Warmer weather

When growing conditions improve, such as the arrival of warmer weather and the longer days associated with spring in temperate regions, growth starts again.

The expanding shoot pushes its way out, shedding the scales in the process. These leave behind scars on the surface of the twig. The whole year’s growth may take place in just a few weeks. The new stem is unlignified at first and may be green and downy.

The Arecaceae (palms) have their leaves spirally arranged on an unbranched trunk.[70] In some tree species in temperate climates, a second spurt of growth, a Lammas growth may occur which is believed to be a strategy to compensate for loss of early foliage to insect predators.[71]

Primary growth is the elongation of the stems and roots. Secondary growth consists of a progressive thickening and strengthening of the tissues as the outer

layer of the epidermis is converted into bark and the cambium layer creates new phloem and xylem cells. The bark is inelastic.[72] Eventually the growth of a tree slows down and stops and it gets no taller. If damage occurs the tree may in time become hollow.[73]