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Step by Step Guide to Growing Dazzling Dahlias!

Step by Step Guide to Growing Dazzling Dahlias!

Hello, Dahlia! Always keeping things interesting, these beautiful blooms arrive in a dazzling array of colors, flower forms, and sizes. From dwarf varieties topping out at 12-14 inches tall (Melody Harmony, for example) - perfect for window boxes and containers - all the way up to the massive dinner plate types (such as Seattle) and the "over the top" Dahlias (like Nick Sr.) with full flowers reaching 12-14" across!  

When it comes to prolific plants, Dahlias deliver! These showstoppers reliably yield magnificent blooms from early summer right on until frost, filling your garden with color and your vases with beauty for months on end. 

While they're not difficult to grow by any standards, Dahlias will turn into tall, spindly plants that flop over when not given a little bit of attention. Are you interested in giving these unbelievably gorgeous flowers a front-row spot in your garden? We'll outline everything you need to know right here, right now! We even have a cute little infographic for some extra information on how to plant Dahlias. 

Where to Plant 

While Dahlias are well-suited to both container and in-ground plantings, they won't thrive in soggy areas and prefer soil that is rich enough to support their "heavy feeding" needs. Therefore, if you notice water puddles 5-6 hours after a hard rain, it's best to scout out another site or amend the soil with organic material. Site your Dahlias where they will receive full sun for the strongest stems and greatest flower production.

When to Plant 

Dahlia tubers are best planted in the spring, but be mindful to wait until the soil warms up to 60 degrees F and the danger of frost has passed. They are winter hardy in zones 8-11, which means those gardening in zones 2-7 can either treat them as annuals or dig them up for winter storage. If you're eager to get a jump on the growing season, start your Tubers indoors in containers before moving them outside. 

Soil Preparation for Planting Dahlias:

  • Break up the soil where you intend to plant your Dahlias, working in some compost to improve the nutrition and drainage. Avoid bringing in "new" soil, as the herbicides and fertilizers so often used in packaged soil will damage your newly sprouting Dahlias.
  • Work bone meal into the soil about 1 inch below where you will plant the tubers. Sprinkle about 1 inch of soil on top of it before planting. 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, adding ground pepper as needed to keep them away. 

How to Plant:

  • For outdoor landscape planting, find a location where the soil drains well, and your Dahlias will receive full sun. Check the mature size and spacing information provided for each variety and design your placement accordingly. Dig holes and plant the tubers 3-4" deep, with the eyes facing up and the crown near the soil line, and 18-24" apart, depending on the variety. Tuck the plants in and tamp down the soil to remove any air pockets.
  • For container planting, select a pot with adequate drainage holes that's large enough to accommodate the mature size of your Dahlias. Use the information provided for each cultivar to choose varieties that grow to 2' or less. Fill your containers with well-drained, humus-rich potting soil, adding peat moss or perlite to improve drainage as needed. Dig holes and plant the tubers 3-4" deep, with the eyes facing up and the crown near the soil line, and 18-24" apart, depending on the variety. Tuck the plants in and tamp down the soil to remove any air pockets. Site your plants where they will receive full sun.

Stake Dahlias to Support Big Blooms

  • Add a support structure for Dahlias that grow taller than 2 or 3 feet to support the abundance of blooms.
  • Stake when you plant the tubers to avoid damaging the plants, ensure a successful harvest, and minimize work down the road.
  • Use bare branches from garden trimmings, wooden stakes with twine crossed at several levels, or even tomato cages to support your Dahlias. Don't worry if it doesn't look super pretty right away - the flower and foliage will soon obscure the supports. 

Watering Dahlias

  • Water the tubers after planting if your garden has not had rain for several weeks, and if you have had rain recently, leave the tubers dry. 
  • Wait for the Dahlias to show top growth after planting before watering again.
  • Water regularly during active growth, slowing increasing the amount as the plants grow larger. Once per week is a reasonable estimate when they first sprout, gradually rising to deep waterings 2-3 times per week as they flower.
  • Adjust watering based on the environmental conditions. Dahlias growing in containers or very hot climates will need more frequent watering than those growing in the ground where temperatures are milder.

Topping Dahlias and Pinching Dahlia Plants

  • Pinch or "top" your Dahlias when they reach 12-16" tall for shorter, sturdier, fuller plants with more blooms. 
  • Use shears, scissors, or your fingers to top the plants, being mindful not to tear the stem. 
  • Expect your Dahlia plants to respond quickly after the pruning, growing rapidly to develop more stems and foliage for future blooms. 
  • Continue to pinch back new growth for even greater bloom production. Where multiple buds are formed, pinching back a few buds will result in larger blooms for those that remain. 
  • Cut the flowers for your vase or bouquets to elicit the same effect as pinching. 
  • Deadhead the blooms as they begin to fade, as this will prevent the production of seeds for reproductive aid and focus the plant's energy on more flowers. 

Alright, there you have it - all of our best-kept secrets for growing dazzling Dahlias! 

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  • Rachel Bortles