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How to Grow Mushrooms in your NZ Garden

Updated: 5 days ago

Outdoor mushroom patches are a brilliant way to both increase soil health, and grow delicious gourmet mushrooms in your home garden. There are two types of edible and useful mushrooms that can be easily grown in Kiwi gardens. Both Grey Oyster and King Stropharia mushrooms are wood-decomposers and can quickly break down biomass such as fresh wood-chips into healthy, rich soil.

This blog post will cover how to set up King Stropharia & Oyster Mushroom patches in your garden - and some expert pointers for success.

We may as well start with the king ...

How to grow King Stropharia in the garden

(Stropharia rugosoannulata) a.k.a. Wine Cap a.k.a. Burgundy Mushrooms a.k.a. Garden Giant

King Stropharia has many names and many uses. It is extraordinary in that it is a primary and secondary decomposer, and has many beneficial properties, including the ability to trap and eat some root-eating nematodes, boost the growth of certain plants such as corn, benefit local bee health & immunity, attract earthworms, and even filter water in an aquaponic or permaculture setting. King Stropharia is an edible mushroom that is easily identified in the garden by its burgundy-wine coloured cap in its younger stage. This species tolerates full sun and can last for years by adding fresh biomass every year for nutrients.

Sourcing Woodchip for the patch:

King Stropharia grows well on a wide variety of woodchip. Arborists mulch from you local gardening center is often readily available and works very well.

Aged woodchip that has been sitting in a large pile for sometime also works well - as king stropharia is a primary and secondary decomposer! Check the woodchip to make sure there is no/ very little visible mycelium already in it like the picture above.

Be sure your wood-chip is actually wood-chip and not pure bark, mushroom do not grow well on pure bark (normal levels of bark in the mix is fine just not 100% bark).

Dyed woodchips are not recommended.

How to setup the mushroom garden bed:

Scrape the intended patch area down to soil or low-cut grass, then add a 2-4 inch layer of fresh wood chip followed by a layer of your >> King Stropharia spawn, followed by another thicker layer of wood chip about 6-10 inches (for larger patches with lots of spawn you can repeat previous steps, layering spawn with wood chip until all spawn is used). The mushroom bed should be no thicker than 12 inches/1 foot thick. Hand spread at a minimum of 1kg of spawn per square meter. We strongly recommend using 2kg of spawn per square meter -- this higher spawn rate is much more likely to establish, survive the winter, and produce mushrooms in the first year!

For the highest chance of success we recommend spreading the spawn densely over 0.5-1m² in the middle of your patch, the mushroom will begin growing in the middle and work its way outwards.

If you are simply wanting to add spawn to existing woodchipped parts of the garden this can easily be done, simply rake back an area of woodchip, check to make sure there is not thick mycelium growth like in the picture above, place the spawn in the raked area and re-cover.

Once you have set up your King Stropharia patch, keep it undisturbed for about 4-6 months. Planting crops/ vegies into the mushroom bed is fine. Inter-planting corn, zucchini, squash and pumpkin in the mushroom patch is especially good for both the crop and the mushrooms. We have noticed pumpkin crops make a humid micro-climate under their leaf canopy leading to abundant fruiting!

After about six to twelve weeks you can check to see how the mycelium is growing by digging a small hole into the wood chip. You should see thick white mycelium starting to grow off of the spawn onto the fresh wood chip, like the photo above. Keep it well-watered through summer, same as watering your veggie garden is sufficient. You can check the moisture content of the wood chip easily by scraping back 1 inch of chip and you can visually see if it is damp by the darker colour of the wood chip.

Before winter, you will want to add a frost protection layer of wood chip, about 3-5 inches, to protect from frost: over winter the mycelium will retract down to protect from frost, and grow back again in spring. Adding any synthetic fertilisers to wood chip is not advised.

Harvesting King Stropharia:

King Stropharia can grow to the height of 30cm with a cap size of roughly 30 cm, hence the name Garden Giant. They are best for cooking if harvested early, as soon as gills are visible -- before the gills begin to darken in colour to a purple- black colour ... and before the bugs get in! While they have a strong red-wine-meaty flavour, they begin to get bitter with age. Everything can be eaten from the cap to the stem, the stems tend to have an asparagus like texture. Make sure you properly identify any mushrooms before consuming!!

How to grow Oyster Mushrooms in the garden

(Pleurotus pulmonarius or NZ-Native Pleurotus Parsonsiae) a.k.a. Pheonix Oyster/ Grey Oyster/ Velvet Oyster

Phoenix Oyster mushrooms are known to boost the immune system, being extremely nutrient dense and full of antioxidants. They are high in amino-acids, beneficial polysaccharides, important vitamins and minerals & fibre and have recently been reported to contain specific compounds known as immunomodulators that help regulate the immune system. There are even ongoing research studies indicating cancer-fighting and anti-inflammatory properties.

Grey Oysters are a great addition in the kitchen, too! They are often found in Asian cuisine and are a great umami flavour addition to a vegetarian/vegan diet. These mushrooms are unique in texture as they can get crunchy like a chip!

Phoenix Oysters are an extremely fast-coloniser that produce well on a wide range of substrates. They contain natural enzymes that break down foreign substances such as petroleum oils, PCBs, pesticides and herbicides, and are even being used in a range of 'mycoremediation' projects such as cleaning up charred toxic-debris from commercial buildings and households after these recent large-scale fires. Mycoremediation could potentially be used on a large-scale as one of the solutions to naturally help clean up NZ waterways by setting up low-tech filtration systems to break down harmful bacteria and toxins from farm run-off.

How to make an Oyster Mushroom garden bed:

Outdoor patches can start producing mushrooms in as little as 40 days from setting up your patch. Building the patch/bed is simple and virtually the same as making a King Stropharia mushroom patch. The process is pretty much exactly the same as setting up a King Stropharia garden bed.

First, break up the spawn (mushroom seed/ starting culture) and spread out the spawn evenly in the desired patch site, then add a layer of woodchip/straw (substrate) on top of the spawn. It is important to keep the patch well-watered for the first month and prevent it from drying out.

Plants/ vegies can be planted directly into the patch and are generally beneficial to producing mushrooms by providing shade and keeping humidity higher under the leaf canopy. The mushroom will rapidly break-down dead plant material to build healthy soil: enzymes secreted by the mushroom will be washed through the soil and help break down any residual pesticides/herbicides and other contaminants in the soil encouraging beneficial bacteria.

When to Harvest Oyster Mushrooms from the garden:

Typically, it is best to harvest oyster mushrooms when they go from convex to concave, basically from turning down to turning up. In the outdoor-patch setting, it is best to harvest early to get to them before the bugs do! Keep a close eye on them when they begin to pop up (as they double in size every day) and pick them as early as possible.

As always, please properly identify ALL mushrooms before consuming!!

For mushroom identification help I recommend checking out this Facebook group:

Further Reading:

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