Growing grapes in cold climate conditions

As a South African and a professional grape grower, learning about the grape vine each day, is my passion. Therefore I’ve done some research on growing grapes in cold climates, something we, here in South Africa, has little problem with. The only time our vines get cold damage is when there is heavy frost early in spring, after the vines sprouted.

Growing grapes in mild and very cold climates do not differ as much as growing grapes in the tropics, and the pruning methods, training methods we use here in South Africa, are used in very cold climate conditions as well.

However, there are a few things a grape grower must consider or think of, before planting grapes in these very cold conditions.

I will be touching on some cold resistant wine varieties and also what the grapes growers do to protect the grape vines.

What Great Wines are Produced in Cold Climates?

The Grape varieties I am going to talk about are hardy to at least -20F/-28C. The various types include Red, White and Table or Juice Grapes. I will list some of the most popular kinds in each group. The first group is the Red Wines that include such varieties as the Baltica, Landot Noir, Savrevois, St. Croix and Swenson Red. Next we will cover the White Wines. Some of the grapes that are in this group include Alpenglow, Brianna, Edelweiss, Frontenac Gris, LaCrosse, LaCrescent, Prairie Star, Swenson White and Vignoles. As for the final category, which is the Table or Juice variety, they include the Bluebell, King of the North, Reliance, Somerset Seedless, Toldi, Trollhaugen and the Valiant grapes.

What is the main concern with cold weather varieties?

Damage to the crop. We will be taking a quick look at how to notice the most prominent damage to the crop when a frost or freeze has penetrated it. In one case, in Southwest Michigan in 2002, over 95% of the crop that was to produce had most primary growth destroyed by the frost.

But before we move on, lets look at the grape bud. A grape bud, is actually three buds. A primary, secondary and tertiary bud. When the primary shoot, or the bud itself is killed by frost or freeze, the secondary bud will sprout. Secondary and tertiary buds, produce less grapes, and grapes of lower quility, but at least the grapes in 2002 (mentioned aboce) produced some grapes, so the grape growers didn’t have a total crop loss.

Cold damage on buds appears dry and shrunken. After awhile, they will crunch when you pinch them with your fingers. Injury to the plant may also include the vascular tissues of canes, cordons and trunks. In some cases, it may even kill the whole vine. That is what happens when a plant has frost hit it. What happens when a freeze hits the plant or grapes? When a plant is hit by a freeze, you will be able to pick it out clearly. The grapes physical body will look water logged and black. It doesn’t have to be dark black to show signs of the damage.

How does a farmer protect from these conditions?

Location, location, location. That’s what they say about business, movies and networking with people. Well, the same seems to be true for the grape crop and protecting it from the elements.
The types of soil used, the slope of the land and even the drainage all have to be taken into consideration when you decide on how to protect your vineyard in down seasons.
The secondary process is finding a suitable covering to protect your plants. In tests, they have found that good old fashion snow cover and geotextile fabrics worked just fine.

They found that if you use soil to cover the grape vine, will protect the vine from cold damage, but it’s not always possible to remove the whole vine from the trellsi it actually helps to breed more disease and inhibits the following seasons production levels.

It seems that geotextile fabrics work best for tender and semi-hardy varieties. They found that snow cover is best where there is a vine without protection and when pinning half of the canes to the ground. This method is most effective in areas that have good drainage and have a southernly slope to the land.

You should probably use geotextile fabrics for any other produce. Just remove them from the trellis if possible, lay them flat on the ground and use the fabric to cover them for the off season.
Covering the grape vine, will not 100% prevent cold damage, but at least there is a chance you vine will survive and you will have grapes to harvest the year to come.

“The Grape Guy”

Autor of the Complete Grape Growers Guide – a step by step guide, how to grow grapes.

Grape Pictures

Hello my dear grape growing friends.

As promised, here are some pictures of my harvest.

My Sultana crop – one of the best I’ve had in years
Look at the berry size – amazing isn’t it?
You must know this vineyard! Yes, it’s the one on my website, where you have
registered for My-Grape-Vine

(Red Globe)

Regal Seedless

We have to cut these bunches in half to be able to pack them propperly!
Looks lovely , he?

Those of you who still had doubts about my ability to grow grapes – well, what do you say now?

LOL……… I would love to hear what your comments or questions are about the grapes.
Have a grape (great) day
Author of “The Complete Grape Growing System” teaching you how to train, prune and grow your grape vine like a pro!

Get your membership for only $29 – click here

Concord Grapes – Grape of the millions

While grapes have been used in production for thousands of years, it was not until the middle 1800’s that the Concord grape was first introduced. This special grape that is known for its’ deep purple color and robust aromas was named after the Village of Concord in the state of Massachusetts. Ephraim Wales Bull was the one who experimented with the seeds from wild grapes in the area and eventually came up with what is known as the Concord grape. Bull created this special grape to ripen as early as possible so there would be no danger of losing them to the harsh winter frosts of Massachusetts. After Bull entered his grapes in a horticultural exhibition and won, his grapes went on to become known worldwide.

Today, Concord grapes are still very well known and are being grown various places around the world. In some cases, people have started growing these lovely grapes for their ornamental value in their yards. Often, people create trellises or arbors to grow these grapes on and they often allow for a shady place to sit and add beauty to the surrounding landscape. Concord grapes are also grown for eating as well. There are a variety of food products that are made from these grapes including jellies, jams and raisins. The Concord grapes have a wonderful taste that makes them a great choice for these food products.

Another purpose of growing Concord grapes includes wine making, too. These robust grapes are used to make a variety of great tasting wines for the drinking pleasure of people around the world. While Concord grapes are not used by some as they tend to have a very fruity and sweet taste, there has been a revival of their use among a variety of small wineries. In recent years, they have been widely used for dessert wines and kosher wines, but more recently they have been used more and more for tables wines as well.

Since Concord grapes are only one kind of grape among many others, you may be wondering why this specific kind of grape is so popular. Shortly after Concord grapes became known worldwide, they were called “the grape for the millions.” This grape became quickly popular after its creation and is still very popular today because of its versatility and its amazing taste. Later in 1869 Dr. Thomas Bramwell Welch came up with the idea of making juice from Concord grapes and led to Welch’s grape juice, which has continued to make Concord grapes popular. Certain companies have also used Concord grapes for dessert wines, table wines and kosher wines, which has also increased the popularity of these grapes.

Yet another contribution to the popularity of Concord grapes have been recent scientific studies that show these grapes have excellent antioxidant properties and can lower the risk of heart disease. Now products that contain Concord grapes have been approved and recognized by the American Heart Association to significantly lower the occurrence of heart disease. These new findings have increased the consumption of Concord grape based products.

Concord grapes are very easy to grow and are mainly grown east of the Rockies. This type of grape can deal with the cooler temperatures of the north and they usually ripen earlier than most other types of grapes. Some of the states that produce large amounts of these grapes include New York, Pennsylvania, Michigan and even West Virginia. While Concord grapes may not be overly picky about the soil they grow in, they usually do better if there is adequate soil moisture during the growing season. Since these grapes are so easy to grow, they have become a productive crop to grow.

“The Grape Guy”

Want to grow a Concord, get your copy of the “Complete Grape Growers Guide” and I will show you how to.

Why is canopy management so important

You probably will ask yourself what canopy management is and why you must manage the canopy. A simple answer is to expose the vine to as much direct sunlight as possible. You will notice that I hammer on sunlight exposure in almost all my newsletters and in the Complete Grape Growers Guide. This is for a good reason, as exposure to sunlight is one of the most important things, you as a grape grower must keep in mind – ALWAYS!

What is a normal or ideal canopy? A few lateral shoots, shoots with big leaves, moderate internodes and a length of 4-5 feet is characterize an ideal canopy. On a canopy like this, almost all of the leaves and buds and shoots are exposed to direct sunlight. The airflow (ventilation) of the vine is good, which will help the prevention of diseases.

When planning a vineyard, no matter what the size, you need to know how fertile your soil is in order to decide the size of your trellis. A too small trellis with a vigorous growing vine, will compact the vine to much and now airflow or sunlight penetration can take place. On the other hand, a too big trellis on a not so vigorous growing vine, is a waste of money, as building a trellis can be quite expensive. The planting distances, also vary on different soil types, which will have a direct influence on the canopy growth. Planting vigorous growing vines too close to each other or making the rows of the vineyard too narrow will also compact the canopy of the vine.

Another reason all grape growers strive to have a well-balanced canopy, is that it reduces the amount of labor it requires to successfully grow grapes. A too vigorous vine will have many shoots to prune during winter, and could take up twice the time to prune than a grape vine with an ideal canopy. Summer treatments, like suckering, removing of leaves, removing of side shoots and the prevention of diseases is much more difficult when the vine has grown too much.

Normally the reason why a grape vine grows too vigorous, or why the canopy of the vine is too compact is because of over-fertilization or over-irrigation on fertile soils. The amount of nitrogen a grape vine needs per year, differ from soil to soil, but a rule of thumb is 120kg N per year. Just to give you an example; one vineyard of Sultana on my farm, gets only 55kg N per year, because it grows on deep, very fertile, sand/clay soils.

If your grape vine is under-vigorous, you can try a few things. Don’t let these vine bear to many grapes, as it will only prevent the vine from growing as it should. Determine why the vine isn’t growing well; look for symptoms of virus infections, see if you have watered the vine enough by digging a hole next to the vine and at the same time have a look at the structure of the soil and how the root system has developed. Sometimes it happens that a clay layer can prevent the roots from spreading into the sub-soil.

If you find, during the growing season, that your grape vine is growing to vigorous and you are the canopy of the vine is getting too compact; there are a few practical things you can do to try to stop the vine before it gets out of hand.

  1. Removing of leaves – this is done by hand and all the leaves close to the cordon or arms of the vine should be removed. Also, remove leaves in the bearing area of the vine (close to clusters). Removing these leaves will ensure better sunlight penetration and airflow. Do not expose clusters to too much direct sunlight, as it will scorch the skin of the grapes, especially if you have a hot climate. Remove leaves after fruit set a then again at varaison (coloring).
  2. Suckering – Remove all water shoots from the cordon or framework of the vine. Under developed and non-bearing shoots can be removed as well, if you find that suckering only water shoots wasn’t enough. Keep in mind that you need prune wood the following winter and never leave less than two shoots on a spur. Suckering shout be done before flowering and never during flowering as this will stimulate more growth that can lead to abortion of fruit.
  3. Placing or twining of shoots – The placing or twining of shoots is a well-known manipulation of the grape vine and this should be done when the shoots are about 12 to 16 inches long. Cover the as much as possible wires on the trellis so vine will have maximum exposure to sunlight.
  4. Summer pruning or topping – When your grape vine grows on an arbor or high trellis, and the placing of shoots is difficult, you can summer prune excessive growth by removing the growing point of the vine. Summer prune when the vine has overgrown the trellis and in this case remove more than just the growing point.

Maintaining an ideal canopy for your grape vine is very important and should be done correctly and at the correct time during the growing season.

For further Reference, see the “The Complete Grape Growers Guide” at

Danie Wium

“The Grape Guy”

Author of “The Complete Grape Growers Guide”

Pierce’s Disease (PD) on Grape Vines

The History of PD

Pierce’s Disease, also referred to as PD, is a disease in specific plant life that reduces their ability to use the soil for its nutrients and water. It is a bacterium that clogs the vessels in the vine that draws these two necessary items from the soil underneath it. Essentially, what happens is that the vine starves, unable to get the necessary elements; it occurs very slowly and ultimately dies. PD (Pierce’s Disease) effect grape vines, as well as stone fruits, citrus, and almonds.

Back in the late 19th century, a pathologist of plans investigate the first Californian outbreak of the disease and thus the disease was subsequently named after Newton Pierce. However, the disease has been in existence since the 1880’s, when it was then known as Anaheim disease, because it was within the Anaheim area that it was first discovered.

Throughout the years, vineyards have had to fight PD over and over. Severe outbreaks have occurred and after much research and testing, it was discovered that Pierce’s disease is spread by an insect.

The Physiology of PD and what parts of the vine it attacks

Pierce’s Disease is a slow killing plan disease. It can take up to one year before the vine will begin to show symptoms and signs of the bacteria. It can then take up to three years before the plan will eventually succumb to death by the disease. How can you tell that the grape vine was withered by PD? Well, once killed it is black and very withered. However, there are signs of other symptoms before it reaches that stage. For example, when infected, the vines may promote shriveled or dried grapes, leaves that are underdeveloped, discolored vines, and even growth troubles, it will not be as large as it should.

The insects that spread this disease through grape vines is called the blue-green sharpshooter and the glassy-winged sharpshooter. These are tiny, flying insects that are essentially known as leafhoppers. They feed on the juice from the plants. Upon feeding, the disease transfers from the mouth of insect to an otherwise healthy plant, infecting it with the disease.

Pierce’s Disease, affects the vascular system of the plant. It multiplies and houses in the xylem of the plant, which is a water system that is similar to piping. As stated it is a slow process and difficult to discover until the plant has been infected for one year.

One good thing about PD, is that is does not affect humans in any way, nor does it affect the quality of the wine produced by these grape vines. It is however, responsible for the death of many grape vines throughout California and other wine producing areas.

The susceptible varieties and what to do to prevent PD infections

The only real combative measure against Pierce’s Disease to date is to be attentive to your grape vines and plant varieties that are resistant to the disease. At this time, even with all the research, plant pathologists and scientists have not been able to produce a rootstock, spray, or solid practice that will prevent or reduce a PD infection.

The only real suggestion is to plan grape vine varieties that are resistant to the disease. Here are the resistant varieties:

Orlando Seedless – This is a table grape with great flavor and fairly easy to grow. It will need some pruning and thinning of clusters to maintain, but produces a great tasting wine. Not only is this variety resistant to PD, but also Powdery and Downy Mildew. It is susceptible to Anthracnose and Black Rot however.

Blanc duBois – This a variety of grape for white wines. There is no need for rootstock in most cases, and produces nice sized berries and clusters. As with Orlando Seedless, it is resistant to Downy Mildew and PD, but susceptible to instances of Anthracnose and Black Rot. This variety is not good for soils that are high in pH and poorly drained.

Other great resistant varieties include Black Spanish, a variety for jellies, juices, and red win, Champanel, a variety for red jelly, Favorite, a child of Black Spanish, and Roucaneuf, a table or white wine grape. As well as Herbemont, Norris, Stover, Lake Emeral, Conquistador, Suwannee, Daytona, Miss Blanc, Miss Blue, and Mid South, are all PD resistant varieties.

The best defense against Pierce’s Disease at this time is to eliminate susceptible varieties and stick with those that have a known resistance, at least until someone develops a solid defense for other varieties.

Danie Wium
“The Grape Guy”
Author of The Complete Grape Growers Guide

Help! My Grape vine is under attack!

The past few 5 weeks, I have answered almost 450 emails! And most of them were about training the grape vine, pruning the grape vine, what varieties to use and many more. But let me tell you of some the real attack you must be looking out for!

How can you, the home grape grower, put a suit of armor on your grape vine? Just like any other living thing, your grape vine needs protection from outside attacks and you will have to ensure that they are ready. Obliging actions can save your vine from these attacks, which can ruin your grape harvest in a matter of days.

You dare not ignore these five enemies, because the grape vine is their main target and oh boy, are they well trained sharpshooters.

1. Frost / cold damage:

For you to understand the dangers of frost and cold damage, you need to know that you probably will not loose your whole crop, but you will endure losses. The reason I say this, is that there are three growing points inside a grape vine’s node (primary-, secondary- and tertiary buds). The primary node is the normally the grape carrier and shoots first when the growing season starts. If frost damage or kill this shoot, the secondary and tertiary buds will sprout. They also can produce grapes, but normally not as much and not as high quality as the grapes produced by the primary bud.

Without digging to deep into the development of frost and factors that cause the air temperature to drop below frosting point, a rule of thumb is, that if it is a wind free, clear sky, and dry evening and the temperature drops below 2.2°C (36°F), there is a chance of cold damage to the vine. The lower the dew point, the higher the risk

There are a few things a home grape grower can do to lower the risk of cold damage.

Sprinkle irrigation can be turned of when the temperature decrease below freezing point 0°C (32°F), the temperature of the water will rise to freezing point and freeze or ice. The freezing process will generate some heat that will raise the temperature of the atmosphere (heat of fusion).
Choose a late variety to plant where frost is a problem, this will ensure that bud break is later, lowering the risk of damage.

Choose the warmest, sunniest spot in your garden, to plant your grape vine.

Prune as late as possible (near bud break), and cane prune at first and later on, after the dangers of frost is gone prune your short bearers where you want them. Refer to the “Complete Grape Growers Guide” how to cane and short prune.

Sandy soils are more hazardous, because they store less water and therefore some sort of ground cover will lower the risk of frost damage.

2. Birds and Animals:

You have probably know that birds and other animals love your grapes. Allowing them to have a feast in your vineyard, will result in total crop loss. You as a gardener, loves nature, and killing these animals will not do any good.

What you need to do is to prevent them from getting to your vine. Easier said than done, but there are a few things you can do.

Cover the bunches with netting will prevent birds from reaching your grapes.
There are safe, commercial sprays you can spray on your plants, that will prevent animals from eating them.

Buy these products online at Garden Alive, or you can enquire at your local nursery about these items.

3. Rain:

Rain during, or close to harvesting your grapes will have a serious effect on the quality of your grapes. Certain varieties are more susceptible to rain damage than others. Varieties like Flame Seedless and Thompson Seedless are very susceptible to rain damage and should be avoided if summer rain often occur. Refer to the page where you downloaded “The Complete Grape Growers Guide” for a list of varieties you can plant that is not so susceptible to rain damage.

There’s not much you can do to stop rain, is there? But you can dust your vine with a copper sulphar dust to prevent the spread of fungus and to try out the cracks on berries, caused by the rain. Remove cracked berries by hand if you have the time, this will ensure that botrytis will not spread to nearby healthy berries – this is a rime consuming job, but well worth a try.

4. Phylloxera:

The cancer of the grape vine! Never underestimate the danger of this disease. If you plant a Vitis Vinifera variety, DO NOT use cuttings.

Phylloxera is a pest of commercial grapevines worldwide, originally native to eastern North America. These tiny, pale yellow sap-sucking insects, related to aphids, attack the roots of grape vines. The insects and secondary fungal infections can girdle roots, gradually cutting off the flow of nutrients and water to the vine and eventually kill the vine.

In the early 1800, Phylloxera destroyed almost the whole wine industry of Europe and more than 60% of the vines were killed!

Be on the lookout for symptoms of Phylloxera as this desease can kill your vine in no time at all.

5. Too dense vines

Ok, so you might say this is no attack on the vine! Fair enough, but a too dense vine will make your vine a sitting duck. A too tense vine is more susceptible to diseases like downy mildew, powdery mildew, botrytis (grey rot) and many other diseases.

Controlling the growth of your vine is sometime not that easy as a vigorous variety like Sultana on a fertile soil, will grow like mad without any fertilizer. The use of a less vigorous rootstock will help prevent the vine from growing to strong.

Always remember that a dense vine looks lovely, until the first rain!

Preventing these attack is better than trying to cure them and it will save you lots of time, money and frustration. The Complete Grape Growers Guide, helps you to put a suite of armor on your vine.

Have a grape (great) day.

“The Grape Guy”

PS: Remember that the X-Mas special on “The Complete Grape Growers Guide” ends soon! Don’t miss out on this one!

Buying grape vines from a nursery:

The are basically two “types” of grape vines you can buy from you nursery and they are grafted and non-grafted vines. The grafted vines has a rootstock from another variety and there are a few reason why breeders do that.

There are a few Vitus Riparia and Vitus Labruska cultivars (with really ugly grapes, if any grapes at all!) that is more resistant to nematodes and phylloxera than some of the cultivars used in the wine and table grape industry. Breeders use these cultivars as rootstock for the non-resitant cultivars, in order to get a more resistant vine.

Sometimes, when a variety is a weak grower, and the grape grower needs a more vigorous growing grape vine for some reason, the breeders then use a more vigorous growing rootstock. Never use a vigorous rootstock on highly fertile soils, but instead use these rootstock varieties on dry-land vines or in very dry conditions.

Many of these rootstock varieties are more resistant to certain soil abnormalities like low pH, very wet conditions or even limestone abnormalities. Make sure you know what is going on inside you soil, before deciding on a rootstock.

I personally never plant a non-grafted vine, because of the danger of phylloxera.

The non-grafted vine is a normal cutting made from a mature vine and and then rooted and planted out. This method is mostly used by the home grape grower as making a scion needs special skills.

In case you are going to buy a grafted vine from your nursery, there are a few things you should look at:

  1. Make sure the graft union has healed properly and that there are no openings between the rootstock and the carrier.
  2. Make sure the union is strong by slightly bending the grafted vine – don’t over bend it, it will break. If the union didn’t attach well, it will brake easily.
  3. The rootstock must have well developed, strong roots, with no signs of defects.
  4. Take a look at the bark of vine, it should be undamaged with a dark brown color – not black as this can be an indication of some fungus spores (from the previous year)
  5. The canes of your vine should have grown at least 8 inches the previous year and preferable there should be more than on cane.
  6. No visible roots should come from the graft union – if there are roots, remember to remove them before planting, otherwise your vine loose its resistance to diseases inside your soil.

buying grape vines


Happy grape growing my friends.

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“The Grape Guy”

You probably know what photosynthesis is, but do you know what really happens inside the grape vine during photosynthesis and why it is so important to expose your vine to enough sunlight?

Photosynthesis is one of the most important physiological processes that take place inside the vine. During photosynthesis, the energy for the salvation of the grape vine is created. This is quite a complex process where sunlight energy, absorbed by the chloroplast inside the mesophyl cells of the vine, is assimilated into CO2 and carbohydrates (mainly sucrose). Water is needed for this whole process to activate and stay active. The following formula explains photosynthesis:

CO2 + 2n H20 + sunlight energy –> chloroplast –> (CH2O)n + O2 + n H2O

All of these carbohydrates are then transferred to the endodermic cells of the vine and transported to the all the growing parts (growing points of shoots and roots), to the reproductive parts (buds and clusters) and some stored in the stems of the vine.

Which factors influence photosynthesis?

1. Environmental factors:

Light intensity: Maximum photosynthesis in a grape vine, takes place when the sunlight intensity is around 25 000 to 30 000 lux. When the canopy of the grape vine is too dense, the sunlight cannot penetrate the canopy enough for photosynthesis to take place. That is why we find yellow leaves inside these kinds of canopies. Photosynthesis can take place from reflected sunlight as well, but the intensity of this light is normally not high enough for optimum photosynthesis. Having a to dense or compact grape vine canopy will reduce the productivity of the vine, because of reasons mentioned above. Canopy control is therefore of utmost importance when growing your grape vine. There are several ways to control canopy growth, like topping of the shoots, removing water shoots, removing (suckering of unnecessary shoots) and the spacing of short bearers. The summer treatments of a grape vine are explained in depth in “The Complete Grape Growers Guide”.

Temperature: Normal photosynthesis takes place between 0 and 60*C (32 * F and 140 * F). The optimum temperature for photosynthesis is between 25 – 28 *C (77 – 82.5*F). During tests in a lab, with controlled environmental conditions, it was found that when the temperature decrease below 20 *C (68 *F) and above 30 * C (86 *F), the rate of photosynthesis drops dramatically. Outside, in nature, many factors influence photosynthesis, and it was found that optimal photosynthesis can take place at an optimum level of 16 *C, if the other factors are in favor of photosynthesis.

Moisture: A grape leaf must have at least 75 % to 85 % moisture to be biochemical active. In the formula of photosynthesis, you will notice that water is needed for the whole process to take place, in other words, the optimal soil moisture, where the grape vine grows, is very important for photosynthesis to take place. The humidity of the atmosphere around the vine influence the effects the rate of photosynthesis – a higher humidity at the same light intensity has a higher rate of photosynthesis.

CO2- and O2 concentration:
Normal CO2 concentration in the atmosphere is around 300 ppm. The rate at which photosynthesis takes place, increase as the CO2 concentration increases up to a point when it reaches 500 ppm, where it slows down and stops at a rate of +- 1000 ppm. Just as the opposite happens when the concentration of O2 (oxygen) increases above 21 %.

2. Internal factors:

The leaf of a grape vine starts to photosynthesize at a very early stage (when it is the size of a matchbox), but only until it is two-thirds of the size of a mature leaf, it is self-supporting. Now you may ask, how does a young grape vine grows with leaves that are self-supporting are non self-supporting? The secret lies in the energy that was stored inside the roots, and stems during the previous growing season. Therefore you MUST make sure that the leaves of the young grape vine reaches at least two-thirds of its mature size as quickly as possible, before the stored energy inside the vine are replenished. Using certain training methods explained in the Complete Grape Growers Guide, this stage of maturity of the leaf would be reached very early.

The need for photosynthetic products increase as the size of your crop increase, therefore you need to control the size of your crop according to the growth of your vine. A young vine with a small canopy and a large crop will not be able to produce enough carbohydrates to ripen or mature the harvest.

3. Genetic factors:

Different varieties react different to the exposure of sunlight from others; therefore, different varieties have different levels of photosynthesis than others. The opening and closing of the stomas of different grape vine cultivars are not the same, and this will influence how much moisture is available for photosynthesis – less moisture, less photosynthesis!

4. Cultivation practices:

As mentioned before; the more leaves exposed to direct sunlight, the better the photosynthesis will and therefore we need to design our trellis system in such a way. Row direction, summer treatments, pruning, planting distances and the irrigation or the vine will all play an important role in photosynthesis.

If we go through this whole process of photosynthesis, there is one thing that stands out – do not let your vine grow out of hand. A too dense vine is an unhappy vine and it will for sure not produce the grapes it should have.

For more information on how to increase the productivity and level of photosynthesis of your grape vine, go visit My-Grape-Vine.

“The Grape Guy”

On 29 November I shared with you the methods I use to cultivate top Sultana Grapes.

Here is a picture to show the effect Gibberellins (Gib) has a Sultana Berry!

Numbers in above picture:

  1. shows you how the gib has stretched the berries – see that little dimple at the bottom of the berry? – they are gonna be huge berries in a few week! Without gib treatment, Sultana has a normal round berry, not big in size and very condensed bunches.
  2. look how the gib thinned out the bunches to make place for a bigger berry size – in a few weeks, these “gaps” will be filled and you will have a 700 gram bunch with berries of +-21 to 23 mm!

This picture was send by one of My-Grape-Vine friends – he has a lovely Sultana vine, but what I need you to look at, is the difference in berry shape and how compact these bunches are.

With bunches like this, you will probably have a reasonable crop, but you will never have that berry size that will let your neighbor say: WOW! Where did you buy that!

Secondly, controlling diseases in these condensed bunches is almost impossible – you will have a problem if your grapes get some disease.

Have a grape (great) day!


“The Grape Guy”

Get the Complete Grape Growers Guide and I will give you step by step instructions on how to train and grow your Sultana vine. Your vine will “crank” out bunches of grapes like you have never seen before!!

Downy Mildew – experiment

Hello everyone,

I did an experiment yesterday to show you how devastating downy mildew can be.
Look at these pictures:
Picture taken 19h30 yesterday
Here you can see an “oily” yellow patch on the top side of the leaf. This is the first signs of downy mildew.
Bottom of the leaf – if you look close enough you will see some white hairy fungus growth
I took the leaf and put it in a wet plastic bag, inflated the bag with hot hear and sealed it with a zip tie. This is the perfect conditions for downy mildew to develop – hot, humid conditions
I took the following pictures exactly 12 hours later:
Nevermind the withering of the leaf, although it’s obvious where it started, but take a look at all the fungus growth in just 12 hours! This disease can destroy your grape vine in 48 hours. Be on the look out for those oily yellow patches on the top side op the leaves – if you find them, be warned and take immediate action. Normally a contact/systematic pesticide will do the job, but prevention is better than cure – spray your vine upfront

Have a great, downy milew-free day :-)

I would like to hear what you have to say about downy mildew … leave a comment.


“The Grape Guy”

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