This time, even if it was far too late (end of November) I transplanted the two plants. So this spring, trying to find a couple of hours, I planned the new structure. Since years I need a sheltered location for my tulip collection. My major problem is the abundant humidity in Summer- Fall- and Wintertime. Even using extreme well drained soil, I had to fight again Botrytis and other fungal diseases. In the last two years I potted each species in deep containers, using well drained soil with enough sand, I mixed some Trichoderma atroviride (mycorrhiza fungi) to antagonize soil born fungal diseases. The containers remain outdoor during the Winter, but protected from too much rain and snow. In late Spring, as the leaves get yellow (it's important not to wait until the leaves are dried), the containers are kept dry until end of October.
This is the structure that I planned. I like light structures, so I decided to use granite slabs (thickness 3 cm). A simple scaffolding is enough to take the slabs in place until the concrete dries off. Just not be too impatient.
One week later, the bottom is covered with a deep layer of gravel and a fabric layer. Well now is time to move the containers. Some species are ready to flower like Tulipa praecox or Tulipa cretica.