Working with nature has its challenges, this viticultural growing season is no different. Here is a nerdy ramble about the Barossa Valley growing season as we wait for the grapes to ripen.
This growing season the vines have been as confused as all of us in Australia, what season is it?!? Flooding rain one day, hot the next and freezing cold after that?! Usually the warm climate and fine sands of the Vine Vale area help with weed control, the sand dries up quickly making it easy to pass with a knife as the shallow rooted growth slows and the vines dig deep. This season however there has been so much water that once the subsoil clay filled to capacity, the free draining fine sand above had nowhere to drain to so it filled up, and overflowed. We had standing water in large parts of the vineyard for weeks on end, almost until the end of November! Needless to say there was a lot of growth and the ducks, frogs and clover loved it (see our instagram).
It all started in Spring, the rain and then the work.
This spring was wet, very wet, some rainfall gauges say the wettest since European records began in the early 1800’s. To put in context against long term patterns this meant 194% above average rainfall in October and 297% above average rainfall in November. It was wet. The season showed signs of being challenging early as budburst was a little later than usual (but I did prune later too), because of this I chose to start early with shoot thinning to open up the canopy and spread out the shoots for more light and airflow. This is a risky proposition as Grenache can set poorly if flowering occurs in unfavourable weather, the flip-side is more light for next year's buds and focusing growth for bigger stronger shoots this season. Dad and I also spent a lot of time layering shoots and installing posts to support low shoots. Where and old vine is falling apart we take a shoot to form new trunk structures and get them off the ground out of the grass and out of he frost zone.
New shoot from the old trunk being given support.
The vines were slow to grow early and there was unbelievable disease pressure but eventually at our site a good flowering window appeared for the Grenache. Because of the strong growth another pass was required to remove leaves from around the bunches. This is done to allow more airflow and light onto the developing fruit, the flavour and aroma pre-cursors begin developing in response to light immediately following flowering, after all the anthocyanins and pigments are the berries sunscreen. If the developing fruit never sees direct light it doesn’t get a strong signal for development of these compounds, why would it? So, we remove leaves on the eastern and southern sides to expose the fruit, this allows direct early morning sun and sun up to midday while protecting the Northern side from burn due to extreme direct sun if it arrives. Grenache can burn but it can also bleach and stop developing colour so it's a delicate act. The orientation of our rows mean that some of the western setting sun does hit the fruit but that’s more because these old vines are large and multidimensional, but late in the afternoon this is of less concern as the sun is much lower in the sky.
Wet, Cool and Cloudy
Even in early February we had cool days of 14 degrees, despite some warmer individual days we are saw the results of this drawn out season impacting on vine development. Normally there is a blush of colour in the developing fruit as it goes from green to red/black in a process known as veraison in January, but even in February its been late to arrive. Last year we had colour early in Feb (see pic) and that was 1-2 weeks behind ‘normal’ in an also cool season. This year the vines are another 2 weeks behind that, so approximately 4 weeks behind ‘normal’. This is shaping up to be the latest season since the early 2000’s and harvest might not be until the April.
Example of delayed season, image with the purple fruit taken Feb 4th 2022 image with the still green fruit taken Feb 4th 2023.
Now below are three charts that I love, if you follow my instagram stories then you would already know that I really like the climate app, if you are in Aus google it. These three charts show the season we have had and also hint at the vintage we are creeping towards. It’s both academic and informative as early intervention in viticultural procedures like thinning and increasing light infiltration can work to get the most out of the season.
October to February rainfall for Nuriootpa (Barossa) source: https://climateapp.net.au/
The first chart shows rainfall, the red line is this season and the dark blue is the 23 year average with each individual season in faded blue, the two closest lines to the current are the 05-06 and 10-11 seasons. Wine nerds can read into what it meant for those vintages. But what is obvious is that the huge rainfall totals we saw fell in Spring, when the vines are meant to be growing, in contrast in other high rainfall seasons recently the rainfall has fallen later in the season with effects on the fruit more than the development of canopies and flowering.
October to February Heat summation for Nuriootpa (Barossa) source: https://climateapp.net.au/
The second chart shows the heat summation, this is a viticultural measure of temperature that is good for growing. At this point this season the vines are 232 degree days behind normal from October. This shows that the season has been quite cool, with only the 2002 season in the feint blue line below this season in the red, interestingly the 1956-57 season is also low like the 2002 season but I don't recall that one nor the implications for wine quality at that time. Either way this season we are definitely on the very low side considering the clustering around the mean. The take home from this is that even with a string of hot days the vines are not going to catch up this heat, hot days may accelerate ripening via desiccation or with lighter crops but the deficit will remain and harvest will likely be later. But... the final chart ties into this as it is not just heat that plants require, there is a link between heat and radiation...
October to February Solar radiation for Nuriootpa (Barossa) source: https://climateapp.net.au/
This final chart shows the solar radiation over the same period, this is a measure of the solar energy hitting the ground, it’s what plants use to photosynthesize, so pretty important. The heat units are lower this season as seen above and associated with this high number of cloudy days means that the radiation too is very low, the average band as you can see is even tighter around the mean than degree days, but this season is low, very low being in the 0% percentile for lowest in this sample. The next lowest was the 2021-22 season and then 2010-11 again, cooler and later vintages.
What does all this mean? Well as an observer it means the season is cool (slow development) wet (high growth, shading, disease and high cropping) and cloudy (low light, lower potential colour, less fruit next year) and overall potentially leaner with high acids. As a practicing viticulturist this means that to balance the season and grow grapes that are healthy, fresh, ripe and make expressive high quality wines some important practices needed to be implemented. The closer we get to harvest the less influence we have, and as harvest is still some weeks away the hard work early will pay off with healthy, ripe and mature fruit of good balance for winemaking. If the current string of warm-hot sunny days continue.
Thanks for sharing the detail of this season, if you like this follow my instagram gdylla and vinya_vella to follow how the season progresses in the sands of vine vale and the many other regions in which I work.
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Cheers
Dylan
