Just like spring means a lot of sowing and planting in the greenhouse, spring is actually the best time to start cultivating edible mushrooms in logs, as the mushrooms develop best at slightly higher temperatures, and you have the whole growing season ahead of you. And if you do it in the greenhouse, the slightly higher temperatures in the greenhouse will allow you to start inoculating earlier, and the slightly higher temperatures will give the mushrooms a good start.

In this article, we will guide you through how to get started cultivating mushrooms in the greenhouse.

Starting mushroom cultivation in the greenhouse

Just as you can start sowing and planting earlier when you have a greenhouse where the temperature is slightly higher than outside in the garden, you can also start earlier with the cultivation of mushrooms on logs. It is important that your newly inoculated logs are not exposed to frost in the first few weeks after inoculation until the mycelium has established itself in the logs. Additionally, mushrooms grow best when the temperature is slightly higher. Later in the spring, you can move the logs to a moist and shaded spot in the garden, as they will not thrive in the hot summer greenhouse.

Guide: Growing mushrooms on logs

If you have some logs lying around in your garden or if you're about to prune or fell a deciduous tree, we'll guide you through how to use them to grow delicious edible mushrooms.

You'll need:

• Dowels (or small wooden sticks with a diameter of 8-10mm) made of hardwood, preferably beech or birch
• A log or tree stump made of hardwood, preferably beech or birch
• Mycelium of the mushroom you want to grow
• An old large jam jar with a lid
• Breathable tape
• Hammer and nails to make holes in the lid
• Alcohol
• Bowl, pot, and colander
• 8-10mm drill
• Beeswax or possibly paraffin wax
• A brush or a spoon

How to do it: 

(1) Soak the dowels in a bowl of water for one to two days. Then boil them for 20-30 minutes to pasteurize and further soften them. Drain and cool the dowels to room temperature.

(2) Make holes in the lid of the jar with a hammer and nail to allow air to reach the mycelium, and thoroughly disinfect the jar with boiling water and/or alcohol.

(3) Place breathable tape over the holes to reduce the risk of contamination.

(4) Pour the dowels and mycelium into the jar. Make sure your hands are clean and touch the dowels and mycelium as little as possible. Put the lid on and shake the jar until the mycelium and dowels are well mixed. Then place the jar in a dark place at room temperature.

(5) Wait three to four weeks while the mycelium runs through the dowels. When the mycelium has spread as a white layer on the dowels, they are ready to use.

(6) Drill holes in the log or tree stump with a distance of about 10-12 cm between them. The shorter the distance, the more dowels you will need, but it also makes it faster for the mushroom to establish itself and for you to harvest home-grown mushrooms.

The holes should be 1/2 cm longer than the dowels to allow a little air at the inner end of the hole. Twist the drill a bit as you drill so that the holes become slightly larger in diameter, and you can easily insert the dowels into the wood.

Place the dowels in the holes - the more mycelium you can get when you insert the dowels, the better.

Melt beeswax in a water bath and spread a thin layer over the holes with a brush.

If you are drilling into the top of a tree stump or log, drill close to the bark as the mushrooms establish themselves best in the layer between the bark and the wood core.

If you use a log, soak it for one to two days before starting.

(7) Arm yourself with patience and wait while the mycelium spreads through the log or stump. If you grow in a log, it is important to water it regularly (once a week) so that it stays moist. It can take up to a year or two before you can expect to harvest mushrooms, but you may be lucky enough to harvest in the fall if you start now.

(8) When the largest cap has fully unfolded and the edge has become "sharp," the mushrooms are ready to harvest.

This guide was developed in collaboration with Funga Farm, where we also obtain our mycelium from.

Location - Start in the greenhouse and move to a damp and shady spot in the garden

If you begin in early spring when there is still a chance of frost, it is a good idea to start with the mushroom log in the greenhouse where temperatures are slightly higher, so the mushroom can get establish. That being said, it can be difficult to choose a shady spot in the greenhouse, but choose the least sunny location or try to create a darker environment where the log isn't exposed to direct sunlight. Once there's no chance of frost, you can move your log to the garden. You can choose to have the log standing up so the mushrooms can grow all around it, or you can lay it down to reduce the risk of it drying out. It's important to keep the log moist by watering it regularly, especially if it's in the greenhouse where it won't receive rain naturally.

When growing mushrooms in solid wood, it can take one to two years before the mushroom can be harvested. On the other hand, there is more nutrition in the log for the mushroom than if you were to grow it in straw or coffee grounds. This means, you can harvest edible mushrooms from the log over a period of several years - how many years exactly depends on factors such as the size of the log.

What type of wood can be used?

You can grow most edible mushrooms in most deciduous trees, so feel free to use whatever you or your neighbour has lying around. If you're unsure, ask your mycelium supplier, which trees the different mushrooms thrive best in. If you're using a log, we recommend using a size of at least 10 cm in diameter and 30-40 cm in length, but try it with whatever you have. Let a freshly cut log dry for one to three months before propagating or use an old dry piece of wood that doesn't have any other mushrooms growing in it. If you're using a stump, we recommend propagating within the first 9-12 months after cutting it down. The fresher the stump, the fewer competing fungi, but even an older stump can be used if it doesn't look decayed.

If you don't have dowels lying around, you can easily make them yourself by carving branches from beech or birch trees. It's up to you how many dowels you drill into your log, but the more, the better. So let patience determine how many dowels you'll use. We usually use around 100 g of mycelium (including the grain it's grown on) for about 60 dowels, but you can get by with less. It just means it might take a little longer before they're ready to propagate.

Happy mushroom growing!