A while back I wrote a piece about green roofs in which I briefly mentioned inoculating plants with symbiotic fungi called mycorrhizae. My reasoning for doing so was to improve the resilience of the plants to the forced drought conditions that can be a feature of a green roof habitat.
At the time I said I'd write about mycorrhizae in more detail in the future. I shan't go as far as declaring that the future is now but here's a little addition to the mycorrhizal story.
After reading Paul Stamets Mycelium Running back in 2009, I was desperate to try out some of these weird-sounding symbiotic mycorrhizal fungi in the veg garden. At this stage I was far from being an experienced gardener (3 months in total!) but I still had a scientific curiosity for such things.
I seem to recall that finding a decent mycorrhizal innoculant was somewhat harder even as little as 3 years ago; my test batch came from the Mushroom Research Centre in Austria. I conducted a simple comparison with mixed salad plants whereby one batch of seeds was sown in a mycorhizally inoculated compost mix and a control group just in plain compost.
Sadly I took no photos or precise measurements so the results are relegated to pure anecdote. Rather to my amazement however, the inoculated seeds all germinated and grew whereas the controls all germinated and died in a spookily timed mini-drought.
Plants and fungi
I knew that the symbiotic fungal mycelia bind to plant roots and effectively massively increase their surface area and hence ability to extract water and nutrients from the soil but I was still astounded to see such a startling demonstration in the 'real' world.
I was personally convinced enough of the benefits that almost everything I have planted or sown since has been inoculated with mycorrhizae. It has taken me a while however to run another semi-controlled comparison and take some pictures.
The test subject was an second early potato and the mycorrizal innoculant came from the Symbio in the UK this time. Each medium sized pot received near identical seed potatoes and the same clay/compost mix as soil.
After planting, each pot got a 5 litre dousing from a watering can and then nothing more. The only difference between the two was that one potato had been 'dusted' with the symbiotic fungal spores and the other had not. This was intended as a genuine test to destruction so the idea was to let nature take its course until both plants' topside foliage was visibly dead.
The non-treated potato plant died back completely a full week before the treated one and the resulting difference in the tubers was fairly well defined. The total weight of the tubers from the inoculated plant was about 26% greater than the other.
This summer I intend to run a very similar test again but by keeping the plants well watered the aim will be to see if the mycorrhizal relationship is able to offer any additional resilience to our old friend blight. I'll keep you posted!