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The annuals are plants that live for one growing season only. Their seeds sleep the droughts away,
sometimes for years, waiting for the right amount of rainfall to awaken them into a frenzy of
growth and rapid blooming, ensuring another batch of seeds will develop in time before the
moisture runs out and the heat begins. The insects that pollinate the blossoms somehow appear
when the blooming occurs, responding to the same triggering devices.
The perennials, plants left to endure year after year, have come up with many ingenious adaptations
to ensure survival. Succulents, including cacti, have waxy coatings to slow evaporation and
can actually soak up and store water within the fleshy plant body itself. The hairs or
spines on many desert plants aid in shading the plant, which slows evaporation and protects the
plant from animals that would eat it. Many drought tolerant plants look silvery. They are
actually green but the hairs covering the plants give them that silvery/bluish color.
Another way drought tolerant plants adapt is by having very small to no leaves at all. To
compensate for the inadequacy of the leaf in producing chlorophyll, most of these plant
themselves are green...the entire plant can produce chlorophyll. In cacti the leaves have been
modified into spines. In plants such as the Scotch broom, the minute leaves are only
present when there is sufficient rainfall, but drop off as soon as the dry, hot season hits. This
is an effort to conserve moisture.
All plants require carbon dioxide to live. Some plants, like catcti, take in carbon dioxide at night, when
temperatures are lower and the humidity higher...a clever adaptation to beating the heat and reducing the loss
of water when the surface pores are open.
Some plants, like the lilac bush, actually secrete a chemical substance that prevents seedlings
of other competitiors, including other lilac bushes, from taking hold too close. This
enables the established plant to utilize all the water within its "zone".
Many of the different varieties of drought tolerant plant life actually have a growth
structure that assists the plant in shading itself. Root systems are either vast and
shallow or incredibly deep (mesquite roots have been found as deep as 175 feet).
Most desert plants flower during the rainy season. Some flower only at night to entice their particular, nocturnal pollinator.
Some bloom only once after many years, (sometimes as many as a hundred), and then die.
Some plants propagate by breaking off from the parent plant, ride around on an animal host
before dropping to the ground where, if conditions are right, it will grow roots. In areas
that experience extreme cold or short summers, again, plants either endure the local climate
or escape from it as the annuals do through their seeds. Perennials that must endure
tend to have a more compact structure. Keeping a low profile helps keep the plant out of
bitter, cutting winds and closer to the warmer surface of the ground.
Shelters used by plants for survival are southern slopes which are warm, sunny and drier:
nooks and crannies among boulders which also radiate more heat from the warming effect of the
sun and within established "forests" where a more vulnerable plant can shelter near a hardier
neighbor. The fuzziness of some plants, that helps with lowering evaporation in the heat, also
helps trap warmer air close to the plant during very cold weather and direct moisture from the
leaf surface to the ground beneath the plant.
Sagebrush and salt brush are just a couple of species that can survive in soils with a higher
salt content. In the Billings area, the soil is moslty heavy clay with pockets of highly
alkaline soil.
Lichens are a symbiotic relationship between two (or three) living organisms. Fungus (which is
believed to provide the water and shade), algae (a primitive aquatic plant which photosynthesizes
and furnishes the food), and occasionally bacteria. Together these plants are able to break down
materials, such as rock, and create soils. They are usually slow growers and the colors vary greatly
due to the type of algae and/or bacteria within the lichen. They grow upon rocks, loose upon the
ground, on trees, houses...they are very adaptable and can thrive in areas of extreme cold and drought.
Reproduction varies: in many cases small bits break off and grow into new lichens. Sometimes
the fungus produces spores that are released along with a few algae cells, or wind-blown spores from
the fungus may encounter free-living algae and develop with them into lichen. Some animals, like the
caribou and reindeer, live off these tiny plants. Humans have used lichens as food, medicine
and sources of dye for hundreds of years.
Mulching is a good way to retain moisture and adds nutrients to the soil. ZooMontana uses
ground up Christmas trees for mulch.
Dottie's Garden has drought tolerant plants from all around the world. We must be careful of
introducing new species into our environment. All our noxious weeds are non-native plants that
were introduced and allowed to naturalize. Check with the County if you are unsure about
a plant before you purchase it and place it in your garden.
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