“What’s wrong with my Cedars? Needles are turning brown and falling off.”
It is a frequent question I get, particularly in October and November. Needles (or scales) of Cedar (Thuja Occidentalis) slowly turn from yellow to rust-coloured, eventually falling in late fall or early winter.
The good news is that there is no need to panic. All conifers, normally lose up to one-third of their foliage annually. Cedars, as a normal part of their life cycle, lose their oldest needles to lighter their load.
All conifers behave the same way. Even Boxwood, Holly and other broadleaf evergreens lose a number of needles annually. For most conifers, needle drop is of little consequence and hardly noticeable.
The two conifers that drop needles most aggressively are Cedars and White Pine. For both, affected needles turn yellow or rust coloured, contrasting sharply with the remaining green, healthy foliage. By late fall, needles drop to the ground forming a noticeable blanket of coloured mulch.
While needle drop is a normal part of an evergreen’s life cycle, several factors contribute to its severity or extent. Stress due to insect activity, poor drainage, wind and dry soil will increase needle drop.
Contrary to what we may believe, needle drop is a good thing. Foliage drops to the ground forming mulch, helping to keep soil moist. Eventually the mulch breaks down building nutrient rich compost.
Spruce (Picea), a popular large growing evergreen always leaves a significant deposit of their oldest foliage, but the effect is hardly noticeable because needles are small and brown, blending nicely with dark soil. Bare branches are hardly noticeable because dense new growth covers the inner bare limbs.
Birds take advantage of new-found space within spruce trees, finding room to make their nests while enjoying protection from predators. Some reports have found that up to 500 sparrows scan find a permanent home within a mature Colorado Spruce tree.
Gardeners can minimize the extend of conifer needle drop by improving soil conditions. A four- to four-inch layer of organic wood mulch or compost over the soil surface will do wonders for a mature conifer. Adding water during the hot dry summer months is advisable. Fertilize if soil is poor.
Losing the oldest, inside foliage of a conifer is a normal process, but losing exterior needles indicates a problem, probably indicating that the tree’s moisture and nutrient needs are greater than what the roots can supply, and the plant can absorb. Other factors may include the presence of insects or disease.