Deciduous plants lose their leaves each
fall and are without leaves during the winter. Evergreen plants
normally do not lose all their leaves at once and retain
individual
leaves for several years. Both types of plants have woody stems
and are represented by many common shrubs and trees.
Cuttings are detached vegetative plant
parts that will develop into complete new plants by reproducing
their missing parts. Cuttings might be made from stems, roots,
or leaves, depending on the best method for each plant.
Many deciduous plants, such as forsythia,
honeysuckle, grape, currant, willow, and poplar, can be propagated
from stem cuttings. Many evergreens, both broad- and
narrow-leaved,
also can be propagated this way. Narrow-leaved (called needles
) evergreens, such as low-growing juniper, arborvitae, and false
cypress, root readily from cuttings. Broad-leaved evergreens—as
camellia euonymus, and cherry laurel—are easily propagated
in this way. This publication discusses propagating these types
of plants from stem cuttings.
Types of Cuttings
Make cuttings of deciduous plants from
stem sections or tips one year old or less. Choose stem tips
to propagate evergreens. The basal part of a cutting is sometimes
older wood.
Tip cuttings probably are the most common type for use with
deciduous plants during the growing season; they generally do
not give the best results at any other part of the year. The
tip section of a shoot is more subject to winter cold damage,
may have flower buds rather than shoot buds, and may not have
the proper internal nutritional and hormonal balance for good
rooting during the dormant season. Simple or straight cuttings,
starting 8 to 10 inches from the shoot tip, are usually more
satisfactory for dormant cuttings.
Tip cuttings are most common for
evergreen
plants and generally give satisfactory results. Cut them about
4 to 10 inches long from stem tips, using stems one year or less
in age. Make tip cuttings from the main shoot or long side
branches.
Large cuttings produce a usable plant in shorter time than small
cuttings but may require more care while rooting.
Simple or straight cuttings from long, one-year-old shoots can be cut into
sections. This is the most common type of cutting for propagating
leafless (dormant) cuttings of deciduous plants. It might
occasionally
be used for broad-leaved evergreens.
Heel cuttings are made from side shoots produced on stems
two or more years old. To make the cuttings, pull the side shoots
from the main stem. Pull directly away from the tip end of the
main stem. This usually leaves a heel of older, main-stem tissue
attached to the basal end of the side shoot. The heel cutting
also can be cut from the main stem with a knife.
Mallet cuttings, similar to heel cuttings, include a complete
cross-section of the older, main stem at the base of the side
shoot. Use a knife or a pair of small pruning shears to make
this cut.
Some evergreens may root better from
heel or mallet cuttings because these plants normally develop
root primordia (specialized cells that develop into roots) in
older stems. These root primordia remain dormant until the stem
bends naturally to the moist soil or until the stem is cut from
the plant and placed in a rooting medium. Some deciduous plants
also produce root primordia.
Several types of hardwood cuttings
made from a narrow-leaved evergreen plant—cuttings also
might be made from very long side shoots.
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Several types of hardwood cuttings
made from a deciduous plant.
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Factors that Affect Rooting
Time of year cuttings are taken may affect rooting considerably.
Expect best results from cuttings of many deciduous plants taken
from late fall to early winter before enough cold weather occurs
to complete the rest requirements of the leaf buds. This allows
the cutting to be rooted under warm conditions without development
of leaves. After rooting has started, however, the cuttings must
be subjected to cold temperatures according to individual plant
requirements. Some deciduous plants only can be rooted from leafy
softwood or semi-hardwood cuttings taken during the growing
season.
Others root readily almost any time of the year.
Expect best results from cuttings of
many narrow-leaved evergreens taken from late fall to late winter.
Exposure of the mother or stock plant to cold temperatures prior
to taking the cuttings stimulates rooting. But cuttings of
broad-leaved
evergreen plants usually root best if you take them during the
growing season after a flush of growth, when the wood is partially
matured. Some plants root readily almost any time of the year.
Softwood cuttings are taken during the
growing season from new growth that has not matured or hardened
significantly. When the wood is partially matured, they are called
semi-hardwood cuttings. Those taken during the subsequent dormant
season when the wood is mature and hardened or from wood older
than one year are called hardwood cuttings.
Age of stock plant may be an important factor with hard-to-root
plants. Cuttings from young seedling plants may root better than
cuttings from older plants. Chances of rooting cuttings from
large, old trees or shrubs may not be very good unless they are
easy-to-root types.
Physical condition of the
stock will affect the rooting
of cuttings. Cuttings taken during the growing season from rapidly
growing, succulent shoots often root poorly. Instead, take
cuttings
after growth has stopped and the wood has begun to harden;
otherwise,
many may rot. Shoots that have grown very little also root poorly.
Neither type of shoot has the optimum physical condition and
nutritional balance for the best rooting.
Too much or too little fertilizer on
the stock plants may hinder rooting ability of the cuttings as
it affects growth and the internal nutritional balance. Because
of better physical condition and nutritional balance, lateral
shoots may root better than terminal shoots from the same plant.
Likewise, where a very long shoot can be made into several
cuttings,
sections from the central part of the shoot may root better than
those from either end.
Shoots with flower buds or flowers may
not root as well as shoots that are strictly vegetative in some
hard-to-root plants. Removal of flower buds sometimes helps
rooting.
Take cuttings only from healthy plants,
free of insect, disease, or nutritional disorders.
Wounding the basal end of the cutting often stimulates
rooting of such evergreen plants as rhododendrons and junipers,
especially if the cutting has older wood at its base. Use the
tip of a sharp knife to make a 1- to 2-inch vertical cut down
each side of the base of the cutting. Stripping off the lower
side branches of the cutting during its preparation also can
be considered slight wounding. For more severe wounding on
difficult-to-root
types or larger-diameter cuttings, make several vertical cuts.
Or remove a thin slice of bark down one or both sides of the
base of the cutting. Expose the cambium (the one or two layers
of cells between the bark and the wood), but avoid cutting deeply
into the wood.
Wounding may stimulate rooting by
promoting
cell division and more absorption of water or applied
root-promoting
chemicals, or it may remove tough tissue that prevents outward
root growth from the cutting. Wounding is used most often on
evergreen plants, but it may be useful on deciduous plants.
The rooting medium provides physical support, oxygen, and water.
Many types of media are available, but sand, perlite, peat, or
mixtures of any of the three are most common. Very fine gravel
sometimes is used.
The rooting medium may affect the success
of rooting and quality of the root system produced. When rooted
in sand, cuttings of some plants produce long, unbranched, brittle
root systems. When rooted in mixtures of sand and peat, the roots
are slender, branched, and flexible. Differences in the air-
and water-holding capacity of various media produce these effects.
The container used for rooting may influence these responses
if drainage is not adequate in the container bottom to prevent
waterlogging.
Wounding a
narrow-leaved evergreen cutting by slicing or scraping a thin
layer of bark from the base of the cutting. |
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If evergreen cuttings or leafy softwood
or semi-hardwood cuttings of deciduous plants are to be rooted,
make sure both container and rooting medium are free of decay
organisms prior to use by heating in an oven. A temperature of
140°F for 30 minutes in the center of the rooting medium
is sufficient. Also take this precaution with hardwood cuttings
of difficult-to-root deciduous plants that will be in the rooting
medium for long periods. If new perlite is the rooting medium,
it will usually be sterile and require no heat treatment, but
be sure the containers for holding the medium are clean.
Leaves on evergreen cuttings and leafy cuttings of
deciduous plants promote root formation through their production
of growth-promoting hormones and food materials (carbohydrates).
Keep as large a leaf surface as possible on the cuttings. There
are disadvantages to this procedure, however. One is the space
required to root some broadleaved evergreen cuttings with large
leaves. In such cases, commercial propagators sometimes clip
off one-third to one-half of the tips of large leaves. Another
problem is that leaves lose water through transpiration. Excessive
loss will interfere with root formation or cause the cutting
to die. Take precautions to reduce water loss. If leaves form
too early on hardwood cuttings of deciduous plants, they may
encourage excessive moisture loss and cause the cutting to die.
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A rooted cutting of a broad-leaved
evergreen
plant—surface was reduced to save space in the cutting bed
by removal of about one-third of the leaf tips. |
Water
is necessary to the life of the cutting. A cutting has no root
system to absorb water, yet water loss continues through the
leaves. The base of unrooted cuttings can absorb small amounts
of water, but this usually will not be enough to keep the cutting
alive and healthy. Commercial growers use an intermittent mist
system to apply a fine mist over the cuttings and maintain a
continuous film of water on the leaves. The moisture lowers the
leaf temperature, creates a humid atmosphere, and reduces water
loss through transpiration.
Most amateurs will not have a mist system
available. However, you can obtain a similar effect by covering
the propagation box with glass or plastic. This will keep the
air humid, although the cooling effect provided by mist will
not be created. Do not expose the cuttings to direct sunlight,
because the temperature inside the enclosure will become too
high. It may be helpful to syringe the cuttings daily with a
spray bottle. Keep the rooting medium moist (not waterlogged),
and provide drainage in the bottom of the rooting medium
container.
Deciduous hardwood cuttings often can
be rooted without mist or even the protection of a covered
propagation
box, unless they take a long time to root, and leaves develop
from dormant buds.
Light
is important in rooting leafy cuttings. It is necessary for
production
of plant hormones or auxins, which stimulate rooting, and for
photosynthesis, which provides the energy to form the new tissues
that become shoots and roots. However, unless leafy cuttings
are misted or the surrounding air is cooled, keep them out of
direct sunlight. Hardwood cuttings of deciduous plants often
root best in the dark, unless they require a long time to root,
allowing leaves to develop from dormant buds.
Temperature must be controlled for optimum rooting. A desirable
temperature encourages root formation but does not cause excessive
moisture loss. Most leafy cuttings do best with air temperatures
of about 60° to 65°F. Additional heat, 5 to 10 degrees
higher than the air temperature and applied to the rooting medium,
encourages rooting. Heating coils often are used beneath the
rooting medium in the propagating bench to provide this effect.
Hardwood cuttings of some
difficult-to-root
deciduous plants will root best if taken in late fall and placed
in a moist medium. Keep the medium temperature at 60° to
70°F until roots have been initiated but are only barely
noticeable on the outside of the cutting. Then lower the
temperature
of the air and storage or rooting medium to about 40°F to
complete the required cold (rest) period of the buds and hold
back further root growth. Cuttings handled in this way are often
tied in bundles keeping the basal ends all in the same direction.
Plunge the bundle into the rooting or storage medium. When the
root initiation and storage period are over, untie the bundles
and plant the cuttings individually, usually outside in a closely
spaced nursery row.
A simple propagation chamber can be
made from two boxes. Top box has glass cover to admit light
(cover
could also be of plexiglass). When closed, interior of box
becomes
humid, giving effect similar to mist chamber. Provide drainage
in bottom box to prevent waterlogging. For small number of
cuttings,
same effect can be obtained by putting plastic bag over a flower
pot. |
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Hormones or plant auxins are commonly used to promote
rooting of cuttings. Auxins are compounds that occur naturally
in plants. Some have been synthetically produced and are available
to plant propagators. They increase the rooting percentage of
many hard-to-root plants. They also may shorten the time for
rooting and improve root quality and quantity. Cuttings of most
plants will benefit from the use of auxins, although some hardwood
cuttings from deciduous plants may show little effect. Hormones
or auxins are an aid to rooting and should not be considered
a substitute for good technique.
Naphthaleneacetic acid (NAA) and
indolebutyric
acid (IBA) are the compounds most commonly used to promote rooting
of cuttings. Both are available as solutions or powders and are
often used in combination. The powders are the most practical
for the amateur because they are diluted with talc to
concentrations
that will not harm the cuttings and because they are easy to
use. Two common commercial root-promoting preparations often
available at local nursery, garden, or variety stores are Rootone
and Hormodin.
Plant species may influence rooting. Many deciduous and evergreen
plants are propagated from hardwood cuttings, but they vary
considerably
in ease of rooting. Honeysuckle, currant, grape, and willow root
readily. Apple and pear are more difficult, while cherry and
lilac are usually very difficult to root using hardwood cuttings.
Among evergreen plants, false cypress,
arborvitae, and low-growing juniper generally root readily. Yew
roots fairly well. The upright junipers, spruces, and hemlocks
are difficult to root. Cuttings of firs and pines usually are
very difficult to root.
Considerable variation exists among
species within these groups. Even genetic variability from plant
to plant may give differences among plants of the same type.
Procedures for
Making and
Handling Cuttings
Evergreen and leafy
deciduous
cuttings
Remove from the parent plant a portion
of stem 4 to 8 inches long with the leaves attached. For most
deciduous plants, a tip, simple, or straight cutting will suffice.
For most evergreen plants, use tip or heel cuttings. Snip off
leaves (or needles) which would contact the rooting medium (the
bottom 11/2 to 2 inches of stem) to prevent
rotting of these leaves. The remaining leaves will continue to
produce substances that aid in root formation on the cutting.
If hardwood cuttings of evergreen plants are used, wound the
base of the cutting using one of the methods described. Use the
more severe methods of wounding for harder-to-root types.
Spread a small amount of auxin compound
on waxed paper or in a clean dish. Dip the base (cut end) of
the cutting in the powder so that some adheres to the cut surface
and wounded areas. Discard leftover powder to prevent
contamination.
Talc preparations lose their effectiveness after about eight
months, even if kept in a closed container and refrigerated.
Make a hole in the rooting medium so
that the powder is not scraped off when you insert the cutting.
Insert the base of the cutting into the prepared hole in the
rooting medium. If bottom heat is used, insert the base of the
cutting nearly to the bottom of the container so that it is close
to the heat source. Firm the rooting medium around the base of
each cutting. After all cuttings are inserted and firmed in place,
apply sufficient water to the rooting medium to settle it around
the cuttings. This "watering-in" procedure will leave
the rooting medium in close contact with the base of each cutting.
Place the cover over the propagation
box or container. Inspect the cuttings daily and remove any leaves
which fall. Syringe the tops of the cuttings, and keep the rooting
medium moist. When the cuttings resist a slight tug and begin
to feel anchored, they are beginning to root. Some types may
require 2 to 3 months or more to form sufficient roots to allow
removal from the rooting medium.
When the cuttings have two or three
roots about one-half inch long, place them in pots about 4 inches
in diameter. Use a good potting soil. Since the cuttings have
been accustomed to the humid atmosphere of the propagating box
(or mist, if used), accustom them to the "outside"
atmosphere by gradually aerating the propagation box (or reducing
the mist) before potting. Another way is to cover the potted
cutting with perforated plastic film for about a week after
potting.
This is called "hardening off."
After potting, do not expose the cuttings
to direct sunlight or temperature extremes until they have had
several weeks to become accustomed to outdoor conditions.
Hardwood cuttings of
deciduous
plants
These cuttings may not need a covered
propagation box or mist unless they require a long time to root,
during which leaves develop from dormant buds. Easy-to-root types
can be taken in the fall and rooted outdoors in the soil in mild
climates, or they can be taken in the spring if winters are cold.
Take difficult-to-root types in late fall. They will require
treatment in a moist, warm rooting medium as described earlier
until rooting begins. Follow by holding in cool, moist storage
until spring weather allows outdoor planting. Wounding and
treatment
with root-promoting chemicals may be of value.
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