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Asexual propagation, as mentioned earlier, is the best
way to maintain some species, particularly an individual that best
represents that species. Clones are groups of plants that are
identical to their one parent and that can only be propagated
asexually. The Bartlett pear (1770) and the Delicious apple (1870)
are two examples of clones that have been asexually propagated for
many years. |
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The major methods of asexual propagation are cuttings,
layering, division, and budding grafting. Cuttings involve rooting
a severed piece of the parent plant; layering involves rooting a
part of the parent and then severing it; and budding and grafting
is joining two plant parts from different varieties. |
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Cuttings
Many types of plants, both woody and herbaceous, are frequently
propagated by cuttings. A cutting is a vegetative plant part which
is severed from the parent plant in order to regenerate itself,
thereby forming a whole new plant. |
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Take cuttings with a sharp blade to reduce injury to
the parent plant. Dip the cutting tool in rubbing alcohol or a
mixture of one part bleach : nine parts water to prevent
transmitting diseases from infected plant parts to healthy ones.
Remove flowers and flower buds from cuttings to allow the cutting
to use its energy and stored carbohydrates for root and shoot
formation rather than fruit and seed production. To hasten
rooting, increase the number of roots, or to obtain uniform
rooting (except on soft, fleshy stems), use a rooting hormone,
preferably one containing a fungicide. Prevent possible
contamination of the entire supply of rooting hormone by putting
some in a separate container for dipping cuttings. |
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Insert cuttings into a rooting medium such as coarse
sand, vermiculite, soil, water, or a mixture of peat and perlite.
It is important to choose the correct rooting medium to get
optimum rooting in the shortest time. In general, the rooting
medium should be sterile, low in fertility, drain well enough to
provide oxygen, and retain enough moisture to prevent water
stress. Moisten the medium before inserting cuttings, and keep it
evenly moist while cuttings are rooting and forming new shoots. |
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Place stem and leaf cuttings in bright, indirect light.
Root cuttings can be kept in the dark until new shoots appear. |
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Stem Cuttings
Numerous plant species are propagated by stem cuttings. Some can
be taken at any time of the year, but stem cuttings of many woody
plants must be taken in the fall or in the dormant season. |
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Tip Cuttings
Detach a 2 to 6-inch piece of stem, including the terminal bud.
Make the cut just below a node. Remove lower leaves that would
touch or be below the medium. Dip the stem in rooting hormone if
desired. Gently tap the end of the cutting to remove excess
hormone. Insert the cutting deeply enough into the media to
support itself. At least one node must be below the surface. |
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Medial Cuttings
Make the first cut just above a node, and the second cut just
above a node 2 to 6 inches down the stem. Prepare and insert the
cutting as you would a tip cutting. Be sure to position right side
up. Axial buds are always above leaves. |
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Cane Cuttings
Cut cane-like stems into sections containing one or two eyes, or
nodes. Dust ends with fungicide or activated charcoal. Allow to
dry several hours. Lay horizontally with about half of the cutting
below the media surface, eye facing upward. Cane cuttings are
usually potted when roots and new shoots appear but new shoots
from dracaena and croton are often cut off and re-rooted in sand. |
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Single Eye
The eye refers to the node. This is used for plants with
alternate leaves when space or stock material are limited. Cut the
stem about 1/2-inch above and 1/2-inch below a node. Place cutting
horizontally or vertically in the medium. |
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Double Eye
This is used for plants with opposite leaves when space or stock
material is limited. Cut the stem about 1/2-inch above and
1/2-inch below the same node. Insert the cutting vertically in the
medium with the node just touching the surface. |
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Heel Cutting
This method uses stock material with woody stems efficiently.
Make a shield-shaped cut about halfway through the wood around a
leaf and axial bud. Insert the shield horizontally into the
medium. |
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Leaf Cuttings
Leaf cuttings are used almost exclusively for a few indoor
plants. Leaves of most plants will either produce a few roots but
no plant, or just decay. |
Whole Leaf with Petiole
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Whole Leaf with Petiole
Detach the leaf and up to 1 1/2 inches of petiole. Insert the
lower end of the petiole into the medium. One or more new plants
will form at the base of the petiole. The leaf may be severed from
the new plants when they have their own roots, and the petiole
reused. |
Whole Leaf without Petiole
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Whole Leaf without Petiole
This is used for plants with sessile leaves. Insert the cutting
vertically into the medium. A new plant will form from the
axillary bud. The leaf may be removed when the new plant has its
own roots. |
Split Vein
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Split Vein
Detach a leaf from the stock plant. Slit its veins on the lower
leaf surface. Lay the cutting, lower side down, on the medium. New
plants will form at each cut. If the leaf tends to curl up, hold
it in place by covering the margins with the rooting medium. |
Leaf Section
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Leaf Sections
This method is frequently used with snake plant and fibrous
rooted begonias. Cut begonia leaves into wedges with at least one
vein. Lay leaves flat on the medium. A new plant will arise at the
vein. Cut snake plant leaves into 2-inch sections. Consistently
make the lower cut slanted and the upper cut straight so you can
tell which is the top. Insert the cutting vertically. Roots will
form fairly soon, and eventually a new plant will appear at the
base of the cutting. These and other succulent cuttings will rot
if kept too moist. |
Plants with large roots
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Root Cuttings
Root cuttings are usually taken from 2 to 3 year old plants
during their dormant season when they have a large carbohydrate
supply. Root cuttings of some species produce new shoots, which
then form their own root systems, while root cuttings of other
plants develop root systems before producing new shoots. |
Plants with Large Roots
Make a straight top cut. Make a slanted cut 2 to 6 inches below
the first cut. Store about 3 weeks in moist sawdust, peat moss, or
sand at 40oF. Remove from storage. Insert the cutting vertically
with the top approximately level with the surface of the rooting
medium. This method is often used outdoors. |
Plants with small roots
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Plants with Small Roots
Take 1 to 2 inch sections of roots. Insert the cuttings
horizontally about 1/2 inch below the medium surface. This method
is usually used indoors or in a hotbed. |
Layering
Stems still attached to their parent plants may form roots where
they touch a rooting medium. Severed from the parent plant, the
rooted stem becomes a new plant. This method of vegetative
propagation, called layering, promotes a high success rate because
it prevents the water stress and carbohydrate shortage that plague
cuttings. |
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Some plants layer themselves naturally, but sometimes
plant propagators assist the process. Layering is enhanced by
wounding one side of the stem or by bending it very sharply. The
rooting medium should always provide aeration and a constant
supply of moisture. |
Tip Layering
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Tip Layering
Dig a hole 3 to 4 inches deep. Insert the shoot tip and cover it
with soil. The tip grows downward first, then bends sharply and
grows upward. Roots form at the bend, and the recurved tip becomes
a new plant. Remove the tip layer and plant it in the early spring
or late fall. Examples: purple and black raspberries, trailing
blackberries. |
Simple Layering
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Simple Layering
Bend the stem to the ground. Cover part of it with soil,
leaving the last 6 to 12 inches exposed. Bend the tip into a
vertical position and stake in place. The sharp bend will often
induce rooting, but wounding the lower side of the branch or
loosening the bark by twisting the stem may help. Examples:
rhododendron, honeysuckle. |
Compound Layering
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Compound Layering
This method works for plants with flexible stems. Bend the stem
to the rooting medium as for simple layering, but alternately
cover and expose stem sections. Wound the lower side of the stem
sections to be covered. Examples: heart-leaf philodendron, pothos. |
Mound Layering
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Mound (Stool) Layering
Cut the plant back to 1 inch above the ground in the dormant
season. Mound soil over the emerging shoots in the spring to
enhance their rooting. Examples: gooseberries, apple rootstocks. |
Air Layering
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Air Layering
Air layering is used to propagate some indoor plants with thick
stems, or to rejuvenate them when they become leggy. Slit the stem
just below a node. Pry the slit open with a toothpick. Surround
the wound with wet unmilled sphagnum moss. Wrap plastic or foil
around the sphagnum moss and tie in place. When roots pervade the
moss, cut the plant off below the root ball. Examples: dumbcane,
rubber tree. |
The following propagation methods can all be considered
types of layering, as the new plants form before they are detached
from their parent plants. |
Stolons and Runners
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Stolons and Runners
A stolon is a horizontal, often fleshy stem that can root, then
produce new shoots where it touches the medium. A runner is a
slender stem that originates in a leaf axil and grows along the
ground or downward from a hanging basket, producing a new plant at
its tip. Plants that produce stolons or runners are propagated by
severing the new plants from their parent stems. Plantlets at the
tips of runners may be rooted while still attached to the parent,
or detached and placed in a rooting medium. Examples: strawberry,
spider plant. |
Offsets
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Offsets
Plants with a rosetted stem often reproduce by forming new shoots
at their base or in leaf axils. Sever the new shoots from the
parent plant after they have developed their own root system.
Unrooted offsets of some species may be removed and placed in a
rooting medium. Some of these must be cut off, while others may be
simply lifted off of the parent stem. Examples: date palm,
haworthia, bromeliads, many cacti. |
Separation
Separation is a term applied to a form of propagation by which
plants that produce bulbs or corms multiply. |
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Bulbs
New bulbs form beside the originally planted bulb. Separate these
bulb clumps every 3 to 5 years for largest blooms and to increase
bulb population. Dig up the clump after the leaves have withered.
Gently pull the bulbs apart and replant them immediately so their
roots can begin to develop. Small, new bulbs may not flower for 2
or 3 years, but large ones should bloom the first year. Examples:
tulip, narcissus. |
Separation Corms
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Corms
A large new corm forms on top of the old corm, and tiny cormels
form around the large corm. After the leaves wither, dig up the
corms and allow them to dry in indirect light for 2 or 3 weeks.
Remove the cormels, then gently separate the new corm from the old
corm. Dust all new corms with a fungicide and store in a cool
place until planting time. Examples: crocus, gladiolus. |
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Division
Plants with more than one rooted crown may be divided and the
crowns planted separately. If the stems are not joined, gently
pull the plants apart. If the crowns are united by horizontal
stems, cut the stems and roots with a sharp knife to minimize
injury. Divisions of some outdoor plants should be dusted with a
fungicide before they are replanted. Examples: snake plant, iris,
prayer plant, day lilies. |