The browned leaves and dead branches are the result of winter injury, likely sustained during the very cold temperatures we had back in January. Broad-leaved evergreens, such as hollies or rhododendrons, are particularly susceptible to damage. Yet, cold temperatures aren’t the only factor. Warm spells in late winter can also injure plants. In fact, rapid temperature fluctuations are usually more damaging than sustained periods of extreme cold. Sunlight and warmth trigger the leaves to start photosynthesis, which causes them to lose water. If the ground is still is frozen, the plants' roots can't absorb the water needed to replenish the supply in plant tissues. As a result, the leaves or needles turn yellow and then brown, a condition often called "winter burn" or "winter kill."
Dead Leaves May Not Mean The Branch Is Dead
However, don't rush to prune out branches because they may not really be dead. Plants may exhibit discolored leaves but still have live buds. Once the ground thaws and the shrub can absorb water through its roots, it may recover. One way to tell whether a branch is alive is to gently scratch a small nick in the bark with your thumbnail. If you see a green layer beneath the outer bark, the branch still is alive. Although it may drop its damaged leaves, it will flush new ones in the spring.
If you do have sections of dead branches, you should prune them out. Hollies are very tolerant of being pruned and will often re-sprout even if they are cut to the ground. Many people do not prune their hollies as they like the symmetrical shape they naturally assume. However, they tolerate pruning very well. Wait to prune your holly until it begins to show new growth in the spring. At this point, you can prune out the dead tissue above the new, emerging leaves.
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