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Genetic Regression
What is going on with this unusual shrub?
By Chris Leinster - September 10, 2025
The accompanying photo perfectly demonstrates an example of Genetic Regression. Genetic Regression occurs when a genetic mutation of a hybridized plant “regresses” back to it’s ancestral form. In this instance, a Dwarf Alberta Spruce, which itself is a genetic mutation of a White Spruce, regressed back to its original form!
All Dwarf Alberta Spruce are clones of mutated branches, often called “witches brooms”, originally found growing in an isolated stand of White Spruce in Alberta, Canada. Botanists took cuttings of the mutated branches, grafted them to a common Spruce root stock, and propagated the miniature, slow-growing, conical ornamental shrubs we now enjoy as Dwarf Alberta Spruce.
For reasons that are not fully understood, and reasons that are irrelevant for this discussion, select cells at the top of this shrub reverted back to the parent White Spruce heritage. While this looks kind of cool, it is usually undesirable. The White Spruce is growing much faster and larger than intended by the design requirements and will continue to do so until it overtakes and eventually kills the host Dwarf Spruce.
Genetic Regression is quite common in many types of variegated plants, plants hybridized and selected for variable or striated colors in the leaves. For example, Emerald Gaiety and Emerald ‘n Gold Euonymus have been selected because they have white and gold margins around a green leaf. Often times, a branch or several branches will regress, displaying only green leaves, usually with more aggressive growth. Ivory Halo Dogwood, Tricolor Beech, and Purple Smoketree are susceptible to regression as well.
The remedy is quite simple. Simply prune or trim off the affected branches as soon as the anomaly is detected. Easy! The sooner the better, as the abnormality can swiftly take over and wreck the integrity of the desired traits of the plant, as the cover photo can attest.
All Dwarf Alberta Spruce are clones of mutated branches, often called “witches brooms”, originally found growing in an isolated stand of White Spruce in Alberta, Canada. Botanists took cuttings of the mutated branches, grafted them to a common Spruce root stock, and propagated the miniature, slow-growing, conical ornamental shrubs we now enjoy as Dwarf Alberta Spruce.
For reasons that are not fully understood, and reasons that are irrelevant for this discussion, select cells at the top of this shrub reverted back to the parent White Spruce heritage. While this looks kind of cool, it is usually undesirable. The White Spruce is growing much faster and larger than intended by the design requirements and will continue to do so until it overtakes and eventually kills the host Dwarf Spruce.
Genetic Regression is quite common in many types of variegated plants, plants hybridized and selected for variable or striated colors in the leaves. For example, Emerald Gaiety and Emerald ‘n Gold Euonymus have been selected because they have white and gold margins around a green leaf. Often times, a branch or several branches will regress, displaying only green leaves, usually with more aggressive growth. Ivory Halo Dogwood, Tricolor Beech, and Purple Smoketree are susceptible to regression as well.
The remedy is quite simple. Simply prune or trim off the affected branches as soon as the anomaly is detected. Easy! The sooner the better, as the abnormality can swiftly take over and wreck the integrity of the desired traits of the plant, as the cover photo can attest.