Transcript elements of climate

OBJECTIVES
The student will be able to…
• Relate the major
characteristics
of the seasons
in terms of plant
growth.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
OBJECTIVES
The student will be able to…
• Explain the effects of frost, snow, sleet, hail, and
frozen soil on plant growth.
• Identify microclimates in his/her immediate area.
• Locate area on the USDA Plant Hardiness Zone
Map and the AHS Heat-Zone Map.
• Recognize outside areas with full sun, partial
sun, and full shade.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
• All parts of the U.S. (except Hawaii & Puerto Rico)
& Canada are considered in the “temperate zone”.
– With normal seasons: spring, summer, fall, and winter.
• Seasons can be classified as “wet” & “dry” in some areas.
• Some U.S. areas are “tropical” or “subtropical”.
– They do not experience frosts and freezes.
• Mainland tropical zones in California & Florida may
have variations of 20 - 30 deg. F in daytime highs
and nighttime lows throughout the year.
– The true tropics lie between the tropics of Cancer and
Capricorn, 23 deg. north & south of the equator.
• With negligible temperature variation through the year.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
• California has a “Mediterranean
climate”:
– A wet winter season.
– Short spring, starting in February.
• Rain slowly tapers off.
– Long summer/fall, until October.
• Little or no rain falls for months.
True also of the desert Southwest.
Winter rains are followed by a short,
spectacular flowering spring, then
a long, hot, completely dry summer.
Figure 4-1 Desertification, enlargement of deserts due to
climate change, will affect ability of existing plants to survive.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
• The growth patterns of plants vary widely from
season to season depending on the plant type.
– Some are spring bloomers, others don’t flower until fall.
– Some begin to grow as soon as snow has left the ground.
• Such as asparagus.
– Others produce no growth until all chance of frost is past.
• Such as lilies.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
Spring
• For the majority of plants in temperate zones, spring
is when the majority of yearly growth takes place.
• This yearly growth flush includes:
–
–
–
–
Leafing out of trees.
Emerging and blooming of bulbs.
Blooming and fruit setting in fruit trees.
New shoot growth in shrubs and trees.
• Some plants, such as grapes, make all new growth
for the year during this 1- or 2-month period.
– Others, such as lawn grasses, continue to produce
new growth as long as the weather is favorable.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
Summer
• Summer is a period of maturing in plants.
– Some plants have their flowering period.
• Tomatoes and corn.
– Others, which flowered in the spring enlarge/ripen fruits.
• Such as fruit trees.
– New, tender spring leaves toughen to a leathery texture.
• Many plants accumulate energy in the summer to
enable them to live through the long winter.
– During which it will have no leaves and be completely
dependent on the food stored in its roots and branches.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
Fall
• Fall is a transitional season for plants that live yearto-year & the end of life for those living one season.
• Those surviving the winter engage mechanisms to
will ensure their winter survival:
– Dropping leaves & stopping new growth.
• A nearly static state to await favorable growing conditions.
• Plants that live one year must have produced seeds
capable of sprouting in the next growing season.
– And must have dispersed those seeds throughout
the area by their own unique evolutionary means.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
CLIMATE AND SEASONS
Winter
• For most plants, winter is a time of waiting.
– When temperatures are below freezing, water is solid
and cannot travel readily throughout the roots and stems.
• Lack of water & leaves drastically slows biochemical
processes in the plant, putting most in a state of
suspended animation.
– Until the return of favorable growing conditions.
• Except evergreen plants such as pines, spruces, firs, junipers.
• It is advisable to water evergreens during during
periods of thaw when soil is able to take in moisture.
– This can help avoid unsightly winter burn.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
• The elements combining to make up a climate
include primarily:
– Temperature; Precipitation; Humidity; Light; Wind.
• Each has a wide range of variation and a dramatic effect on
plant growth.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Temperature
• Temperature, largely determines the geographic
range over which a plant will grow.
– Particularly minimum winter temperature.
• The lowest temperature that a plant can withstand
is called its cold hardiness or cold tolerance.
• For many plants about 28 deg. F is the minimum
because at this temperature the liquid contents of
the plant cells freeze and the plant dies.
– These plants are designated as frost-tender.
• Includes many vegetables and flowers.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Temperature
• Plants that are able to survive temperatures lower
than freezing are called frost-hardy.
– They vary widely in tolerance to subfreezing temperatures.
• In some cases the woody portions or root system
may be frost-hardy but not the flowers and leaves.
• Some garden flowers die to the ground in fall but
grow back from the roots the following spring.
• Some houseplants and many tropical plants suffer
chilling injury at temperatures less than 50 deg F.
– This is why bananas turn black in the refrigerator.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Temperature
• Minimum winter temperature limits areas where
many plants can live.
– For some plants lack of cold prevents survival.
• Fruit trees such as apple & cherry; Flowers like peony & tulip.
• For temperate-zone fruits, an adequate number of
cold days per winter, the chilling requirement, is
essential for normal growth and fruit production.
– Such as apples and cherries.
• Each type of & variety of fruit has its own specific requirement.
• Each crop also needs a certain number of
adequately warm days in order to mature.
– The growing degree-day requirement.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Temperature
• A baseline temperature below which very little
growth occurs is established for each crop.
– Subtracted from the average temperature for a given day.
• These daily measurements can then be added and
compared to an established standard for that crop
to determine when the crop will mature.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Frost
• Understanding frost types & weather conditions
that favor each is important because of damage
done to frost-tender plants.
– A frost can be one of two types: Radiation and hoar frosts.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Frost
• Radiation frost - occurs when the air is cool and
calm and skies are clear.
– Warmth from the sun accumulated by soil and plants
in the day is lost at night as heat radiating upward.
• If the day was warm and the night only slightly below
freezing, heat in soil & plants may last all night and
offer frost protection.
– If not, frost damage will result.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Frost
• When plants are covered by a barrier blocking flow
of heat to the sky, frost can often be prevented.
– Clouds form this barrier, and radiation frosts seldom
occur on cloudy nights.
– On clear, protection by layers of newspaper, cloth,
smoke, or plastic film can serve the same function.
• Sprinkler irrigation of plants is also used to prevent frost.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Frost
• The second type of frost is caused by a cold air
mass moving into an area.
– Carrying off heat from the plants, which are then frosted.
• Frost often leaves ice crystals on plants and the
ground in the early morning, are called hoar frosts.
– Called black frosts, because the first sign of their
occurrence is the blackening of injured plants.
• Appearance of frost in some areas, but not in others
close by is due usually to elevation differences.
– Cold air is heavier than warm air & flows down to
the lowest area.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Frost
• The northern parts of the U.S & almost all of Canada
experience freezing of the ground during the winter.
• In unseasonably cold years many plants may
“freeze out” as a result of the temperature around
the root zone being too cold for the plant to survive.
• Freezing of the soil causes water contained in it to
expand, and may cause frost heaving.
– Soil pushes up around the roots of plants leaving cracks
over the root area, exposing them to drying winter winds.
• Gardeners frequently lay a thick layer mulch over root
areas of plants they know to be borderline cold-hardy.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Precipitation
• Precipitation can take many forms including rain,
snow, hail, and sleet.
– Rain is of greatest value to outdoor plants.
• Lack of rainfall is a limiting factor to plant growth.
– Particularly in the western U.S., where irrigation is
essential to grow plants.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Precipitation
• Excessive rain or rain occurring out of season can
be as detrimental to plants as lack of rainfall.
– Excessive rain can kill plants adapted to dry areas.
• Unseasonable rain near harvest can make strawberries
watery-tasting, and split unpicked apples & grapes.
• Frequent rains spread plant diseases by splashing
microorganisms from one leaf to the next.
– Triggering the growth of dormant disease organisms
present on plants.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Precipitation
• Snow cover plays an important role in plant survival
in areas with cold winters.
– Protects low-growing plants low-temperature damage
due to the chill factor or drying injury due to sublimation
of the frozen water from the plants.
• In sublimation, frozen water turns directly into its
gaseous state without ever melting.
– The process used in the food preservation technique
known as “freeze drying”.
• Requires energy in the form of heat, taken from the plant.
– Damage is caused by the water lost from internal
parts of the plant, as well as from the surface.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Precipitation
• Sleet, hail, and freezing
rain can be very injurious
to plant health.
– Sleet & hail tear leaves &
bruise or knock off fruits.
– Freezing rain often causes
branch breakage on trees.
– Heavy snowfall can cause
breakage due to its weight.
Figure 4-2 A rosebush shows effects of a heavy snow
load & freezing rain. Courtesy Susan Brandt Graham.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Precipitation
• Dew is most likely to occur when the air is warm
and humid.
– After sunset, air temperature drops, and the atmosphere
is unable to contain the water it held during the daytime.
• Water precipitates out, in the small droplets called dew.
• Although its effect on most plants is not great, it can
be a factor in the spread of diseases in turfgrass.
– It is also an important water source for plants that absorb
water readily through their leaves.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Humidity
• Humidity may determine how well a plant will grow.
– Defined as the amount of water the air contains relative
to the amount it is capable of holding.
• At that specific temperature.
• Often higher humidity improves plant growth by
reducing the rate at which plants lose water.
– Low humidity will not seriously hinder growth of most
outdoor plants if there is adequate water around the roots.
• Indoors plant in cold-winter climates are commonly damaged
by insufficient humidity.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Humidity
• Fog and mist, can influence
plant growth greatly.
In coastal California climates,
the moisture from fog and
mist is absorbed by plants,
supplementing meager rain.
At the same time this vapor
retards loss of water from
leaves.
Figure 4-3 Fog in a redwood forest of coastal California.
The moisture-laden air is the only source of water during
the dry summer months. Photo by Rick Smith.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Light
• Light duration, intensity, and quality affect growth
of outdoor and indoor plants.
– May control flowering and growth rate.
• Light duration in any particular region depends on
distance from the equator and season.
– At the equator, day & night are equal length all year.
• North or south of the equator, days become longer
in the summer and shorter in winter.
– The further from the equator, the greater the difference
between the longest summer day and shortest
winter day.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Light
• The duration of daily light a plant receives is
important, as it determines the period of time it can
manufacture the carbohydrate necessary for growth.
– Duration of the night also affects the start of some plant
processes, such as flowering.
• Light intensity or brightness affects photosynthesis
because, in general, the brighter the light intensity,
the more photosynthesis occurs.
– Moderate to bright intensities are most beneficial.
• Latitude will alter intensity.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Light
• At the equator the sun passes overhead all year.
– In the northern U.S. it is nearly overhead in summer.
• Low in the southern sky in winter.
• Winter intensity is lower because of the distance
through the atmosphere the rays must travel.
– Lesser amounts of light signals plants to become dormant.
– For evergreens, lower light intensity of winter is sufficient
to continue photosynthesis and sometimes growth.
• Indoor plants can be seriously retarded by the
decrease in light, as many are already growing
at subsistence light levels.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Light
• When buying plants for the garden, it is essential to
know light preferences of plants being purchased.
– One must know the approximate amount of light the area
receives in order to choose a plant that will grow healthily.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Light
• Areas around the home can be classified as:
– Full shade - areas in which the sun rarely shines directly.
• Northern sides of houses, narrow areas between houses.
• Under large trees & other areas shaded almost all day.
– Partial-shade - areas which receive direct sunlight for
about one-third to one-half of the day.
• East- and west-facing walls of houses
• Under small/finely foliaged trees that admit “filtered sun”.
– Full sun - found on the south sides of houses.
• Or where there are no trees, shrubs, or structures to block light.
• Full sun can also be on the west side of houses in the western
U.S., as the afternoon sun in these areas can be very strong.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ELEMENTS OF CLIMATE
Wind
• Wind is the fifth climatic element governing growth.
– Ocean wind limits the number of plants that can be grown
near the shoreline.
• By salt spray, which browns plant leaves.
• By the intensity, which whips and breaks leaves and branches.
– Hot desert winds increase the rate of moisture loss from
soil & plant leaves, intensifying drought conditions.
– Subzero winds in cold northern areas damage evergreens
by removing moisture from foliage, freeze-drying it.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FACTORS MODIFYING CLIMATE
• Natural factors modifying climate include distance
from the equator, elevation, terrain, and the nearby
presence of large bodies of water.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FACTORS MODIFYING CLIMATE
Elevation
• Changes in elevation can give areas only a small
distance apart completely different climates for
plant growth.
– The higher the elevation of an area, the colder the
average year-round temperature
• Every rise of 300 feet (91. 4 meters) causes an average
temperature decrease of 1 deg. F.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FACTORS MODIFYING CLIMATE
Terrain (Topography)
• Changes in terrain alter climate, particularly rainfall.
– Most rainstorms move from west to east in North America.
– In a narrow range of hills, west-facing slopes often receive
much more rainfall than east-facing slopes.
• Heaviness of the water in rain clouds prevents them from
passing over mountains until most of the precipitation has
been released.
– The drier region on the eastern slopes often is referred
to as a rain shadow.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FACTORS MODIFYING CLIMATE
Terrain (Topography)
• Sloping terrains can vary in temperature by several
degrees from the top of the slope to the valley.
Cool air, heavier than
warm air, will flow down
a slope and collect at the
bottom, a phenomenon
called air drainage.
Plants growing higher on
the slope are less likely to
be damaged by cold than
those at the bottom.
Figure 4-4 Typical cold-air drainage on sloping land.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FACTORS MODIFYING CLIMATE
Bodies of Water
• Large bodies of water like the Great Lakes & oceans
exert strong effects on the climate of nearby land.
– The enormous volume of water absorbs heat in summer,
making adjacent land cooler, and gives it off in the winter,
raising the temperature.
• On the North American continent, the influence of
large bodies of water on agriculture is considerable.
– Warmer winter temperatures along the Great Lakes make
these regions large commercial growing areas for fruits
such as grapes, cherries, and peaches.
– Most of the Pacific coast is warm enough to grow certain
vegetables all winter, but inland these crops would freeze.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
FACTORS MODIFYING CLIMATE
Climate Modification by Humans
• People can modify climate either intentionally or
unintentionally.
– Among the most widespread unintentional causes of
climate change are air pollution and consequent smog.
• Smog affects plant growth by temperature modification,
acting like an insulation layer, preventing heat from escaping.
• Particulates settle onto leaves & decrease light reaching plants.
– Smog affects plant growth is through foliage injury by toxic
gases entering leaves, causing them to partially brown and
sometimes to die.
• Plants classified as intolerant (many pines, for example)
cannot be grown in smoggy areas.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
• Microclimates are small areas with slightly different
climate characteristics than the surrounding land.
– May be less windy, shadier, moister, warmer, or in any
other way different from the typical climate.
• These differences affect plants, sometimes helping and
sometimes hindering growth.
• Microclimates may be either artificial or natural.
– They can be formed by the natural terrain & vegetation.
• Or unintentionally created by structures, fences, roadways.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
• Although they often go unnoticed, they can be used
by the observant gardener to provide the specialized
growing conditions favored by different plants
In some cases they make
it possible to grow plants
not normally considered
cold-hardy in that area.
Figure 4-5 A microclimate for a fern would
be under trees or against a north wall.
Courtesy of B. J. Fundaro, Sonoma State
University, Rohnent Park, Calif.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Outdoor Microclimates
• A natural microclimate example is a frost pocket.
– Colder, possibly moister due to water runoff.
• Suitable for moisture-loving plants not easily damaged by cold.
• Another natural microclimate is found under trees.
– Shadier/cooler in summer, good for shade-loving plants.
• Or growing indoor foliage plants outdoors in summer.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Outdoor Microclimates
• Plants in the microclimate under the eaves of a
house live under different environmental conditions
than plants living away from the house.
– Shielded from rainfall by an eave, so the soil will be drier.
– The wall may afford protection from cold or drying winds
– Radiates warmth from the heated dwelling.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Outdoor Microclimates
• During cool periods, additional warmth speeds up
or prolongs growth, but if a wall faces south it may
be excessively hot in summer & damage can occur.
Frequently the case with
parking lot trees, which
become overheated due
to heat radiating from the
asphalt.
Figure 4-6 Scorch on maple due to
excess heat.
Courtesy Dr. R. E. Partyka, Columbus, Oh.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Outdoor Microclimates
• At night when temperatures drop, objects begin
losing heat to the cooler night air.
– Heat radiating from the ground and buildings can
protect plants from frost & extend the growing season.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Outdoor Microclimates
• Wind can be intensified or lessened in a
microclimate.
– A plant by a wall will generally receive wind protection
unless it is directly in the path of prevailing winds.
• When two walls are parallel, a wind tunnel can be
formed, and wind conditions will be worse there
than in a completely unprotected area.
– Frequently formed between closely spaced buildings.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Indoor Microclimates
• Indoor microclimates with varying temperature,
light, and humidity are found in houses/apartments.
– Upstairs rooms may be warmer than downstairs ones.
– A basement may be up to 20 deg F cooler
– The north side of the house may be cooler than the south.
• Even within a single room, cool microclimates will
be found adjacent to windows in cold-winter areas.
– Because of cold entering through the glass.
• Microclimates of varying humidity are also common.
– In the kitchen and bath, evaporation raises the humidity.
• A basement is also usually humid.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
MICROCLIMATES
Indoor Microclimates
• Light microclimates are easy to detect, being
governed by the size and location of windows.
– The farther from a window a plant is, the less light it will
receive, and each foot/meter of distance can be thought
of as a different microclimate.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ADAPTIVE STRATEGIES OF PLANTS
FOR CLIMATE TOLERANCE
• Plants have evolved adaptive strategies to cope
with adverse environmental conditions.
– The most common adaptation is winter dormancy.
• Plants in desert areas develop the ability to store
water in their leaves, making leaves fleshy & thick.
– Cacti take this to an extreme in that they have no leaves.
• Only a thickened stem that forms the bulbous body of the plant.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ADAPTIVE STRATEGIES OF PLANTS
FOR CLIMATE TOLERANCE
• Desert plants (xerophytes)
can protect themselves
from excessive sun.
– A most interesting example is
the “baby toes” plant.
• Native to the Cape Province
of South Africa.
This small cone-shaped plant
lives almost entirely underground
with only a transparent “window”
at the soil level through which
light penetrates to the interior
cells, for photosynthesis.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
Figure 4-7 Baby toes (Fenestraria sp.), a
South African plant adapted to a very arid
climate. Paloma Colomer Arroyo, Jaen, Spain.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ADAPTIVE STRATEGIES OF PLANTS
FOR CLIMATE TOLERANCE
• Water loss from leaves in less severely dry climates
can be reduced in two ways…
By a wax layer the
plant excretes to
cover its leaves.
Or a thick covering
of silvery hair that
reflects sunlight
and also insulates
the leaf from air.
Figure 4-8 A closeup of the thick hair covering lamb’s ears, a garden plant originally native to Northern
Turkey and Southern Iran where it grows on rocky hills. Courtesy of Mary Hanks.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
ADAPTIVE STRATEGIES OF PLANTS
FOR CLIMATE TOLERANCE
• At high elevations both cold temperature and
drying winds become factors in plant survival.
– The term tree line refers to the elevation at which
trees can no longer grow due to climate extremes.
• In growing conditions without much sun, leaves
of plants are very large to expose the maximum
amount of leaf area to the available sunlight.
– Forest floor vegetation in tropical forests and
the source of many of our best indoor plants
for growing in limited light.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
• The question of where in the country a specific plant
can be grown is important to every gardener.
– There is little to worry in plants bought at local nurseries.
• Nursery owners seldom sell plants that don’t grow in their area.
– When consumers mail-order plants, they must ensure
plants they have selected will grow in their area.
• This valuable information is usually given in the
written descriptions of the plant, found in gardening
books from a library, or on the Internet.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
USDA Plant Hardiness Zones
• The USDA has prepared maps showing zones of
minimum winter temperatures in the U.S. & Canada.
– After determining minimal plant survival temperature, one
must determine minimum winter temperature of the area.
• Eleven zones are outlined, ranging from completely
frost-free areas in Florida, Texas, and California.
– To a -50 deg F. or colder zone in Canada.
• The map takes into account cold mountain climates
in warmer zones, as shown in Colorado.
– For the most part, it is made of bands that correlate
minimum winter temperature & distance from the equator.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
USDA Plant Hardiness Zones
• The USDA zone map is not the only plant hardiness
map that exists, but it is the most widely used.
– Some states with climates influenced by many factors
have designed more detailed maps.
• The University of California at Davis lists twenty-one
separate climate zones, due to the influences of the
Pacific Ocean and mountain ranges.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
American Horticultural Society Heat-Zone Map
• The USDA Plant Hardiness Zone Map addresses
plant hardiness in excessively hot temperatures.
– Instead of excessively cold temperatures.
• Knowledge of heat zones may be more important
in the future, especially during drought periods.
– Heat damage is less apparent than damage from cold.
• Death of the plant due to heat generally is gradual.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
American Horticultural Society Heat-Zone Map
• In addition to scorch, heat symptoms such as failure
of flower buds to open, bleaching of leaves to a
paler color, failure to grow at a normal rate, or
failure to produce fruit may all occur.
– Leaves may droop even though the plant is receiving
regular watering.
• Plants may also become more attractive to insects.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
American Horticultural Society Heat-Zone Map
• The American Horticulture Society Heat-Zone Map
divides the U.S. into twelve heat zones.
– By the average number of days per year that the areas
experience temperatures over 86 deg F.
• The range is from 0 to 210 heat days per year.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
American Horticultural Society Heat-Zone Map
• Heat tolerance rating of a plant in will soon be listed
next to its USDA cold-hardiness number on care
tags, in gardening references and in catalogs.
• A plant will have two ranges.
– For example: Lily 3–8, 8–1.
• The first range (3–8) will designate the USDA
low-temperature hardiness by zone.
– According to the lowest average temperature in winter.
• The second (8–1) will designate heat tolerance.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
American Horticultural Society Heat-Zone Map
• If you live in USDA zone 7 & AHS heat zone 7, you
know a lily will survive both the winter temperatures
& hot summer temperatures of your area.
• Not all plants have been coded by AHS heat zone.
– Even when so coded, some plants may survive out of,
or fail to thrive within, the zone area specified due to
unseasonably warm or cool years.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
PLANT GROWING ZONES IN NORTH AMERICA
American Horticultural Society Heat-Zone Map
• Stresses that will independently & together alter the
ability of a plant to grow within a specific heat zone:
– Light deprivation and microclimates.
– Soil characteristics & plant nutritional status
• In all cases, the classification assumes that the plant
is receiving adequate watering.
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458
END OF
CHAPTER
Practical Horticulture 7th edition
By Laura Williams Rice and Robert P. Rice, Jr.
© 2011, 2006, 2003, 2000, 1997 Pearson Education, Inc.
Pearson Prentice Hall - Upper Saddle River, NJ 07458