Spring Leaf Drop
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It’s normal for evergreen plants to shed their oldest leaves, which are closer to the trunk than the newly emerged younger leaves at the ends of branches. While the term “evergreen” may make one think that the leaves last forever, evergreen leaves may last between one to several years before being replaced by new leaves.
Don’t panic if you see your evergreen plants dropping large amounts of yellow leaves in the spring! These are actually older leaves giving up their nutrients to the flush of young leaves that seem to sprout up overnight as the temperature warms. You might worry that leaves turning color and falling to the ground indicates that your evergreen plant isn’t happy or is stressing, but this spring leaf-fall is very much a vital, living process that prepares the plant for a giant growth spurt each spring. As I discussed in another post, leaf drop is only possible if the leaves are attached to a plant or branch that is alive. In fall, leaf drop is a preparation for winter dormancy; in spring, it is a sacrifice of nutrients from old leaves into young leaves that need an injection of critical nutrients to expand and mature quickly for the growing season.
Spring leaf drop from our evergreen Sugarbush (Rhus ovata). This is a normal response to the flush of new growth in spring and early summer. “Out with the old and in with the new” is the agenda that moves valuable nutrients from older leaves into new, fast-growing spring leaves. After transferring their nutrients to the new growth, the old leaves fall to decompose and release their remaining nutrients into the soil as a continuing fertilizer…so their death keeps recycling vital gifts.
People are used to seeing deciduous plants shed their foliage at the end of the growing season in autumn, over-wintering with bare limbs and branches. “Leaf-peepers” travel around the country every year to watch the spectacle of leaf colors as groves of deciduous trees prepare for their autumn leaf drop and winter sleep. But we are not as accustomed to the often significant leaf drop of evergreen trees just as spring entices new growth.
As spring triggers new growth, older leaves are busy sending their accumulated stores of essential minerals, sugars, and other hard-won products out of the leaf, and sending them to the fast-growing cells of new leaves. As minerals like iron, phosphorus, and other valuable nutrients are transported off-leaf, color changes paint the older leaves yellow and orange, a visible sign of the chemical transformations happening within each old leaf during its sacrifice before it falls.
So don’t stress over the overnight yellow apron of leaves underneath your evergreen trees and shrubs that appeared just as spring kicks into high gear. It’s just the elders making way for the next generation of youngsters…as we will all end up doing.
Notice that only the older leaves are turning yellow on this evergreen shrub, Sugarbush (Rhus ovata), not the newer leaves near the branch tips. The older leaves are transferring nutrients to the flush of new spring growth.
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