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Dahlia FAQs: Troubleshooting For Dahlia Plants

Dahlias can be easy to grow, but they are not immune to challenges! If you’re new to growing Dahlias, or if you have concerns about your Dahlia plants this season, this guide will help. Learn more about common concerns with pests, weather, watering, and more. 

Top 6 questions about Dahlias:

Why isn’t my Dahlia flower exactly the same as the photo? 

Dahlias are available in a huge range of colors and styles - the flowers have diverse genetics that allow them to express many exciting characteristics like color, petal form, size, and more. At the same time, that can also lend to a lot of variability and inconsistency when the flowers bloom. 

Occasional occurrences when growing Dahlias:

  1. A bicolor Dahlia may produce flowers with two colors one year, but grow one-color flowers the next.
  2. Dahlias with solid flowers, as a result of stress or genetic mutations, may grow a bi-color flower one year.
  3. Single-color flowers can express a range of colors, depending on the plant, your growing conditions, and the weather. Cafe Au Lait, one of the most popular Dahlias, is known for growing blooms that express a range of colors, from buff white to pale pink to pale yellow. 

Factors that influence Dahlia flower colors:

  • Heat and cold can affect growth rate, flower size, and flower production.
  • The nutrients in your soil and your growing conditions can affect flowering.
  • As flowers mature, you may see a shift in coloring as the petals open and expand. Some colors may become brighter, while others may fade. Enjoy the beauty of every phase!

Of course, Dahlia tubers may occasionally be mixed up from field to delivery. If the flowers you’re growing look like they’re not even related to the flowers you ordered, please let us know!

Dead Dahlia foliage after a hard frost.
Dead Dahlia foliage after a hard frost.

Why do Dahlia leaves turn brown or yellow?

There could be a few reasons for brown or yellowing leaves. 

  • Too much fertilizer: Use only the recommended amount, and fertilize no more than once per month while the plants are growing.
  • Not enough water: Growing in full sun in mid-summer, Dahlias need regular watering. If leaves are yellowing, brown, or have crisp edges, or if the soil is dry or even compacted, these are all signs of underwatering.
  • Poor drainage: Dahlia tubers are susceptible to rot if the soil doesn’t drain well. You may see poor drainage when tubers are planted in clay soil or compacted soil that is not amended before planting.
  • Frost: Dahlias are only winter hardy to zone 8, and while they like cool weather, they cannot tolerate a hard frost. When it happens, you'll know - leaves will turn dark brown-black after a frost hits. (This is a good time to Dig & Store Dahlia Tubers for Winter!)
Dahlia petals with holes chewed through them
Dahlia petals with holes chewed through them

What pests can harm Dahlias, and how can I protect my plants? 

In hot, dry conditions, Dahlias and other plants are susceptible to pests, such as spider mites. Spider mites puncture leaves, causing them to become brown and leathery, and they move from lower leaves upwards.

  • You can remove damaged leaves to discourage their spreading, spray leaves with water to remove them, and apply horticultural oil or soap to kill these tiny pests. Keep plants and soil consistently watered to avoid stressed and vulnerable plants. 

Slugs and caterpillars may also nibble on your Dahlias, especially while plants are young. If you notice small holes in foliage or flowers, you can easily pick slugs and caterpillars off of your plants. (Remember, caterpillars become butterflies and moths, and are beneficial food sources for birds!)

  • Try using deterrents such as coffee grounds, egg shells, or natural pellets around the base of plants. Avoid using pesticides to keep your garden habitat - and pollinators - healthy.

Critters like deer, rabbits, and squirrels may also make a snack of your Dahlias.

  • If you have hungry wildlife in your yard, you may consider protecting your Dahlias with fencing or using a deterrent spray or pellets to keep critters away.

Why did my Dahlia plants die? 

If your Dahlia was off to a good start, but didn’t survive the summer, it’s usually a case of extremes.

  1. Poor soil preparation can result in poor drainage in clay soil or compacted soil, which can lead to rotted tubers. Good soil preparation is very important for Dahlia tubers to grow successfully. See our guide for How To Grow Dahlias for tips on preparing your soil.
  2. Too much moisture - either due to poor soil preparation or as a result of overwatering - can also cause rotten tubers.
  3. On the other hand, if there is extreme heat and dry weather, even sun-loving plants like Dahlias can be scorched. They need consistent watering to thrive. In the hottest climates, you may want to choose a location where they receive some shade or protection during the most extreme heat of the day.

Why are my Dahlias not flowering, or missing flower buds?

There can be several culprits that may reduce flowering on your Dahlia plants.

  1. Too much fertilizer: Use only the recommended amount, and fertilize no more than once per month while the plants are growing. Too much nitrogen could be the culprit! Too much nitrogen is typically seen when plants are over-fertilized, or if the fertilizer includes high nitrogen ratios. Nitrogen encourages leafy growth, but not buds or flowers.
  2. Not enough water: underwatering can result in reduced flowering. Growing in full sun in mid-summer, Dahlias need regular watering to reach their full potential.
  3. Not enough sunlight: Dahlias need at least 6-8 hours of sunlight per day to grow to their fullest potential.

Why are my Dahlias drooping or flopping over? 

  1. Overwatering may cause Dahlias to wilt and droop. Too much water, from either overwatering or poor soil drainage, causes tubers to rot, which may lead to yellowing or spotty leaves.
  2. As far as toppling over or flopping over, some Dahlia varieties with large, heavy blooms do require staking to keep the plants upright. See our guide for How To Grow Dahlias to see tips for staking!

Still have questions?

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