What Is Plume (Bloom)?

Plume — also called bloom — is a natural crystalline secretion that forms on the surface of cigar wrappers during aging. It occurs when the essential oils in a well-fermented, properly stored cigar migrate slowly to the surface of the wrapper and crystallize there.

It's a positive sign. Plume indicates that the cigar has been aging in proper conditions long enough for the oils to move, and it's associated with the same chemical processes that improve flavor complexity over time.

What plume looks like: A fine, white or slightly yellowish dusting on the surface of the wrapper. Evenly distributed — not concentrated in spots or patches. A crystalline, slightly powdery texture when observed closely. Present on the surface only — it doesn't penetrate the wrapper.

How plume behaves: It wipes off easily with a clean, dry cloth or your finger, leaving the wrapper intact and undamaged underneath. It doesn't smell musty or unpleasant — the cigar should still smell like tobacco, possibly more aromatic than normal. It tends to appear after extended aging, typically a year or more, in proper conditions.

Plume is one of the positive indicators you're looking for during scheduled aging check-ins. See Cigar Aging Guide for a complete framework on aging and what to look for at each stage.

What Is Mold?

Mold on cigars is a fungal growth that occurs when humidity is too high for too long, when airflow inside the humidor is poor, or when contaminated materials are introduced. Unlike plume, mold is a biological organism that's actively growing — and it can spread to other cigars in your collection if not addressed promptly.

What mold looks like: Fuzzy or fibrous texture with clear dimensional structure — unlike the flat crystalline texture of plume. Typically blue-green, gray, or white. Spotty and irregular — appears in patches rather than evenly distributed. May cross from the wrapper onto the cap or foot. Can appear on the cedar interior of the humidor, not just on cigars.

How mold behaves: When you wipe it off, it leaves discoloration or damage to the wrapper underneath. It has a musty, unpleasant odor distinct from tobacco. It spreads — a mold colony on one cigar can spread to adjacent cigars and to the cedar lining. It penetrates the wrapper over time rather than sitting on the surface.

The Wipe Test

If you're uncertain whether what you're seeing is plume or mold, the wipe test is the most reliable diagnostic. Take a dry, clean cloth or your fingertip and gently wipe the affected area.

  • Wipes off completely, leaving a clean undamaged wrapper: Plume. No action needed.
  • Smears, leaves residue, or the wrapper looks damaged underneath: Mold. Take action immediately.

The smell test is a useful supplement: plume-affected cigars smell like tobacco. Mold-affected cigars have a musty, earthy odor distinct from the tobacco's natural aroma.

What to Do About Mold

Step 1: Remove and Quarantine Affected Cigars. Remove any cigar with visible mold from the humidor immediately. Place it in a separate sealed bag or container. Inspect all adjacent cigars carefully.

Step 2: Inspect the Humidor Interior. Check all cedar surfaces — walls, tray, lid, dividers — for any sign of mold growth on the wood.

Step 3: Address the Source. The most common causes: humidity consistently above 72–74% RH (the primary cause — consider switching to a two-way system like Boveda); poor air circulation (a tightly packed humidor creates humidity pockets); contaminated cedar from previous storage or transport.

Switching from one-way to two-way humidity control is one of the most effective preventive measures against recurring mold. Boveda Packs and Humidity Control Explained covers how to make the transition.

Step 4: Clean the Humidor Cedar. Remove everything from the humidor. Wipe all cedar surfaces with a clean cloth barely dampened with distilled water — not isopropyl alcohol (alcohol damages cedar). Allow the humidor to air out completely with the lid open for 24–48 hours. Do not use chemical cleaners, bleach, or soap.

Step 5: Re-Season Before Reloading. After cleaning, allow the humidor to dry completely, then re-season it before putting cigars back in. The cleaning process removes moisture from the cedar.

The re-seasoning process follows the same steps as initial seasoning. How to Season a Humidor covers the full process.

What to Do With Mold-Affected Cigars

A cigar with surface mold that hasn't penetrated the wrapper can sometimes be rescued — carefully wipe off the mold with a clean, dry cloth, allow the cigar to dry slightly in a well-ventilated area, then inspect again in 24–48 hours. If the mold doesn't return, the cigar may be smokeable.

A cigar where mold has penetrated the wrapper, where the cap or foot are affected, or where the mold smell has permeated the tobacco is typically a loss. When in doubt, discard. The cost of a few cigars is much less than the risk of reintroducing mold to a recovered humidor.

Preventing Mold

  • Keep humidity at or below 72% RH. The most important preventive measure. Mold thrives above this threshold. If you're currently running 72% or higher, consider dropping to 69% or lower.
  • Maintain stable temperature below 70°F. Mold development is faster at higher temperatures.
  • Don't overcrowd your humidor. Dense packing limits airflow. Cigars touching each other trap moisture between them. Leave space and rotate periodically.
  • Inspect regularly. Monthly visual inspections catch mold before it spreads.
For specific humidity targets that keep you in the safe zone for your wrapper types, see Ideal Humidity Levels for Different Cigars.