Grapes are a great kind of fruit, because they are full of nutrients like vitamins, minerals, antioxidants and anti-inflammatories in their pulp as well as skins. They are also low in calories and fats, and are devoid of cholesterol, so, anyone can snack on them without any guilt.
They are great not only because they are good for health and versatile enough to be eaten fresh as well as dried as snacks and added to baked goods and various desserts and also made into wines, but also because they have an ability to grow in various types of climates. Thus they can be grown in most gardens.
As all may know, grapes grow in clusters of 15 to 300. They come in a plethora of colors such as dark blue, green, pink, black, crimson, yellow and orange.
There are even “white” grapes, but they are actually green and are derived from the purple grapes evolutionarily. Two regulatory genes of white grapes undergo mutations due to which production of anthocyanins stops. Anthocyanins are responsible for the color in purple grapes.
Most grape varieties come from cultivars of Vitis vinifera, the European species native to the Central Asia and Mediterranean. A small number of fruit and wine from Asian and American species, like:
Vitis amurensis – A most important Asian species
Vitis mustangensis (mustang grape) – occur in Alabama, Oklahoma, Texas, Louisiana and Mississippi
Vitis rotundifolia (muscadines) – native to the Southeastern United Sates from the Gulf of Mexico to Delaware and used for jams and wine
Vitis riparia – a wild vine in North America but native to the entire Eastern U.S. and north to Quebec, sometimes used for jams and wine
Vitis labrusca (including the Concord cultivar) – the table and juice grapevines of North America but native to Canada and Easter United States, sometimes used for production of wine.
By far, early spring is the best season for starting grapevine plantation so that the young vines get maximum time to get established before their first winter. Typically grapes need hot and dry climate with temperatures ranging from 60-105°F (15-40°C) and experiencing little humidity, mild winters and limited yearly rainfall.
Roughly, grapes are classified into table grapes (to be eaten fresh) or wine grapes (used for wine making) depending on the purpose with which they are grown. But basically all of them are of the same species i.e. Vitis vinifera.
However, there are remarkable differences created by selective breeding. While table grape cultivars tend to produce large, seedless fruit with quite thin skin, wine grapes are smaller, typically seeded and with thick skins (since most of the wine’s aroma comes from the skin). Also wine grapes are sweeter (24% sugar) than table grapes (15% sugar).
Choosing a Suitable Variety
If one wants to add a grape vine/s to their garden, it’s a good idea to think upon which variety can be suitable to the garden. Particular varieties of grapes grow better in certain areas and have different appearances and flavors.
Grapes can be roughly categorized into three types:
Muscadine grapes commonly occur in the Southern US. European variety occurs commonly in Europe and Northern US, whereas American grapes thrive best in the warm sunny climates such as that of central California.
Each of these general categories is again divided into various species, each offering their own color, flavor, size and texture. It’s better to visit one’s local nursery to get an advice about which variety would fit one’s requirements and environments.
One should choose 1-year old grafted grapevine plants that appear strong and healthy. If possible, these plants should be certified virus-free to ensure their continuous healthy growth.
The root distribution of these plants should be even and canes should be symmetrical.
Preparing One’s Own Grapevine Cuttings
If one has a friend having a grapevine, they can plant from it by taking a cutting and planting it in a new location.
To use one’s own cuttings:
One should cut the sections straight from the vine or from recently pruned off. The cutting should be 3 nodes long (nodes look like bumps). A cut should be made at an angle at the bottom of the cutting. Such a cut should be ¼ to 1-inch above the node and should be at 45° angle.
One should plant as many cuttings at as many locations as possible for a higher chance of success. Additional plants can be given away later.
Choosing a Good Location
Grapevines are long term plants having a lifespan from 50 to 100 years. Hence they should be planted in a location that is a permanent one and would offer ample room for future grapevines. The thriving conditions for grapevines include hilly, sloped areas offering adequate sunlight and drainage. If possible, one should plant their grapevines on the downward slope of a hill, in a space that is devoid of other trees and large plants.
If one wants to plant grapevines in cold areas, they should plant them in a sunny area, possibly facing south, because a south-facing location may protect vines from frost. Also, “frost-packets” i.e. low-lying locations or a base of a slope should be avoided because cold air can pool there and destroy the crop.
However, if one lives in the Southern Hemisphere, they should prefer north-facing slopes for planting grapevines because they are sunnier there.
Grapevines can be grown with other plants and flowers (roses, for example) in the garden and backyard and as such can be very decorative. In such case, note that there is somewhat larger demand for nutrients and water on such positions.
Preparing the Soil
Grapevines are a bit sensitive about their soil conditions.
Hence one should make sure to make the soil right just before planting. The soil should be slightly sandy or rocky with a pH just above 7. Adjust the soil to facilitate good drainage if required, as water-logged roots are not favorable for healthy grapevines.
To ensure the best results, a soil sample should be tested in a soil testing laboratory or an agricultural extension office. This is often free or cheap. If this is not possible, the soil pH should be tested with an at-home kit and then add pH adjusters if needed.
It may seem counterintuitive, but grapevines don’t like soil that is overly nutrient-rich. Hence one should avoid heavy fertilization of soil and follow the advice from an experienced local grower or a soil test result.
Preparing Trellis for Grapevines
Since grapevines are vine plants that grow upwards with the support of a structure, one should plant them either near a fence or similar structure or buy or construct a trellis for them to grow along. A trellis is usually a wooden structure made of interweaved boards around which the vines can wrap and get a sturdy support.
If one doesn’t have enough funds or ability to buy a trellis, a simple homemade trellis can be made by attaching latticed wood and wire to fence posts.
One should never use a single stake (as is often used for tomato plants) since it won’t offer adequate support for grapevines once they start growing. Stakes are fine during the 1st or 2nd year when plants are very small.
Choosing the Right Time to Plant
Rather than planting the vines on an impulse, one should wait for a frost-free day in late winter or early spring to plant grapevines. Also such a day should be chosen for pruning in the upcoming years. One’s local agricultural service can be contacted for exact planting dates.
Based on the species of grapes one has selected, spacing will be different for each plant. E.g. for muscadines, a larger space is needed i.e. around 16 feet (4.9 m). For European and American varieties, there should be a space of 6 to 10 feet (1.8 to 3.0 m) between each two plants. The cuttings should be planted in a trench with the center and basal bud covered. The top bud must be slightly above the soil surface. The soil should be firmly pressed around the newly planted grapevine cuttings.
The depth at which one should plant the vines depends on the size and age of each plant. However, the vine cane should not be buried any higher than the first bud; but the roods should be totally covered in the soil.
The plants should be given a good watering. Heavy rain or watering is not preferred by grapevines; therefore, after the first watering, one should keep the amount of water to a minimum. Water should be kept near the roots so that most of it gets absorbed instead of getting evaporated by the sun. If one’s area doesn’t receive much rain, they should set a drip system straight at the roots so that the vines would get small amounts of water regularly.
Pruning the Grapevines
During the first year, the vines should not be allowed to produce any matured fruits because the young vine can be damaged due to their weight. All the fruits, as well as the vines barring the strongest ones branching off the cane, should be cut back. In later years, one should prune the vines as required as per the established local practices, and prune back 90% of the new growth on older vines every year.
Pruning should always, always be done when the vines are dormant. Otherwise they will bleed their sap and lose vigor. This is normally in late winter when there is no enough cold to frost outside.
A layer of mulch around the plant will retain water, regulate soil temperature and minimize weeds.
Dry leaves should be removed. They can be simply plucked off if they are loose enough. But if they are still firmly attached to the vine, they can be snipped off with a clean pair of scissors.
Since grapevines are naturally very robust, only a little pest control is required. One can keep weeds away by regularly hand-weeding and keep the vines covered in a bird net to keep birds at bay if needed.
Guidance for combating the Vine Moth should be sought from one’s local agricultural extension or gardening club.
To prevent powdery mildew, one should make sure to plant the vines so as to receive adequate airflow. (More on this below)
Grapevines commonly face the problem of aphids. Ladybirds are a natural enemy of aphids and will save the vines from getting damaged further.
Instead of using pesticides, predator insects should be attracted to the area. For this, rows of flowers should be planted along the borders of the property and close to grapevines. These will attract beneficial insects. Still if the problem continues, a mild mixture of soap and water should be sprayed on the leaves and thus spider mites and aphids can be kept at bay.
Harvesting Grapes at Appropriate Times
One has to wait for 1 to 3 years to get strong, edible fruits. When the first fruits will appear, the grower should pick a few grapes from different areas and taste them for ripeness. If they are sweet, the grower can start picking them as they are ready for harvesting and consuming.
It should be remembered that grapes don’t continue to ripen once picked (as other fruits do), so, one should not pick them prematurely.
Size and color are not always good indicators of ripe fruit. The fruit should be picked only after tasting them and ascertaining that they are ready.
While grapevines are typically grown from grafts or cuttings, they can also be reproduced from seeds, provide the grower is determined and patient, because it’s a quite tough process.
Choosing Grape Seeds
Grapes come in thousands of varieties. In order to succeed in growing grapevines, one should choose the variety that would work the best for them. While researching about grape varieties, one should keep following things in mind:
Why is one growing grapes? For eating, to make wine, to make jam or just to add beauty to one’s garden with the beautiful grapevines? Once the grower decides the intention, they can find a suitable variety to meet their purpose.
In what type of climate one will grow the grapevines? Different varieties of grapes thrive in different types of climates and geographic conditions. One should know the type of climatic conditions they have and then find a variety that will thrive in those conditions.
What are the natural variations among grapes developed from seed? Even in a particular type of grapes, there are certain genetic variations and so, the grapes grown by the grower may not be exactly the way they expect them to be.
Therefore the grower should keep their mind open and be ready to experiment.
Once the aspiring grape-grower decides that they’ll grow a particular variety of grapes, they can obtain seeds of that variety from a nursery, from the grapes he has purchased or from another gardener.
Once he obtains seeds, they should make sure that the seeds are healthy enough and in good condition. For this, one can do the following:
- They should squeeze the seed lightly between two fingers. If the seed is firm, it’s healthy.
- They should also check the seed’s color. A healthy seed will have a pale gray or white endosperm under the seed coat.
- They should put seeds in water. Healthy seeds will sink while any seeds that will float are unhealthy and should be discarded.
Washing the Seeds
The grower should now take the healthy, viable seeds and thoroughly wash them so as to remove any pulp or other substance. Then the seeds should be soaked in a little amount of distilled water for around 24 hours.
Stratifying the Seeds
Several grape seeds need a period of cold, humid conditions to start the germination process. In the nature, this is done when seeds remain in the ground throughout the winter. These conditions can be imitated through the process of stratification. The best period for starting stratification of grape seeds is in December (the northern hemisphere winter). The grower should follow these points:
- A bed should be prepared for the seeds. An airtight bag or other type of capsule should then be filled with a soft material like sand, paper towels, peat moss or vermiculite which should be dampened. By far, peat moss is the best one because having anti-fungal properties, it can prevent the seed-damaging mold.
- Now the seeds should be tucked into the bed and covered with around ½” (1.25 cm) layer of growing medium.
- Now the seeds should be refrigerated. The best temperature for stratification is a stable 35-40°F (1-3°C). Hence, the process can take place perfectly in a refrigerator. The seeds should be refrigerated for 2 to 3 months. However, they should not be allowed to freeze.
Planting the Seeds
The seeds should be taken out from the refrigerator in early spring and planted in pots filled with good soil. They should be planted individually in small pots or in bigger pots with minimum 1 ½” (3.8 cm) distance between them. Some points should be kept in mind:
- Seeds should remain warm enough. They need daytime temperature of at least 70°F (20°C) and nighttime temperature about 60°F (15°C). The seeds should be kept at an appropriate temperature by using warming mats or a greenhouse.
- The soil should be kept moist but not too wet. The surface should be misted with a fine spray of water whenever it would start looking dry.
Grape seeds usually sprout between 2-8 weeks.
When seedlings will grow to around 3” (8 cm), they should be transplanted to 4” (10 cm) pots. For their healthiest growth, they should be kept indoors or in a greenhouse until they reach a height of 12” (30 cm), and have at least 5-6 leaves and a good network of roots.
Moving the Grapevines Outdoors
The location to move the grapevines should be chosen carefully. Grapevines need a form of support, correct amount of sun and proper drainage, to thrive.
So, a spot that receives 7-8 hours of full sun daily should be chosen to plant the vines for best results.
There should be ample space. Plants should be around 8’ (2.5 m) apart for proper growth.
Note: although growing own grapes from seeds in the end can bring a lot of personal satisfaction and even pride, certified grafted grapevine plants are highly recommended for novice growers.
Preparing Soil before Planting
Grapevines need well-drained soil. If the soil is clay or other poorly drained soil, it should be augmented with sand, decomposed compost or other soil amendments to improve drainage. Alternatively, a raised bed filled with a mixture of a good sandy loam and compost should be used.
Before planting the vines, the pH of the soil should be checked. Different varieties of grapes thrive well with different levels of soil pH (e.g. 6.5-7.0 for vinifera, 6.0-6.5 for hybrids and 5.5-6.0 for natives). Hence, either the vines should be planted in an area with a pH level in the correct range or adjust the pH of soil before planting.
If the grower intends to grow grapes for wine, they should know that the flavor of grapes will be affected by the type of soil (silty, sandy, rich in clay or rich in limestone).
The grower should add a little amount of 10-10-10 fertilizer two weeks after planting. The fertilizer should be added to the soil surrounding the base of the young plants. This process should be repeated once a year every spring after that.
Supporting the Grapevines
For proper support, grapevines need a trellis or arbor. 2 years after the plants grow from seeds (1 year in case of growing from cuttings), when the plants are still small, stakes can be used to support them and to keep them off the ground. Once they grow further, the grower should train them to the trellis or arbor. For this, the tip of the shoots should be tied to the wire and allowed to grow along the wire. If one is not so sure about how to train and prune the grapevines, they should seek help from a nursery or a horticulturist.
Grapevines take usually three years to begin producing fruits. During these three years, plants should be taken good care of and trained which is essential for getting the best fruits. Here are things grower should do during all these years.
1st Year: Plants should be watched for growth. Find three strongest shoots on the plant and only allow them to grow, while pinching off others. This will help the three remaining shoots grow stronger and more forceful.
2nd Year: A balanced fertilizer should be used to fertilize. Flower clusters should be removed as soon as they emerge because letting the vine fruit this early will drain its energy. Any shoots or buds growing below the three chosen ones the previous year should be removed. Pruning should be done carefully and properly. Now, long shoots should be tied loosely to the trellis or arbor.
3rd Year: Fertilizing and removing low shoots and buds should be continued. A few flower clusters can be allowed to remain and produce a small crop of grapes.
4th Year and Later: Fertilizing and pruning should be continued. This year and after that, all the flower clusters can be allowed to fruit if the grower wishes.
While pruning it should be remembered that grapes will fruit on one-year old wood (which means wood grown during the last season).
Seedless grapes are not only easy-to-eat but are also easy-to-grow and healthy. So, it’s natural that anyone would want to grow them more than the seeded grapes.
How are Seedless Grapes Seedless?
Several people wonder how grapes can be seedless and a fear develops in their mind that seedless grapes may have been developed in a lab with genetic modification. However, growth of seedless grapes is a biological occurrence called “stenospermocarpy”. This is a system, or rather genetic defect, in the plant that creates underdeveloped seeds or small seeds that have no hard outer coats like normal seeds do and are hardly visible inside the fruit.
However, vines of seedless grapes too require pollination to grow fruit. But having no seeds means that the plants won’t proliferate themselves from seeds. Most cultivars of grapes are grown from rooted cuttings or grafts anyway, which ensures the grapes have the qualities the grower expects from the variety he chooses to plant.
Out of the three varieties, viz. table grapes, muscadine grapes and wine grapes, table grapes may be seeded or seedless, whereas the other two are commonly seeded. Table grapes can be used for making juice or even wine; but they are ideal for eating fresh. Their flavor is more desirable when eaten fresh and their sugar content is lower than that of a wine grape.
This variety is seedless and self-pollinating, and brings the best of both worlds. It’s the offspring of two varieties - Thompson and Concord, so, retains the light sweetness of Thompson and the rich flavor of Concord. Its vines are heat-tolerant and fruit ripens in August.
This variety was developed by the University of Arkansas and is seedless and self-pollinating. Grapes of this variety are exceptionally juicy and crisp. Their clusters are tight and gorgeous containing sweet-tart, thin-skinned, crack-resistant, bright fruit. Fruit ripens in August.
This variety is seedless and self-pollinating, and has a distinct strawberry-like flavor. Their clusters are heavy and compact containing medium-sized table grapes. They are perfect for eating fresh and making jelly. This variety is vigorous, cold-hardy and disease-resistant. Fruit ripens in August.
Some varieties of seedless grapes may develop tiny or shrunken seeds or traces/remnants of seeds depending on the variety and weather in which they are grown. Some varieties may develop from cross-pollination of seeded grapes; but this is not very likely.
Growing Seedless Grape Vines
Since seedless grapes have no seeds, a grower may wonder how he can sustain the continuance of this abnormal species. The simple answer is by choosing an alternative technique of reproduction – cloning.
The process of creating fruits without the fertilization of seeds, which leaves them seedless, is called parthenocarpy. Seedless grapes are created from cuttings. These are amputated parts of a vine having the genetic error that causes it to grow seedless grapes.
Such a cutting is dipped into a rooting hormone and then planted in the soil. This cutting starts growing in a vine just like any other grapevine, barring that its grapes, like its parents’, are seedless. The newly grown vine is an exact duplicate i.e. clone of the original vine.
Is Growing Seedless Grapes in a Home Yard Possible?
Most new grape growers and small vineyard owners find it quite challenging to produce high-quality seedless grapes. However, if the grower keeps up the efforts, they’ll learn more about the process and how the grapevines adapt in the new climate.
During the learning process, the grower may make mistakes that can cost them their crop. Thus, it takes some time and knowledge, and poses some risk. Growing seedless grapes is a fulfilling experience though it’s not an easy process. But the grower should keep trying.
Spring is the Best Season
Not only for seedless grapevines, but for all other grapevines, spring is the best season for starting plantation so that the young vines get maximum time to get established before their first winter.
Planting as Soon as Possible
If the grower orders vines from online sources or catalogs, they will receive the plants as dormant and bare root. They should be kept in a cool place with the root system moist. If the plants are bought from one’s local nursery, they are generally potted. Both these types of vines should be planted as soon as possible.
Choosing the Correct Location
The best location for seedless grape vines should be sunny with fertile, loamy soil and excellent drainage and air circulation. Measure off spots around eight feet apart and set a trellis or arbor at each spot.
Dig the Hole
The size of the root system of the vine should be assessed and then a hole twice as big should be dug. Then the vine should be placed in the hole spreading the roots out. Soil should be filled back till the hole is three-quarters full. Watering should be done to let the soil settle. Then filling should be finished with soil and again it should be watered.
The plant should be cut back to two buds. They should be encouraged to grow in opposite directions along the trellis. Then every following year, old/dead canes should be pruned off to make room for the most vigorous canes.
Newly planted vines require more water than established vines. So, they should be watered weekly for the first year, particularly in hot/dry spells.
When seeds develop, a hormone is secreted by them named gibberellin that encourages the fruit’s growth. More than 120 forms of gibberellin have been recognized in plants so far. Seedless grapes typically tend to grow small; therefore commercial growers apply gibberellin to help fruits grow bigger.
Applying Gibberellic Acid
Only a few table grape cultivars can produce grapes of significant size. However their size can be remarkably increased by applying gibberellic acid (GA3) to grape clusters at around two weeks after bloom. The GA3 induces the division and elongation of cells in the berries, thus increasing their size.
The quantity of GA3 required to optimize berry size depends on the cultivar and several other factors; however, 10 to 60 g/acre is a usual application rate. GA3 may be applied once or many times. In case of certain cultivars, multiple applications may increase efficacy. The timing for application also varies depending upon the cultivar.
For several cultivars, the first application should be done at berry set or when diameter of berries is around 3-5 mm. Applying GA3 later than this may delay the fruit maturity and stop color development in black- and red-fruited cultivars. Breeding programs have constantly been developed for producing large berries; hence, several newer cultivars need less GA3 to attain larger size.
Seeded grapes are often less responsive to GA3 treatment than seedless varieties, and hence applying GA3 to increase the size of seeded grapes is usually not recommended.
Other Plant Growth Hormones
Forchlofenuron (CPPU) is a synthetic cytokinin and is also helpful to increase berry size. It’s applied alone or in combination with GA3, since the combination may have a synergistic effect on berry size. Application of CPPU tends to form a rounder shape than non-treated berries. This compound being highly potent is to be applied in very low amounts (1 to 3 mg/L). Larger amounts can delay maturity, retard coloring and spoil the taste.
WARNING: Plant Growth Regulators (PGRs) like GA3 come under the class of pesticides and are subject to the same severe regulatory framework. PGRs may not be permitted for grapes in certain areas or for certain cultivars. Such an unapproved use of PGRs may lead to contaminated crops with illegal pesticide residues. Hence growers should seek guidance from a professional pest control adviser prior to applying any PGR to their grapes.
Note: personally, backyard gardeners should limit the use of chemicals (hormones included) as much as possible. You have small grapes? Grapes' fragrance, texture and aroma are important, not the size ... IMHO of course :)
Several grape-growers stop watering their vines once they harvest the crop. This can be a big mistake. It should be thought upon why the vines shouldn’t be watered? – just because they don’t have any fruit on them now? Thus, do only fruits need water? – logically not!
The fact is that in spring, growers water the vines when they see the first signs of bud break. Next, with the arrival of summer, vines are more stressed and their need for water increases with the rise in temperature, growth of shoots from vines and increase in the size of the canopy. The increased canopy size and temperature will cause higher transpiration figures and the vines themselves will use more water as the grapes begin developing and gain size.
After the removal of grapes, the stress on the vines will be reduced a lot and the requirement of water also reduces gradually. Here it’s important to remember that the vines don’t stop using water after grapes are removed; they only use less water.
With the start of fall, days will become shorter and temperature reduces; during this time, the vines will be ready for winter and slowly become dormant – but they are still active.
Here it’s important to remember that the longer the green leaves sustain on the vines, the longer the assimilation of carbohydrates will continue. And for this, the vines will need a source of energy i.e. water. The longer the carbohydrate assimilation, the better will be the ripening of the shoots of the vines, thus making the vines more winter hardy. Some growers living in cold regions strip the leaves from the vines to prepare them for the cold season – this is not recommended! However, in tropical climates it’s recommended to strip leaves to force vines into dormancy as the temperature there is not lowered much.
Thus, watering should not be stopped immediately after grapes are picked; it should be slowly cut back until the vines are totally dormant (this happens normally at the end of fall). During dormancy, the vines need very little water and 90% of the time, no water, except if the winter is very dry.
Weeds and Grass
When it’s the growing season for grapes with new leaves popping up, signs of bud break and even some grapes, unfortunately it’s also the growing season for weeds and grass. These are the biggest enemies of a young grape vine. Weed infested young vines usually have to struggle a lot to reach the trellis during the first year. So, it’s necessary to minimize the competition for water and nutrients against weeds and grass growing near the grape vines.
This applies not only to a vineyard, but also while planting grapevines in one’s backyard or even in an established lawn. It’s recommended to remove a patch of sod minimum three feet around the vine so as to prevent weeds growing near the roots.
It’s also a good idea to spray a weed killer on the land where the vines will be planted about 4-5 weeks before planting the vines. This will ensure there will be no active growing weeds or grass for minimum two months during the growing season.
Mulches or ground covers not only suppress weed growth, but also minimize moisture loss, thus keeping the soil evenly moist. Decomposing mulch will enhance the soil structure and add some much-desired nutrients to the soil.
However, mulches have some disadvantages too!
Mulch poses a risk of fire during hot, dry summers. Also, depending upon the type of mulch used or from where the mulch has been sourced, it can also carry seeds of unwanted weeds, which will sprout and grow in the mulch itself.
During wet seasons or in poorly drained soils, mulches can hold excessive moisture. This can force growth to fail to harden off in the fall and lead to injury or collar rot in winter.
To prevent the problems arising from the mulch, a layer of mulch should be applied at least 4 inches thick to cover all the sides of the vine. In case of a row of vines, the whole ridge should be covered whereby most roots are sure to get correct moisture and weed management. While laying out mulch this way, keep it away from the vine’s stem since decomposing material can damage the stem (especially of new vines) which is known as collar rot.
A grower can use mulch or not, but it’s important to keep the vineyard weed-free, particularly around newly planted vines.
Many growers face the problem of either having no grapes or too small berries or not enough grapes. There can be many reasons for these problems. Here are tips to improve a grapevine’s fruitlessness.
Not Enough Sunlight?
The first and foremost thing to check is whether the grapevines are getting proper sunlight. Adequate sunlight is necessary to start the development of flower clusters inside the buds. If one looks at a grapevine’s green shoot, he can see hundreds of buds located between the leafstalk and the shoot.
This bud is a compound bud with a primary, secondary and tertiary bud located beside each other. Thus, if the grapevine is too compact or is growing in shade and not receiving sunlight in the canopy, the crop will be lighter in the next years. Thus choosing the right spot for the vines is very important.
Wrong Style of Pruning
Correct pruning method is also as important as choosing the right location for planting grapevines that can receive ample sunlight. It should be remembered that fruitfulness of grapevines varies from variety to variety; therefore some varieties should be pruned with canes whereas some other should be pruned with spurs.
Varieties like Crimson get buds that start flower clusters from the 4th (from the shoot’s base) bud onwards. If a dormant cane is pruned back to 2-3 buds, the most fruitful part of the cane where majority of grapes are is removed. Thus by pruning without proper planning and just pruning everything away, the grower will reduce the crop size.
Too Vigorous Growth
Overly vigorous grapevine or excessive fertilization can also be problematic in the blooming stages. Just like any other fruit plant, grapevines too produce flowers that need to be pollinated for reproduction. The basic instinct of grapevines is to survive and reproduce new grapevines.
If, in such a case, a grapevine grows too vigorously, it ‘thinks’ that ‘Okay, everything is fine with me and I don’t need to have too many grapes!’ Hence, it sheds flowers which makes crop lighter. Also in a vigorously growing vine, sunshine can’t penetrate properly.
Diseases and Pests
Not only diseases but pests too are responsible for reducing grape production. Diseases like botrytis and powdery mildew attack flower clusters and thus abort flowers whereas mites attack buds on grapevine themselves. Bud mites feed on internal bud tissue, while rust mites mainly feed on the outer bud scales, both damaging the small flower clusters within the buds.
Use of GA3 (Gibberellic Acid)
Gibberellic acids are growth hormones produced naturally in plants and affect cell elongation and division in leaves and stems.
Therefore it’s used by commercial grape growers to increase berry size. Unfortunately, GA3 kills fruitfulness of grapevines.
Therefore using GA3 properly is extremely important - or don't use it at all!
Most commercial grape varieties grown nowadays produce male and female flowers due to which cross pollination is not required.
However, certain grape species such as Vitis reparia, produce only male flowers. These come in literally thousands and therefore an average grower may become happy. However, later it’s seen that these flowers just fall off without producing grapes.
Those who want grapevines only to decorate their pergola or other structure with their beauty and not for grapes can buy vines that produce only male flowers.
Thus, a grower needs to find out the reason why their grapevines are not producing grapes or are producing fewer grapes and then they can solve the problem.
Many grape growers wonder why the leaves of their vines turn yellow long before fall. Although there are a score of reasons for this, the most common reason is magnesium deficiency. It’s become increasingly evident how magnesium is important for optimum grape quality.
What does Magnesium do in Grapevines?
Magnesium is a part of the chlorophyll molecule. As everyone knows, chlorophyll is the green pigment in most plants. Everyone also knows that the green leaves (and other green parts) of the plants are where carbohydrates are produced and then transported to the remaining plant.
Like for all other plants, these carbohydrates are essential for optimum growth, immunity and proper development of fruits in grapevines.
Symptoms of Magnesium Deficiency
Usually, symptoms of magnesium deficiency are neglected while growing red or black grapes, since white varieties show magnesium deficiency more prominently.
Symptoms are seen on the older basal leaves and yellowing begins from leaf border slowly moving inward. Veins of leaves stay green the longest and areas between them become pale green and usually creamy white. In case of red grapes, a reddish coloring may occur between the veins.
Magnesium deficiency not only affects the leaves and production of carbohydrates, but can also cause premature fruit drop.
How to Resolve the Problem?
A common mistake made by most growers, when they diagnose the magnesium deficiency, is to add a lot of magnesium to the soil or foliar. Actually, it is not the shortage of magnesium that causes the symptoms, but more commonly it’s a pH problem or magnesium-potassium imbalance.
The problem begins when grapes are grown in more acidic soils. Magnesium gets attached to the soil particles and become increasingly unavailable to the vines, as the pH reduces.
The first thing that should be done before planting vines is to increase the pH of the soil. However, most growers don’t consider that by adding elements like potassium and lime to rectify the pH, more magnesium can become unavailable to the plants.
Soils with high levels of potassium will have very little magnesium available, just because potassium will just displace magnesium cations (Mg ++) making less Mg anion available to the plant.
Put simply, if the soil has low pH (less than 5.5) and the grower wants to increase it without binding the magnesium, they should apply dolomitic lime (this is high in magnesium) in the proportion of two to four tons per acre. However, even before this, they should get the soil analyzed. Magnesium values of soil between 100-250 ppm are considered sufficient for growing grapes.
If symptoms are increased during growing season, a petiole analysis (leaf stock analysis) of the vine is recommended for determining what is wrong with the vine. A foliar spray of magnesium sulfate (15.0 to 20.0 lbs./100 gal. and 200 gal./acre) can temporarily rectify the problem. But Epsom salt (magnesium sulfate) can cause fruit and foliar damage if mixed with other products; therefore the soil should be analyzed.
Powdery mildew is a major fungal disease affecting grapevines every season. The fungus is named Uncinula necator.
Unfortunately, by the time growers notice this disease, it reaches a much advanced stage. It affects all green parts of the plant and fruit. The fungus looks like white dust and can be rubbed off. Berries with this fungus dry up and crack open. If the infection spreads too fast, it can cause complete loss of crop.
The period between immediate pre-bloom and fruit set is extremely critical to control powdery mildew. Poor fungus control and canopy management can cause this infection.
Free water such as rain, overhead irrigation or high humidity and heat are ideal for the growth and spread of powdery mildew.
Controlling Powdery Mildew
Chemical Control: There is a huge range of fungicides, most registered to use on vines. But the best one among them and best time to apply it are important. Insufficient spray coverage or too long interval between sprays can make the control poor rather than reduced efficacy of the fungicide.
Since the period between immediate pre-bloom and 4 to 5 weeks after fruit set, failure to control during this period can cause crop loss. Applying a fungicide with an active ingredient named strobilurin or DMI fungicides during this period can achieve the best control.
Organic Control: Organic control of powdery mildew is much more difficult. Since moisture and heat are needed for fungus proliferation, proper airflow and sunlight penetration are important for ensuring a ‘drier’ micro climate inside the vine and thus inhibition of fungus.
Direct contact with sunlight can kill the fungus spores and reduce the risk of crop loss. Good canopy management can achieve this.
Of course, there are other diseases that threaten the grapevines, but having healthy and strong plants is the basis for fighting them.
Long Story Short: Growing grapevines in the backyard is possible with a great desire, patience, consistency and hard work. Over time, the grower can become an expert on the topic and also can enjoy the sweet fruits of their labor.
Grapevines can provide shade, tasty grapes, can be very decorative and can be mixed with other berries and flowers as well - just be sure to check the plants and soil periodically.
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