By Brad Haire
University of Georgia
A single nickel won’t buy you much these days. But a little bit
of nickel, the metal, might help tree nursery managers save one
of their best-selling plants.
Betula nigra, or river birch, is one of the most popular
landscape trees in the United States. It grows well and fast in
rural and urban environments. Its bark peels into flaky, paper-
like pieces that can turn orange, white or dark brown. And its
simple green leaves turn bright yellow in the fall.
Bad birches
But over the past decade, something strange has been happening
to some river birches in nurseries. Their leaves have started to
curl, and growth has been stunted, said John Ruter, a
horticulturist with the University of Georgia College of
Agricultural and Environmental Sciences.
Some of the trees look like witches’ brooms. Nobody wants to buy
them.
This problem has been called leaf curl, little leaf, squirrel
ear and a few other names by nursery owners, he said. But most
call it mouse ear.
“Nobody could explain why this was happening,” he said. “But it
became a problem that got a lot of attention from growers.”
Horticulturists were baffled.
Because of mouse ear, many Southern nursery managers say they’re
going to stop growing river birches, Ruter said.
Most commercial river birch trees come from Southern nurseries,
which grow about 400,000 each year. About half of these trees
are grown in pots with soilless mixtures, which can contain
sand, pine bark and peat moss. Over the past decade, this
practice has become popular among growers for economic reasons,
Ruter said.
Pot mystery
But only the trees growing in pots show signs of mouse ear.
Trees growing in nursery fields, where they have access to
native, natural soils, are fine, he said.
“(I) knew that the trees rooting directly in the ground were
getting something from the native soils,” he said. But that
something remained a mystery.
Another scientist mentioned to Ruter that some pecan trees
developed mouse ear, too. The pecan trees weren’t getting enough
nickel from the soil.
Ruter took this idea and applied a little nickel to afflicted
river birches growing in pots.
“It was a breakthrough,” he said. “The results were dramatic.”
In just six weeks, trees treated with nickel fully recovered.
Nickel’s worth
The trees simply weren’t getting enough, if any, nickel from the
soilless mixtures they were planted in. The nickel may stimulate
an enzyme inside the tree that helps it normally produce leaves
and branches.
More tests will have to be conducted, he said. Most research on
nickel documents its hazard to the environment. It may take the
nursery industry time to accept nickel as a micronutrient
important to plants and trees like river birches.
Ruter has shown a few nursery managers what nickel can do for
their potted river birches, and they’re happy with the results.
