Winter (or Autumn at last)

A very warm Autumn in 2016 has postponed the usual start of pruning. Leaves finally began to yellow only at the end of May. Photo below was taken 30th May 2016

Calendar Winter = Start of 2016 Autumn
Calendar Winter = Start of 2016 Autumn

This was followed by actual cold weather for the first week of June, commencing with a light frost on the 1st, about a third have yellowed and dropped 6/6/2016.  It will be interesting to see how this affects the start of the season.  There are a couple of truffles with hints of aroma and promising colour.
General opinion is it requires several strong frosts to kick off the season, yet during 2015, which was very cold right from the start of April, our truffles still only properly ripened the first week of July.  Two months more cold weather, yet only one week earlier than average. So there is something seriously missing from our understanding of truffle ripening factors.

Truffle eruptions slowed significantly in May. This would be partially attributed to less sugars from the host tree, and the increasing depth of formation which is observed.  Although this direct nutrition is proven source of truffle growth, there is clearly also carbon stored in the mycelium itself, which is a mechanism most fungi use.
This matches a couple of observations.  First that tree’s can skip a year’s truffle production, akin to unthinned apple tree’s which tend to produce every second year, the resources must be stored somewhere during the non yielding year.

live truffle on dead tree
New truffle, on a dead tree

Secondly it explains this tree; which has just produced it’s first truffle… but the tree died in the extreme drought conditions this past summer (it wasn’t very healthy the summer before).

This has been observed in Spain also.

The late autumn yellowing is occuring throughout the Yarra Valley, so it’s not a microclimate unique to my orchard. Driving around, 7th June, oaks, willows etc are mostly yellowed and just commencing leaf drop, same as the truffiére.
There’s some other interesting variations this year, of uncertain relevance to truffles. {there’s a new lesson each year, generally leading to more questions than answers, therefore ongoing observation & research}
The pine mushrooms, Saffron Milkcaps & Slippery Jacks, were both quite late in forming this year, usually found in April, there were only a few occurences, with the main crop finally starting mid May.  Additionally, my patch of silver birch, which has birch boletes (and abundant fly agarics), has had only two mushrooms to date, compared with 30-50kg April last year. Like truffles, these are all ectomycorrhizal (ECM) fungi, so there may be some useful correlation with the late warmth and extended drought.
An additional clue may lie in the fact that ECM within the truffiére, which received irrigation through the drought conditions in Dec-March, produced fruiting bodies at the normal time.
Temperature and sufficient moisture seem to be the prime factors.
Partial watering on the silver birch if next summer is also dry may provide some clues.