Outdoors

Our gardening editor’s guide to growing mushrooms

Article by Your Home and Garden

Follow gardening editor Mary Lovell-Smith’s fun guide and conjure up your own edible delights

Novel, rewarding, delicious and nutritious, growing your own edible mushrooms can be easy to do at home. Not only does it take the anxiety out of harvesting in the wild, chances are you already have the perfect shady spot.

Multiple reasons can be summoned for growing mushrooms in garden beds – or on inoculated logs and in plastic bags. Thankfully, all these processes have been simplified, with all the necessary bits and pieces now readily available from specialist suppliers.

While several species of edible fungi can be grown at home, the easiest is the grey oyster mushroom (Pleurotus pulmonarius). This robust, fast-growing (often described as aggressive) fungus tolerates a range of temperatures and substrates, which in their case can be straw, sawdust, grains, woodchips, books even.

A guide to growing mushrooms outdoors

What: Grey oyster mushrooms.

How: Mushrooms reproduce with spores, which germinate when landing on a substrate with the right combination of moisture, heat and nutrients. The newly formed cells then extend outwards, creating super-fine structures called hyphae. On meeting compatible others, the hyphae join up, exchange genetic material and their growth accelerates, resulting in a large interwoven mass called mycelium. Mycelium produce the fruit – the mushroom – which in turn releases billions of tiny spores into the air. The cycle continues.

The simplest way for a beginner to start growing mushrooms in the garden is to purchase spawn, which is the commercial name for mycelium in a substrate.

When: To maximise production, these mushrooms are best started once temperatures start to rise in spring. Then two harvests can be expected before winter’s cold takes hold. The optimum growing temperature is about 15°C, give or take a few degrees.

Then: Cover the square metre with cardboard to suppress weeds. This is optional and not recommended if you plan to grow vegetables in with the mushrooms. When space is at a premium, larger-leafed vegetables, such as pumpkins and courgettes, are valuable in providing shade and increasing humidity. In turn, the mushrooms improve the soil structure as they break down organic matter into plant-friendly nutrients.

Now: Place a layer of straw (your substrate) about 5cm to 8cm thick, spray it well with water and sprinkle a third of the spawn over it. Repeat the straw, water, spawn, finishing with a layer of straw. Untreated wood chips (not bark) can be used instead of straw. The secret is to never let the bed dry out – and some patience. Within six weeks you should be seeing the rewards.

Take a look at what’s happening by peering into the straw, it should by nowbe a mass of white string-like filaments of mycelium, which will be eating (and thus decomposing) the substrate. Check daily for any mushrooms that will soon be popping up, some rather speedily. To harvest, gently pull out once the tops start to turn up – and do it sooner rather than later. Like many garden crops, insects are as fond of them as humans are.

While other, less edible, fungus species may also love the conditions you have created for your mushrooms, grey oysters are, fortunately, easily identifiable and reasonably distinct from any intruders. Nonetheless, it is unwise to eat any mushrooms or fungi fruits growing in your garden without positive identification.

To ensure a second crop in autumn, keep the bed damp. Ensuring a crop the following spring is more difficult but not impossible, especially in warmer regions. Just remember, cold and drought is this mushroom’s biggest enemy. So, pile on more straw to coddle them through winter and keep the hose handy.

Log it: Mushrooms may also be cultivated outdoors on logs with holes drilled in them into which inoculated dowels are inserted. As well as the grey oyster, dowels for pink oyster, the native velvet oyster, shiitake, enoki, turkey tail and the natives, tawaka and pekepeke-kiore (aka lion’s mane), are available in New Zealand. Although it can take between six and 18 months for the logs to become colonised and bear fruit, the wait is worth it as production can go on for many years, depending on the size of the log. Pekepeke-kiore, for example, is very slow, especially when compared to the oysters. Detailed instructions on growing are provided with the log dowel kits, which may include everything needed but the logs, for which freshly cut hardwoods are generally considered the best.

Inside out: The beauty of growing in bags and on fruiting blocks is, of course, that they are designed for indoors and the time of year is irrelevant. In essence, these kits contain a plastic bag of spawn or a sawdust block, which are either cut into, sprayed, splashed or soaked in water. Then, all going well, it’s pretty much just a matter of waiting for the mushrooms to appear. Most readily available in New Zealand as kits are shiitake, pekepeke-kiore, and the various oyster mushrooms.

Advice is at hand: As well as detailed cultivation instructions and informative websites, New Zealand’s two main mushroom spawn and kit suppliers, Sporeshift in Canterbury and Raglan’s Mushrooms By the Sea, both offer friendly and prompt advice to customers. Online, the likes of Facebook and Reddit have several active mushroom-growing groups and forums that are great for
advice and discussion on the finer points of cultivation.

By the by: Prized by gourmands worldwide, morel and chanterelle mushrooms are difficult to cultivate because they are mycorrhizal fungi, getting their energy through symbiotic relationship with trees and some other plants. While the likes of shiitake and oyster mushrooms are primarily decomposers, breaking down the substrate to gain the energy they need.