2.4.4.b.e How can plant extracts be obtained?

Growing your own plants

Growing your own plants is not a simple matter, another option is to purchase from a professional who will be familiar with all the techniques for growing, picking/harvesting, drying, storing and preserving the plants.
When a private individual decides to grow the plants intended for plant extracts, several factors need to be considered:

• Harvesting must be carried out in accordance with specific conditions: some plants require early morning picking, others may require picking at solar noon or even in the evening. Plants have different development cycles and may need to be picked at different times of the year. For example, some herbal teas involve the flowers, which are usually the most fragile part of the plant and must be harvested with care.

• Drying is a crucial step when preparing dried plants. The temperature required can vary depending on the plants but in general should not exceed 35°C.

• Storage and preservation must also follow precise procedures: temperature, humidity and light exposure can be harmful to the preservation of some plants and/or preparations.

The preparations require water, which ideally should have a slightly acidic pH between 5.5 and 7. Rainwater is preferable when possible.

Using an external supplier

If a winegrower decides to use an external supplier for their preparations or fresh/dry plants, it is their responsibility to be familiar with the nature of these preparations, and their harvesting, drying and storage conditions.

Respecting shelf life: fermented extract preparations can be bought ready to use, since they have already been fermented. Other products, i.e. all or part of the plants, juices, macerates, decoctions and herbal teas, must be used as close as possible to their production/preparation. Their shelf life is short either to avoid fermentation or to guarantee the plant extract properties. Plants, whether fresh or dried, are a living raw material which must also be used in compliance with precise storage conditions and periods in order to safeguard their properties.

Plant extracts: a general functional use that must be carefully evaluated

Preparations based on plant extracts (herbal teas, decoctions, fermented extracts, etc.) can have various effects on the vine. They can act as biostimulants, PDSs, or as basic substances (horsetail and willow) in order to reduce the use of phytosanitary products. Some of these preparations have a more powerful effect due to the presence of certain active ingredients:

• Alder buckthorn and Rhubarb (Anthraquinones)
• Horsetail (silica, phenolic compounds, Hetero-Trans-Glucanase, etc.)
• Willow (salicylic acid)

While these biocide, fungistatic and other actions have been verified for some preparations, there are additional parameters to study, such as the stability of these active ingredients, optimal storage conditions, and the doses to apply according to the situation (growth stage, threat, etc.). Storage conditions and periods, and efficient doses for each active molecule have not been thoroughly studied.

Moreover, the use of plant extracts is generally determined on the basis of their containing a specific molecule. The conversion of these extracts into a preparation may reveal the presence of a "cocktail" of active ingredients whose effect on vines is still unknown. Further research therefore needs to be carried out.