Madeira is a difficult place to grow grapes. Nearly all the island’s vineyards are planted on tiny step-like terraces called poios, carved from the red or grey basalt bedrock. Although most of the newer vineyards are cordon-trained, most vineyards are planted on low trellises (known as latada) similar to those of the vinho verde region on the Portuguese mainland. These serve to raise the canopy above the ground, making the grapes less vulnerable to the fungal diseases that thrive in this damp, subtropical climate. With a mean annual temperature of 19 °C/66 °F and high rainfall, powdery mildew and botrytis bunch rot are constant threats.