Interplanting in Viticulture

Technical articles

Climate resilience Pruning and training of the vine

Small vine

The main objective of complantation is plot improvement: replacing dead or deficient vines in order to maintain the required density for the appellation and restore the profitability of the plot. This technique consists of replacing dead or diseased vine plants with young ones. Young shoots and old plants coexist in the same rows.

While this ancestral technique has many advantages, it is costly, delicate to perform, and its success is not guaranteed. Indeed, it is difficult for a young plant to develop in an established vineyard, due to competition from other vines with powerful root systems, soil condition, diseases, and its fragility to mechanized work. For all these reasons, successful complantations are not easy and require sustained attention. Complantation must be part of a true vineyard renewal strategy alongside other methods.

Details on the technique

Complantation is divided into 3 consecutive steps:

1. Identification and removal of dead and diseased vines
2. Making the holes that will receive the new plants
3. Planting the young plants

Trials conducted at the regional level show that the success of complantation is strongly linked to climatic conditions and practices. It also emerges that it is better to favor plants with long roots and long rootstock stems, and avoid mineral fertilizer inputs at the time of complantation. Replacing missing vines in a plot is essential if one wants to maintain a profitable yield level. On non-declining plots, complantation can be an interesting solution. But in the field, the success of this technique is often not commensurate with its cost and implementation constraints. Therefore, the Chambers of Agriculture of Vaucluse, Bouches-du-Rhône, Var, Drôme, and Gard, the Côtes du Rhône Winemakers' Union, the Serres Agricultural High School (Vaucluse), the Organic Agriculture Research Group, and the Vaucluse Nursery Growers' Union conducted a series of trials between 2013 and 2016 to determine the most favorable factors for complantation success.

Factors favoring complantation success

Long roots and long stems improve plant survival

The results first favor plants with long roots, whether Grenache or Syrah. Indeed, in the first year following complantation, growth of plants with long roots is always higher than for plants with short roots (this difference tends to decrease in subsequent years). Then, the overall mortality rate is much lower with plants with long roots. Finally, these plants slightly accelerated establishment, with a few more plants already having a shoot at the 4th leaf stage. The pruning of the rootstock stem also seems important. But beware, these results only apply to plants with long roots. Thus, mortality of plants with long stems and long roots is much lower than that of plants with short stems. It should also be noted that longer plants make maintenance easier, whether soil work, weeding, tying, or rootstock regrowth…

Influence of root length on total mortality rate of complants (observations on 13 plots)

Roots arranged in a star pattern

Root arrangement at planting

Long roots show real interest in these trials. They theoretically have a larger reserve stock than short roots for the plants, roots being the primary storage site.

However, depending on their arrangement, they may not colonize the soil well, which could penalize the longevity of the complants. To verify this hypothesis, advisors compared planting plants with long roots arranged in a star pattern, clustered on one side along the row direction, and plants with short roots.

Roots arranged on one side

Observations made 4 years after planting show that roots preferentially establish in the direction in which they were initially positioned.

Star-shaped or short roots end up developing over nearly three quarters of the colonizable surface, while roots clustered on one side develop over only about one third.

However, star-shaped roots spread more near the surface, whereas short roots, and to a lesser extent roots clustered on one side, tend to go deeper.

Overall, the star arrangement appears to be the most effective for plant development. Thus, total mortality at the 4th leaf stage is almost zero and plant establishment is much faster. When the root system is clustered on one side, mortality remains very low, but shoot formation takes longer. For plants with short roots, as in other trials, mortality is very high (around 40%).

Beware of nitrogen fertilizer inputs at complantation

During trials, nitrogen fertilization at planting did not particularly promote plant growth. It even caused significantly higher plant mortality compared to unfertilized treatments (up to twice as many dead plants). It is therefore better to avoid it. The tested organic amendment had no effect on plant development.

Plot effect is predominant

The plot has a predominant effect on plant establishment. Soil properties, its mechanical maintenance, plant material, weather conditions, and presence of possible pests strongly conditioned the success of experimental complantations.

Complants mortality is overall high—close to 30% on average across all treatments by the 2nd leaf stage. Vigor remains low in the first years and the time to establish shoots is often quite long. This confirms that complantation is a complex, demanding practice that can only be effective if given the utmost care.

Implementation of the technique

Frequency of complantation

It is essential to regularly perform counts of diseased or dead vine stocks to accurately estimate the percentage of holes per hectare. If the number of missing plants exceeds the threshold set at 5% (representing about 200 to 250 holes per hectare), they must be replaced with young plants. It is important to carry out complantation shortly after identifying the missing plants.

Making the holes

• In clay soil, always work on well-dry ground to avoid smoothing the hole walls. For spring planting, it is advised to make the holes the preceding autumn so that the soil crumbles properly due to frost and reduces cavity formation.
• In loam soil, the soil must also be properly dry. Planting must be done immediately after making the holes, otherwise the soil may close up at the first heavy rain.

Holes can be made using various tools available to viticulturists:

Hydraulic auger

• Augers: Several manufacturers offer this type of tool for sale. It is preferable to choose an auger with a spade screw (2 opposite blades for good penetration with crumbling) with a minimum diameter of 400 mm and a depth of at least 40 to 50 cm. Models with wire guards are also preferable.
• Excavator spade: multi-purpose (removal of vines + hole preparation), this tool works the soil without a hardpan or smoothing, over 70 cm wide and up to 60 cm deep. This spade is safe for trellising as it works under the wires.

Planting

Two periods are possible for planting complants:

• in autumn, with potted plants: these plants are resistant to "usual" frosts. Large pots are preferable (1 to 3 liters) because they contain more potting soil, and the plants are more vigorous with better-developed roots. They must be specially ordered from the nursery, and their cost ranges from 2 to 3 euros (for 3 liters). They should be planted outside periods of severe frost to avoid partial root damage.
• in spring, with traditional (bare-root) plants. In the case of poorly aerated soils (white boulbènes, very clayey soils), a mixture of sand/potting soil can be used around the plant. A handful of compost can be placed at the bottom of the hole, which will not provide nitrogen but will locally improve soil functioning. Never place mineral fertilizer, especially nitrogenous, in the planting hole.

Maintenance of young plants

Maintenance of young vine plants is essential to ensure good establishment and to make the most of the work done.

Rigid protective sleeve

• Staking and plant protection are mandatory and immediate. The stake must be tied to the support wire, preferably using rigid protections (such as Tubex or others) against herbicides and rabbits, which are less traumatic in case of wind. Moreover, they protect the foliage and create a greenhouse effect in spring. Shoot thinning must also be carefully done.
• Beware of scorching risks inside the protections during hot weather: in some cases, they may need to be removed to avoid plant mortality. They can also serve as a refuge for snails, which cause significant damage to buds in spring.
• Depending on soil condition and growth, weeding may be necessary if the soil has closed up in summer (e.g., battant boulbènes). Watering should be planned in summer if needed, regardless of planting technique.
• It is possible to apply a small amount of nitrogen, localized at the base, but not before the second year of growth due to the risk of ammonia toxicity and imbalance between root and aerial system development. It is preferable to use, for example, ammonium phosphate, which is lower in nitrogen and less harmful to roots, or organic fertilizers.
• Phytosanitary protection of young vegetation must be thorough, especially once it exceeds the protections. The foliage, very sensitive, must remain free of downy mildew mosaic until lignification of the main shoot, which generally occurs later than in adult vines (longer active growth).

Cost of complantation

The cost of complantation varies according to production strategies.

Regulations

The complantation technique allows managing vine mortality in a vineyard and thus ensures good profitability of the operation, but also a good vineyard density. This last point is important because appellation decrees impose a minimum number of vines per hectare. Complantation allows respecting imposed quotas.

Appendices

S'applique aux cultures suivantes

• Vine