-stem cutting displays. Examples: Cafe Au Lait, Breakout.
Conclusion
Growing dahlias can feel intimidating at first, but with the right planting dates, soil preparation, watering schedule, staking, and pest management, your garden can thrive. By focusing on the unique needs of your garden, you can enjoy a cutting garden full of gorgeous blooms from July through October.
Visit the Learn section of our website learn more or check out our Dahlia Growing Guide, our Beginner Dahlia Grower Email Course → for monthly email instruction with short how to video’s during the growing season, our blogs for more detailed information, and our instructional video’s for a deeper dive into a specific topic!