Even in elementary school, children learn that conifers keep their needles even in winter - with one exception, the larch. This colors its soft needles beautifully yellow in autumn and then sheds them. However, various causes mean that evergreen species also lose their needle dress. In this case, a precise clarification of the causes is necessary.

Coniferous trees also shed old needles
However, discarding the needles is not always pathological, but sometimes quite natural. The needles of the conifers are shed at regular intervals anyway, so that the tree can grow new needles. Since this process takes place continuously, it is only sometimes noticeable - for example, if a tree sheds a particularly large number of old needles in one year. How often this happens depends on the specific tree species: pine needles, for example, are renewed every three to five years, while fir needles can remain on the tree for up to eleven years.
Causes of pathological needle ejection
However, if the tree suddenly sheds numerous needles that previously turned yellow to brown and may also show other causes of disease, then there is a more serious problem behind it. Finding the exact cause is not always easy.
dryness
Many conifers shed their needles during periods of long drought, which is particularly the case in late summer. However, dry frost (especially in connection with bright sunshine!) and insufficient watering of potted plants also lead to needle dropping due to lack of water. Solution: Water the conifer penetratingly.
Waterlogging / compacted soil
But the opposite can also lead to needle dropping if the tree is permanently in too moist soil. There are many reasons for this: frequent watering, heavy rain, lack of drainage, compacted soil… in this case, the only thing that helps is to provide drainage afterwards and to improve the soil in the long term.
Nutrient deficiency / over-fertilization
Conifers want to be carefully fertilized because they are very sensitive to both under and oversupply of nutrients. This also applies to pollutants from the air, as these are stored in the leaves and can literally poison the tree from there - after all, the needles often remain on the tree for years.
Tree does not grow after (re)planting
Needle shedding is not uncommon after planting or transplanting and indicates difficulties with growth: the tree often has to feed the upper parts of the plant that have not been cut back with a reduced root ball, which it cannot do. A pruning and thorough watering can help.
pest infestation
Plant lice and spider mites in particular often cause the needles to turn brown and become shed.
tips
Another reason for the discoloration and shedding of the needles is the limitation of the root space, for example by walls or foundations. In this case, the tree can often no longer absorb enough water and nutrients.