About 4 years ago, a company planted 11 blue spruces in my yard. The following year, 4 of them died and the company replaced them. The next year, 3 died and the company replaced them. Last year 2 died. The soil is mostly clay and that side of the yard sometimes stays damp. I also have a lawn sprinkling system which waters them each day when hot. Any ideas on what’s happening? The remaining trees, now 9, don’t look very blue like blue spruce should, and are kind of yellowish.
Colorado blue spruce (Picea pungens) is native to the Southwestern U.S., not Michigan. It prefers rich, well-drained, yet moist soil in full sun. They are overused by landscapers for screening and large vista plantings because they have greater tolerance for less than ideal growing conditions. Unfortunately, your clay soil holds water like a sponge. “Moist soil” does not equate with saturated soil. Since your yard stays damp and you are augmenting it with lawn irrigation, the roots are simply drowning. The chlorotic needles are also an indicator of excess water in soil that does not drain.
The tree roots are in the top two feet of the soil. Sacrifice some turf grass for 2 to 3 inches of organic compost to enrich the tree roots out to the drip line. Redirect your sprinkling system away from the trees, and reduce the frequency of water, if possible. Consider installing a field drain to move water out of the area. Trees and lawns simply have different water needs.
If you lose any more blue spruces, try replacing them with white spruce (Picea glauca), a Michigan native that also has a pyramidal shape and a blue-green cast to the needles. Consider breaking up the monoculture by interspersing lacy Eastern hemlocks (Tsuga canadensis). They will tolerate more moisture. Still want groundcover? Consider a mix of low-maintenance sun and shade perennials. Canadian ginger (Asarum canadense) works well in shade, and woodland geranium (Geranium maculatum) will work well in the sun-shade margin at the turf line, with a bonus of light purple flowers in late spring.
LEARN MORE: The Blue Spruce at The Morton Arboretum