A baby-leaf crop will now be defined as the young leaves and petioles of any plants grown for harvest beyond the seedling stage (after true leaves have formed) but before the eight true-leaf stage – in other words, any salad crops harvested before eight true leaves will be classed as baby leaves. That means products that are currently authorised for use in crops such as spinach, lettuce, chard, beet leaves, rocket, lambs lettuce and land cress can no longer be used on these crops when they are grown as baby leaves. They can only be used if the crops are grown and harvested past eight true leaves.
Leaves complete their growth within one week to several weeks, depending on the kinds of plants that produce them. At first, the unfolding leaf must get all its food from older leaves or from food stored by the plant. Soon, however, the young leaf turns a deeper green and begins to make its own food. Gradually, the leaf produces extra food, which is sent to the rest of the plant. During the growing season, the color of the leaf changes from bright green to a duller green. The leaf also becomes tougher because its cells develop thicker walls. During this time, a special change occurs in the leaves of deciduous trees and shrubs. A corky layer of cells known as the abscission zone develops where the stalk of the leaf joins the stem. This zone breaks down in autumn, causing the leaf to separate from the stem.
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