Growing Grapes

Latest Update 8th August 2016.

Table Grapes
  • You can propagate Thompson Seedless grapevines by taking cane cuttings, by grafting softwood cuttings or grown from seed.  The easiest method is to take cane cuttings from an existing vine in late autumn to early winter. 
  • Careful pruning of new vines is required to ensure they are given a sound structure capable of supporting a heavy load of grapes.  Commercial growers train their new plants along horizontal wires supported by timber posts.
  • They remove all the side shoots on a new vine each spring until it grows tall enough to reach the wire, and the next spring they prune the shoots leaving the top 2 strongest ones in place.  These are trained to grow in opposite directions by tying them along the wire, after cutting them back to 12 buds from the parent cane.
  • My grapevine was planted at the end of a fence, and both lateral canes were trained in the same direction along it; one above the other.  It works fine and in summer the vine completely covers the fence with foliage.
  • The following and subsequent years are all about pruning the spurs growing from the laterals back to 2 buds in winter.
  • Once the plant starts to set bunches of grapes, trim the bunches back about 25% to increase the size of the remaining grapes.  Remove enough foliage in early summer to expose the grapes to sunlight and allow air to flow freely through the plant.  Removing this foliage helps redirect some of the plant's energy to growing bigger grapes.
  • Fresh table grapes taken off your own organic vine are simply delicious and are very nutritious.  I'm inclined to make a pig of myself on grapes when they are ready for harvest. 
Details.
  • Variety:                                                    Thompson Seedless (Sultana).
  • Family Group:                                           Vitaceae. 
  • Garden bed type:                                       Drip line irrigated organic bed. 
  • Recommended soil pH:                               5.5 - 6.5.  
  • Plant Spacings (centres):                           2000mm (trellis).  
  • Good Companions:                                     Geraniums, Mulberries, Hyssop, Basil, Tansy.  
  • Climate:                                                     Warm Temperate.  
  • Geographic Hemisphere:                             Southern
Nutrition. Growing Conditions. 
  • Prefers hot dry conditions once established. 
  • Minimise soil disturbances to maintain a natural structure.
  • The soil must be free draining. Grapes do not like wet feet. 
  • However, don't allow the soil to dry out completely especially when it is young and its roots are still comparatively shallow. 
Feeding the Soil
  • Remove spent mulch and any dead leaves or prunings from the previous year in Winter and dispose of them in your compost heap. 
  • Apply a 60mm top dressing of home made compost and cover with straw mulch.
  • Keep the mulch clear of the main stem to prevent collar rot. 
Propagation
  • Propagate a new grape vine in winter from existing stock.  Cut a strong cane grown during the previous season and select the strongest shoot.  Cut the top of the cane on a 45 degree angle 10mm above the shoot and remove all the other shoots.  Cut the bottom of the cane square so its 300mm long.
  • Bury the cutting 100mm deep with the bud facing upwards in fresh compost in a propagator.
  • The new roots will grow from the bottom end of the cutting and from the lower laterals where they have been cut back to the main stem.  Water it in with rainwater or filtered water. 
  • It will take more than a year to establish itself but you should be able to plant it out in the following spring. 
Cane Pruning 
  • This pruning method is used on grape varieties like Thompson Seedless which don’t have flowering buds in the lower parts of their canes.  Instead they carry bunches of grapes near the ends.
  • Grow your vine in the middle of a wire trellis strung between strong posts set 2 metres apart.
  • In the first season train the strongest of the canes vertically to make a trunk.
  • Prune the vine in late winter at the end of the first season by remove all the canes except the selected trunk.  
  • Then remove all the buds on the trunk except for the 3 strongest ones at the top.  These will produce canes during the warmer months.
  • Once dormant in the following winter, identify the 3 canes growing from these buds, and select the 2 strongest.
  • Trim each of them back to 12 buds, and wrap them around the trellis wire (one in each direction).  Tie the ends to the wire.
  • Rapid growth of grape vines in a warm temperate climate will produce a few inferior bunches of grapes in the second year, but these are best removed early so the vine will put its energy into growing a strong structure.
  • The following and subsequent years are all about pruning the spurs growing from the laterals back to 2 buds in winter (at 10mm from the second bud).
  • Once the plant starts to set bunches of grapes, trim the bunches back about 25% to increase the size of the remaining grapes.  Remove enough foliage in early summer to expose the grapes to sunlight and allow air to flow freely through the plant.  Removing this foliage helps redirect some of the plant's energy to growing bigger grapes.
  • Reduced watering once the grapes are near to maturity, increases their sweetness.
Harvesting and storage.
  • Thompson Grapes will begin to turn into a paler green or light beige colour, but the best way to be sure they are ripe is to taste one.
  • Once you are satisfied with the taste of the grapes in a bunch, cut the whole bunch off with enough stem for handling purposes.
  • We only have one vine, so we use the grapes as they ripen and give surpluses to family and friends. 
  • Thompson Grapes are very acceptable seedless table grapes, and when dried can be stored as sultanas.
Organic Pest Control. 
  • Slugs and snails.
    • Grapes should be protected against slugs and snails using self adhesive copper tape bonded around the base of your raised garden bed.
    • If these molluscs get into your bed as eggs laid in your compost, kill them with organically approved iron based snail pellets as soon as you discover them.  You should only need to use a small number of pellets.
  • Caterpillars.
    • At the first sign of caterpillar damage, spray the crop thoroughly with Bacillus thuringiensis (Dipel in Australia)  This natural soil dwelling bacterium once ingested by the caterpillars produces toxins which paralyse the caterpillar's digestive system causing it to stop feeding.  It dies within a few days.
  • Greenhouse whitefly.
    • Aerated compost tea strengthens the plants foliage against whitefly damage.  
    • Control any infestations by spray your crop thoroughly with organic horticultural oil (Eco-oil in Australia).
    • Spray again in a few days to ensure second generation whitefly do not survive.
  • Aphids (greenfly).
    • Use the same method as described above for whitefly.
  • Powdery mildew.  
    • A monthly foliar spray of aerated compost tea is a useful deterrent against powdery mildew.
    • If an infestation occurs, spray with Eco-oil.
  • General:
    • Regular applications of aerated compost tea boost the natural defences of plants by colonising the leaf surfaces with beneficial microbes.  They defend the plant against airborne pests and diseases.
    • Similarly, proper soil preparation including regular applications of home made compost boosts the community of beneficial microbes, which defend the plants roots against plant pathogens.
    • Exclusion netting stops birds stealing and damaging blackberies, and takes the edge off hot sunshine with a 20% shade factor.