Dwarf Alberta Spruce is a cultivated mutation of Norway Spruce. Once in a while, a branch reverts to the parent — and a wild mutant limb grows out of the side of an otherwise tidy little dwarf tree.
Walk past enough suburban front yards in South Jersey and you’ll see this exact thing: a tidy little cone-shaped Dwarf Alberta Spruce, three or four feet tall, with one wild, fast-growing branch sticking out of the side at twice the height of the rest of the tree. It looks like a mistake. It looks like the tree got infected with something. It is, in fact, a textbook case of cultivar reversion — and once you know what you’re looking at, it’s one of the most interesting little stories in residential horticulture.
View from the Field · Paul Biester · Tree Awareness
“This is a Dwarf Alberta Spruce. It’s made from a genetic mutation on Norway Spruce called witches’ broom. They cultivate the genetic material from that, and every once in a while it reverts back. So this looks like a mutant hanging off the side of this tree — in reality what it is, it’s the parent. The parent DNA, or the parent tissue that they used to cultivate the witches’ broom from. So it’s reverting back. It’s kind of a cool thing.” Paul Biester · NJ LTE #408
A witches’ broom is a dense, abnormal cluster of stunted twigs growing out of a single point on a tree — the result of a localized genetic mutation, an insect injury, a fungal infection, or a parasitic mistletoe. They’re common on Norway Spruce (Picea abies), Pine (Pinus spp.), and a long list of other conifers. Most of them go unnoticed by the public.
The interesting thing is what happens next. A nurseryman who finds a stable, dwarf, ornamental witches’ broom on a Norway Spruce can take cuttings from it and propagate them. The cuttings carry the localized mutation, so the resulting tree is a permanently miniaturized version of the species — same needles, same form, but a fraction of the size. Dwarf Alberta Spruce (Picea glauca var. albertiana ‘Conica’) is the most famous example in the American nursery trade. Originally selected from a witches’ broom found in Alberta in 1904, it’s been propagated by cutting ever since.
Here’s where it gets interesting. A cultivar like Dwarf Alberta Spruce is a chimera — the same individual plant carries the parent (full-size, normal-growth) DNA and the mutated (dwarfed) DNA, and which one expresses depends on which tissue the new growth comes from. The vast majority of the buds are mutant tissue, so the tree stays dwarf. Occasionally, a bud forms from the original parent tissue underneath. That bud isn’t carrying the mutation. It grows the way Norway Spruce wants to grow — vigorous, full-sized, with normal-length needles.
That’s the “mutant” branch on the side of the dwarf. It looks like an aberration. It’s actually the original DNA that the cultivar was selected away from.
The practical answer for a homeowner is straightforward. Prune off the reverted branch. Cut it back to the trunk, flush with the surrounding dwarf wood, the same way you’d remove a sucker. If you don’t, the reverted branch will outgrow the rest of the tree (it has parent-DNA growth rates) and the dwarf form is permanently disfigured. If you cut it cleanly, the tree resumes its compact shape from there.
Two species notes worth knowing. Don’t leave the cut surface exposed in mid-summer — spider mites are the most common pest of Dwarf Alberta Spruce, and a fresh wound flush with the trunk during peak heat is a stress event the mites will exploit. Time the pruning for late dormant season or early fall when possible. Don’t shape the dwarf with shears — the species responds badly to being sheared into hedge form. Selective hand pruning of single branches is the right approach.
Reversion is one of those small horticultural details that says something larger about how cultivated landscapes work. Almost every “dwarf” conifer on the market traces back to a single found witches’ broom on a wild parent tree. The dwarf form isn’t the natural state. It’s an instability the nursery industry has stabilized through propagation — and once in a while, the original wants to come back.
If you’ve got a foundation conifer with an off-looking branch, a quick walk-through can tell you whether it’s a reversion (cosmetic, prune it) or something else. Schedule a Plant Health Care visit →
