Plumpton Notes: Part 2

Index 4. Vine Rootstocks 5. Vine Training Systems 6. The Winter Pruning of Grapevines 7. Vine Propagation & Grafting 8. Planting Vines 9. Vineyard Design

4. Vine Rootstocks

4.1 Reasons for using rootstocks

4.1.1 Phylloxera

Phylloxera vastatrix was first identified in Europe in 1863. Accidentally introduced from the US, this louse destroyed two-thirds of European vineyards in the late 19th century. In 1872, Laliman discovered that the roots of American vine species were not destroyed, and so recommended grafting V. vinifera on rootstocks of American vine species.

The only other effective remedies for Phylloxera are growing vines on sandy soils or flooding the vineyard for 40 days a year.

Symptoms of Phylloxera

4.1.2 To influence the vigour of the vine

Different rootstocks have different vigour levels and take up nutrients at different rates, which influences the scion's vigour.

In general, high vigour plants will have:
– Greater yield – Longer vegetative cycles – Berries with lower sugar and higher acidity – More susceptibility to disease

4.1.3 To confer resistance to nematodes

Nematodes (also called round, thread or eelworms) are very common in soils but are usually too small to be seen by the naked eye.

Some (such as Pratylenchus and Meloidogyne species) cause damage by feeding off the roots, while others (such as Xiphinema index) transmit virus diseases.

Rootstocks have differing susceptibilities to nematodes.

4.2 How to select the correct rootstock

The majority of rootstocks used today originate from crosses of three American species: Vitis riparia, V. rupestris, V. berlandieri.

Vitis riparia rootstocks are low in vigour but suffer from iron deficiency (chlorosis) in chalky soils

Vitis rupestris rootstocks are very vigorous, with a deep rooting system, but are also very susceptible to chlorosis

Vitis berlandieri is very vigorous, deep rooting, and highly resistant to chlorosis. Its cuttings have a very poor ability to root, so it is rarely used as a pure species.

Many hybrids of these species have been developed, and the correct choice depends on many factors:

The principal rootstocks used in the UK are SO4, 3309C, Fercal, 101-14, 5BB, 41B and 420A.

5. Vine Training Systems

A training system refers to the way a vine is positioned in space.

It incorporates the trellis and how the vine is manipulated to cover it. The aim is to maximise quality and yield and reduce costs (facilitating mechanisation).

In cool climates, the most appropriate way growers can improve yield & quality is to increase the interception of light.

When selecting a training system, the choices to be made include: Planting mode: – Plantation density – Distance between rows – Distance between plants – Row orientation

Plant shape: – Trunk length – Shape of canopy

Trellis systems

There is no one ideal training system for vines, and choice will depend on climate, soil, cultivar, rootstock, and economic constraints.

5.1 History

Before the Phylloxera epidemic, vines were planted very close together in a random arrangement, untrellised or trellised on individual stakes.

After Phylloxera, European vineyards were planted in straight lines to allow cultivation using animals. The higher-quality northern vineyards could afford to buy stakes & wire to erect standard trellises.

In the 1950s, over-planting + technological improvements + cultivar improvements —> massive overproduction —> drop in prices

So vine growers had to reduce costs, and the very severe winter of 1956 helped.

Many growers removed alternate rows, and culture systems such as the Lenz Moser and the Sylvoz were developed.

Often these systems cut costs but did not produce quality wine, so they have been replaced by systems such as the GDC, the Lyre and the Scott Henry.

5.2 Planting mode

5.2.1 Plantation density

This is calculated on a field of 1 hectare (100m x 100m)

Plantation density = number of rows x number of vines in a row = (100 / Alley width) x (100 / Distance between plants)

There is little direct correlation between high-density planting and quality, although high densities often increase the effective leaf surface in a vineyard.

There must be a balance between the vine’s root system and its canopy, and the vigour of the cultivar, the planting density, the fertility of the soil and the training system determines this.

The poorer the soil, the higher the root density to obtain the right balance. As vine vigour is low in poor soils, it is best to plant high densities.

The exception to this is in low-water situations, where plants need to exploit a large amount of soil.

On a high-potential site, low-density planting is preferable.

Minimum legal densities for quality wines: – Burgundy: 9,000 – Bordeaux: 4,500 – Muscadet: 6,500 Most high-quality European vineyards are in the 5 – 10000 range.

5.2.2 Distance between rows

This is a compromise between different factors. Factors that favour narrow alley widths:

Factors that favour wide alley widths:

5.2.3 Distance between plants

The correct distance between plants will give a shoot density of 15 shoots/m. This is a function of the trellis system's ability to support the plant's vigour.

Generally, the wider the alleys, the greater the distance between plants, as the plants have more vigour (they have more soil space available) and so need more trellis space.

5.2.4 Row orientation

Can be dictated by the following: – Shape of the field – Direction of the slope – Prevailing wind

In N-S rows, maximum interception in the morning & afternoon, minimum at midday

In E-W rows, and vice-versa, the maximum light is intercepted at midday
Note that in midsummer, more light is intercepted by N-S rows, but in spring and autumn, E-W rows receive more light.

However, N-S has the advantage that both sides of the trellis receive the same amount of light.

5.3 Plant shape

5.3.1 Trunk length

Increasing trunk length has the following effects:

5.3.2 Canopy shape

Features of an ideal canopy (for cool climates):

5.4 Criteria for selecting trellis systems

Note this is a permanent decision:

6. The Winter Pruning of Grapevines

6.1 Background

Parts of the vine

The vine life-cycle The vine vegetative cycle: Budburst –> shoot growth –> bud formation –> shoot ripening –> dormancy

The vine reproductive cycle: Floral initiation –> bud dormancy –> budburst –> flowering –> fruit set –> veraison –> ripening

Floral initiation is essential to the reproductive cycle as it sets the maximum production potential for the following year.

It is promoted by adequate heat, light and plant photosynthesis.

6.2 Reasons for pruning vines

Winter pruning is the second most costly manual intervention in the vineyard.

6.2.1 To organise the plant on the trellis

Pruning enables the vine to be well-organised on the trellis so that:

An ideal canopy is homogenous along the row (15 shoots/metre) and has an average leaf thickness of 1-1.5.

6.2.2 To allow for the passage of machinery and manpower

Winter pruning organises the plant along the trellis so that personnel and machines can pass along the alleys without causing damage, and mechanical operations such as spraying and harvesting are more efficient and effective.

6.2.3 To produce a balance between the crop and leaf area

Unpruned vines produce: – Many short shoots further and further away from the trunk – Many small bunches of high acid low sugar berries – Irregular yields

In order to get quality fruit, there must be an appropriate balance between the crop level and leaf area on each shoot.

The number of flowers on the vine shoot is determined in the previous year according to conditions at floral initiation.

The size of each shoot (and therefore its leaf area) is determined at pruning, as the more buds are left on, the weaker their individual vigour. This is because more shoots have to share the limited amount of winter reserves and the capacity of the plant’s root system.

A heavy crop on short shoots will lead to over-cropping, which produces high yields of low-quality fruit and weakens the vine the following year.

Shoots with a disproportionally low crop will be over-vigorous and may carry on growing past veraison, to the detriment of the quality of the fruit. Furthermore, they will have many large leaves and laterals, which will cause canopy shading.

6.3 Factors to be taken into account when pruning

6.3.1 Pruning depresses vigour

A vine’s vigour is measured by the weight of wood it produces in a year.

Heavily pruned vines will grow fewer shoots the following summer than lightly pruned vines and fewer leaves. This reduces the vine's total photosynthetic capacity, and so reduces its vigour.

This effect is particularly important in young vines, which should be pruned lightly to allow them to establish themselves. Flower removal is also a good idea.

In older vines, lightly pruned vines are devigourated by increasing fruit production.

6.3.2 The notion of ‘Charge’

One of the aims of winter pruning is to produce an ideal balance between fruit and leaf area. This balance depends upon the yield and quality desired, which is determined by the returns on the sale of the wine.

As a rough guide, the ideal balance between fruit and leaf occurs on a shoot with a moderate yield of about pencil thick, 12 – 15 nodes long, and an internodal length of 60 mm. These weigh about 30 – 40 g in winter.

To calculate how many buds to leave on a vine at winter pruning (the charge), the vinegrower can:

The charge is increased significantly in young (< 8 years old) vines and by 5 – 15% in mature vines to compensate for buds that won’t break due to winter injury.

6.3.3 The choice of wood retained at pruning

The wood retained at pruning should be in a good state of health.

Look out for spotting due to Botrytis (grey rot), powdery mildew, Phomopsis, and poorly ripened wood.

Canes with deformities such as double buds and ‘twinning’ may be infected with viruses and so should be eliminated if possible.

6.3.4 Choice of buds

The buds on canes formed in the previous year are the most fruitful.

If a vine is pruned severely, old buds on the trunk will break, but the embryonic flowers within these will have degenerated, and so they will produce little fruit.

6.3.5 Large pruning wounds damage the vine

Wounds over 30 mm in diameter will never heal properly but will die back and may affect the sap flow in the trunk. They will also deepen due to frost cracking and may allow the entry of parasitic fungi such as Eutypa.

If large pruning cuts have to be made, leaving a short stump that can be cut back the following winter is a good idea.

On the other hand, canes must be cut back to the old wood, or the surviving basal buds will turn into watershoots.

6.3.6 The end-point principle

Vines will grow more vigorously at their extremities, so the buds at the ends of canes will tend to break first and produce the most vigorous shoots.

The longer the cane, the greater the difference in vigour between shoots at the end and those in the middle, leading to uneven canopies.

6.4 Pruning by the Guyot system

The Guyot system is a traditional practice popularised by Charles Guyot in the 1860s. It is a cane-pruned system with spurs.

The cane buds grow into shoots that produce the yield in the following season.

The spur buds produce shoots that can be used as canes the following year, thus preventing the vine from sprawling too far along the trellis. Often, spurs become part of the old wood.

In a single Guyot, only one spur and one cane are left at winter pruning. In double Guyot, two spurs and two canes are retained.

The choice between single and double Guyot is decided by the vigour of each individual plant.

6.4.1 The choice of spur and cane

The spur should always be selected first. It should be: – Not too low or under the crown – Pointing along the row and not into the alley – Not too high or centrally located on the crown – Nearer the roots than the cane

The cane should be selected so that it is further from the roots than the spur, and it should be able to be tied down (bowed) so that: – It does not protrude into the alley – It does not invade the neighbouring vine’s trellis space – The buds are evenly spread along the trellis

Canes are often tied down in the shape of an arch to regularise shoot vigour along their length.

6.4.2 Establishing young vines in the Guyot mode

Young vines must be pruned carefully to ensure that they have a straight trunk and that their crown is well positioned in relation to the fruiting wire.

It is important to remove badly positioned shoots as they grow and all flowers should be removed from the least vigorous young vines.

6.5 Pruning cordon systems

Cordon systems are those where the cane is left permanently attached to the fruiting wire so that it becomes a permanent cordon.

The canes coming off these cordons are often spur-pruned. The shoots arising from these spurs can be trained either upwards or downwards.

The most common cordon system used in UK vineyards is the Geneva Double Curtain (GDC), but there are many others, such as the Cordon de Royat, the Sylvoz and the Lenz-Moser.

The advantages of cordon systems are that:

The GDC has other advantages, such as increasing the exposure of basal buds and fruit to sunlight, which can produce higher yields of finer-quality grapes.

The systematic method for cordon pruning is to: 1. Count the charge 2. Count the number of growing points 3. Divide the charge by the number of growing points 4. Leave that number of buds per growing point

However, most pruners will prune each growing point according to its success in the previous season.

6.5.1 Problems encountered with cordon systems

The loss of growing points along the cordon This can be reduced by keeping cordons short and pruning according to charge. If this fails, the cordon will have to be replaced.

The lengthening of growing points This can be controlled by pruning using the alternate crenel system.

6.6 When to prune

Earlier pruning will encourage earlier budburst and so increase the risk of spring frost damage.

However, it should not be left too late, as when the buds start breaking, it takes longer to bow down the canes, and many young shoots may be damaged.

6.7 The use of pruning

These can be collected and used as fuel or mulched in the alleys.

Mulching is easier and increases the humus levels in the soil, but some diseases, such as Eutypia and Blackrot, can overwinter on the canes. Prunings should be immediately burnt if these diseases are present in the vineyard.

7. Vine propagation & grafting

7.1 Vine propagation

7.1.1 Seeds

Used to produce new cultivars, hybrids & rootstocks, but not in commercial viticulture nurseries, as:

7.1.2 Layering

It occurs naturally, often used commercially for species like Vitis berlandieri & rotundifolia (which are difficult to root from cuttings) or for replacing missing plants in vineyards.

Carried out at winter pruning Cane is buried in the ground, leaving the last bud or two above Can twist a wire around the cane to constrict the sap flow.

During the growing season:

7.1.3 Cuttings

Cuttings are pieces of parent plants (stems, roots, leaves) that will develop into a new plant when placed in the right conditions.

In viticulture, use: – Hardwood cuttings (commercial) – Softwood cuttings (research) – Meristematic tissue (in vitro research)

Important to choose hardwood cuttings carefully:

Length of cutting 30 – 45 cm, depending on how deep the roots need to be: the lighter the soil, the longer the cutting

Cuttings are bundled, labelled, and then stored.

Could heat-treat by placing at 50°C for 30 minutes. This will eliminate Phylloxera, nematodes, mycoplasmas (grapevine yellows & Pierce’s disease), Phytophthora & crown gall.

If they are to be grafted, they should leave in water overnight.

Otherwise, store in a cool (1 ~ 4°C), damp place, maybe buried in moist sand or sawdust.

If cuttings are not to be grafted, they can plant straight away into a nursery or pot in a greenhouse.

In order to encourage this:

7.2 Grafting

Grapevines are grafted to:

7.2.1 Field grafting

Traditional practice where the rootstocks are planted in the vineyard first, then top grafted

7.2.2 Bench grafting

Carried out indoors during the late winter/early spring :

Grafted rooted cuttings are either sold as:

7.2.3 Top-grafting

Used to change cultivars in an established vineyard.

7.2.3.1 Cleft grafting

Usually carried out on vines less than 15 years old with trunk diameters 2 ~ 6 cm:

Good success rate (60 % minimum) 2/3 of a normal harvest is expected the following year.

7.2.3.2 Bud grafting

Now more common, as the success rate is better.

Both methods require scion cuttings to be collected in the winter and stored at 1 ~4ºC, 90% humidity.

The two methods most commonly used are chip-budding and T-budding. The two methods can be used in succession to ensure success.

Aftercare of plants is very important:

Works well in warm climates, but difficult to succeed in the UK.

8. Planting vines

All in the planning and preparation.

The planting calendar:

8.1 Removing existing vegetation

8.2 Levelling

Dips in which water accumulates can cause root asphyxiation and problems with passing machinery, so best level them. Best to remove topsoil, level subsoil, and then replace topsoil. Don’t try it on wet soils.

Assess the risk of erosion at this point. Erosion is influenced by:

If there is a risk of erosion:

8.3 Terracing

8.4. Subsoiling

Used to break up the subsoil at depths of 50 – 100 cm. Single tine, often with vibrating action. Requires 4-wheel drive & over 50 hp. Benefits:

Watch out for stones or bombs!

8.5 Corrective fertilising

Soil test is vital. Soil nutrient deficiencies must be corrected

Some people put in up to 10 years’ supply of slow-releasing fertilisers. Shouldn’t be a need to put nitrogen, as this will leach out before the plants can reach it and may lead to over-vigorous growth in the young plant.

However, common to raise organic matter levels above 2% by adding FYM, thus improving the structure.

pH should be increased above 6.5, if possible, by liming. Generally, use calcite (lime-CaCO3), magnesite (magnesian limestone – MgCO3) or dolomite, a mixture of both.

Gypsum (CaSO4) can be used to improve structure. It reduces the dispersion of surface soils & minimises swelling of sub-surface soils (improves permeability & aeration). Particularly good for sodic clay soils, which crust.

8.6 Deep ploughing

Depth of 20 – 50 cm Advantages:

In heavy soils, best done in autumn to benefit from freeze-thawing action during winter.

8.7 Deep cultivation

A power harrow, spader or rotary cultivator produces a medium-fine tilth to a depth of 200 ~ 300 mm.

Aims: * Makes planting easier by loosening and levelling the soil * Destroys weeds * Helps establishment of vine roots
This must be done on dry soils.

8.8 Tracing out the plantation

Must be done carefully to ensure vine rows are straight and evenly spaced.
Unless planting by machine or using plastic mulching, this can be done well before the day of planting.

8.9 Planting

Best to plant rooted cuttings as early as possible, but it is important to wait until the spring frost risks are over and to be able to prepare the ground effectively.

If the plants are delivered before being planted, they must be protected from drying out by keeping them in a dark, cool place, either in the plastic bags in which they were delivered or in buckets of water.

Potted plants can be planted as late as July.

8.9.1 Planting by hand

8.9.2 Machine planting

Planting machines are usually tractor-trailed and often laser-guided. Their success rate is even more dependent on the quality of the soil preparation than hand-planting.

8.10 Plastic mulching

The plants are planted without their supporting stakes.

A film of plastic (high in UV inhibitors) about 1 m in width is unrolled using a trailed implement that buries 200 mm on each side to a depth of 150 mm.

Holes are then cut in plastic to allow the vines to poke through. Canes or stakes are then planted next to the plants. Advantages:

Disadvantages:

8.11 Tree guards

These can be either rigid grow tubes or polythene sleeves.

They are placed on the plant after plantation and secured to the supporting stake.

Advantages:

Disadvantages:

8.12 Care for the young plantation

This is very important; twice as much time is often spent on young plantations as on established vines.

9. Vineyard Design

Topic —
Macroclimatic Evaluation Heat (summation, ripening month)
Rainfall (total annual & distribution)
Sunshine hours
Mesoclimatic Evaluation Frost risk
Aspect & Elevation
Wind exposure
Site Survey Map
Soil survey (texture, structure, depth, drainage, pH, nutrients)
Risk of erosion
Vine Variety Legislation
Market research
Local vineyard survey
Rootstock Selection Soil assessment (chalk)
Vigour requirement
Nematode risk
Culture System Fertility of field (plant density, alley width)
Cost of establishment & maintenance (mechanisability)
Microclimatic advantages
Block Design Windbreak requirements
Row length & orientation
Mechanisation Field accessibility (alleys, headlands, pylons)
Storing, cleaning, loading areas
Pre-planting Operations Clearing
Soil preparation (levelling, sub-soiling, fertilisation, cultivation)
Planting Operations Method (manual, mechanical)
Plastic mulching, polythene sleeving
After-care of Plantation Watering
Pest control
Wind protection
Summer pruning