Grapes


(Genus: Vitis vinifera - Family: Ampelidacee)

 

The grape and its origins

Originating in the East, grapes predate life on earth and evidence exists that they have grown wild since pre-historic times. 

The Vitis vinifera vine is the most important species in Europe, from which most modern cultivars exist.  Seeds found in the Travertine of central Italy are of wild vines dating back to the Quaternary period.

Grapes have been associated with making wine for thousands of years.  There are two basic categories of grapes, those grown for winemaking and those grown for eating.

 

How to plant grapes

For best results, plant grape vines from autumn onwards and no later than March.  If the climate has a cool winter, wait until as late in March as possible before planting.  As soon as the vines are planted, add a layer of mulch, plastic or fleece to protect the emerging shoots from frost.

The vines are vigorous climbers and can reach great heights but need much support, they are not self supporting.  Grapes can grow with a variety of supporting mechanisms but typically, in the home, they should be planted against walls, trailing a pergola, a fence or with a specially designed support to facilitate their growth.    

Choose a cultivar that is suited to your climate, this plant typically enjoys full exposure to sunlight which is a key determinant in its final sugar content.  

Soil should be loose and fast-draining.  Typically, grapevines require a pH between 6.5 and 7.5 and thrive in both sandy and clay-based soils.  Where necessary, adjust the soil with some well-rotted organic matter to provide nutrients and improve drainage. 

There are a wide variety of training and pruning systems that you can adopt to grow grapes; two of the most common are the Guyot system and the Cordon system.  The system you choose will determine your spacing when planting.  Guyot is used when grapes are grown in the outdoors and involves building a support structure for the vines, each will be 1.3-1.8m apart.  Cordon is typically used when grapevines are attached to a wall, pergola or greenhouse, it is often referred to as rod and spur. Each vine will be planted 1.5-2.5m apart.

Fertilising the soil is essential to improve the crop.  For grapes grown for eating, prepare the soil with xxxxx xx at a dose of XX kg per m² and for wine making grapes use xx kg per 100 m². Alternatively, use xxxxx every 2-3 months. When planting, use the same products at a dose of 100-150g per hole and also apply plenty of manure to keep the soil rich and fertile.

Care must be taken when watering, over-watering can encourage fungal diseases.  Only water in the event of a severe drought or dry spell.

Grapes are vigorous growers and require pruning to keep them in check and encourage production.  Pruning should mainly take place over the winter months but they have fast growth so should be maintained throughout the year.  Pinch out new shoots and thin fruits for a more successful crop.  Fruits grow on year-old or older wood, so care must be taken to maintain a balance between old and new shoots when pruning.   

 

When to harvest a grape

Grapevines are fast paced growers and begin flowering in early summer, followed closely afterwards by small bunches of grapes.  The number of flowers produced is dependent on the cultivar and could be up to 100.  Each flower has five petals but the shape of the cluster also depends on the variety. The large lobed leaves are alternate and simple, they can reach 15cm. 

Harvesting takes place when the grapes are ripe and is usually in late summer.  Stalks should be cut to remove the grape cluster and leaving 10-20cm of branch behind to allow for future fruit production.  The grape cluster’s shape, size and colour is also dependent on the cultivar chosen and can vary from bright greens to deep reds. 

Once harvested, to maintain freshness, the grapes should be refrigerated, where they can last between 7-8 weeks.  To delay harvesting grapes grown for eating, cover the vines with a plastic sheet to slow down growth.  

 

Propagation of grapes

Most grape cultivars are propagated from cuttings, rootstocks or grafts.  Rootstocks combine robust and hardy roots with vines that flourish and bear excellent fruit.  Choose a rootstock according to the soil and conditions in the locality.  Select rooted grafts that have 1-2 years growth before transplanting. 

A common rootstock for fertile soil is the distinguished "Kober 5BB", and the "420A" for dry hilly areas .  "140 Ruggeri" and "1103 Paulsen" are ideal for calcareous soils and areas that suffer from drought.

 

Diseases and insect affecting Grapes:

  • Powdery mildew,
  • Botrytis,
  • Downy mildew
  • Ringworm of grapes,
  • Grape moth,
  • Leafhoppers,
  • Thrips,
  • Spider mites and yellow.

 

Did you know?

Grapes have multiple uses, as drinks they not only contribute to a wide selection of wines across the world but are also suitable for juices and even for spirits such as brandy.  They can be dried to make raisins and are also perfect for preserves and jams. 

Between 1858 and 1862, a parasite arrived in Europe from North America, which threatened to wipe out all of the European vines.  The solution was to graft a European vine into the rootstock of American vines that were already immune to this parasite and so, Vitis vinifera survived the destruction.