This week we visit Tohono Chul Park In
Tucson, Arizona and will introduce some terrific desert
plants, many of which can be used in your own homes, even
gardens. Often when thinking about desert we think hot,
dry, barren. But that is not always the case. You'll be
surprised at the vivid colors.
Barbara McDonald with the Tucson Convention
and Visitors Bureau introduces us to Tucson. Tucson comes
from the Native American, Tohono Otom tribe, and it means
"spring at the foot of black mountain. It was originally
pronounced in a way that sounded like "chucksan,"
over time it became Tucson. Many think a desert will be
barren looking. However, there are many wonderful plants,
especially during spring blooming time. There is color everywhere.
As well, the mountains provide a wonderful backdrop against
the desert. Tucson is indeed a unique, beautiful place.
One of the best places to see the native
environment in Tucson is Tohono Chul Park. Russ Buhrow is
the Curator of Plants at this wonderful park and our guide
today. Russ says one must realize these plants are happy
in this environment. When first coming to this area go into
the desert, go into the mountains, go after it's rained
and it is beautiful. You'll see some amazing, magical plants.
Tohono Chul is a plant persons place.
It is known as a cutting edge place for new plant introductions
because they're bringing many native plants into the landscape
trade that aren't available anywhere else.
Desert plants deal with extreme conditions.
The sun, for example is intense. The average person can
get a sunburn in as little as 10-15 minutes. It has very
high solar intensity. Plants can't hide from the sun, they
can't duck into the shade. The lack of humidity or lack
of moisture also causes the sun to be more intense and adds
stress to the plants because they lose water more quickly.
An example that brings the point home is-if you pull a weed
in an area with a humid environment and throw it on the
ground that weed will wilt within a few minutes and be dry
in several days, if you pull up a weed here, it will be
dry in a few seconds and crispy in an hour. Occasionally
this area has high winds, but normally they are less than
10 miles an hour. Water is a key issue. Average rainfall
is 12 inches per year and that varies from 6 inches to as
much as 20 inches. If every month they received an inch
of rain everything would be fine, but that's not the way
it works. The last time they had a bunch of rain was 1983.
Two months passed with no rain then 12 inches fell within
two days. The plants need the ability to hold and to store
water and use it over a longer period of time. Many of the
plants can use water stored in the soil, others need to
be very patient and wait for water. This area has two specific
rainy periods, one happens in winter, from October through
March and the second, with about twice as much water comes
in the summer, usually late June to early September. Plants
may have to go 3 or 4 months without water. This is not
only inconsistent water but the temperature extremes are
also harsh. The highest recorded Tucson temperature was
117 degrees, the minimum 13, although it may have been as
low as 0. The plants become highly specialized in order
to survive. The soil is also unique. Although variable,
like other parts of the country, it ranges from gravel and
rocks to clay. In this desert the soil rarely gets wet below
2-3 feet. The soluble nutrients in the soil are leached
downward, the water stops going down, gets sucked back up
by the plants and dry air, the leached solids are deposited
and a sub soil develops. It is called Caliche and is a Spanish
word that describes the calcium contained within. It is
a rock. To break it one needs a jackhammer or something
called a Caliche Bar, a pointed digging bar with a spade
on the other end. One starts digging, when the Caliche is
hit one can tell the quality of Caliche because when reasonably
good Caliche is hit it's hard, like hard pan. When a really
good gem grade Caliche is hit fire shoots from the end of
the digging bar. If the Caliche is not too thick, one can
break through it. Once done, since sand is underneath the
Caliche, there is perfect drainage. If the Caliche is too
thick or tough, raised beds may be the only answer.
Holding water is important for these plants.
We look at the root of a Prickly Pear, it is waxy, completely
sealed. The feeder roots are active and still pulling water,
indicating there is still some water in the soil. When this
root is completely dormant the feeder roots will die back,
leaving the main waxy root. When the rains come the feeder
roots will explode out. The morning after a rain, Russ has
seen, within an inch of the roots, all the water extracted.
Literally within 24 hours a plant can go from dormant to
the main feeder root exploding with all the smaller roots
developing and absorbing water. Within 2-3 days the Cactus
will go from a sort of shriveled state to fully expanded,
thick pad state. It can then hold on to water for months
If you live in a part of the country where
it gets hot in the summer and that's just about everywhere,
think about the temperature inside your hose. If leaving
it on a hard surface like asphalt or concrete the temperature
of the water inside the hose may reach over 100 degrees.
So, turn on the water, let it run a little until the water
on your hand doesn't feel hot. Otherwise it could burn your
plants, especially if they're in a container or young and
The diversity of plants at Tohono Chul
is amazing. We look at several that don't fit the typical
desert stereotype. Sacred Datura, made famous by Georgia
O'keefe is found throughout the Southwest. It is drought
tolerant, it does this by going to sleep. If it's really
cold or really dry it dives into the ground. When it rains
or the temperature warms it explodes out of the ground and
can be several feet tall within a couple of days. The flower
is beautiful, the length of the tube is amazing. The nectars
are at the bottom, thus ideal for long tongued insects.
The flowers are very white, they're night blooming which
helps them conserve moisture and attracts night flying animals.
It doesn't have spines but instead protects itself through
chemistry. It is loaded with toxins and alkaloids. An animal
takes a bite, gets sick, starts to hallucinate, gets disoriented
and learns not to bother that plant again.
Bouvardia Glaberrima is a red-orange plant,
native in Arizona in elevations of 3,500-6,000 feet. It
does fine in the mountains but needs irrigation in the valley.
Hummingbirds love this plant. Hummingbirds look for plants
with red or bright colored flowers and long tubular flowers.
Hummingbirds are not only looking for nectar but also looking
for insects and spiders. With these plants the flowers are
far enough away from the foliage so that the Hummingbirds
can easily get to them.
In full sun or in hot weather use cool
color plants. Verbena is a good choice, the light purple
contrasts with the hot sun. This plant is Native Gooddings
Verbena. It grows in the mountains and will grow in Tucson
with a little extra water. It will last from 6 months to
about 2 years. The term perennial means it's supposed to
live more than a couple of years but some are very short
lived while some live long periods of time. Verbena is a
great choice if in well drained soil, keep moisture off
the leaves and in the winter they hate wet feet. It's a
great choice for this part of the world or any place where
it gets hot and dry.
Desert Marigold has an intense yellow
flower and silvery foliage. It is a native of low desert
elevations and is a common roadside weed. Plants in this
part of the world have a pubescent or fuzz all over the
stem. It helps reflect the sun and offers shade. Overhead
irrigation isn't a good choice, they don't do well with
water on their leaves and they don't like humidity. This
is a perfect environment for them.
Eupatorium Greggii has light purple, soft
fluffy heads and serrated foliage. Butterflies like this
plant, in particular an orange butterfly called "The
Queen," a miniature relative of the Monarch. The male
Queens come to the plant, get a chemical out that makes
them irresistible to females. It's an aphrodisiac. A favorite
variety of this plant is called "Boot Hill" and
got its name because it was collected next to Boot Hill,
near Tombstone Arizona, home to the fight at the OK Corral.
Fallugia Paradoxa or Apache Plume is a
native plant that grows between 4,000-6,000 feet in the
mountains. It has white flowers which are followed by clusters
of fruit. The fruit also looks like flowers or a plume,
even a paint brush. It looks like it has two flowers. They
like a little bit of water but aren't heavy water users
- low to moderate. They would grow in many parts of the
country, have adapted to cold temperatures and should be
good down to around zero. If grown in the Eastern U.S. add
limestone, not lime, to the soil to make it more alkaline.
When placing plants like Cactus and Yucca,
which are native to a lot of different parts of the country,
be careful in terms of visual energy. The plants are striking,
very upright, have a huge bloom, are reasonably coarse textured
and command attention. Only place these plants where you
want to draw the eye, where you want the eye to linger.
When selecting trees consider height and
spread, the leaves and flowers but also consider the bark.
The Foothill Palo Verde is a native tree found all over
Tucson into the upper parts of the valley towards the mountains.
It's bark is almost chartreuse. It has become a hot tree
to dig up and take to Los Angeles. It grows to a large size,
this one, the biggest known, is about two feet thick, 30
feet across and 25 feet tall. It provides filtered shade
enabling quite a few plants to thrive underneath. They don't
like wet feet, they're good down to the low 20's or teens.
Be careful in pruning, they die back below the cuts, like
an Olive. It's often better to prune them when little or
let the branch die and break them off, providing more of
a wild feel. They get very brittle when dry allowing them
to be snapped easily. They look spectacular at night with
Mesquite Prosopis Velutina is an important
tree to the native people in this area. They collected pods,
crushed them and made flour, then food. We know the Mesquite
timber because it is frequently used in barbecuing, providing
a wonderful flavor. These trees grow in different parts
of the country. It has a lovely dark bark, is fairly small,
will grow to 80 feet across, about 6 feet thick and 50 feet
tall, depending on the moisture it receives. The root system
is extensive. They'll have lateral roots that might go out
to the side 3-4 times its' height. There are records of
roots being found in mines up to 400 feet deep. The dark
bark with lights behind it make a stunning contrast. Another
idea is to put them against a flat stucco wall, when the
light comes through it provides dramatic lighting on the
Thank you Russ for taking time from your
busy schedule to show us this magnificent garden. These
plants represent the area but may adapt to other parts of
the country, as well.
Link :: Tohono Chul
Park and Westward
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