How to Plant Dahlias for a Season of Stunning Blooms

Dahlias are the showstoppers of the late summer and fall garden. They produce abundant blooms in a dazzling array of colors, shapes, and sizes. Whether you’re a home gardener or a flower enthusiast looking to grow your own cutting garden, planting dahlias is easier than you might think!

At Peterson’s Patch Flower Farm, we grow dahlias specifically for cut flowers. We choose varieties that thrive in our climate and produce long, sturdy stems. If you’re ready to add these beauties to your garden, here’s everything you need to know about planting and caring for dahlias.

When to Plant Dahlias

Dahlias are tender perennials. They don’t tolerate frost at all. The best time to plant them is after your last spring frost. This usually occurs when the soil has warmed to at least 60°F (16°C). In Sterling, CT, that’s typically around mid-to-late May.

How to Plant Dahlia Tubers

Follow these simple steps to ensure healthy, vigorous plants:

1. Choose the Right Location

Dahlias love full sun. Pick a spot that gets at least 6–8 hours of direct sunlight each day. Good air circulation is also important to prevent disease.

2. Prepare the Soil

Dahlias thrive in well-draining, fertile soil with a pH between 6.5 and 7.0. Before planting, loosen the soil about 12 inches deep and add compost or well-aged manure for nutrients. Avoid heavy clay soil. If needed, mix in sand or organic matter to improve drainage.

3. Plant the Tubers

• Dig a hole about 4–6 inches deep.

• Lay the tuber horizontally, with the eye (growing point) facing up.

• Do not water immediately. Wait until you see green shoots emerge to prevent rot.

• Space plants 12–18 inches apart for good airflow and healthy growth.

  
  

4. Provide Support (for Tall Varieties)

Many dahlia varieties can grow 3–5 feet tall. Therefore, adding stakes or a support system at planting time helps prevent them from flopping later. You can use:

• Bamboo stakes

• Tomato cages

• A horizontal netting system (great for flower farmers!)

  
  

Caring for Your Dahlias

Once planted, your dahlias will need some care to thrive.

Watering

Once the sprouts emerge, water deeply 2–3 times per week. Aim for 1–2 inches of water each time. Avoid watering overhead to reduce the risk of disease.

Pinching

When your plant reaches 12 inches tall, pinch out the center growth tip. This encourages bushier plants and more blooms.

Deadheading

Regularly remove spent flowers to encourage continuous blooming.

Fertilizing

Feed your dahlias every 3–4 weeks with a low-nitrogen fertilizer (like 5-10-10). This supports flower production rather than excess foliage.

Pest & Disease Management

• Keep an eye out for aphids, slugs, and spider mites.

• To prevent powdery mildew, plant in a sunny, well-ventilated area and avoid overhead watering.

  
  

When to Expect Blooms

Dahlias typically take about 90–100 days from planting to bloom. In our region, they usually start flowering in mid-to-late summer and continue until the first fall frost.

Extending the Dahlia Season

Dahlias will keep blooming until frost, so if you want to enjoy them longer:

• Cover plants with row fabric on chilly nights.

• Cut flowers regularly to encourage more blooms.

• Avoid letting seed heads form, as this signals the plant to slow down. If you want to collect your own seeds, just know that each seed will produce a completely different flower than the dahlia plant. This can be fun! You could create your very own dahlias!

  
  

In our area of the Northeast, dahlias must be dug up and stored after the last frost. Otherwise, the tubers will rot due to too much moisture during our wet winters. One option is to cover them with a thick layer of mulch and plastic, which may offer some protection with less work.

Ready to Grow Gorgeous Dahlias?

Dahlias are one of the most rewarding flowers to grow. They are perfect for cutting gardens, wedding florals, or simply to enjoy in your yard. With the right care, they’ll reward you with months of stunning, long-lasting blooms!

If you’re looking for cut flower-quality dahlia tubers or want to see them in bloom, keep an eye on Peterson’s Patch Flower Farm. We might just have some available for local pickup!

Happy planting!