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Aborted Mushroom Pins: Why Pins Stop Growing and What to Do
Aborted mushroom pins are pins that stopped growing before they became mushrooms, usually recognizable by a small size and a dark, almost black cap. A few aborts in every flush are normal: a kit forms more pins than it can feed, and the weakest stop. Many aborts at once usually point to the conditions, most often a drop in humidity or temperature right after pinning.
What does an aborted pin look like?
An aborted pin looks like a small mushroom that froze in place. Compared to the pins around it, it:
- stays the same size for two or more days while its neighbors grow;
- has a cap that turns dark brown to black, often darker than the stem;
- feels softer and may look slightly shriveled;
- sometimes has a little wet or glassy look at the base.
Do not confuse aborts with young pins that have a naturally dark tip. Healthy pins of most cubensis strains start with a brownish cap and lighten as they grow. The difference is that a healthy pin grows visibly from day to day.
Why do mushroom pins abort?
Pins abort when the conditions change just as they start to develop, or when the kit simply formed more pins than it can support. The most common causes:
| Cause | What happens | What to check |
|---|---|---|
| Normal competition | The kit sets more pins than it can feed | A few aborts among many healthy pins |
| Drying out | The surface loses moisture right after pinning | Droplets on the inner wall of the bag? |
| Temperature drop | A cold night slows pins that just formed | Thermometer reading in the morning |
| Too much air or draft | Frequent or long airing dries the pins | How often and how long is the bag opened? |
| Heat | Temperatures above 27 °C stress young pins | Direct sun, radiator, heat mat too high |
| Handling | Touching or bumping the surface damages pins | Was the kit moved or touched? |
Count before you worry
Look at the ratio. Five aborts among fifty healthy pins is normal. Twenty aborts among thirty pins means something in the environment changed, and that is worth investigating.
What should you do with aborted pins?
Leave aborted pins in place during the flush and remove them at harvest. Picking them off while the rest is growing disturbs the surface and the healthy pins around them. When you harvest the flush, take out all aborts along with the mature mushrooms, so no dead tissue stays on the kit before the next soak.
Aborted pins are still mushroom tissue. They do not spread anything to the rest of the kit, but over time dead tissue in a humid bag is a place where mold can start. That is why they should not stay on the kit into the next flush.
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How do you prevent aborts in the next flush?
Prevent aborts by keeping conditions steady in the days right after pins appear. That is when pins are most sensitive.
Our guide to fruiting conditions explains the balance between humidity and fresh air in more detail, and the winter temperature guide helps if your house cools down at night.
Do some strains abort more than others?
Yes. Slower, denser strains such as Penis Envy are generally more sensitive to changes during pinning, and our guide on how to grow Penis Envy covers that strain separately. Forgiving strains such as Golden Teacher and B+ usually show fewer aborts under the same conditions.
When are aborted pins a sign of a bigger problem?
Aborts are a sign of a bigger problem when they come with other symptoms. Look further if you also see:
- green, black, pink or orange patches on the substrate;
- a sour or rotten smell when you open the bag;
- slimy, wet pins or mushrooms;
- no new pins forming at all over the following week.
In that case, read our guide to contamination and our article on a grow kit that is not fruiting. If you are unsure, take clear photos through the bag and contact Mondo support with your order number.
Stable fruiting conditions with Mondo
Every Mondo product comes with a step-by-step manual on our site, and orders ship discreetly with tracking.
Shop grow toolsQuestions about aborted pins
During the current flush, yes. Remove them at harvest so they do not stay in the humid bag for the next flush.
If all pins darken and stop growing within a day or two, the kit most likely dried out or got cold. Check humidity and temperature first.
No. A flush with aborts can be followed by a perfectly normal flush once the conditions are stable again.
Use clean fingers or disinfected tweezers and lift them out at harvest time. Try not to tear up the surface; small holes are fine, large chunks are not.
Yes. Long or very frequent airing dries the surface. Brief air exchange one to three times a day is enough.
