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 December
2002
 Pedicularis
kanei ssp kanei
November
2002
Crocus
tournefortii
October
2002
Cyclamen
mirabile
September
2002
Sternbergia
sicula
Colchicum
byzantinum album
August
2002
Gentiana
septemfida
July
2002
Oxytropis
shokanbetsuensis
June
2002
Silene
caroliniana
 May
2002
Jeffersonia
dubia
April
2002
Tulipa
vvedenskyi
March
2002
Draba
aizoides
February
2002
Diapensia
lapponica
January
2002
Chamaecyparis
obtusa 'Nana'
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1997
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Plant
of the Month
May
2002
Jeffersonia
dubia
by Iza Goroff
Jeffersonia
dubia is a member of the Berberidaceae, the barberry
family, which in addition to the woody barberries contains
the popular genus Epimedium, as well as several lesser known
genera. Jeffersonia dubia is a
native of Manchuria and North Korea where it grows in
woodlands.
 Unlike
many American woodland plants
Jeffersonia dubia is not
ephemeral; its leaves last until winter. It flowers before
and during its leaves arising and blooms for about two weeks
in mid-spring. The mature plant can grow as high as 12" (30
cm). In bloom it is about 6" (15 cm) tall. The leaf is a
rough circle about 3" (7 cm) in diameter with a cut to the
center attachment of the leaf petiole and a shallow dip on
the edge opposite the cut. The flowers are about 1" (3 cm)
wide, a light but bright lavender blue which carries well in
the shade rock garden.
My first
two plants of Jeffersonia dubia
came from the late Henry Fuller in 1978, who advised me to
plant them on a slope so that seeds would fall and be
carried away from the parent plants and form a colony; seeds
which fell and stayed close to the parents would produce
plants which could not compete with their parents. Although
Jeffersonia dubia is not
ephemeral, its seeds are; they must be planted soon after
they are mature. The only practical means of propagation is
seed. Jeffersonia dubia is very
long lived; my original plants are still going strong.
Jeffersonia
dubia is a plant for the (not too) shady rock garden.
It grows well in a standard shade rock garden soil such as
approximately equal parts of topsoil, humus (sphagnum peat
moss is OK), and sand. It grows equally well with an organic
(e.g. bark chips or oak leaves) or gravel mulch. It is hardy
to at least -32 F (-36 C).
The genus Jeffersonia
contains only two species: Jeffersonia
dubia and J. diphylla.
Jeffersonia diphylla is a
native of Eastern North America. Their close relationship is
one of the many pieces of evidence that in the very distant
geological past the Eastern coast of North America was
connected with the Eastern coast of Asia.
Jeffersonia diphylla is
interesting for its foliage; its leaf forms two triangles,
their apexes intersecting at the stem. Its flowering is much
inferior to Jeffersonia dubia, since its white flowers last
only a few hours before its petals fall.
Jeffersonia diphylla and
J. dubia should NOT be grown
near each other. They hybridize, and the resulting hybrids'
foliage loses the separate character of each species.
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