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Cercidium hybrid ‘Desert
Museum’
This semi-evergreen,
Thornless, Palo Verde
hybrid exhibits
qualities found in
Foothill, Blue and
Mexican Palo Verde,
provides ample shade,
distinctive rich green
trunks and branches
that, similar to the
Palo Brea, remain smooth
as they mature, and
abundant brilliant
yellow flowers that
appear in spring and
intermittently during
the summer months.
Nothing heralds the
arrival of the desert
spring (and in some
years 100 degree
temperatures) as
brilliantly and
conspicuously as the
blooming of the Palo
Verdes. With a
succession that includes
Blue (Cercidium
floridum), Foothill,
Mexican and Sonoran,
Palo Verdes color the
desert a brilliant
yellow from spring to
early summer. Other than
Mexican Palo Verde
(Parkinsonia aculeata)
all the Palo Verdes are
popular and widely used
landscape trees. All
these species are so
closely related
botanically that
hybridization between
species is quite common
in native and nursery
environments. In the
past this hybridization
went largely unnoticed
or was mistaken for
genetic seed variation
within a single species.
The potential for
hybrids to offer
advantages like
increased vigor, greater
cold hardiness, enhanced
flowering and absence of
thorns eventually
brought them to the
attention of
horticultural
professionals.
In the late 1970's Mark
Dimmitt with the Arizona
Sonora Desert Museum (ASDM)
began noticing Blue Palo
Verdes that exhibited
characteristics
suggesting they were
hybrids of other Palo
Verde species. He
collected and planted
seeds from the assorted
trees he had observed
and began evaluating
them. By 1981 he had
identified a thornless
seedling as clearly
superior to the others
collected. Careful
evaluation of the
genetic composition of
this hybrid, named
'Desert Museum',
revealed it to be a
complex hybrid having
genetic characteristics
from Mexican, Blue and
Foothill Palo Verde.
Dimmitt suspects that
'Desert Museum' gets it
vigorous growth, sturdy,
upright branching habit
and bright flowers from
P. aculeate, and its
small delicate leaves
from the Cercidium
species. Trees have
tolerated temperatures
of 15 degrees without
damage in Tucson. The
most remarkable and
unique feature of this
hybrid is the absence of
thorns. Flowers are
slightly larger than
those of P. aculeata and
other Cercidiums and
trees have been observed
to flower abundantly as
early as mid-March in
southern Arizona with
intense, full bloom
lasting into late spring
and early summer.
Intermittent flowering
can continue into the
mid to late fall.
Pruning and staking is
best done during the
growing season when the
trees limbs are more
flexible. The v-shapes
branching, thornless
growth and ample shade
make Desert Museum a
pedestrian friendly
desert adapted tree that
could be used in a wide
array of landscape
applications.
Variety
'AZT':
Arid
Zone Trees makes
selections from
thousands of trees
propagated from seed.
Only Individual trees
having the most
desirable physical
qualities (branching
habits, leaf color, leaf
canopy, and flower
color) and sound
horticultural
characteristics
(rooting, cold hardiness
and growth rate) are
selected for further
study. These trees
are then cloned (vegetatively
propagated) and planted
at our nursery for
evaluation. Only the best of
these trees are then
placed in cloning
production and are
designated Variety
'AZT'. Since no one
single selection of any
desert tree specie is
best adapted to all
landscape applications,
we continually search
for new additions to our
Variety 'AZT'.
Arid Zone Trees
propagates
'Desert Museum'
with the guidance and
permission of the
Arizona Sonora Desert
Museum.
Cultural Practices:
Foster the development
of a more dispersed root
system and reduce the
risk of wind throw by
arranging irrigation
emitters at varying
distances from the trunk
to encourage roots to
"seek out" water and
nutrients. Irrigation
emitter arrangement
along with other
information on
irrigations practices
for desert trees can be
found at
www.aridzonetrees.com
and click on the FAQ
link.
Prune as needed to
reinforce the structure
and form of the tree.
Periodic thinning is the
most desirable method of
pruning. Avoid hedging
or heading back desert
species, as this will
only stimulate excessive
branching. Do not remove
more than 30% of the
canopy during the summer
as this can lead to
sunburn injuries that
can later be invaded by
wood boring insects.
Always use clean, sharp
tools that are cleaned
regularly in a 10%
solution of bleach. For
detail pruning guide see
www.aridzonetrees.com
and click on the FAQ
interactive button.
Periodically
insect pests can be a
problem on some desert
trees. On young trees,
insect infestation can
slow typical seasonal
growth. Inspect trees
during the growing
season for common garden
sucking insects such as
aphids, thrip,
whiteflies or psyllids.
During dry months, (May
and June) in dusty
conditions, spider mites
can appear. Monitor for
infestation and apply
controls as needed.
Spray applications of
water or water and Safer
Soap give short-term
control (3 to 7 days)
for small insect
population. For heavy
infestation or longer
control use federally
registered insecticides.
A contact insecticide
application will kill
existing adults. An
application with a
systemic soil drench
will provide 8 to 12
weeks control for any
post application insect
hatchings or migration
of insects. Before using
pesticide for the first
time or on new plants or
cultivar, treat a few
plants and check for
phytotoxicty.
Always read label and
follow label instruction
before using pesticides.
For pesticide control
recommendations contact
a
licensed pest control
advisor.
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