Dahlias are a true garden treasure, learn how to grow and care for dahlias in this simple step by step guide.
How Are Dahlias Grown?
Dahlias are grown from tubers. They are often considered a bulb but their root system is actually called tubers. A tuber serves as a food reserve and bears buds from which the Dahlia plant will grow.
Healthy tubers should have an eye, feel firm and show no signs of rot. Proper care of tubers will ensure that you have a garden full of Dahlias year after year.
Always purchase tubers from a trusted source. Personally, I grow Dahlias from tubers that I received from Twig and Vine. Once you have purchased Dahlia tubers, they should be stored in cool, dry place until ready to plant.
Tubers will grow large enough that after several years they can be divided and separated into multiple tubers. This is a great way to multiply your stock, therefore, having many Dahlia tubers for years to come.
When to Plant Dahlias
Dahlias should be planted in the Spring when the ground temperature is around 60 degrees. Generally, this means that they can be planted in late April or early May, but wait until your last frost date has passed before planting.
Tubers should not be planted in cold, saturated, muddy soil. Always wait until the soil is warm and has dried out. We had a very rainy spring in 2019, and therefore, the Dahlias were not planted until mid June.
Where to Plant Dahlias
Dahlias should be planted in an area with direct sunlight. To have the best blooms and growth, Dahlias need at least 7-8 hours a day of sunlight. In locations that have extreme heat, provide morning sunshine and evening shade.
How to Plant Dahlias
Dahlias are best planted in well drained soil. Break up the soil, work in some compost to improve the nutrition of the soil. Then, add a light layer of bone meal before mixing the soil. Bone meal nourishes the tubers and the root structure of your developing plants.
To plant, dig a hole around 4-6 inches deep. Then, lay the tuber on it’s side with the eye facing up. Don’t pull the tubers apart, leave them intact. Once planted, refill the hole with dirt.
Depending on the variety of Dahlia that is being planted, spacing may vary. Dwarf varieties can be spaced 14″ apart, while medium height varieties can be planted 12-18″ apart. The large dinner plate varieties should be planted 24-30″ apart.
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How to Water Dahlias
Once tubers have been planted, they do not need to be watered until the first green shoots appear above the soil. Personally, I often plant my Dahlia tubers in raised garden beds the day after it rains. Over watering can cause tubers to rot before they can grow.
Dahlias need consistent watering throughout their growing season. Watering deeply 2-3 times a week as they grow should be sufficient.
Pinching Dahlia Plants
Pinching back dahlias results in sturdier dahlia plants that produce more blooms. Removing the top of the plant, tells the plant to refocus the energy from producing flower buds, to instead develop more stems and foliage. This will then result in many more blooms throughout the growing season.
When dahlia plants are 12-16″ tall, pinch off the top of the plant just above the 3rd set of leaves. Always pinch back dahlias by using shears, or scissors, taking care not to tear the stem. The more stems you cut, the more the dahlias will bloom!
If you want the dahlia to develop large gorgeous blooms, remove the side blooms and allow only one bud per stem to develop and bloom.
As dahlia blooms fade, pinch back the spent blooms. This is know as “dead heading”. Removing the faded dahlia blooms will cause the plant to to continue producing blooms.
How to Stake Dahlias
Dahlias can grow tall and need to be supported. When planting the tubers, add the dahlia support structure. Adding support structures at the time of planting helps reduce the risk of damaging the tuber.
Each plant can be individually staked or you can use twine to coral multiple plants. In the photo above, the stakes were added to the side of the raised garden bed. Then, twine was woven from stake to stake in order to hold up the dahlia plants.
Other options for staking plants are to use tomato cages, peony cages, or even bare branches from a tree. However, with most support structures, they will rarely be seen as the foliage from the plant will generally cover it up.
Pests and Diseases for Dahlias
Dahlias are susceptible for certain pests and diseases. Slugs, snails and earwigs are among the most common pests that will affect dahlias. Most generally, Sluggo Plus, is a great organic option to manage these pests.
Powdery mildew will appear as a whitish coating on the leaves. This is often caused by not having enough air circulation between the plants. If powdery mildew appears, apply appropriate fungicide.
When to Harvest Dahlias
Dahlias don’t open much once they have bloomed. It is best to harvest the blooms when the petals are about 3/4 of the way open but before the back of the bloom begins to fade. Floral preservative can be used in the water to preserve the blooms even longer in the home. Generally, dahlia blooms will last 5-7 days.
Dahlias are a favorite in many gardens and it is easy to see why. They bloom in many dazzling colors, forms and sizes. They bloom from early summer up until frost, filling the garden with color.
In areas that get cold, such as Zone 5 here in Missouri, dahlias have to be dug up each year. This is done in the fall after the plant has died back. I will be sharing a post soon on how to store the dahlia tubers through the winter.
Dahlias are not difficult to grow, but they do require some attention, preparation and care. I hope that covering all these steps in, how to grow and care for dahlias, will encourage you to plant dahlias in your garden.