How to Save Dahlias from Rot

A dahlia tuber that rotted in storage. Int this case, this tuber leg would be entirely removed from the clump.

Found a tuber that's gone soggy? All is not lost. Here's our SOS guide to saving dahlias from rot.

Dahlia tubers are amazing and the heart of any dahlia garden. However, they can sometimes take a turn for the worse, succumbing to rot before or during the growing season. Whether you’re dealing with soggy tubers, or mysterious stunted growth, this guide will walk you through the steps you can take to try to salvage your tuber, and hopefully rescue your dahlia.

Bonus: We've attached a video of Pam's experience saving tubers from rot and shared some hands-on tips from the trenches.

What Does Dahlia Rot Look Like?

Stunted growth: If a planted tuber shows minimal or no growth while others thrive, it’s often an early indication of tuber rot.

Mushy to touch: The area affected by rot will be soft and soggy.

Dahlia tuber with early shoots, stunted due to tuber rot

Why Do Dahlia Tubers Rot?

Before diving into rescue techniques, it’s important to understand why tubers rot in the first place. Knowing the causes helps prevent future issues:

• Improper storage: Failing to dry tubers before storage or keeping them in unventilated or overly moist conditions invites rot.

• Unfavorable growing conditions: Planting tubers in cold, wet soil or overwatering, especially during early growth stages, can lead to rotting.

  
  

Step-by-Step Guide to Saving Rotted Dahlia Tubers

If you suspect tuber rot, don’t despair. Here’s how to give your plants a fighting chance:

Step 1: Remove Rotting Areas

When rot sets in, the first step is to trim away the damage:

1. Inspect the Tuber: Dig up the affected tuber. Check for soft, mushy areas. Healthy tubers should feel firm and have white, crisp flesh.

2. Trim Carefully: Use clean, sharp scissors or a knife to remove rotted sections. Cut back to healthy, firm tissue.

3. Let It Dry: Allow the tuber to air dry for about 24 hours. This scabbing process helps protect the cut areas from further rot.

4. Replant with Care: Once dry, replant the tuber in well-draining soil. Ensure the soil is lightly moist, not wet.

   
   

   

   A dahlia tuber with area of rot removed.

Step 2: Propagate with Cuttings

If the tuber is too far gone or has limited viable growth, you can still save the plant if it has green growth:

1. Identify Healthy Growth: Look for green stems or sprouts.

2. Take a Cutting: Snip the stem with a small portion of the tuber’s neck attached. This improves the cutting’s chance of rooting.

3. Root the Cutting: Place the cutting in fresh soil and keep it in a warm, sunny location. Water lightly to encourage root formation.

4. Be Patient: Root development can take several weeks, but healthy new leaves signal success.

   
   

   

   Dahlia tuber that has rotted with a small amount of growth. Area to cut to create cutting is highlighted.

   
   

   Step 3: Address Stunted Growth

   Occasionally, you’ll notice a planted tuber that sprouts but stops growing. In many cases, this signals hidden rot.

   1. Dig It Up: If other tubers are thriving while one lags behind, gently remove the rotted tuber from the clump.

   2. Check for Rot: Examine for mushy or discoloured areas. If multiple tubers are attached, trim off any affected parts.

   3. Restart Growth: Allow the tuber to dry and heal for 24 hours, then replant. Healthy tubers will usually restart growth once replanted in fresh soil.

Preventing Dahlia Tuber Rot

An ounce of prevention is worth a pound of cure. These tips will help keep your tubers healthy:

1. Store Tubers Properly: Before winter storage, dry tubers thoroughly. I’ve had great success wrapping individual tubers in cling film to block excess moisture while allowing limited air circulation.

2. Use Well-Draining Soil: Whether storing or planting, choose a mix designed for good drainage.

3. Avoid Overwatering: Water lightly and only when necessary, especially during early growth stages.

4. Inspect Tubers Regularly: Check stored tubers for signs of rot and remove damaged ones immediately.

5. Label Tubers: If handling multiple varieties, label them for easy identification and tracking.

   
   

Pam's Experience Saving Tubers

Last year I managed to save a tuber that appeared healthy but had stopped growing. I dug it up and discovered early signs of rot. By trimming the affected areas, drying the tuber for 24 hours, and repotting it in fresh soil, the plant eventually restarted growth.

Dahlia cutting progress, showing root progress over the course of weeks.

Another time, I faced a fully rotted tuber. With no viable tissue left, I took a cutting from the remaining green growth. After two months of care, the cutting developed roots and sprouted new leaves, turning into a thriving plant.

Check out my video to see exactly how I managed these rescues and what to watch out for!

Dahlia Tuber Rescue FAQs

Q1: Can I save a fully rotted tuber?

If there’s no firm, healthy tissue remaining, it’s likely unsalvageable. However, any green growth may still provide a chance through cuttings.

Q2: How long does it take for a cutting to root?

Q3: Should I fertilize a rescued tuber or cutting?

Q4: What’s the best way to store tubers?

Q5: Can I plant tubers immediately after cutting off the rot?

Q6: How do I prevent stunted growth in tubers?

Saving Dahlias from Rot: A Labor of Love

Rescuing dahlias with rotted tubers can feel daunting, but it’s a rewarding challenge for gardeners. By understanding the causes of rot, using the right techniques, and staying patient, you can bring struggling plants back to life.

So grab your gardening gloves, sharpen those scissors, and give your tubers a fighting chance. With care and determination, even the most damaged tubers can surprise you with stunning blooms.

Happy gardening, and don’t forget to watch Pam's video for more tips and tricks!

Good Luck & Happy Gardening!