Horticulture Ch6 Seeds

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Horticulture Ch-6Seeds
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Horticulture Ch-6

• Objective To propagate at least one plant using
  seeds.
• Competencies to be Developed
• After studying this chapter, you should be able
  to
• Identify the parts of a seed and the function of
  each.

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Horticulture Ch-6Seeds

• Differentiate between direct and indirect seeding
  methods.
• Prepare a medium for seeds, sow seeds, and
  provide the proper conditions for germination.
• Water, fertilize and harden off seedlings before
  transplanting.

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Horticulture Ch-6Seeds

• Transplant seedlings into flats or pots.

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• WHAT IS PROPAGATION?
• There are many ways of propagating or reproducing
  plants. The most common method of reproducing
  flowering as well as vegetable and cereal crops
  is through the use of seeds. This is a sexual
  process and requires the union of pollen (the
  male sex cell)

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• with the egg (the female sex cell) in the ovary.
  Male and female cells may be from the same parent
  (self-pollination) or from separate parents
  (cross- pollination) .

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• Seeds are a means of rapidly increasing the
  number of a certain plant. However, not all
  plants come true to seed (reproduce exact
  duplicates of the parent plant from seeds). Wheat
  and barley are examples of plants that do come
  true from seed.

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• Others, such as rhododendrons, azaleas, and
  apples, do not come true from seed, causing the
  off- spring to differ from either parent.

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• Plants that are not produced directly from seeds
  or do not produce seeds that will grow, such as
  some hybrids, must be propagated by another
  method to obtain exact duplicates,.

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• Hybrids are the offspring of two different
  cultivars (the term cultivar is often
  interchanged with the term variety) of one plant,
  each of which possesses certain characteristics
  that are desired in the new plants.

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• A female plant of one cultivar and a male plant
  of another cultivar are crossed (bred) to produce
  offspring with the best characteristics of each
  parent.

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• However, when hybrids themselves are reproduced
  from seed, their offspring do not have the same
  characteristics as the parents rather, they have
  a variety of combinations of traits possessed by
  the plants originally used to produce the
  hybrids.

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• To produce exact duplicates of these plants,
  asexual reproduction is used. This is not a
  sexual process, and no seeds are used in this
  method. Instead, the plant is propagated from one
  of its parts, such as the leaf, stem, or root.

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• Propagation may be accomplished by division of
  roots by cuttings of leaves, stems, or roots or
  by budding and grafting. The strawberry
  reproduces itself by runners the lily by tiny
  bulblets. The reproduction method of the
  strawberry and lily occur naturally. Cuttings,
  budding, and grafting, however , have been
  developed or improved upon by humans.

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• Asexual reproduction is possible because each
  single cell of a plant contains all the
  characteristics of the entire plant and can
  re-grow any missing art. Thus, a stem cutting
  removed from the roots of the plant develops new
  roots from cells along and at the base of the
  stem.

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• Root cuttings develop new stem tissue in the same
  manner .
• Plant propagation predates recorded history. Very
  early humans planted seeds or divided plants to
  increase plant numbers and to carry them over the
  dormant or resting season.

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• The quality of plants was improved by using seed
  from the best plants to produce other plants, or
  by separating naturally propagated plants of
  superior quality from the parent and planting
  them.

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• One of the newest approaches to plant propagation
  is a method called tissue culture or micro-
  propagation. This is an asexual method in which a
  growing shoot, tip, or bud of the plant is
  separated and grown on an agar gel or other
  nutrient medium.

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• Through this method many thousands of new plants
  exactly like the parent plant can be produced
  very quickly. This is a good way to rapidly
  increase a new, superior plant and get it on the
  market years sooner.

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• This method has been used for years with orchids
  and some other plants and is now being adopted as
  a commercial method in the propagation of many
  plants. Tissue culture is discussed in greater
  detail in Unit 7.
• Figure 6-1 shows the various kinds of plant
  propagation that are discussed in this section.

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Horticulture Ch-6

• PROPAGATION OF PLANTS FROM SEEDS
• In the 'horticulture industry , many plants are
  started from seed because it is a quick and
  economical method. For successful germination,
  the proper environmental and cultural conditions
  must be provided. These conditions include
  temperature, moisture, light, and medium.

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• Seeds of annual plants (plants that complete
  their life cycle in one year) from named
  cultivars that are not hybrids generally come
  reasonably true from seed. Named cultivars are
  specific individual plants that have been named
  to indicate their particular traits.

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• The tomato plant has numerous named varieties
  such as Better Boy and Marglobe, each of which is
  different in size, days needed to mature, growth
  habits, and disease resistance Seeds should not
  be saved from hybrids and planted, since the
  resulting plants would not come true from seeds
  Many perennials are grown from seed, figure 6-2

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Horticulture Ch-6

• SPECIAL TREATMENT OF SEEDS FOR GERMINATION
• Some seeds have a hard seed coat that must be
  soaked or scratched before the seeds are able to
  germinate.

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• This process is called scarification. Examples of
  this type of seed are the red bud, Judas tree,
  and sweet clover. Sandpaper, scratching, or an
  acid bath may be used to weaken the seed coat.

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• Other seeds require a moist, cold rest period
  (dormant stage) at temperatures below 37F (3C)
  for eight weeks or longer. Examples of seeds that
  require a rest period are the apple, peach, pear,
  tree peony, maple, and yew. These may be buried
  or stratified in moist sand and kept cool.

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• Still other seeds must go through alternate wet-
  ting and drying. Some must have light to
  germinate others must have darkness. These
  specific requirements must be met when these
  seeds arc planted. Always follow instructions on
  seed packets or enclosed planting directions.

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• COMPOSITION OF SEEDS
• The basic parts of a seed are the seed coat, the
  endosperm (stored plant food), and the embryo,
  figure 6-3.

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Horticulture Ch-6

• SEED COAT The seed coat is the outside covering
  of the seed that protects the embryonic plant.
  The seed coat makes it possible for seeds to be
  transported and stored for long periods of time.

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• ENDOSPERM (STORED PLANT FOOD) The endosperm is
  the food storage tissue that nourishes the
  embryonic plant during germination (the first
  start of growth in a seed)

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• EMBRYO (OR EMBRYONIC PLANT) The embryo is a new
  plant that is developed as a result of
  fertilization. During germination, it extends its
  roots and seed leaves to form a new plant, figure
  6-4.

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• IDENTIFICATION AND SELECTION OF SEED
• There are several important steps in the
  selection of seed.

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• .Identify which seeds are grown locally.
• .Select seeds that have been tested for the
  current year's growing season for germination
  ability and purity. These tests must comply with
  state regulations.

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• .Purchase the seeds from a reliable dealer to
  assure that the variety or cultivar is true
  (pure) and that germination ability is acceptable.

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• .Choose hybrid varieties for greater vigor,
  uniformity, and flowering ability.
• .Select uniform heavyweight or primed seeds.

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• Some new things have been done with seeds to
  improve germination and uniformity of growth.
  First, seed quality has been improved and seeds
  have been sorted by weight. This results in all
  seedlings coming up at the same time. Heavier
  seeds tend to grow faster and produce larger
  plants. These seeds are usually worth more and
  are a good investment.

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• Second, seeds are primed or enhanced. This is
  done by soaking the seeds in salt solutions of
  potassium chloride (KCl) or ethyl alcohol. This
  treatment causes the growth hormones or enzymes
  to become active, and the seed radical or young
  root starts to grow. By regulating the amount of
  moisture and chemical, growth of the radical is
  stopped at a point where the seed may still be
  safely stored.

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• Seeds treated this way come up much sooner after
  planting. Where seeds are planted outside in the
  field, this is a great advantage. The sooner the
  seed comes up after planting, the less chance for
  soil insects and diseases to damage or kill the
  young seedling.

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• Young plants become much more disease resistant
  in just a few days and many more survive if
  growth is fast
• Plants from primed or enhanced seeds are more
  uniform in growth and more of them are ready for
  harvest at the same time This is a great
  advantage where a once-over machine harvesting is
  done.

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• The selected and treated seeds as mentioned above
  cost more but out yield ordinary seeds and more
  than return the extra cost.

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• Small difficult-to-plant seeds, the ones you al
  ways plant too thickly, are now coated or
  pelletized to make them larger and easier to
  plant. Some companies even glue them to a tape
  with the proper spacing. All you do is stretch
  out the tape and cover it with soil.

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Horticulture Ch-6

• GERMINATION MEDIUM The best medium for
  germination has a favorable pH level and an
  adequate supply of plant nutrients. It is firm,
  porous, uniform in texture, sterile, and free of
  weeds, insects, and disease organisms.
• A good germinating medium contains one or more of
  the following ingredients.

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• SOIL The soil should be a loam composed of45
  percent mineral matter, 5 percent organic matter
  , 25 percent air, and 25 percent water.

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• CONSTRUCTION GRADE SAND This is the best type of
  sand to use because it is more porous than some
  other sands, thereby allowing for better aeration
  and drainage. Sand particles do not hold plant
  nutrients in the medium as strongly as particles
  of soil or peat moss.

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• PEAT MOSS Peat is partially decomposed vegetation
  that has been preserved under water. The peat is
  collected from marshes, bogs, or swamps. Peat has
  a very high capacity for holding water. It
  contains about 1 percent nitrogen and is low in
  phosphorous and potassium.

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• SPHAGNUM MOSS Sphagnum moss is the dehydrated
  remains of acid bog plants. It is used in
  shredded form in seed germination.

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• HORTICUL TURAL GRADE PERLITE Perlite is a
  gray-white material of volcanic origin that
  expands when it is heated. It is most commonly
  used to improve aeration of media. Horticultural
  grade perlite consists of large particles,
  thereby providing good drainage and aeration.

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• VERMICULITE Vermiculite is a very light- weight
  mineral. It is neutral (has a pH of 7) and has a
  very high water-holding capacity.

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• JIFFY MIX Jiffy Mix is composed of equal parts of
  shredded sphagnum moss, peat, fine grade Terrlite
  vermiculite, and enough nutrients to sustain
  initial plant growth.
• Although germination media are usually made up of
  one or more of the materials in the list above,
  good grade, sterilized topsoil provided with the
  proper drainage is sufficient.

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• Sand or perlite should be added if the soil needs
  greater drainage and aeration. Peat, sphagnum
  moss, or vermiculite may be added to improve the
  moisture-holding capacity of the soil. For
  general purposes, a good mix consists of
  one-third soil, one-third sand or perlite, and
  one-third peat moss, sphagnum moss, or
  vermiculite.

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• If the soil is heavy (with a high clay content) ,
  more sand or perlite may be needed if it is
  sandy, less sand and perlite are required.

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• Soil used in any seed germination medium should
  be sterilized or pasteurized by heating it at
  180F for one-half hour. Sterilized or
  pasteurized soil may also be purchased at garden
  stores. It may then be mixed with other materials
  to form the desired medium.

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• INDIRECT SEEDING
• Indirect seeding is a process in which seed is
  sown in a place separate from where the plants
  will eventually grow to maturity. The seedlings
  are trans- planted one or more times before
  reaching the permanent growing area.

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• FLATS When growing seeds, horticulturists often
  select a flat. Flats are made of plastic and come
  in many shapes and sizes. Size selection should
  be deter- mined by the number of seeds to be
  sown. The medium selected is placed in the flat
  and leveled off to about l to 3 inch below the
  top of the flat. This is done with a tool called
  a skew, sized to fit the flats. See figure 6- 5.

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• After the flat is filled, rows are made in which
  to sow the seeds. A row marker may be used, or
  rows may be made one at a time using a straight
  board as a guide.

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• It is best to sow seeds in rows because if
  disease strikes one row of seed, it can be
  removed without disturbing the others. Also, when
  several different varieties or cultivars are in
  the flat, it is easier to label them by rows and
  much easier to transplant seedlings (young plants
  that have been germinated several days).

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• INDIVIDUAL CELLS IN CAVITY SEEDLING TRAYS
• New seeding machines that can place one seed at a
  time in a series of small cell-like pots are now
  available. This allows the use of flats made up
  of many small pots.

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• One or two seeds are planted in each with less
  root damage than from solid mat flats. Figure 6-9
  shows a flat planted to begonia seedlings.

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• WHEN TO SEED As businesspersons who must operate
  at a profit to survive, commercial plant growers
  must be sure that their plants are ready for sale
  at the correct time for outdoor planting and for
  holidays.

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• Seeds must be planted on certain dates so that
  the resulting seedlings are ready for
  transplanting at the proper time. The chart in
  figure 6- 7 gives planting information for seeds
  of various plants.

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• SOWING SEEDS To sow seeds properly, use the
  following procedure. Take the packet of seeds and
  shake the seeds to the bottom of the packet. Hold
  the seed packet with the open end slightly lower
  than the rest of the packet and gently tap the
  packet.

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• The seeds will move out slowly and gradually,
  making it easy to sow the seeds properly spaced
  in rows.

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• . Follow directions on the package for
  determining the distance apart the seeds should
  be sown. If flats with individual cells are used,
  place one or two seeds in each cell.

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• After the seeds are sown, cover them with
  shredded sphagnum moss, fine perlite, or fine
  sand. Cover with a layer of medium measuring
  about twice the thickness of the seed. (The seed
  package may have directions for depth of
  planting if so, follow them for best results.)
  Some seeds, such as lobelia, petunia, and
  snapdragon, need light for germination and should
  not be covered when sown.

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• As soon as the seeds are sown, they are labeled
  with the name, variety, and date, figure 6-8. All
  labels should be printed clearly with pencil or
  waterproof marking pen. Ballpoint pen should not
  be used since it washes out when the seedlings
  are watered.

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• WATERING THE SEED FLAT Water aids in germination
  by making the seed coat soft so that the
  embryonic plant can germinate. Water itself is an
  important nutrient and also acts to dissolve
  other nutrients present in the medium, making
  them available to the growing plants.

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• To water freshly seeded flats, set the flats in a
  tub of water. This allows the seeds to be watered
  by capillary action. (the water is drawn up into
  the spaces between the soil particles to
  thoroughly moisten the medium.) After the medium
  is moistened, the flat is removed from the tub.

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• If the flat is watered from the top, care must be
  taken to avoid washing the seeds out of the flat.
  Very small seeds should never be watered from the
  top because they may be washed too deeply into
  the soil.

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• CONDITIONS FOR GERMINATION Seed flats containing
  seeds for germination should be located in a
  semi-shaded area of the greenhouse and receive a
  bottom heat of 65 to 70F (18 to 21C).

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• (Some cool-season crops germinate well without
  bottom heat.) This may be accomplished in several
  ways. Location of the containers above the heat
  coil or hot water pipes or the use of a special
  propagating mat that is controlled with a
  thermostat are two possibilities.

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• After the seeds are sown, the containers are
  covered with a pane of glass or clear plastic
  film to retain humidity. The covering should not
  touch the medium while the seedlings are
  germinating.

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• Some seedlings, such as verbena, dusty miller,
  pansy, and portulaca, require a three-day period
  of darkness for germination. For these plants,
  newspaper is used instead of glass or plastic.
  The paper is removed as soon as the seeds
  germinate so that the new seedlings receive light
  immediately.

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• After germination, the medium is kept moist but
  never wet. The flats are watered with a gentle
  mist or from the bottom so that the small
  seedlings are not washed out.

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• The proper seedling medium is low in fertilizer
  elements. Seedlings should be fed weekly with a
  water-soluble fertilizer. As the seedlings
  approach transplanting size, a cooler temperature
  (55 to 60F) (13 to 16C) is provided to prepare
  the seedlings for the shock of transplanting.

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• This is known as the hardening-off process. The
  process may also include a modest withholding of
  water to slow active growth.

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• Many seedlings are now sold as plugs, see figure
  6-9 There is less transplant shock since the
  roots are not ton1 apart as they are when
  seedlings are transplanted from flats.

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• Seeds may be sown in pots, pans, or trays in a
  manner similar to that used for flats. The
  horticulturist should remember to provide
  drainage and uniform moisture. The containers
  should be watered from the bottom if possible.
  Plastic, newspaper, or glass is placed over the
  container to retain uniform moisture until the
  seeds germinate.

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• TRANSPLANTIN G SEEDLINGS After seeds germinate,
  they develop seed leaves or cotyledons, the first
  leaves to appear on the plant, figure 6-10. The
  plant should be allowed to grow until the first
  true leaves are present before it is
  transplanted.
• When handling seedlings, hold them by their true
  leaves using the thumb and forefinger.

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• Do not hold by the stem if the stem is badly
  bruised, the seedling could die. A bruised leaf
  is not nearly as serious an injury. While
  carefully holding the seedling, use a pot label
  to reach under the roots and lift, pushing the
  seedling out of the germinating medium. This
  exposes the roots. Do not shake the medium off
  the roots-exposure to air causes them to dry out.

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• Plant the seedlings one by one about 2 inches
  apart in a flat. Using a dibble (a tool used to
  make the hole for transplanting seedlings),
  insert the seedlings to a depth slightly deeper
  than that at which they grew in the seedling
  flat. Gently press the medium around the roots.

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• Water the seedlings at the soil surface with a
  gentle stream of water to settle the soil around
  the roots. The new seedlings are now ready to be
  grown to saleable size. (An alternate method
  involves using a trowel or fork when digging
  seedlings for transplanting.)

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• It is sometimes convenient to transplant
  seedlings into peat pots or market packs rather
  than flats. When a peat pot is used, one plant is
  placed in a pot and later transplanted directly
  to the garden with the plant remaining in the
  pot. Market packs generally hold six to twelve
  plants and are sold to the customer as such.

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• The plants are then separated from the pack and
  planted individually in a permanent location.
• Another indirect seeding technique is to plant a
  single seed in a Jiffy 7 peat moss pellet. These
  pellets, when soaked in water, expand to seven
  times their original size.

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• They contain all the necessary nutrients to feed
  the small seedling until it is planted in a
  permanent site. This eliminates the seedling
  transplanting stage prior to permanent planting
  and allows the young seedlings to be transplanted
  to the garden with less transplant shock.

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• The Jiffy 7 pellets are placed in plastic trays
  or flats for ease of handling. Manufacturer's
  directions should be followed when using these
  pellets.

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• PROCEDURE TRANSPLANTING TO POTS
• (Seedlings or Rooted Cuttings)
• I. Work from a large table. Place the pots in a
  row on your right side.
• 2. Place all other material to your left side.

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• 3. Cover drain hole with pottery or coarse
  sphagnum. (If using peat pots, this is not
  necessary.)
• 4. Hold the plant to be transplanted in the pot
  with the left hand.

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• 5. Fill the pot to the rim with soil or soilless
• mix, gently holding the plant at the proper
  planting depth with the left hand.
• 6. Gently firm the planting medium around the
  plant by pushing down along the edge of the pot
  with the thumbs. Do not push hard enough to tear
  or bruise plant roots.

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• 7. Label the pots or growing area according to
  variety, name, and date.
• 8. Move plants to growing area and water until
  water runs through the pot and out the drain
  hole.

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• PROCEDURE TRANSPLANTING PLANTS FROM POTS
• I. Work from a large table. Spread fingers of the
  left hand around the plant stem and over the top
  of the soil surface.
• 2. Invert the pot and gently tap the pot edge on
  the edge of the table.
• 3. Remove the pot from the root ball as it
  loosens.
• 4. If roots are pot bound, gently unwind them.

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• Single seeds of squash, cucumber, and melon may
  also be planted in 2-inch peat pots in
  preparation for direct planting to the garden at
  a later time. These crops transplant with
  difficulty and the peat pot permits transplanting
  without disturbing the root system.

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• Seedlings of nursery stock plants such as trees
  and shrubs are generally planted in a flat and
  trans- planted directly to the nursery row
  outdoors. Seeds of these plants may also be
  seeded directly in the nursery row.

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• DIRECT SEEDING
• Many seeds are planted directly in the permanent
  growing area. This is-referred to as direct
  seeding. It is the most economical method of
  seeding. Plants such as corn, melons, beans,
  beets, peas, lettuce, carrots, and most other
  vegetable crops are grown by this process.

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• Some vegetables, such as tomatoes, peppers,
  cabbage, and eggplant, are generally trans-
  planted as plants to the garden. Some trees and
  shrubs are also grown by direct seeding.

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• In direct seeding, the planting medium is the
  soil. The soil is prepared by removing all large
  clods or lumps of earth so that the seeds are
  uniformly covered. In some cases, manure, grass
  clip- pings, or compost may be added to the soil
  to improve its structure. In direct seeding, it
  is important to plant the right cultivar at the
  right time in the right soil.

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• Seeds may need treatment to prevent disease or
  insect damage. Weather conditions largely
  determine germination and initial growth.

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• The same conditions are needed for germination in
  direct seeding as when seeding in a flat there
  must be sufficient moisture and aeration the
  seedbed must allow firm contact with the seed
  and the temperature must be high enough to
  support the germination process.

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• Requirements for germination of specific seeds
  are given in the directions on the label of the
  seed packet.