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If yellow mushrooms grow in the flower pot, it is usually the so-called yellow parasol (Leucocoprinus birnbaumii). But where does this fungus come from and what can you do about it?

In a nutshell

  • besides white ones, yellow mushrooms are most commonly found in flower pots
  • as far as is known, the yellow parasol is not a plant-damaging fungus
  • it is primarily an optical problem
  • Poor quality potting soil and moisture promote fungal infestation
  • caution should be exercised in the case of allergy sufferers

Causes of fungal infestation

Yellow mushrooms basically always grow where organic material decomposes. Purchased potting soil usually has a high humus content, which is particularly the case with simple and inferior potting soil. The reason for this is the use of too much peat. In high-quality products, the likelihood of yellow fungi growing is much lower, provided there are no serious care mistakes. Other factors that often play a role are the water content in the soil, the humidity and the room temperature. A permanently moist soil as well as high temperature and humidity can promote the growth of fungi.

Source: Zinnmann, 20220714 Leucocoprinus birnbaumii - 04, edited from Plantopedia, CC BY-SA 3.0

What should I do?

The yellow parasol (Leucocoprinus birnbaumii) is easy to spot. Both cap and lamellae as well as the stalk are sulfur yellow. It can appear in flower pots all year round and disappear after a while. The following year, around the same time and in the same place, it reappears if nothing is done about it. The best way to combat this fungus is to repot it in fresh and, above all, high-quality soil.

  • move the affected plant outdoors
  • Take the plant out of the flower pot, remove all of the soil and dispose of it
  • Rinse off any remaining soil under running water
  • Shorten the roots if necessary
  • either use a new flower pot or thoroughly clean the old one
  • inside and out with warm vinegar water and a brush
  • then put a drainage layer of potsherds or expanded clay on the bottom of the pot
  • Drainage protects against waterlogging and removes the breeding ground for fungi
  • Fill in high-quality substrate and insert plants
  • Press and water the substrate
  • only water when the soil has dried
  • if possible, always water from below
  • Ventilate the rooms concerned regularly

If you don't want to take any risks with the potting soil, you can make your own mixture from mature compost and coconut fibers. Both materials are structurally stable and promote the aeration and storage capacity of the soil. Horn shavings can also be used to add nitrogen.

Tip: Simply pulling out the mushrooms is not enough, as this only removes the fruiting body and not the actual mushroom. It grows underground as a so-called mycelium and cannot be easily removed.

Avoid yellow mushrooms

If you want to prevent an infestation with fungi, especially the yellow parasol, there are a few things you should pay attention to. It is particularly important to prevent waterlogging with the right substrate, because this is one of the main reasons for the growth of fungi.

Source: Ryan Van Gelder, Leucocoprinus, edited from Plantopedia, CC BY-SA 3.0
  • Avoid potting soil containing peat if possible, also for the sake of the environment
  • Peat substitutes such as wood or coconut fibers or bark humus are recommended
  • Irrespective of the type of substrate, water as needed
  • Adapt the watering rhythm to the season and room temperature
  • avoid excessive humidity
  • Remove excess irrigation water in cachepots and saucers regularly and promptly

Tip: Additional protection against waterlogging can be provided by grit, pebbles or expanded clay, with which the coasters are filled. If some irrigation water then collects there, the roots will not get wet feet so quickly.

Effects on humans and plants

According to current knowledge, these yellow fungi are primarily a visual impairment. Nevertheless, the parasol is not an edible mushroom. Some species are poisonous, others are suspected to be poisonous. There is usually no danger to the plants in question. There are also no known effects on human health. However, it has been shown that intensive mycelium formation in the potting soil attracts fungus gnats and encourages them to lay eggs.

frequently asked Questions

Do the mushrooms have to be removed?

These fungi mainly grow in poor-quality potting soil. It contains a lot of humus, which the fungus feeds on. The decomposition of humus promotes the compaction of the substrate, which in turn means that waterlogging can form more quickly.

Are these mushrooms a health hazard?

Since there are still no meaningful studies on the toxicity of the yellow parasol, it is definitely advisable to eliminate it permanently. Since it releases its spores into the air, sensitive people could have an allergic reaction to it. In addition, the pretty look of the mushroom could encourage children to touch it or even nibble on it. To prevent this, it should be removed as a precaution.

What should be considered when choosing the substrate?

Above all, you should avoid potting soil that contains a lot or generally peat. In most cases these are cheaper ones. In high-quality substrates, mushrooms usually hardly stand a chance with optimal watering.

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