Complex sentence: The plants are climbing, and pea sticks or a trellis or other support system is required for optimal growth; they are capable of climbing to 2 m high but are more commonly grown to around 1-1.3 m for ease of harvest.
Split into simpler sentences: The plants are climbing, and pea sticks or a trellis or other support system is required for optimal growth. Some cultivars are capable of climbing to 2 m high but are more commonly around 1-1.3 m for ease of harvest.