The plants which are to be planted in the Botanical Garden are all from areas with a Mediterranean climate (mainly characterized by a hot and dry summer and mild and wet winter). However, many micro climates exist in these areas and plants are very sensitive. For example, some species grow only on mountain slopes with a given orientation, others only grow in sheltered gorges or open areas very exposed to wind and sun. To ensure the successful implementation of these plants, it is necessary to study and recreate their own microclimates.
Means of action.
To do this various lines of action are necessary. First, a suitable landscape should be created through for example the use of rock fill, earth formations and the creation of an artificial river. Then, we will have to unite compatible plants, bearing in mind their need for sunlight or shade. In addition, the soils needed vary from one plant to another (clay soil, humus, sand ...) so it is necessary to imitate these substrates. Similarly, irrigation should be adapted in quantity (frequency, intensity) and quality (pH, fertilizer). Finally more specific ways like misting and heating will be used to re-create specific atmospheres such as high humidity or to assure a frost free environment.
To see if the right microclimate has been achieved, we will be monitoring this here as well as the health of the plants. To do this sensors for temperature, humidity, wind speed and solar radiation will be installed at various points. Plant health will be assessed by monitoring and continuous observation and by measuring their chlorophyll content using a chlorophyll meter (SPAD502 + Konica Minolta). Chlorophyll is a pigment essential for photosynthesis, which is the process essential to the proper development of the plants. Its content and its evolution is therefore a good indicator of the state of the plants. In addition, the amount of water used for irrigation will be measured in order to adjust it as accurate as possible.
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To offer a consistent layout (see left) we have been working on the final designs ever since the start of the project. Improving it yearly with the knowledge we gain from the test gardens. The coloured circles help to identify the plants, designated by numbers from our database. Attached to each number are all the necessary information to place each taxon in the drawing, including its size at the time of planting and also after 5, 10, 20 and 50 years. If we change the information, the design will automatically change accordingly.
The final goal is to provide a "natural" landscape while mastering its development.
We work with nurseries and specialized seed suppliers, but despite this we remain vigilant about the veracity of the identification. Our procedure includes the following steps:
On receipt of the plants, the taxa all get a label that they will keep as long as they stay in the nursery.
At the first bloom of a taxon we take pictures and we check the accuracy of the identification. These photos are then integrated into the database and provide confirmation of the identity.
In the test garden they remain labeled but are also geo-localized. Once planted definitively we list each plant with a geometrical system (Total-Station Hilti, centimeter accuracy).
Thus it will be possible to merge the real and virtual through a connected tablet, it will allow visitors to walk around and access multiple data, and garden workers to optimize their work. This last step will be put in place during 2018.
In order to mimic the natural environment as closely as possible, we have to buy seeds at seed specialists because very few plants can be purchased directly from nurseries.
When we acquire seeds, we entrust them to specialized nurseries (Arven, Issa, Railhet, Arvan, Cavatore and Monde des Fougères) who ensure the germination in their greenhouses (see photo) where we visit from time to time or we raise them in our own climat chamber. Once the plants can survive outdoors we retrieve them to grow on site.
The plants are first grown on the terrace (for the most fragile of them) or in sandboxes (to protect the roots from too much variation in temperature). This also allows us to gather plant collections before planting them in test gardens that are also nurseries.
Some plants are not transplantable and are therefore raised in containers until they are planted permanently. They are therefore placed in specialized nurseries as our nursery for Eucalypts. We grow them in Airpot® because they do not make big roots and the small roots are stopped by the light without turning in the pot.