“C” horizon
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- this is a soil transition layer below the subsoil but
above the rock that is the parent material. This zone
consists of rock in various forms of transition to soil due to leaching,
freezing and thawing
and other geological actions.
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calcareous |
- refers to a soil rich in calcium carbonate (lime)
which will tend to have
an alkaline
pH. |
callus |
- a type of plant tissue that grows over an open wound or
graft
union on woody plants which protects it against drying
out or other injury. |
calyx |
- the outermost whorl of organs of a flower, the outer set of perianth segments or floral envelope
of a flower, usually green in color and smaller than the
inner set.
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cambium |
- one of the "living" layers of plants capable of
producing new cells (i.e. meristematic tissue) and
thus, growth. On dicotyledon trees, it is the layer just beneath the
bark which produces new xylem and
phloem cells resulting
in the annual rings.
If the cambium layer is damaged or
killed and can no longer produce new cells, that part of
the plant above the damage will die. If it is interrupted around the
entire circumference of a tree, it is called
girdling and
results in the death of the tree.
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campanulate |
- usually refers to bell shaped flowers such as those
produced by members of the genus,
Campanula. |
cane |
- term used to describe woody stems of many plants
including
roses,
grapes and
brambles. The multiple
shoots produced by certain ornamental shrubs such as
forsythia or
lilacs may also be called canes. |
canker |
- generally a fungal or
bacterial disease that causes
the death of the bark, cambium and sapwood on a tree or
shrub. It results in a sunken, open wound in the bark.
Cankers are common on certain
species such as silver
maples. They are also caused by damage to bark caused by
lawn mowers or weed whips. More on
Cankers |
capillary mat |
- type of bottom watering system sometimes used beneath flats and
pots in greenhouses. It often consists of a fiber
mat which will distribute water to the bottoms of pots.
The water will then work its way up through the drain
hole and into the pot by capillary action. |
capillary water |
- openings in the soil or growing medium are called
capillaries. Water moves through these spaces by the
forces of adhesion and
cohesion. This water is generally available for use by
plant roots. |
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capsule |
- a dry, dehiscent fruit
on certain plants which develops from two
or more carpels. |
carbohydrate |
- perhaps the key output of the process of
photosynthesis are chemical compounds called
carbohydrates. In the chlorophyll, the plant captures
the energy of the sun and combines molecules of
carbon,
hydrogen and
oxygen to produce carbohydrates which are
later converted to sugars and starches. These compounds
are then used for the growth and metabolism of the
plant. |
carotene |
- an orange colored pigment that gives color to
many plant organs such as carrots, oranges and flowers |
carpel |
- the bearing structure of a flower; each carpel
encloses one or more ovules.
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carpet bedding (carpet bed) |
-
plants that, due to their evenness of growth, symmetry,
and/or lateral spreading qualities, produce a
flat-topped or carpet appearance when displayed in a
bed
or border. They usually require close
planting. See Bedding
Plants |
cation |
-
a positively charged atom (+). From a gardening
standpoint, it comes into play when talking about the
ability of a soil to hold onto
nutrients and then make
them available to the plant roots. This is expressed by
a term of Cation
Exchange Capacity which is reported on every
soil test. |
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cation exchange capacity (CEC) |
-
measure of a soil’s ability to retain nutrients and
represents the sum
total of exchangeable cations that a soil can absorb. Clay
soils and organic matter have a high CEC and, therefore,
hold onto nutrient such as phosphorus and
potassium
tightly. Sand has a low CEC and
nutrients tend to wash
or leach through them quickly making them unavailable to
plants.
More on
Cation Exchange Capacity |
catkin |
-
a spike like inflorescence of either male or female
flowers without petals found only in woody plants such as
willow or
birch. |
cellulose |
- a carbohydrate that makes up the primary substance of
solid plant cell walls |
cell-packs |
- a plastic container of transplants in which
each seedling has its own root area. Annuals are
commonly sold in cell packs that fit into larger flats.
See Bedding Plants |
centered-out |
- occasionally, when
hostas, ornamental grasses and some
other perennials get "old", the center of the clump
i.e. the oldest part of the plant, will die out.
Often, these plants may be
rejuvenated by
dividing the clump
into smaller pieces. Cutting into the
crowns will
also stimulate new, vigorous growth. |
certified plants |
- nursery stock that is produced according to requirements of
a program having the objective of producing
pathogen-free plants. |
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chelate |
- chemical compounds that are formulated to not react
with the soil or potting media. Iron chelates are
commonly used to supplement plants. They can be mixed
with water and sprayed onto the leaves thus avoiding the
possibility that the iron would be tied strongly to the soil
particles and made not available to the plant. |
chilling requirement |
- many plants require exposure to cold temperatures
during their yearly cycle before they will produce flowers and
fruit. Normally, there is a specific low temperature
requirement and a specific time period of exposure
needed. For example, tulips need around 13 weeks of
exposure to temperatures below 40 degrees F in order to
produce flowers.
Other examples of plants with a chilling requirement are
daffodils,
apples,
cherries,
lilacs, and
peonies. |
chimera |
- cells of more than one genotype (genetic makeup)
sometimes occur adjacent to each other in plant tissue.
The most common chimeras exhibit themselves as
variegation in certain plants. The cells in a variegated
leaf all originated in the same apical
meristem of
the shoot, but some cells lack the ability to synthesize
chlorophyll. These cells appear white rather than green even
though they are components of the same tissue system. |
chimeril
rearrangement |
- at times, the pigments of plant tissues may change
causing a change in color. An example would be a gold margined
hosta producing a gold centered
or all gold division.
When the color changes from a variegated pattern back
to the original base leaf color, it is referred to as a
"reversion". |
cholinesterase |
- this enzyme is produced by
animals to ensure proper
nerve function. Organophosphate or carbamate
insecticides
inhibit or damage the production of the enzyme. A
person's level of exposure to these poisonous chemicals
can be determined by measuring the cholinesterase in
his or her blood. |
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chlorophyll |
- this molecule absorbs sunlight and uses the radiant energy to synthesize
carbohydrates from carbon dioxide,
nutrients and water. This process is
known as photosynthesis and is the basis for sustaining the life
processes of all plants...and by extension all life on earth. It
reflects the green light spectrum resulting in the typical color
of most plants. |
chloroplast |
- disk-like structure containing
chlorophyll inside a plant
cell. |
chlorosis |
- (adj. chlorotic) the loss of
chlorophyll which causes plant tissue to
appear yellow when it
should be green. These tissues are said to be chlorotic.
See necrosis |
chronic toxicity |
-
often used in relation to the impact of
pesticides on
animals (including humans) where the exposure to small
amounts over a long period of time causes a problem
later in life.
See
acute toxicity. |
clay |
- the smallest of the three soil components (sand,
silt &
clay) with generally tiny (0.0002 to 0.002 millimeters),
flat, plate-like particles. Soils high in clay have
small pore spaces and, thus, suffer from low levels of
oxygen
and poor drainage. These conditions are generally
detrimental to most plant life. Clay soils also tend to have a high
CEC which allows
them to
hold onto
nutrients tightly...sometimes too tightly. |
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cleistogamous |
-
production of seeds by self-pollination in the unopened
flower. Tomatoes fall into this category. |
clone |
- a group of genetically identical
individual plants produced by
asexual propagation such as
division, cuttings, grafting or
tissue culture.
In Hosta, the
most common techniques for producing hosta clones are division and
tissue culture. |
colchicine |
- this is a chemical that is extracted from the bulb
plant,
Colchicum. It is a medicine for certain human
ailments and is also used by plant
hybridizers. Flowers
treated with colchicine during pollination may produce
double the numbers of chromosomes (tetraploids) in the resulting
seedlings. This technique is often used by
daylily
plant breeders. |
cold frames |
- garden structures with glass or plastic tops similar to hotbeds but usually
without a source of supplemental heat. They are used to
provide frost protection for tender plants. |
cole crops |
- plants of the genus
Brassica, includes
broccoli, Brussels sprouts, cabbage, cauliflower and
kohlrabi. |
columnar |
- the height of the plant is several times greater than
its width and the plant’s width is fairly uniform. Most
branches have a vertical orientation. |
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common name |
- the non-Latin or non-scientific name or names by which plants,
animals, and
insects are known, for example,
pine,
oak,
marigolds, horse, ladybug, etc.. Often more than one common name
is used around the country and the world for the same
plant or animal which may be confusing. See
binomial nomenclature. |
compaction |
- this
term as it relates to horticulture is generally applied
to the soil in the root zone of the plants.
Clay soils
already have very few pore spaces but under the pressure
of foot traffic or equipment movement will "compact"
further. Such soils lack the air and water spaces
necessary for plant root growth. |
complete fertilizer |
-
a fertilizer containing all three of the
major plant
nutrients:
nitrogen (N),
phosphorus (F), and
potassium (K). |
Composite Family (Compositae) |
-
Those plants whose
compound flowers are daisy or aster-like. Each “petal” of a daisy
is actually an entire tiny flower, called a
ray flower.
Tiny flowers cluster to form the compact center of
the bloom and are called disc flowers. Examples of
composites are
chamomile,
dahlias,
marguerites,
marigolds, and
sunflowers.
Chamomile is a composite that
often produces only disc flowers in a button-like head.
Note: This plant family has changed name to
Asteraceae. |
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compost |
- everything that is alive will one day die and
decompose back into the basic elements of life.
Composting in the backyard consists of accumulating a
pile of dead plants and plant parts and allowing them to
decompose. When you cannot tell what it was before, it
is compost.
Compost is not a fertilizer. It is generally low in
nutrients needed by plants. However, it is a wonderful
soil amendment which helps clay soils have better
drainage and sandy soils to hold water and nutrients
better. It also encourages earthworms and other
micro-organisms that contribute to the "health" of the
soil. It is GREAT STUFF as a soil conditioner! More on
Composting. |
compound leaf |
- a minority of plant species have compound leaves which
consist of a petiole and two or more leaflets. Examples
would include
roses,
walnut,
ash, and
honeylocust.
There are several types of compound leaves including:
- ternately compound - leaflets are in 3's
- palmately compound - 3 or more leaflets that
arise from a common point and resemble the palm of
your had with the leaflets spreading out like
fingers.
- pinnately compound - 3 or more leaflets along a
common stem (rachis), or if only 3 are present, the
terminal leaflet has a petiole
- odd pinnate compound - the terminal leaflet is
present and the total number of leaflets is odd
- even pinnate compound - no terminal leaflet is
present and the total number of leaflets is even
See simple leaf. |
concentric |
- pertaining to circles with a common center but
different diameters. In
horticulture, this is often used
to describe the symptom of a disease such as
bacterial
canker. |
conifer |
- plants such as
juniper,
cypress,
fir, and
pine
that are sometimes called evergreens. Some
species are not
evergreen, but all produce seeds in a cone-like
structure.
Four types of conifers are deciduous and drop their
needles each fall including Bald Cypress (Taxodium),
Dawn Redwood (Metasequoia),
Larch (Larix) and
Golden Larch (Pseudolarix). |
contact pesticide |
- this is a chemical that kills its intended target upon
contact with the skin or epidermis. It does not have to
be ingested or breathed in to be effective. These are
the opposite of systemic
pesticides. |
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container-grown |
- herbaceous
plant material grown from seedling to
the point of sale in a container. Trees and shrubs are
generally consider container stock if they have been
grown in the container for at least one year (and not
necessarily from seed). More on
Types of
Nursery Stock |
controlled-release fertilizer |
- also called slow
release fertilizer. These products are formulated with
some sort of hard covering to the individual granules
which controls the rate of release of the
nutrients
inside. The cover may need to be broken down by
microorganisms or by repeated exposures to water over
time. |
cordate |
-
heart shaped,
generally referring to leaf bases or
blades. |
cordon |
- used to describe a type of
espalier where trees are trained along a horizontal
wire capable of bearing arms, spurs and canes. |
core aerification |
- a procedure using a power machine which inserts tubes
into the soil under pressure and removes a plug of soil
which is the deposited on the ground surface. Aerification helps to
loosen compacted soils in lawns and is also used to help
decompose thatch layers. To be effective, there should
be a hole punched every 3 inches in all directions to a
depth of 2 inches or more. |
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corm |
- underground storage organ similar to a
bulb but
consisting of a swollen stem tissue. Examples include
gladiolus and
windflowers (Anemone blanda). |
cormel |
- corms multiply by developing new, little corms on
buds around
their circumference. |
corolla |
- this is the collective term
for the set of petals and
sepals that are sometimes fused together into
tepals in plants such as
hostas. When the parts are separate and distinct, the parts
are called petals and the corolla is called polypatalous.
When the parts are united either as a whole or in
parts, the parts are teeth, lobes or divisions and the
corolla is called gamopetalous.
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corrugated |
See
seersuckering |
cortex |
- region of tissue between the epidermis
and the phloem inside stems and roots |
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corymb |
-
a nearly flat-topped inflorescence with
the outer flowers on the structure opening first. |
cotyledon |
- often called
a seed leaf, this organ is a food storage
structure that provides energy for germinating seeds
until they can form true leaves and begin
photosynthesis. |
crawler |
-
scale insects are generally protected beneath there
hard shells. However, once a year, they reproduce and
their young, called crawlers, move around the stems
seeking a place to begin feeding. During this 2 or 3
week period, the crawlers are susceptible to control
with insecticides or
insecticidal soap.
Each species of scale has its own timing for when
crawlers are produced. |
crenate |
- describes leaf margins with shallow,
rounded
teeth. |
critical photoperiod |
- the daily ratio of light hours versus dark hours that
are necessary to trigger certain responses in plants
such as flower
bud development or germination.
See Long-Day
Plant, Short-Day Plant
and Day Neutral Plant |
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crop rotation |
-
Plant diseases and
insects may overwinter in the
debris (leaves, mulch, etc) from the garden. If the same family of vegetables
(tomatoes, vine crops, cole crops, etc.) are grown in
the same spot every year, the
diseases and
insects of those plants will
buildup and increase. By moving the crops to different parts of the
garden each year, this problem is minimized. - in the
landscape, this concept can also apply to the continued
use of the same annual bedding plants in the same
locations year after year. |
cross-pollination |
- occurs when the pollen from one plant is used to
pollinate the
pistil of a different plant.
See
self-pollination. |
crown |
1) Trees - point where a main stem (trunk) and root join at or
just below the soil surface.
2) Trees - sometimes used to describe area of the
tree that is covered with foliage
3) Herbaceous Perennials - generally, the fleshy
structure beneath the ground which survives the winter
each year and produces buds for the following year's
growth. |
cultivar |
- a contraction for the phrase
"cultivated variety". Many people use the term "variety” interchangeably with
cultivar. Technically, a variety is a naturally occurring
variation of the species. A cultivar may arise naturally or
through cross-pollination (with or without human assistance),
mutation or
sporting of the original
plant. A cultivar is a plant that is clearly
distinguished by unique physical characteristics and
maintains these characteristics through properly applied
vegetative (asexual)
propagation
techniques. Most named cultivars do not reproduce their characteristics
reliably from seed. Cultivar names are surrounded by
single parenthesis i.e. Hosta 'Sum
and Substance'. |
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cultural control |
- used for ways of controlling or managing
disease or
insect problems through the use of cultural
techniques such as proper
watering, adequate
nutrition,
providing proper air movement, etc. These methods help
to reduce or eliminate the need for chemical
pesticides. |
cuneate |
- wedge-shaped leaves that are triangular at the base
and taper to a point. |
cupped |
- a leaf blade having the
center of the leaf lower than the margin, concave and looks like
a cup. Often caused by the tissue at the edge of the leaf
growing slower than that in the center. Also called the
drawstring effect. |
cuticle |
- a thin, waxy layer formed of cutin
and wax that covers the epidermis of aboveground plant
parts including leaves, herbaceous stems and fruit. If
insecticidal soaps are improperly applied, they may melt
the cuticle and the leaf tissue will dehydrate. |
cutting |
- a
propagation technique in which a part of the shoot,
leaf or, in some species, root is removed from the plant
and placed in a rooting medium such as
perlite or
vermiculite. It will then develop
roots and become a new plant with exactly the same
genotype of the parent i.e. a clone. This technique is
based on the fact that certain plant tissues have
adventitious buds which can be induced to become roots
under the proper conditions. |
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cutting garden |
- a bed, border or part of the vegetable garden devoted
to growing plants that will be used as cut flowers. The
plants may also be grown as part of the landscape design or
in rows. More on
Cut Flowers |
cyad |
- these are plants that look like palms but are not.
They are plants with evergreen, pinnate leaves that are
found in tropical and subtropical regions. Cyads are
dioecious meaning the each plant is either male or
female. They are gymnosperms like coniferous plans such
as pines and spruce. Therefore, they bear cones with
seeds (female plants) that have no seed coats. |
cyme |
- a rounded or flat-topped
inflorescence in which the
inner or topmost flowers open first. |
cytokinin |
- a naturally occurring plant hormone that promotes cell
division, stem
elongation,
bud formation, breaking
dormancy, and other
plant processes. |
cytoplasm |
- inner substance of a cell exclusive of the nucleus. |
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