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Crocus Rot

Disease

Crocus rot is a fungal infection that attacks the underground corms of crocus plants. It is a serious issue because it destroys the base of the plant, often leading to total collapse before the gardener even notices a problem.

Symptoms by part

Roots

The corm becomes soft and mushy, often covered in a white or grey fungal mat, and eventually turns into a dark, decaying mass.

Causes

  • Poorly drained soil that stays soggy for long periods.
  • High humidity levels around the soil surface.
  • Planting corms too close together, which prevents airflow.
  • Overwatering during the dormant phase.

Could be confused with

  • Wireworm damage · Wireworms leave clean, small holes in the corm, whereas rot causes a generalized, mushy decay.
  • Natural dormancy · Natural dormancy leaves the corm firm and healthy, while rot makes the tissue soft and foul smelling.

Treatment

  1. Dig up the affected crocus corms immediately to prevent the fungus from spreading to healthy neighbors.
  2. Inspect nearby corms for any signs of softness or discoloration and remove those as well.
  3. Dispose of all infected plant material in the trash, never in your compost pile.
  4. Leave the soil in the affected area empty for at least 2 years to allow the fungal spores to die off.

Without chemicals

  • Improve soil drainage by adding grit or organic matter before replanting.
  • Space corms further apart to increase airflow.
  • Use a raised bed to ensure water drains away from the corms.
  • Avoid watering the soil directly over the corms during the summer dormancy period.

Preventing it

  • Always inspect corms for soft spots or mold before planting.
  • Plant in well draining soil, ideally on a slight slope or in a raised bed.
  • Avoid overwatering, especially when the plants are not actively growing.
  • Rotate your planting site every 3 to 4 years to break the disease cycle.

Season

The warm growing season, especially during periods of heavy rainfall or high soil moisture.

Spread risk

Moderate

Severity

High

When to act

Act the moment you notice a plant failing to emerge or showing stunted, yellowing growth. If the corm is mushy, remove the entire plant and the surrounding soil immediately.

Think it's Crocus Rot?

This guide covers the general picture. Pocket Botanist looks at your actual plant from a photo and tells you what's really going on, how serious it is, and what to try first. Identification and a health check are free.

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Questions people ask

Can I save a corm that has started to rot?
Unfortunately, once the rot has taken hold of the corm, it is nearly impossible to stop. It is best to remove and discard the plant to protect the rest of your garden.
Will the rot stay in my soil forever?
The fungus can persist in the soil for several years. By avoiding planting crocuses in that specific spot for at least 2 years, you allow the pathogen to die out naturally.

Plants it affects

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This guide was generated with AI and is general information, not horticultural advice. Read about how we build these guides.