In this article, I want to share with you the importance of understanding the annual lifecycle of the grape vine. Often new grape growers make the mistake of thinking that if they prune their grape vines during the dormant season, they have done enough to ensure their grape growing success.
Off course, pruning a grape vine is important, don’t get me wrong, but there’s so much more to growing grapes, than simply just pruning.
A single manipulation, like pruning, is only part of the bigger picture when it comes to growing grapes but to be a successful grape grower, you need to know what to do during each and every stage of the annual lifecycle of the grape vine. Leaving out only one important manipulation, like leaf pulling as explained in a previous post, can result in having poor quality grapes or even no grapes at all.
The annual lifecycle of a grape vine:
The first signs of bud break in spring.
This time of the season, the shoots that develop, are very susceptible to frost damage so you need to protect it from frost damage. It is also the best time to plant your new grape vines.
Depending on your climate, the first leaves will open about 4 weeks after bud break. Your grape vines are still very susceptible to frost damage, so protect them. With some very fruitful varieties, the first grapes will be visible as well. This is the time when the grape vine starts building up energy through the process of photosynthesis.
When the shoots are about 5 to 6 inches in length, your need to spray for powdery mildew. Protect the surface of the small leaves from diseases to maximize photosynthesis. And as soon as the flower clusters developed, it is imperative that you keep your vine fungus free.
Now it’s time to do suckering (removing of unnecessary shoots) and also to remove water shoots to ensure all energy goes into forming and developing the flower clusters. On some very fruitful varieties, you can start reducing the crop by removing flower clusters before they start flowering. Your grape vine’s shoots should be well developed by this stage.
Flowering:
About 10 weeks after bud break, depending on your climate and variety, the first flower clusters will start to flower. Flowering or blooming is the stage where the pollination and fertilization of the grape vine takes place,to develop the grape berries.
While the grape vine is flowering, the ideal climate is mild, wind-free days with no rain. Unwanted climate conditions (rain, too hot or too cold days, and lots of wind), can prevent proper pollination and could result in too compact bunches or too loose bunches with only a small number of berries per bunch
Grape vines are very susceptible to powdery and downy mildew during this stage, so keep your spray program up to date.
Fruit set:
Just after flowering, the grape vine goes through a stage we call fruit set. During this stage, all the fertilized flowers will start to develop into berries and those that didn’t, will fall off. The conditions during flowering will greatly determine how many berries will develop and how many not.
During fruit set, it is critical that you grape vines don’t dry out too much as this is the stage where cell division takes place. The more cells that will develop, the more there are to enlarge (next stage) and the bigger berries you grape vines will bear.
Cell enlargement:
During this stage the cells that developed in the previous stage (fruit set), will increase in size and it is a crucial time of the year for developing larger berries. Your grape vines will start to use more water as the berries increase in size.
Once the berries are the size of a pea, the thinning out of bunches by hand or chemically will ensure loose bunches, with larger berries and less diseases. You absolutely must ensure that your grape vines are not water stressed during this stage.
Some varieties are very susceptible to sunburn or scald and most of the damage to these varieties takes place during cell enlargement. Maintaining a closed canopy will help prevent sunburn.
Colouring (Veraison):
Veraison is when the berries start to soften and turn colour and signal the beginning of the ripening process. Normally takes place around 40-50 days after fruit set. The early stages of veraison is where you will notice a dramatic increase in berry size.
In the Northern Hemisphere, this is around the end of the July into August and between the end of November into January for the Southern Hemisphere. During this stage the colours of the grape take form-red/black or yellow/green depending on the grape varieties. This colour changing is due to the chlorophyll in the berry skin being replaced by anthocyanins (red wine grapes) and carotenoids (white wine grapes). In a process known as engustment, the berries start to soften as they build up sugars.
Some varieties tends to have poor colour, so opening up the canopy and removing leaves around the bunches, will help colour development.
Berry maturity:
Many home growers make the mistake of thinking the grapes are ready for harvest when it start
to colour. The colouring of the skin is a good indication that the grapes are nearly ripe enough
to harvest, but not ready yet.
The ripeness of grapes is measured in Degrees Brix (symbol °Bx). This is a measurement of the mass ratio of dissolved sugar to water in a liquid. A 25 °Bx solution is 25% (w/w), with 25 grams of sugar per 100 grams of solution. Or, to put it another way, there are 25 grams of sucrose sugar and 75 grams of water in the 100 grams of solution.
There is an instrument called a refractometer, that measures the sugar levels of the juice squeezed from a few berries. This instrument unfortunately is quite expensive and only if you plan to make your own wine, I would recommend buying one.
Dormancy:
It should be close to winter now, and the leaves of the grape vine will start to change colour and fall off and your grape vine will go into rest (dormancy). During this time of the year, the grape vine accumulates carbohydrates in the canes, trunk and roots of the vine for the upcoming growing season.
This is the time of the year when the grape vines need to be pruned. In colder climates, it is best to wait until early spring, before you prune the grape vine.
Remember my friend, for you to be a succesfull grape grower, you need to know what to do in every stage of the development of the grape vine. Without this, you will have little or no chance of succeeding!
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