Bud swell and break — Season Tee Off ⛳️

Rise and shine 🌅

As we leave the dark days of winter, we can now start looking forward towards a new vine growing season, yay 🥳. When temperatures start to rise and our sunglasses are coming out, the vines also start waking up from their winter dormancy. That makes it the ideal time to dig a little deeper into the workings of the vine and its “morning” routines after the winter period.

Vine juices start flowing as last year’s prune wounds start to bleed

If you were like me, one of the last things we did before the winter period was pruning the vines, making ready for one of the hardest seasons — winter 🥶! Well, actually, it are these pruning cuts that show the first signs of a rising vine. As displayed in the picture above, last year’s pruning wounds start to “bleed” as juices within vine start flowing. No worries… it is no actual blood but the internal juices of vine. These juices start to flow when temperatures increase. In the case of the vine the critical temperature is mostly around 10 degrees Celcius or 50 degrees Fahrenheit. Whenever this temperature is reached, the vine gets an extra boost of energy and sends its juices throughout its canes and buds. The movement of these juices starts the hydration process of the buds, delivering delicious minerals, sugars and hormones 🤤. As the buds are injected with some healthy nutrients, the metabolic activity inside the bud get activated, motivating the bud to start growing. This process is referred to as bud swelling.

Bedtime prep 🛏️

But… wait a minute… lets first take one step back and go back in time, back to those cold and dark days of winter 🥶. It is interesting to see what happens when winter kicks in before we continue with the boot procedure of the vine.

As soon the temperatures start dropping, the vine prepares itself to go in hibernation. During this period, the buds on the vine transform and are injected with a tissue called Phloem. Phloem makes sure the vine becomes water resistant by applying a cork-like layer on top of the buds. Furthermore, the existing water in the buds get drained through another type of active tissue, called Xylem. Thanks to these processes, the buds are all dried up and get a nice protection from the ice crystal that are created during freezing temperatures, preventing frost damages during winter.

Just like the hibernating animals, vines also make sure they store enough nutrient to survive the dormant season. In this case the nutrients are contained of carbohydrates and nitrogen reserves. These reserves also play a vital part when the vine starts waking up as it needs to use all the available energy to start the new season’s growth. This means that it is very important that growers allow the vine to create these reserves at the end of each growing season. When the vine has been defoliated early (no photosynthesis possible) or harvest is delayed too long (energy is used by other parts of the vine), the vine may enter the winter with inadequate reserves — causing issues for new growing season possibly resulting in a weak shoot growth.

Sleepy buds 😴

Even though the buds are dormant throughout the winter, when spring time hits a lot of things are happening underneath it's covers. Inside the dormant buds, a fully formed compressed shoot is developed. This is called the primary bud and contains the starting points for the first leaves to be grown as well as the beginning of the clusters to form in a later stage of the growing season. As a backup of the primary buds there are also secondary and tertiary buds. These come into play whenever the primary buds get damaged. This could be due to frost or any other damage throughout the (winter) season. However, these buds do have much less potential. In most cases they do contain less leaves and almost no clusters. Result: your vine will look nice and green, but the crop itself will be poor 😢.

https://www.lodigrowers.com/important-structures-features-of-grapevines/
Primary and secondary bud on the vine’s cane, covered in Phloem and showing the first signs of swelling

Bud break 🌺

So, let’s fast forward again to the nice warm temperatures of spring 🌻! As the juices continue to flow, hydrating and feeding the buds, the buds start swelling. At a certain point they burst open and we see the first green tissues, representing the new shoot — almost as magnificent as giving birth to a child. This process is called bud break. It marks the start of a new growing season as we see the first evidence of a something that will grow out to be a full grown shoot, bearing our precious grapes 🍇.

A bud break in action where we see the first signs of this year’s growth

Bud break is also THE moment that vine can take a deep breath and use its natural processes, such as photosynthesis to power its energy. However, it also a dangerous period as growers still need to monitor the temperatures closely as the vine is very vulnerable at this stage. Frost can be devastating at this point, damaging the emerging shoots. Protection of the vineyard against freezing temperatures is vital. If everything else failed, growers can better pray the secondary and tertiary buds are able to provide them with a new chance!

Influencers

One last thing to take into account is that the process of bud swelling and bud break are very subdue to different conditions. As mentioned in the beginning, temperature is in most cases the most important condition for the vine waking up. However, there are many other as well. Some of the most important influencers are:

  • Air temperature — As mentioned in this post, air temperature will start waking up the vine and gets its juices flowing. Who doesn’t want to wake up with the sun in their face?
  • Soil temperature — As the soil warms up during the spring period, the roots of the vine also start absorbing water from the soil, up through the vines vessels and to the buds, starting the juice flow.
  • Pruning — In certain regions prone to especially cold winters, delaying pruning until after the coldest winter temperatures have passed will help to delay bud break. This could also help in preventing frost damage during bud break when chances on spring frost are high.
  • Rootstock genotype — Each variety is unique in its characteristics. This also applies to the behaviour related to bud swelling and bud break.

TL;DR 🤓

  • When temperatures rise, the vine juices start flowing and buds start swelling
  • Make sure that the vine can build up its reserves by harvesting on time and not defoliating the vine too early
  • Primary buds will have the best growing potential, but, although less efficient, secondary and tertiary buds are the backup plan when the primary bud has been damaged
  • After a certain period of bud swelling, the bud breaks. Bud break is the appearance of green tissue through the bud scales or the emergence of a new shoot from a bud during the spring
  • Bud break is influenced by several conditions such as air temperature, soil temperature, pruning, variety, …

An IT architect with a very big interest in technology. In my spare time I am indulging myself into the world of viti- and viniculture