Learning how to grow dahlias in Colorado is much easier than you may think. I was hesitant when we first moved to our mountain homestead at 8,000 feet. I’d seen beautiful pictures of dahlias, but could they really grow in Colorado?
The answer is a resounding yes! After several years of growing dahlias, here’s what I’ve learned about growing these gorgeous blooms in Colorado (or any other colder climate).
Key Takeaways
- Dahlias can thrive in Colorado with proper care and suitable varieties.
- Planting at the appropriate time and providing proper care is crucial for success.
- Expanding your dahlia garden and experimenting with different varieties can enhance your landscape and improve your gardening skills.
How to Grow Dahlias in Colorado
When it comes to growing dahlias in Colorado, there are several factors to consider in order to achieve the best results. These factors include the weather, temperature, light, soil, and hardiness zones of your planting area.
Colorado’s climate can be quite varied, so it’s important to pay close attention to the temperature in your specific area to know when to plant your dahlias. Dahlias prefer warmer weather and will not tolerate frost. Therefore, it’s recommended that you plant your dahlia tubers only when night temperatures consistently stay above 55°F (13°C). This usually occurs between mid-May and early June in most parts of Colorado. We generally divide our dahlia tubers in April.
At our farm we usually pre-sprout tubers in the greenhouse in May and then plant them outdoors at the beginning of June. You can certainly skip the sprouting process, but it does give the tubers a head start if your growing season is short.
In terms of light, dahlias generally prefer a sheltered location with morning sun exposure. Some varieties can handle full sun, but most will thrive in partial shade due to Colorado’s strong sunshine. Ensure your chosen location receives at least 6 hours of sunlight daily in order to promote optimal growth and flowering.
Soil plays a significant role in the success of your dahlias. They prefer well-draining soil with a slightly acidic pH level of around 6.0 to 6.5. Colorado’s soils can vary from clay-heavy to sandy, so it’s crucial to amend your soil to meet these requirements. Adding organic matter like compost or well-rotted manure can help improve soil texture and drainage, creating a suitable environment for dahlia growth.
Lastly, you may be wondering are dahlias annuals or perennials? Meaning, do you have to plant them every year, or do they just stay in the ground and come back each season?
The answer is, it depends on your climate. Dahlias are generally hardy in zones 8 to 11 but can be grown as annuals in colder zones if proper care is taken to protect the tubers from freezing.
The hardiness zones in Colorado, generally range from USDA zones 3 to 7. If you live in the warmest conditions you could successfully overwinter dahlias in zones 6b/7. But for everyone else you’ll want to plan on digging up your tubers each fall and replanting in the spring. I grumble about this chore every year, but when the blooms fill the garden in late summer I’m glad I made the effort!
Planting Dahlias
Before planting, inspect the tubers for any signs of rot or damage, and make sure they are firm to the touch.
When selecting a planting location, choose a spot in your garden with well-draining soil and plenty of sunlight. Dahlias thrive in areas that receive at least 6-8 hours of direct sunlight per day. If you’re growing dahlias in containers, use pots with drainage holes and fill them with good quality potting mix.
Dig planting holes that are about 6-8 inches deep for standard-sized dahlias, and adjust the depth for smaller or larger varieties accordingly. In Colorado, it’s often helpful to amend your garden soil with organic matter, like compost, to improve drainage and nutrient content.
Place the dahlia tubers in the planting hole with the eye (the small bud on the tuber) facing upward. Gently cover the tuber with soil, leaving about 2-4 inches of soil on top. If sprouted, the new growth should just barely poke through the surface.
Spacing between plants depends on the size of the dahlia variety. I plant my dahlias about 10 -12 inches apart. You want to ensure the plants have plenty of sun and airflow, but since it’s so dry in Colorado I’ve never had any problem planting them closely.
Be sure to water the tubers only after the sprouts have appeared above the soil surface. Overwatering before sprouting can cause rot and impede the growth of your dahlias. Once they’ve started to grow, keep the soil consistently moist but not waterlogged.
Dahlia Care and Cultivation
Cultivating dahlias in Colorado is a rewarding experience as long as you provide the appropriate care. To ensure your dahlias thrive, follow these care and cultivation tips.
Soil Preparation: Prepare the soil with 6 to 8 inches of well-draining soil, rich in organic matter. A proper foundation will encourage healthy growth.
Planting: Plant your dahlia tubers flat on their side, 6 inches deep, and 18-24 inches apart. This spacing is necessary because the plants can grow quite large, potentially reaching over 5 feet tall.
Watering: Dahlias require consistent moisture, so water deeply once or twice a week, depending on your local climate, especially during dry periods. Keep the soil moist, but avoid overwatering to prevent diseases.
Fertilizing: Dahlias benefit from a balanced fertilizer with low nitrogen levels, as too much nitrogen promotes excessive green growth at the expense of blooming. Apply a 5-10-10 (N-P-K) fertilizer once a month, according to the package instructions.
Pinching: When your dahlia plants reach around a foot (30.5 cm) high, pinch off the top few inches to encourage branching and a bushier growth habit. This will lead to more blooms.
Staking: Taller dahlias require support to prevent falling over. Provide strong stakes at the time of planting or soon after to avoid disturbing the roots.
Deadheading: Regularly remove spent flowers to keep your dahlias looking their best and to promote continuous blooming throughout the growing season.
Midsummer Care: To keep plants healthy, apply a layer of mulch around your dahlias to conserves moisture and control weeds.
Fall Care: In the fall, after the first frost, cut the stems back to 4-6 inches above the ground and carefully dig up the tubers to store them for winter.
By following these guidelines, you can confidently and successfully grow beautiful dahlias in Colorado’s unique climate. With proper care, your dahlias will provide stunning blooms and enhance the overall beauty of your garden.
Dahlias for Different Purposes
When deciding to grow dahlias in Colorado, it’s essential to consider the purpose for which you are planting them. Dahlias can serve various purposes in your garden, such as cut flowers, borders, or simply for their attractive appearance. Here are some factors to keep in mind when growing dahlias for different purposes:
Cut Flowers: If your primary goal is to grow dahlias for cut flowers, choose varieties with long stems and good vase life. These types will produce beautiful and long-lasting arrangements, brightening up your space and impressing your guests. Remember to harvest the flowers early in the morning or late in the day and place them in water immediately, as this will prolong their shelf life.
Border Dahlias: For a vibrant and varied border, consider planting different colors and forms of dahlias. Their size and branching habits make them an excellent choice to fill gaps, create visual interest, and complement other perennials or annuals in your garden. With their wide range of colors, including red, orange, yellow, pink, and white, dahlias will bring life and diversity to any garden border.
Size and Form: Dahlias are available in a variety of sizes and forms, from dwarf plants that grow to just 12 inches tall to statuesque varieties that can reach up to six feet. Be mindful of their mature size when selecting the perfect spot for them in your garden. Larger varieties are ideal for creating focal points or anchoring the back of a mixed border, while smaller plants work well in containers or along walkways.
Purchasing Dahlias
Dahlia tubers are in hot demand these days and it can be challenging to get quality tubers. Be sure to sign up for email lists and plan to shop the day they are released. These are three farms I have shopped from that offer a great, high-quality selection:
FAQ: How to Grow Dahlias in Colorado
When should dahlia tubers be planted in Colorado?
Dahlia tubers should be planted in Colorado after the last frost has passed, typically in mid-May. Make sure to plant them flat on their side, 6″ deep, and 18-24″ apart to ensure the proper growth and bloom of your dahlia plants.
What are the best practices for growing dahlias in pots in Colorado?
When growing dahlias in pots in Colorado, use a good quality potting soil, and ensure the pots have drainage holes to prevent waterlogging. Position the pots in a location with part to full sun exposure. Water regularly at soil level, rather than overhead, to keep the soil evenly moist. Fertilize the plants with a regular application of organic water-soluble plant food to support their growth and blossoming.
How can I overwinter dahlia tubers in Colorado?
To overwinter dahlia tubers in Colorado, dig them up after the first hard frost. Carefully remove excess soil and let the tubers dry for a day or two. Wrap the tubers in newspapers or place them in plastic bags containing slightly moistened peat moss or vermiculite to prevent them from drying out completely. Store the tubers in a cool, dark place at temperatures between 40-50°F (4-10°C). Check the tubers periodically throughout the winter for signs of rot or excessive drying.
Do dahlias return every year in Colorado?
Dahlias are perennial plants in warm climates, so they have the potential to return every year. However, in colder climates like Colorado, they may not survive harsh winters unless their tubers are properly overwintered as mentioned above. Replant the tubers in spring after the last frost to enjoy their beautiful blooms year after year.
What are some useful dahlia growing tips specific to Colorado?
Given Colorado’s unique climate, consider these tips for growing dahlias:
- Amend native soil with compost to ensure proper drainage and nutrient availability.
- Provide taller dahlia plants with stakes or supports to help them withstand Colorado’s strong winds.
- Be prepared to protect plants from hailstorms by covering them with a cloth or mesh protection.
- Choose dahlia varieties that are suited to higher elevations or more tolerant of variable weather conditions.
- Keep an eye out for pests, such as aphids or spider mites, and treat them promptly to prevent damage to your plants.
More Dahlia Care Articles
Looking for more info on growing dahlias? Check out these articles:
