All About Dahlias

Your Guide to Planning, Planting, and Growing Dahlias

One of the best things about dahlias is how abundantly they bloom. The plants begin flowering in midsummer and continue non-stop right through the fall. Just plant the tubers in spring and prepare to be amazed!

See all 8 types of dahlia flowers HERE.


Start with a Better Plant

We sell grade #1 dahlia clumps, which are the largest size available. These photos show the difference between a large clump of grade #1 tubers on the right and a smaller clump of #3 tubers on the left. With a larger clump, you start out with more tubers and more growth points, so it take less time to get a large plant and lots of flowers.

Plan for Success

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:  Though dahlias are only winter hardy in zones 8-11, gardeners in zones 3-7 can grow dahlia as annuals. Plant the tubers in spring, and the plants will be blooming by mid to late summer. Don't know your hardiness zone? You'll find the USDA Hardiness zone map here.

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 growing dahlias in areas where the soil is soggy or compacted.

When to Plant: Dahlias tubers should be planted in spring after all danger of frost has passed. If you live in a cold climate and want your dahlias to bloom as soon as possible, you can start the tubers indoors or in a greenhouse 4 to 6 weeks before the last frost date. Fill 6" or 8" pots with growing mix and plant one tuber per pot. Put the pots in a warm, sunny place and transplant them into the garden when the weather outside is warm and settled.


Where to Plant Dahlias

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 grow just 18-24" 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 the garden to screen an unwanted view.

Vegetable Gardens: Dahlias like the same growing conditions as vegetables. Plant them at the same time as tomatoes and peppers. When you are harvesting your dinner, you can also bring in fresh flowers for your table.

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


How to Plant Dahlias

1. Dig a hole to 4-6” deep in well-drained soil.

2. Set the tubers in the hole with the stem facing up. The crown of the plant (where tubers connect to the stem) should be 1-2" deep.

3. Replace the soil and water only if the soil is very dry. Sprouts will appear in 2-4 weeks.

Watch our video: How to Plant Dahlias


Tips for Success

Choose a sunny spot. Dahlias bloom best in full sun.

To give your dahlias the best possible start, prepare the soil by adding compost or rotted manure, and an all purpose (5-5-5) granular fertilizer.

Position the tubers in the hole so the stem, where the tubers are joined, is upright.

Sprouts will develop where the tubers join the stem. This junction should be no more than an inch below the soil surface.

Once your dahlias are 8-10" tall, begin fertilizing them with an all-purpose liquid fertilizer every 3 to 4 weeks.

Pinching dahlias when they are about 10" tall will give you bushier plants with more flowers. See how to do it HERE.

When the first flower buds appear, cutting back a couple of the tallest stems will help the plant fill out and produce more flowers.


How to Support Your Dahlias

If you are growing full size dahlias with large flowers, the stems may need support to prevent them from breaking. You can use stakes, cages or a corral method.

If you are using stakes, plan on at least one sturdy, 6-foot-tall stake per plant. Drive the stake into the ground 8 to 10" deep. As the stems grow, tie them to the stake every foot or two. Inserting the stakes at planting time means you won't damage the plant or tubers later in the season.

Another method is to surround each plant with a tomato cage or a custom cage made of reinforcing wire. This is a quick and easy solution and the cages can be used year after year. Put them in place shortly after planting.

Flower farmers often use a corral method to support rows of dahlias. Insert stakes every 3 to 4 feet down both sides of the row. Wrap twine from one stake to another so the plants are contained within the corral. As the plants grow, you may need to add a second or even third row of twine. For double rows of plants, adding a center stake makes it possible to provide even more support.


Growing Dahlias in Containers

Dahlias grow well in pots and planters. Though they can be combined with other plants, they grow best when planted on their own. Full size decorative dahlias and dinnerplate dahlias need large pots. The bigger the better. For full size dahlias, the pots should be a minimum of 18" deep and 18" wide.

Border dahlias can be grown in smaller pots with a minimum of width and depth of 12". Container-grown dahlias should be fertilized every few weeks (or use a slow-release fertilizer). Water deeply to ensure all the soil in the pot gets wet. This may be a daily task from midsummer on. 


Caring For Dahlias After They Bloom

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:

• Make sure each plant is labeled so you know which tubers are which, because they all look alike. After the first frost, cut off the stems to within 4” of the ground. Wait about a week before digging to give the tubers time to develop next year's sprouts, also called "eyes".

• Begin digging carefully, 10-12" away from the stem. Gently lift the tubers from the ground, using caution as they are fragile. If weather permits, allow the entire clump to air dry for a few days (protected from rain and frost). This will encourage the tubers to toughen their skin for winter storage.

• Dahlia tubers are usually divided before they're replanted in the spring. You can divide them in the fall, or store the clumps and divide them in the spring. Both techniques work equally well. It really depends on your time and storage space. 

• Trim back the stems to 1" and gently place the tubers into pots or bins that are filled with sand, sawdust or vermiculite. If you are putting multiple tubers into one container, it's best to layer them so they don't touch each other. Store the containers in a cool (40-50°F), dark place and check them monthly to make sure they are not too wet (rotting) or too dry (getting wrinkly). Adjust the humidity level accordingly.


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