Monday, 31 March 2014

Got Mycorrhizae?

Fungi are amazing organisms. They're everywhere, but their lives go on unseen, in secret, for the most part. They're crucial for decomposition and recycling of waste. They grow like plants but are made of chitin like insects and other invertebrates and, just like humans, they produce vitamin D when exposed to sunlight - in fact, some consider fungi to be more closely related to animals than to plants. They can absorb toxic waste and chemical pollutants, using them as food and rendering them harmless. They can MAKE IT RAIN! Their rootlike mycelium - the main body of the organism - can spread underground for miles (the largest fungus on earth is believed to be a honey fungus which covers nearly nine square kilometres in Oregon's Blue Mountains!) while the mushrooms and toadstools we see on the surface are just their flowers and fruits! And it's fungi that form the vast underground network which scientists believe allows plants to communicate, warning each other of pest attack and other troubles.

These mycorrhizal fungi - fungi which connect to the roots of plants and form a symbiotic relationship with them - have other benefits for their hosts too; a vast mycelium acts as a secondary root system for a plant, bringing nutrients and water from far deeper and further away, effectively increasing its root system by up to 700 times! Plants with roots colonised by mycorrhizal fungi establish faster, grow better thanks to the additional nutrients, have more resistance to pests and disease, and suffer less in drought. It's estimated that 90% of land plants have associations with these fungi. Just one gram of woodland soil can contain over a million microscopic fungi, and in one square inch of decomposing organic matter, such as a decaying tree trunk, there can be 70 miles of mycelium. The stuff is everywhere!

Well, not everywhere. Guess where you won't find mycorrhizal fungi...

You won't find it in the kind of sterile shop-bought compost you raise young plants in. And you won't find it on highly-cultivated, regularly disturbed allotment soil. Nope.

So I think it's pretty cool that you can now buy it in a packet. :-)

The fungi spores, native to the UK and grown here, are dried and bound in clay. To use them you just sprinkle them in the planting hole when transplanting, or add them to a drill under a sprinkling of soil before sowing seeds. I have put mine into an old herb jar with a shaker top for easy application!

Needless to say, I will be using this this year, especially under my new perennials, and have already added it when planting my strawberries and asparagus, and sowing my broad beans. Of course, switching to no-dig growing and using ground-covers will mean that fungi can survive much better in our soil from now on, and should colonise the area nicely, so personally I can't see myself using it year on year, but it certainly looks like it has great benefits for growers whatever their methods (look here for some photos comparing plants with and without mycorrhizae) and the RHS particularly recommends it when planting out trees, roses and shrubs, to ensure less transplant shock and help plants establish faster.

Mycorrhizal fungi apparently don't help brassicas, since brassica roots release a natural anti-fungal defence which stops them thriving, nor acid-loving plants such as cranberries, blueberries, heathers, azaleas and rhododendrons. Some other plants however, like grapes and roses, depend heavily on the mycorrhizae and can really struggle without them, and a few species of orchid cannot live without them at all.

It's crazy to think that our traditional method of digging the soil over before growing crops actually breaks this beneficial natural relationship that does so much good in the wild, and stops us benefiting right where we need it most. It's another one-up for no-dig gardening, and I can't wait to see the results!

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