Plant Docotor Blog
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written by Joseph Cash
Annuals and Perennials
| How to remember the difference --
Annuals are like a high school annual yearbook - they are good for one season.
Perennials can be considered like an entire school career.
|| An annual is a plant that is grown for
a single season. The term includes plants that complete their life cycle,
flower, and produce seeds within a year, an example is marigold or a corn plant.
The term annual also includes tender perennials, plants that
live for years in climates where there is no frost, but die wherever freezing
occurs, an example is the geranium. These plants can sometimes be brought
indoors through the winter and replanted outdoors the next summer. Some plants
are said to be half hardy, that is they will survive very
light freezing. An example is gerbera daisy.
Annuals are often reproduced by planting their seeds. They are
also available as small plants ready for transplanting in the spring. They
can be purchased at garden centers as individual plants or inexpensively
in six packs. Many more varieties and colors are available through mail order seed companies.
|| A perennial is a plant that survives more than
two seasons. It is generally grown as a nearly permanent fixture in a garden
and typically grows as a clump that expands outward through time, bearded iris is an example. Perennials
often die back to the roots in winter. Whether a plant is a perennial in
a particular area depends on the local climate. The length and severity of
the winter is the prime factor, particularly how deep the ground freezes.
New perennials are typically made by dividing the clumps though
some grow easily from seeds. Dividing clumps creates new plants and helps
keep the old clump growing and flowering vigorously.
be obtained from garden centers and by mail order. Choose the species, variety
and color carefully since they are more expensive than annuals and are
replaced less often.
Most perennials have fairly short bloom seasons, typically two
to four weeks. It is common practice to grow annuals and perennials together
to provide color throughout the growing season. Growing a variety of perennials with different blooming seasons is another strategy to provide continuous interest in the garden.
||Biennials take two years to complete their life cycles.Typically,
they do not flower and produce seeds until the second year. They are not
as common in the garden as annuals or perennials, an example is the carrot plant which grows its root the first year and flowers and produces seeds the second.
Sun and Shade
|| A plant that is described as needing full sun
needs more than six hours of unobstructed sunlight
each day. These plants often do best on the south or west side of a house.
|| Plants that do best in half shade
benefit from some shade for half the day, typically
they do best if they receive unobstructed sun in the mornings, but have shade
during the afternoon. Often these plants would do best if planted
on the east side of a house. Another term often used is partial shade.
| Plants growing best in light shade prefer
less than three hours a day of direct sun, typically they prefer
direct sun only during the cooler parts of the day. During
the rest of the day, they would benefit from dappled shade or the kind of
open shade that one has under a large tree that has no limbs close to the
ground. Of course, different trees have varying densities of shade.
When a plant description says, "does well in shade
"it usually refers to light shade. Gardeners should be aware that shade
varies from month to month as the angle of the sun changes. Also trees
that lose their leaves may have little shade beneath them in the spring but
dense shade in July.
|| A plant needing deep shade would suffer from
any significant amount of direct sun. Often these are planted on the north
side of structures or close under trees or shrubs with very dense foliage.
Weather, Climate, and Microclimates
|| Weather is the day-to-day or even minute-by-minute atmospheric
conditions of temperature, air pressure, humidity, precipitation, wind,
cloud cover, pollution, etc.
|| Climate is the usual seasonal range of
temperatures, types and amount of precipitation, wind, cloud cover, etc.
Climate is weather over a long period of time, years or decades. Climate
changes are relatively slow.
For gardeners, climate controls what type of plants can be grown. The length of the growing season is one important factor.
The Growing Season is the time of year between the last frost in the spring and the first frost of the fall. The growing season is the period of the year when no freezing weather occurs.
While it varies from year to year, the average growing season for a particular area determines what crops a farmer can grow. For example, farmers in Wisconsin do not attempt to grow cotton since their growing season is seldom long enough for the cotton plant to mature and produce a profitable crop. Growing seasons are short in cold climates, but are year round in tropical areas where no frosts occur, such as southern Florida.
Also important are the extremes of temperature. Plants have a
limit as to how cold a temperature they can survive. Most annuals die if
exposed to freezing weather. Perennials usually die back to the roots during
winter, but even perennial plants will die if the freeze exceeds a limit specific
to that type of plant. The more deeply the soil freezes, the more types of plants will die.
The US Department of Agriculture has published a map of Hardiness Zones.
Perennials are rated according to which zone they can survive from 1 to 12. One being the coldest.
Heat also matters. Some plants thrive in high temperatures, but
plants native to cool regions will likely shrivel in hot weather.
|| Most yards provide a variety of environments for growing plants. A southern exposure has sun all day. A northern exposure may get no direct sun at all. Eastern exposures tend to provide shelter from the hottest rays of the sun.
Trees, fences, houses, and other structures provide localized shade.
These shady areas change in shape as the sun migrates through the day and
through the seasons.
Structures, trees, and shrubs also change the wind flow. They
will block wind from some areas and funnel it into others.
Houses and fences may partially block rainfall in some spots but concentrate
precipitation in others. Down spouts from gutters may flood a spot during
A sloping landscape also affects plants. Soil on a slope drains more quickly, but moisture accumulates at the base. A south facing slope is warmer than a flat landscape. A north facing slope gets less sun and warms more slowly in the spring.
Trees and shrubs will compete strongly for nutrients in the soil
as well as moisture. Their thick roots can out compete many garden plants.
A site that will help calculate sun angles is at
Soil, Clay, and Sand
|| Soil is the naturally occurring material that
garden plants are rooted in. It is made up of several elements including
rock that has been broken up or weathered to the point of sand
grains or smaller.
Many soils get their character from the parent rock that was their
main source. The weathering of rock involves not just breaking down the bedrock
into smaller and smaller fragments, but chemical changes that occur in some
minerals in the rock.
Generally some rocks break down to produce sandy soils while other
types of rock produce clay soils. The process can take centuries.
Soil is more than ground up rock. Living organism can greatly modify
and improve soil. Good garden soils are a complex community of micro-organisms
and includes larger creatures such as earthworms and insects.
The living part of the soil does such things as take fallen tree
leaves and break them down so their nutrients can be recycled and reused
by plants. A rich soil is crawling with biological activity.
| Sandy soils are said to be lighter, that is they are easier to dig. The grains make the clumps looser and they fall apart more easily.
Sandy soils have fewer nutrients for plants to use. Fertilizers wash through the soil more easily. It has more air spaces due to the granular nature of the soil so that plant roots can penetrate more readily.
In the spring, sandy soils warm more quickly, however, water also drains
quickly. Since it holds water poorly, gardens in sand need more frequent
watering. Sandy soil has a gritty feel.
|| Soils made mostly of clay are called
heavy soils and are much harder to dig. The clay particles clump together and are sticky or slippery when wet.
Clay becomes hard and brick-like when dried out.
Clay has more nutrients than sand, and clay soils are usually more
fertile. Clay holds moisture rather than letting it drain away. However, roots have a harder time growing through
clay, and clay has less air space.
In spring, clay soils warm slowly since they are denser and usually
contain more moisture.
|| Silt is a soil composed of partiles smaller than grains of sand but larger than clay particles. It has a slightly gritty feel. When wet, silt feels muddier than sand, but is not as sticky as clay.||Loam
|| Loam is the term for a soil that has a favorable mix of
sand, silt, and clay. Loam often contains considerable amounts of organic material. It falls in between in most soil characteristics. It cultivates
moderately well and is often fertile. Loam also holds moisture fairly well with reasonably good drainage.
All in all, most gardeners prefer to garden in loam or sandy loam,
it avoids the problems the other types of soil pose. However all soils can
be improved for gardening by adding organic matter such as compost.
|Top Soil|| Top Soil is the uppermost layer of natural soil. It can vary greatly in thickness from an inch to a number of feet. In temperate climates where the soil has not been eroded or otherwise disturbed, top soil averages six to nine inches in depth. It contains most of the soil's nutrients, and good top soil is usually dark brown in color and contains the most plant roots. Having thick top soil makes for favorable gardening conditions.
Below the top soil, is the subsoil. It may have a number of layers or horizons each with their own characteristics. Subsoil is not as fertile as top soil and may be less developed or more similar to the underlying rock (or sand or clay deposit, etc.) from which the soil has developed.
| Organic gardening fertilizers
improve the soil's growing capacity by the addition of
natural materials such as manure or compost. Organic fertilizers include
the same minerals as chemical fertilizers but in smaller quantites that
are released to the soil more slowly. Organic fertilizers are derived from living materials such as manure tea.
Organic fertilizers have additional benefits such as improving
the soil's texture and water holding capacity as well as nuturing micro-organisms
important for a soil's overall capacity for growing plants.
| Chemical fertilizers are manufactured
chemicals designed to give a boost to plant growth and supply nutrients that
are lacking. Usually the most important of these are nitrogen. Nitrogen
(N) is important for leaf growth.|
Phosphorous (P) is needed for root
health. Potash (K) is used in flower development.
These are the primary
chemicals in "complete" fertilizers. Often, small amounts of other chemicals
such as sulfur, iron, magnesium, also are included.
"Organic" versus "Nonorganic"
|| Organic gardening means growing without any artificial chemicals, such as herbicides, insecticides, or chemical fertilizers.; Non-organic
The use of manufactured chenmicals in gardening in order to destroy weeds, kill insects, or promote growth through fertilizers.
|| According to chemistists, organic chemistry refers to any compound involving the element Carbon "C". According to most chemists, their is no real difference in foods or flowers grown by either "organic" or "nonorganic" means. They are chemically indistinguishable.
Organic supporters say that chemicals used to produce plants are toxic and that organically grown foods are safer and more healthful.
Everyone can agree that many artificial chemicals can be very damaging to the environment and to people. Their use should at least be kept to a minimum and natural substances should be used instead whenever possible.
|| A garden flower is a plant grown mainly for the ornamental value of its blossoms or leaves. Flowers are generally considered less permanent in the garden and have non-woody stems. Examples include: tulips, daisy, geranium, pansy, and sunflowers.
|| A weed is any plant growing in an unwanted spot in a garden, lawn, farm field, landscape, or any cultivated setting. A weed is often herbaceous (nonwoody stem) but can be a grass, a vine, a shrub, or even a tree seedling.
| Groundcovers are plants grown to look good with little or no maintenence. They are often used in places where lawn grasses or garden flowers would not grow well such as shady areas or steep slopes. Many goundcovers are evergreen and look good even in winter. Example include vinca major, English ivy, hosta, lirope, and moneywort.
Trees and Shrubs
|| Shrubs are woody plants often with multiple stems or trunks and are shorter than 12 feet in height when mature. Trees are more than 12 feet in height when grown. Most trees have single trunks, though there are a number of exceptions. If it is a plant that you can climb, then it is likely a "tree". All trees and shrubs live more than one season in their native habitats.