Home » Gardening

All About Dahlias!


“American Dawn” from Longfield Gardens, is a modern dahlia that’s been bred for amazing color, abundant flower production and sturdy stems. Photo courtesy of Longfield Gardens

Follow This Plan And Prepare To Be Amazed

Dahlias provide some of the garden’s biggest and most spectacular blooms. The flowers come in a rainbow of colors and many different styles and sizes, and all are excellent cut flowers. One of the best things about dahlias is how abundantly they bloom. The plants begin flowering in midsummer and produce more and more flowers each week, right through the fall. Just plant the bulbs in spring and prepare to be amazed!



It’s easy to see the difference in a quality dahlia when you compare two plants side by side. Dahlia tubers are graded by size. Grade #1 tubers are the largest size available. The photo shows a grade #1 tuber on the right and a smaller, #3 tuber on the left. Larger tubers give you a fuller plant with more stems and more blooms.



Dahlias are incredibly easy to grow. Here are a few tips to help you get the best results.

Sun and Shade: Dahlias are sun-lovers and need a minimum of 6 hours of sunlight per day. The more sun they get, the better they’ll bloom, so it’s best to plant your dahlias in the sunniest location you can.

Zone: Dahlias are only winter hardy in zones 8-11. Planted in the spring, they will grow quickly and the plants will be blooming by mid to late summer. (The USDA Hardiness Zone map puts the Houston metro area in Zone 9A .)

Soil: Most plants, including dahlias, grow best in loose, fertile, well-drained soil. To improve the quality of your soil, add compost and an all purpose fertilizer at planting time. Avoid planting in areas where the soil is soggy or compacted.

When to Plant: Dahlias tubers are planted in the spring after all danger of frost is gone. Fill 6-inch or 8-inch pots with growing mix and plant one tuber per pot. Put the pots in a warm, sunny place until the plants are several inches tall and the weather outside is warm.



Flower Gardens: Dahlias bloom from late summer through fall and hit their stride as most perennials are starting to fade. Consider each dahlia variety’s ultimate height when placing them in your borders, with tallest ones in back, mid-size dahlias in the middle and border dahlias up front.

Entryways, Patios and Decks: Decorate your home and welcome guests with a brilliant display of dahlias. Border dahlias are ideal for containers. The compact, bushy plants stay just 18-inches tall and cover themselves with flowers from midsummer to frost.

Along Fences or for Screening: Dahlias can be functional as well as decorative. Full size varieties can be planted along a property line to add privacy. They can also be planted in pots to enclose a space or in a garden to screen an unwanted view.

Vegetable Gardens: Dahlias are great companions for almost any vegetable. Just plant them at the same time you’re planting tomatoes and peppers. When you harvest your dinner, you can also harvest fresh flowers for your table.

Cutting Gardens: Dahlias are fabulous cut flowers, and just a few plants will give you armloads of blooms. Planting several different flower styles will give your bouquets a professional look.

Plant the tubers 4-6 inches deep, stem up, in well-drained soil

Plant the tubers 4-6 inches deep, stem up, in well-drained soil



  1. Dig a hole to 4-6 inches deep in well-drained soil.
  2. Set the tubers in the hole with the stem facing up.
  3. Replace the soil and water only if the soil is very dry. Sprouts will appear in 2-4 weeks.



  • Choose a sunny spot. Dahlias bloom best in full sun.
  • To give your dahlias the best possible start, improve the soil by adding compost and an all purpose (5-10-5) granular fertilizer when planting.
  • Dahlia tubers should be planted 4-6 inches deep. Position the tubers so the sprouts are facing up. If there are no sprouts, plant the tubers horizontally.
  • Once your dahlias are 8-10 inches tall, start fertilizing them with liquid fertilizer every two to three weeks.
  • Pinching dahlias when they are about 10 inches tall will give you bushier plants with more flowers.
  • When the first flower buds appear, cut back a couple of the tallest stems. This will help the plant fill out and produce more flowers.



If you are growing full size dahlias, they should be staked to support both the stems and the flowers. Use at least one sturdy, 6-foot-tall stake per plant. Drive the stake into the ground 8 to 10 inches deep. Inserting the stakes at planting time means you won’t damage the plant or tubers later in the season. As the stems begin to grow, tie them to the stake every foot or two.


Many gardeners treat dahlias as annuals. When the season is over, simply dig up the plant and the tubers and add them to your compost pile. If you want to save your dahlia tubers for the next growing season, here’s how to do it:

  • When the foliage begins to lose its color or is killed by frost, cut off the stems to within 6 inches of the ground. Wait about a week before digging to give the tubers time to develop next year’s sprouts, also called “eyes.” Label each plant so you can identify it next spring.
  • Dig around the plant and gently lift the tubers from the ground, using caution as the tubers are fragile. Allow the entire clump to air dry for a week (protected from rain and frost). This gives the tubers time to toughen their skin for winter storage.
  • Trim back the stems to 1 inch and remove any fine root hairs from the tubers. Tag the base of the stems so you can identify the tubers later.
  • Place each clump of tubers into a pot, bucket or bin and surround them with sand, sawdust or vermiculite. If you are putting multiple clumps in one container, layer them so they don’t touch each other. Store the container in a cool (40-50°F), dark place. Check the tubers monthly to make sure they are not rotting (too wet) or shriveling (too dry). Adjust the humidity accordingly
Here a colorful combination of dahlias make a beautiful arrangement.

Here a colorful combination of dahlias make a beautiful arrangement.


Dahlias In Containers

Many gardeners treat dahlias as annuals. The spectacular blooms come in a rainbow of colors andmake excellent cut flowers. Photo courtesy of Longfield Gardens.

Few plants can compete with the flowering power of dahlias. These easy-to-grow, heat-loving summer bulbs bloom non-stop from midsummer through fall, and with each week, their flowers keep getting bigger and better.

While most dahlias grow 3 to 5 feet tall, border dahlias are much more compact. At just 15 to 20 inches high, they are an ideal height for growing in pots and planters. Don’t let their small size fool you. These low-growing dahlias flower with the same incredible energy as their full size cousins. The perfectly formed, brilliantly colored flowers keep decks, patios and entryways, looking bright and fresh all season long.

After evaluating many different types of border dahlias, we have found that Melody and Gallery border dahlias produce the biggest blooms and the most flowers.



A border dahlia is a bushy plant with a dome-shape top. On its own, a single plant will nicely fill a 10-inch to 12-inch planter. Pots of this size are easy to move around, so you can add splashes of color whenever and wherever they’re needed. In a larger pot, two or three border dahlias will give a nice, full look. You can stick with a single variety in each pot or combine several different colors.

Here are some sun-loving container plants that make good companions for border dahlias:



Creeping Jenny



Sweet Potato Vine

Million Bells

Elephant Ears


Dahlias are high-energy plants that need at least six hours of direct sunlight each day. The more sun they get, the more flowers they produce. In southern areas, dahlias appreciate a little shade from hot afternoon sun. Dahlias will not tolerate freezing temperatures and they dislike cold soil. Don’t put them outdoors until all danger of frost has passed.


When plants are well established and 5 to 6” tall, start fertilizing them twice a month.

When plants are well established and 5 to 6” tall, start fertilizing them twice a month.



Dahlias have vigorous root systems ➝ that need plenty of room to develop. Each border dahlia tuber will need a 10-inch to 12-inch diameter container or 2-gallon pot. Larger containers can accommodate more than one dahlia tuber or some other types of plants. Pots should always have a drainage hole on the bottom to prevent the soil from getting waterlogged.

Here’s how to pot up a border dahlia. Fill the container a little more than half way with good quality potting mix. Find the place where the tubers come together, which is the base of the old stem. Set the tubers on the soil with the stem area on top. It should be at least 5 inches below the top of the pot. Cover the tubers with about 2 inches of soil and water well. Put the pot in a warm, sunny place where it will get six or more hours of sun each day. As the tubers start to grow, you can gradually add more soil until the pot is almost full.

Once the plants are well established and 5 to 6 inches tall, start fertilizing them twice a month. When the first flower buds appear, cut back the tallest two or three stems to about half their height. This will help the plant fill out and increase total flower production. During the growing season, removing faded flowers will stimulate growth and keep the plant looking its best.

Dahlias should not be overwatered. It’s best to let the top couple inches of soil get fairly dry between waterings.

TIP: Dahlias dislike cold weather. Though a chilly, early summer night won’t kill them, it can set them back by several weeks. Pamper your young dahlia plants by keeping the pots in a warm, protected place until nighttime temperatures are consistently in the 60s.


Article and images provided by Longfield Gardens (www.longfieldgardens.com) and reprinted with permission. ©2016 Longfield Gardens

Comments are closed.