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Step by Step Guide to Growing Dazzling Dahlias!

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Step by Step Guide to Growing Dazzling Dahlias!

Dahlia blooms come in a dazzling array of colors, flower forms and sizes, from dwarf dahlia plants topping out at 12-14 inches tall - perfect for window boxes and containers - all the way up to dinner plate dahlias and "over the top" dahlias with blooms fully 12-14" across! 

Dahlia flowers

Dahlias produce their magnificent blooms from early summer right on until frost, filling your garden with color and your vases with beauty for months at a time. Knowing this, many people plant dahlias every spring, hoping for spectacular results, only to get tall, spindly plants flopping over in the mud instead. Dahlias are not difficult to grow, but they do require some attention, preparation and care to become the deserving center piece of your garden - and we will cover all of that, step by step, right here!  

Don't let the length of this post deter you. The payoff of beautiful dahlias is so great, and the potential disappointment so deep, that we are being extra thorough.  You might prefer to review our infographic for the dahlia planting steps right here. You can do this!  :)

Dahlia Planting Guide

At least 80% of the success of your dahlias takes place when you first plant them!

Where and When to Plant Dahlias:
Dahlia Tubers to Plant
  • Start with large, healthy dahlia tubers. Good tubers will produce not just this year, but for many to come. Even in bitterly cold climates, dahlia tubers can be stored for the coming spring. Quality matters, so get your dahlia tubers from a source that provides great quality. 
  • Plant your dahlias after the last frost. The ground temperature should be about 60°F.In cold winter climates, you can plant your dahlias indoors for a jump on the growing season. When you are ready to move them outdoors, follow the advice in this planting guide.
  • Full sun for the best bloom production. Plant your dahlias where they will get 8 hours of direct sun each day. If you are in a very hot climate, be sure to provide morning sun for your dahlias, with afternoon shade.
Soil Preparation for Planting Dahlias:
  •  Break up the soil where you will plant your dahlias, working in some compost to improve the nutrition and drainage. Do not bring in "new" soil. The herbicides and fertilizers so often used in packages soil will damage your newly sprouting dahlias.
  • Dig a hole about 4-7 inches deep, wide enough to spread out the tubers.
  • Work bone meal into the soil about 1 inch below where you will plant the dahlia tubers. sprinkle about 1 inch of soil on top of it, before planting your dahlia tubers. Bone meal will nourish the tubers and the root structure of your developing plants. Beware of pets and other animals becoming attracted to the bone meal you add. Add ground pepper to the bone meal where foraging carnivores are a nuisance.
Planting Dahlia Tubers:
  •  Leave dahlia tubers attached, do not pull them apart, or cut the tubers like you would potatoes, just plant each clump of tubers intact, spreading them out in the hole, with the eyes facing up.
  • Plant dahlia tubers 4-6 inches deep, 12-24 inches apart, depending upon the mature size of the plant. Dwarf dahlias that grow up to 14 inches tall should be 12 inches apart. 3 foot tall dahlias, should be planted 18 inches apart. Give dinner plate dahlias a full 24-30" spacing between plants. 
  • Position the stakes or support structures at the time you plant your dahlia tubers.  More information on how and why to stake dahlias follows below.
Planting Dahlias in Containers:
Dwarf Dahlia Gallery Series
  • Dwarf dahlias, like the Gallery series, will grow and bloom beautifully in 12" containers. Allow 1 tuber clump per container, and plant as above.
  • Larger dahlias can be grown in larger containers, like whiskey barrels. You can successfully grow 3 full sized dahlia plants in a whiskey barrel.
  • Maintain an even moisture for your dahlias in containers. The soil should be cool to the touch, not wet or muddy.
  • Plan to fertilize container grown dahlias at least twice a month with a low Nitrogen formula.
  • Add the support structure to the container at the time of planting your dahlias.
Stake Dahlias to Support Big Blooms
  • Add your dahlia support structure when you plant the tubers! Dahlias that grow two - three feet tall or more should be staked to support the wealth of blooms that will develop. 
  • Stake now to avoid damaging the tubers. Adding a support structure after the dahlia plants are partially grown really risks damaging the tubers with an errant stake. Instead, add the support structure at the time of planting to both ensure a successful harvest and to minimize work down the road.
  • There are a variety of options for staking your dahlias.  Bare branches from garden trimmings, wooden stakes with twine crossed at several levels between each stake, even tomato cages make quick and easy dahlia support structures. Don't be dismayed by the looks of your stakes before the dahlia grows. The foliage will soon obscure the supports, and the incredible blooms to follow will be well worth the effort!
Watering Dahlias
  • If your garden has not had rain for several weeks, water in your dahlia tubers when you have finished planting them. If you have had rain recently, leave the tubers dry. After planting, wait for the dahlias to show top growth before watering again.
  • Water your dahlias in relation to their size. Growing dahlias should be watered more as they grow larger. Once a week when they first sprout, with more water as they grow, until you water deeply 2-3 times per week as they flower.
  • Adjust watering for your dahlias' conditions. Dahlias growing in containers or very hot climates will need more frequent watering than those growing in the ground where temperatures are more mild.

*Congratulations! Your dahlias are now planted perfectly for success! Just a bit more care for truly spectacular results for months to come!*

Topping Dahlias and Pinching Dahlia Plants
Topping dahlias diagram
  • Pinching or "topping" dahlias results in shorter, sturdier, fuller dahlia plants that produce more blooms. This is true for the dwarf dahlias, the dinner plate dahlias and every style and size in between.
  • Pinching back your dahlias should be used in two ways. First, when your plants are 12-16" tall, pinch off the top of the plant just above the 4th set of leaves, as shown in this diagram to the right. Pinching off the top of the plant is referred to as "topping" your dahlia plant.
  • Top your dahlia plant cleanly, using shears, scissors or your fingers, taking care not to tear the stem.
  • Removing the top of your dahlia plant temporarily refocuses the plant's energies from producing flower buds, and instead the plant develops more stems and more foliage - capable of producing and supporting many more blooms. You and your garden will benefit from topping your dahlias for months!
  • At this stage, your dahlias are growing quickly, rapidly recovering from the pruning.
  • As your dahlia plant grows, and sets flower buds, continue to pinch back new growth for more bloom production. Where multiple buds are formed, pinching back a few buds will result in larger blooms for those that remain. 
  • Cutting dahlias for your vase will have the same effect as pinching back your dahlia plants. 
  • Dead head your dahlias. As dahlia blooms fade, pinch back the spent blooms. Known as "dead heading", removing spent dahlia blooms prevents production of the seeds the plant is producing to aid in reproduction. By removing the spent blooms, you are causing your dahlia plant to produce more blooms in its quest for reproductive seeds.

There you have it! These simple steps are the "secret" to spectacular dahlias! 

Dahlias Edge of Joy and Mick's Peppermint

I would love to learn what you think - will you be planting dahlias this spring? I cannot decide between the perfect blooms of Dahlia Edge of Joy and the enormous, casual blooms of Dinner Plate Dahlia Mick's Peppermint. I may just have to plant both!  :)

I will be posting information about storing your dahlia tubers for the winter in a few months.  In the mean time, 

Happy gardening!

Kathleen

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  • Kathleen McCarthy
Comments 2
  • Alex
    Alex

    Hi, Kathleen.
    That was very helpful. I have purchased several of the Gallery dahlias and am excited to plant them. Do you pinch the dwarf dahlias above the fourth set of leaves as well?
    Do recommend fertilizing dahlias throughout the growing season? If so, how much and how frequently?

    Thanks,
    Alex

  • Donna Jones
    Donna Jones

    Great article Kathleen! Very through! I have 12 in the ground from last year and check every day for sprouts! Such rewarding plants!

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