Why Mushrooms Sometimes Produce Smaller Harvests
- Merit Mushrooms
- 14 hours ago
- 6 min read
Growing mushrooms at home is rewarding because every kit feels alive. You open it, mist it, give it fresh air and watch as small pins begin to form. Over time, those pins grow into mushrooms that can be harvested and cooked.
Sometimes, though, the harvest may be smaller than expected. The mushrooms might be fewer in number, smaller in size or slower to develop. This can be disappointing, especially if you were expecting a large flush.
The good news is that smaller harvests are usually linked to simple growing factors.
Mushrooms are responsive to their environment, which means moisture, airflow, temperature and timing can all influence the final result. A smaller harvest does not always mean that the kit has failed. It may simply mean the mushrooms needed slightly different conditions.
What This Article is About
This guide explains why mushrooms sometimes produce smaller harvests when grown at home. It covers common causes such as dry conditions, poor airflow, delayed opening, temperature changes and natural variation between kits.
It also explains what you can do to support better growth, when to keep misting and why later harvests are not always the same size as the first. If you are using a Merit Mushrooms kit, this article will help you understand what may be happening and when to get in touch for advice.
Mushrooms are affected by their environment
Mushrooms are not like houseplants or garden vegetables. Mushroom growing is unrelated to gardening, so the usual ideas about soil, sunlight and watering do not apply in the same way.
Mushrooms grow from mycelium, which develops through a suitable food source. Once the mycelium is ready and the conditions are right, mushrooms begin to form. This stage is called fruiting. During fruiting, mushrooms respond closely to the environment around them. If the air is too dry, growth may slow. If there is not enough fresh air, mushrooms may struggle to develop properly. If the temperature changes too much, the timing and size of the harvest may be affected.
This is why two mushroom grow kits can sometimes behave slightly differently, even when they are the same variety. Mushrooms are natural products, so some variation is normal.
The kit may have been opened too late
Timing is one of the most important factors when growing mushrooms from a kit. Merit Mushrooms kits must be opened within 5 days of dispatch. If this is not possible, customers should contact Merit Mushrooms for advice.
This matters because the kit is already alive when it arrives. The mycelium inside is active, so leaving it unopened for too long can affect how well it fruits.
If a kit is opened late, the mushrooms may still grow, but the first harvest could be smaller than expected. In some cases, the kit may become stressed before it has had the chance to fruit properly.
For the best results, always open your kit within the recommended timeframe and follow the instructions supplied.
Not enough misting can reduce the harvest
Moisture is vital during mushroom growing. If the kit dries out, the developing mushrooms may stay small, stop growing or fail to form in the expected numbers.
Misting helps maintain the humidity around the growing area. It is especially important when mushrooms are beginning to pin, because these early growth points are delicate. If the surface dries out at this stage, the harvest can be affected.
Misting should continue until harvest and after harvest too. It is not something you only do at the start. Even after the first mushrooms have been picked, the mycelium may still be active and preparing for further growth.
Poor airflow can affect mushroom size
Fresh air is just as important as moisture. Mushrooms benefit from high oxygen and low carbon dioxide. If they are kept in a closed, stale or poorly ventilated area, the harvest may be smaller or less well formed.
In some cases, poor airflow can lead to long stems, small caps or slow development. This happens because the mushrooms are searching for better conditions.
A suitable indoor space could include a living room, dining area or hallway, as long as the conditions are right. Bathrooms are not recommended because of mould risk.
The kit should not be shut away in a cupboard or sealed container unless the instructions specifically advise otherwise. Mushrooms need access to fresh air to grow well.
Temperature changes can slow growth
Mushrooms grow best when their environment is reasonably stable. If the room is too cold, growth may slow and the harvest may take longer to appear. If the room is too warm or the kit dries out quickly, the mushrooms may not develop as strongly.
This does not mean you need specialist equipment. Most home growers can achieve good results with sensible indoor placement and regular care. However, it does mean that seasonal changes can affect the final harvest.
A kit grown in a warm, dry room may behave differently from one grown in a cooler, more humid space. Growth may also take longer than estimated due to environmental factors.
If your mushrooms are growing slowly or seem smaller than expected, the cause may be the conditions rather than the kit itself.
Natural variation between mushroom varieties
Different mushroom varieties can produce different harvest patterns. Some may produce a generous cluster all at once. Others may produce a smaller flush or grow in a slightly different shape.
Merit Mushrooms’ current oyster varieties include Blue Oyster, Black Pearl Oyster, Summer Oyster, Yellow Oyster and Pink Oyster. Each one has its own character, colour, texture and growth behaviour.
A Pink Oyster harvest may not look exactly like a Blue Oyster harvest. Yellow Oyster mushrooms may form delicate clusters, while Black Pearl Oyster mushrooms may develop with a different structure. This variation is part of what makes mushroom growing interesting.
Later harvests are often smaller
Many growers hope for more than one flush from their kit. This can happen, but it is important to keep expectations realistic. Later harvests are often smaller because the substrate has already used some of its available energy. The mycelium may still produce more mushrooms, but the flush may be lighter than the first.
This is completely normal. A smaller second or third harvest does not mean something has gone wrong. It simply reflects the fact that the kit is gradually using up the food source inside.
Harvesting too late can affect future flushes
The timing of harvest can also make a difference. If mushrooms are left too long before picking, they may begin to dry out, flatten or release spores. This can reduce their eating quality and may affect how much energy the kit has left for future growth.
Harvesting at the right stage helps you enjoy the mushrooms at their best and supports the kit’s ongoing condition. After harvesting, continue misting and keep the kit in suitable conditions. Do not assume that care stops once the first flush has been picked. The period after harvest can be important if you want to encourage further growth.
The substrate may be running low on energy
Mushrooms grow by drawing nutrients from the substrate. Over time, this food source becomes less productive. After one or more harvests, there is naturally less energy available to produce another large flush.
This is why spent mushroom substrate may produce smaller harvests or stop producing altogether. At that stage, it can often be composted or reused outdoors, provided it is healthy and free from unpleasant smells or heavy contamination.
A smaller harvest near the end of a kit’s life is normal. It means the kit has already done its main job by producing fresh mushrooms for you to enjoy.
What you can do to support a better harvest
If you want to give your kit the best chance of producing well, focus on the basics.
Open the kit within 5 days of dispatch. Follow the instructions carefully. Keep misting until and after harvest. Place the kit somewhere with fresh air, suitable natural conditions and no strong draughts or drying heat.
Avoid bathrooms due to mould risk. Avoid sealed cupboards or places with poor airflow. Check the kit regularly, especially once pins begin to form.
If growth takes longer than expected, do not panic. Mushrooms can respond slowly when conditions are not quite right. If you are concerned, contact Merit Mushrooms for advice.
Smaller harvests can still be part of successful growing
A smaller mushroom harvest can feel disappointing, but it is not always a sign of failure. Mushrooms are natural and responsive, so their growth can be affected by misting, fresh air, temperature, timing and the condition of the substrate.
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