The dwarf Alberta spruce tree (Picea glauca Conica) is a popular plant but is not without its problems. It is common for homeowners who have been enjoying the plant for a few years to notice, all of a sudden, that their tree is dropping needles (often after they have turned brown or yellow). When your tree experiences needle drop, it is important to investigate why this is happening right away. If the leader of the dwarf Alberta spruce is okay, the plant still has a chance, but you should take immediate action.
Causes for Needle Drop on Dwarf Alberta Spruces
One reason why this problem is so challenging is that there are a number of possible reasons why your dwarf Alberta spruce may be dropping its needles, including:
- Excessive heat
- Winter burn
- Too much water or not enough water
Environmental Factors That Impact Dwarf Alberta Spruce
The first four of these reasons fall under the general heading of environmental factors (which include issues of location and care). No plant will perform well if you fail to give it an environment where it can be happy. Dwarf Alberta spruce grows best in full sun. It needs a well-drained, consistently moist soil. If planted in a container, water when the top 3 inches of soil is dry.
Dwarf Alberta spruce is a plant for zones 2 to 6. If you are trying to grow it in a zone with hotter summers, you are just asking for a tree with brown, falling needles, due to the excessive heat.
What can be more puzzling is that the plant can succumb, too, to environmental conditions at the other end of the spectrum. You might not think that a species whose native range includes Alaska would be subject to winter burn, but it can. That is because, when a plant suffers from "winter burn", the issue is not simply cold weather. Winter burn is a complex phenomenon that can stem, for example, from a plant's not hardening off properly in fall to prepare for winter. Pruning your tree too late (late summer or early fall) is one thing that can cause it not to harden off properly (pruning promotes a flush of new growth that is easily damaged in winter), so avoid such pruning.
Needle drop may also be due to lack of water, or else the other extreme: too much water. The former will be indicated by dry soil and is easily remedied by watering the plant more often and more deeply. Possible remedies for the latter problem include:
- Transplanting the trees
- Improving the soil's drainage
Wait till fall to transplant your dwarf Alberta spruce (to a sunny area with good soil drainage) so the plant is not trying to acclimate to its new location during the heat of the summer. In the meantime, if you have a clayey soil and suspect the problem could be poor drainage, consider building a quick, makeshift French drain to improve soil drainage in the area.
There are many good street trees, but dwarf Alberta spruce is not one of them. It is not very tolerant of either road salt or other forms of pollution. If your tree is located near the road and is dropping its needles, try transplanting it to another area of the yard.
Avoiding these stressful environmental conditions also makes your plant less susceptible to diseases such as Cytospora canker.
Pest Problems for Dwarf Alberta Spruce
Another possible reason for brown or yellow needles and dropping needles on your tree is an attack from pests. One pest that attacks them is the spruce spider mite.
There are different kinds of spider mites. The type that bothers spruce trees come in a variety of colors (black, green, pink). They usually go after the inner needles on your tree. Signs of their presence are yellowing needles and/or tiny spider webs. They are most active in the cool temperatures of spring or fall. To kill them, spray with a miticide.