|
 December
2001
 Iris
unguicularis
November
2001
Hymenoxis
herbacea
October
2001
Pellaea
atropurpurea
September
2001
Zauschneria
garrettii
August
2001
Platycodon
grandiflorum
'Sentimental
Blue'
July
2001
Callirhoe
involucrata
 June
2001
Helianthemum
nummularium
hybrids
May
2001
Viola
pedata 'Bicolor'
April
2001
Anemonella
thalictroides
March
2001
Fritillaria
pudica
February
2001
Castilleja
rupicola
January
2001
Lupinus
lepidus var. lobbii
Archive 2004
Archive
2003
Archive
2002
Archive
2000
Archive
1999
Archive
1998
Archive
1997
|
Plant
of the Month
June
2001
Helianthemum
nummularium hybrids
by Iza Goroff
Helianthemum
nummularium is a member of the Cistaceae, the Rock
Rose family. It is found throughout much of Europe. It has
been hybridized with H.
apenninum and H. croceum
to give rise to many hybrids, the exact parentage of which
have been obscured through many generations of crosses.
Helianthemum
nummularium hybrids vary in size, color, and growth
habit. Most have leaves about 2 cm (0.8 ") long and less
than 1/3 as wide which vary in color from dark green to
silver, some with hairs, others shiny, frequently with an
indumentum (hairy coating) underneath.  Some
of the hybrids are prostrate, no more than 4" (10 cm) high,
but spreading to 18" or more. Others are more upright,
though none are really tall. Flower color of the species is
yellow. By hybridizing and selecting varieties have been
developed with colors ranging from white and yellow to
orange and red.
Helianthemum
nummularium hybrids must be grown in sun. They
require a sandy, well drained soil. The pictured plants are
growing in a 10" (25 cm) layer of coarse sand over regular
garden soil with a 1" layer of pea gravel as a mulch. While
they may grow well in a richer soil, they may die during a
severe winter. They are on the edge of hardiness in the
coldest areas of the USA. Expect three or four years of life
from one of these little shrubs.
Helianthemums
may be propagated by layering or by cuttings, protecting the
young plants over winter. They may be raised from seeds, but
seedlings from hybrid parents will not be identical to their
parents.
Helianthemum
nummularium hybrids are valuable for providing color
in early and mid summer when the rock garden would otherwise
be rather dull.
|
