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ASEXUAL =
PROPAGATION OF=20
PLANTS
Asexual propagation does not involve =
exchange of=20
genetic material, so it almost always produces plants that are =
identical=20
to a single parent. Delicious apple and Bartlett pear are two =
examples of=20
species that have been asexually propagated for decades. Asexual=20
propagation methods include cuttings, layering, division, =
grafting,=20
budding and tissue culture.
CUTTINGS
Cuttings involve removing a piece from =
the parent=20
plant and that piece then regrows the lost parts or tissues. Both =
woody=20
and herbaceous plants are asexually propagated by cuttings of =
stems,=20
leaves and roots. New plants can be grown from parts of plants =
because=20
each living plant cell contains the ability to duplicate all plant =
parts=20
and functions. Mature cells can change into MERISTEMATIC=20
(mare-ah-ste-MAT-ick) cells that are found at rapid growth sites =
like=20
buds.
There are many types of cuttings. =
Often, a plant=20
can be propagated by more than one method of cutting. Some plants =
will=20
reproduce readily from cuttings and others take a considerable =
amount of=20
time and care.
STOCK PLANTS are the parent plants used =
in=20
asexual propagation. Stock plants must be in excellent health and =
should=20
possess characteristics desirable for production of new plants. =
Herbaceous=20
cuttings are those taken from nonwoody plants, such as perennials =
and=20
houseplants.
Softwood cuttings are pieces of new =
growth taken=20
from woody stock plants. These cuttings must be taken before the =
new=20
growth starts to harden. Hardwood cuttings are taken from tissue =
which has=20
become woody. Other forms of cuttings are leaf cuttings and root=20
cuttings.
The gardener must try to duplicate the =
conditions=20
needed for a plant to root from a cutting. High humidity, indirect =
light=20
and soil temperatures of 70 to 80 degrees F are best for most =
cuttings.=20
These conditions may be created by keeping cuttings enclosed under =
glass=20
or in plastic bags in dappled shade. Cuttings must be shielded =
from direct=20
sunlight, especially if they are under glass or =
plastic.
STEM=20
CUTTINGS
When a cutting is made, injured xylem =
and phloem=20
cells plug the tubes so that precious fluids are not lost. Usually =
a=20
CALLUS forms at the cut. Cells near the callus area reorganize to =
form=20
adventitious roots.
Stem cuttings are the most commonly =
used method=20
to produce houseplants. Select vigorous, new growth with no flower =
buds.=20
Stem sections should be free of diseases and insects. Each cutting =
should=20
be 2 to 4 inches long and have 2 or 3 leaves attached.
Make a cut 1/4 inch below a leaf node =
and pull=20
off the leaves that are at the nodes that will be below the =
surface of the=20
rooting medium. ROOTING HORMONE helps to stimulate rooting, but is =
optional. Pour a small amount of the rooting hormone into a clean=20
container to prevent contamination of all of your rooting hormone. =
Dip the=20
base of the stem, including the node area, into the rooting =
powder. The=20
stem should be dry when dipped.
Commercial rooting products often =
include a=20
fungicide. This is a good idea given the damp conditions required =
for=20
rooting success. Tap off excess powder, since too much hormone can =
inhibit=20
rooting.
Poke a hole in the medium before =
inserting the=20
cutting to avoid loss of the rooting hormone. Insert treated =
cutting in a=20
moist rooting medium. A suitable rooting medium is half perlite =
and half=20
sphagnum peat moss. Any disinfested container with drainage is =
acceptable=20
for use.
Cover container and cutting with a =
plastic bag=20
tent to maintain high humidity. Place unit in a warm area with =
indirect=20
light. Check the rooting medium every few days to make sure it =
remains=20
moist. Rooting can take from a few days up to several =
months.
After a few weeks, test for rooting by =
gently=20
tugging at the cutting. If there is resistance, rooting has =
started and=20
the plastic cover may be removed. More detailed instructions on =
stem=20
cuttings are provided in Fact Sheet 1226, Reference =
Prop.1.
LEAF=20
CUTTINGS
In this method, a leaf blade or leaf =
with petiole=20
is used to propagate new plants. The same steps are followed as =
for stem=20
cuttings. Choose a healthy leaf from a vigorously growing plant. =
Cut it=20
close to the stem with a sharp, disinfested razor or knife. Trim =
off 1/4=20
of the leaf and dip into rooting hormone, if desired. Insert the =
leaf into=20
rooting medium so that 1/3 of the leaf is below the =
surface.
One or many new small plants form at =
the base of=20
the leaf. African violet leaves will produce many new plants. =
Begonia=20
leaves can be divided into segments for propagation; however each =
leaf=20
piece must contain a major vein. With leaf cuttings, the original =
leaf is=20
not a part of the new plant and is usually discarded.
Many succulent plants, such as sedum, =
jade, and=20
peperomia, can be propagated by leaf cutting. Some plants such as=20
Kalanchoe pinnata or K. bryophyllum, piggy-back or =
air=20
plants, form their own new plantlets in this fashion. See Fact =
Sheet 571=20
on leaf cuttings, Reference Prop.2.
ROOT=20
CUTTINGS
Cultivation of root cuttings probably =
started=20
after gardeners observed new plants growing from pieces of root=20
accidentally left behind in the soil. Take cuttings from newer =
root=20
growth. Make cuttings 1 to 4 inches long from roots that are 1/4 =
to 1/2=20
inch in diameter. Be sure that the roots collected are from the =
chosen=20
plant and not neighboring plants.
Cuttings should be taken during the =
dormant=20
season when roots have large carbohydrate supplies. However, they =
also may=20
be taken throughout the growing season. Cut straight through the =
end of=20
the root closest to the stem. Cut the other end on a slant. This =
allows=20
you to remember which end is the top (the straight cut) and which =
is the=20
bottom (the diagonal cut).
Store cuttings from dormant roots for 3 =
weeks in=20
moist rooting medium at 40 degrees F. Remove from storage and =
plant=20
upright in the growing medium. Keep moist and warm, in a bright =
location=20
until growth and weather permit acclimatizing to the =
outdoors.
If root cuttings are taken during =
active growth,=20
skip the storage period and place cuttings directly in the rooting =
medium.=20
For smaller plants, take 1- to 2-inch sections. Place cuttings=20
horizontally a half inch below the surface of the rooting medium. =
These=20
cuttings should be handled indoors or in a HOTBED. The fine roots =
of many=20
perennials are used for propagation. Root cuttings of some =
variegated=20
plants will lose their variegation.
SOFTWOOD=20
AND HARDWOOD CUTTINGS
Softwood cuttings are taken from =
first-year=20
branches that have not yet become woody. Flowering shrubs are =
often=20
propagated by softwood cuttings. Late spring and early summer are =
the best=20
times for success with this method. Take cuttings after it rains =
or water=20
is applied in the cool morning. Make a diagonal cut. The larger =
diagonal=20
cut gives more area to develop roots. Keep cuttings in water =
before moving=20
them into rooting medium.
Make cuttings 2 to 10 inches long. =
Larger=20
cuttings produce larger plants sooner. Make cuts slightly below a =
leaf=20
node. Follow the same instructions for disinfested containers, =
rooting=20
medium and light and moisture conditions used by other cutting =
methods.=20
Rooting hormones may be used with this method. The base of the =
cutting=20
should be dry before dipping it into rooting hormone =
powder.
Hardwood cuttings are taken once the =
tissue=20
becomes woody and the plant is dormant. Cuttings can be taken =
anytime from=20
late fall after a killing frost until late winter. Select healthy =
wood=20
that was produced the previous summer. Several cuttings can be =
made from=20
the same branch of some shrubs.
Make cuts at a slant, 5 to 12 inches =
long. Basal=20
cuts should be just below a node, while the upper cut should be =
slightly=20
above a bud. Dip the basal end in rooting hormone. Mark the most =
terminal=20
end of each cutting with a tag.
Bury cuttings vertically in moist =
vermiculite or=20
sand. Cuttings should not freeze, but must remain cool. A callus =
will form=20
on the lower cut end during storage. Callus formation indicates =
that=20
cuttings are ready to root.
In spring, remove the cuttings from =
storage.=20
Plant in a hotbed or other protected site with morning sun =
exposure or=20
filtered light. Leave 1 to 2 inches of cutting above ground. Keep =
cuttings=20
moist until a root system forms. Transplant the cuttings the =
following=20
spring while they are still dormant.
LAYERING
Layering causes roots to develop on =
shoots that=20
are still attached to the parent plant. The stem is not cut from =
the main=20
plant until it has rooted. Use this method when other propagation =
methods=20
are unsuccessful. Layering is a good propagation choice when only =
a few=20
plants are needed.
Simple layering is done by bending a =
branch to=20
the ground and burying a portion of it. The tip remains uncovered. =
A light=20
soil increases rooting success, as will wounding or girdling the =
buried=20
section. Treatment with rooting hormone is helpful.
Hold the branch in place with a rock or =
peg.=20
Layering is done in early spring while plants are still dormant or =
in late=20
summer on wood that has not become woody. Plants with flexible =
branches=20
are particularly suited to this method.
Other types of layering include =
serpentine or=20
compound layering, continuous or trench layering, and mound or =
stool=20
layering.
Fact sheet 1091, Reference Prop.3, is =
on air=20
layering.
DIVISIONS
Division is the cutting or breaking up =
of a crown=20
or clump of suckers into segments. Each segment must have a bud =
and some=20
roots. These segments are replanted and grow into new plants =
identical to=20
the parent. Most perennials should be lifted and divided when they =
become=20
overgrown and begin to lose vigor. Vigorous growth in most =
perennials=20
occurs on the outer segments of the clump. Old growth in the =
center of the=20
clump is discarded.
Carefully dig the plant, loosening the =
roots and=20
lifting the plant from the soil. Split apart the main clump with =
two=20
spades or forks or chop with a shovel or hatchet if the clump is =
firmly=20
massed. In some cases outside segments of the plant can be removed =
and=20
replanted without disturbing the rest of the plant.
A good rule of thumb is to divide =
fall-flowering=20
perennials in spring and spring- and summer-flowering perennials =
in=20
fall.
Some shrubs that form clumps or crowns =
are=20
suitable for division. Divide in early spring while dormant. =
Shrubs used=20
for division should have several clumps that are two years old or=20
older.
BULBS =
AND=20
CORMS
Bulbs can be propagated by removing =
small=20
bulblets or offsets that form at the base of the parent bulb. =
These small=20
bulbs take 2 or 3 years to mature into plants that flower. Place =
offsets=20
in rich, light soil for their development. This same procedure =
should be=20
followed for plants which form from corms, such as =
gladiolus.
Many lilies can be multiplied by =
removing scales=20
from the mature bulb. Dust the scale with a fungicide and place, =
base end=20
down, in a moist growing medium in a warm, protected area. =
Bulblets will=20
form at the base of the scale. In 1 to 4 years these bulblets will =
grow=20
and be ready to flower.
TUBERS AND=20
RHIZOMES
Tuberous plants can be dug up and the =
TUBERS=20
separated. In separating the tubers, each must have a segment of =
the crown=20
that contains at least one eye or bud.
Rhizomes grow and develop buds along =
their=20
length. The rhizomes can be dug and cut into sections that each =
contain at=20
least one eye or bud.
GRAFTING
Grafting involves the joining of =
different=20
segments of two different plants of the same species. A branch or =
bud is=20
joined to an UNDERSTOCK. In grafting, the cambium layers of the =
two=20
different segments are aligned and grow together. Some plants =
graft=20
naturally. Ivy commonly grafts itself. Natural grafting occurs =
where two=20
branches are in close contact over several years.
Grafting allows gardeners to produce =
plants=20
identical to a parent plant. It also allows growers to control =
size and=20
shape of a tree or shrub. Apples are grafted onto root stock that=20
regulates the ultimate size of the tree.
Grafting can produce more vigorous, =
earlier=20
fruiting, or two varieties can be grown on the same tree to =
provide=20
pollination as with apples.
On the negative side, some grafting =
attempts will=20
be rejected. This is called graft incompatibility. This might not =
occur in=20
the first year, but may in successive years. Wind or winter cold =
can=20
damage a GRAFT UNION. Some grafted trees or plants produce large =
numbers=20
of SUCKERS. These can crowd out the desired plant or tree and are=20
unsightly. If the graft union is planted below the soil surface, =
the SCION=20
will root and the rootstock will die.
Grafting is usually done in the spring. =
It=20
involves collecting small branches called scion wood. These =
branches are=20
1/4 to 1/2 inch in diameter. Gather them several weeks before =
grafting is=20
to occur. Collect wood that grew the preceding year. Select only =
wood with=20
leaf buds, not flower buds.
Scion wood should be gathered in winter =
when wood=20
is dormant, but not frozen. Use sharp clippers so that wood is not =
crushed. New growth over 1 foot in length is usually =
best.
Discard the wood at both ends of the =
branch and=20
use the middle section. End growth is too succulent for grafting =
and wood=20
closer to the base will graft more slowly. Label the scion wood, =
wrap it=20
in moist paper towels or sphagnum peat, enclose it in an airtight, =
plastic=20
container and place it in the refrigerator.
Scion wood must be joined to the =
understock in=20
spring when buds swell. It is critical that the two pieces are =
nearly the=20
same size and that sap has begun to flow. The day before actually=20
grafting, remove scions from the refrigerator and snip off the =
bottom=20
ends. Place the clipped scions in a pail of water =
overnight.
It is critical that the cambium layer =
on the=20
scion precisely matches that of the understock.
For precise directions on joining scion =
to=20
understock, see Fact Sheet 760, Reference Prop.4. Grafts can be =
placed on=20
a root or stem and be joined by any of several methods. The union =
is held=20
firmly in place using wax, tape, plastic wrap, rubber bands or =
plastic=20
tubing.
The grafted area must be protected from =
anything=20
that will move the scion out of alignment. Bracing some grafts is =
advised.=20
Side sprouts should be removed the first summer. Sucker shoots =
that sprout=20
from below the graft also should be removed. If growth of new =
graft is=20
satisfactory, do not fertilize the plant during the first year. =
There is=20
danger that top growth will be very brittle and it could fail to =
harden=20
off before the first frost.
BUDDING OR BUD=20
GRAFTING
Bud grafting is faster, easier and less =
messy=20
than other forms of grafting. Cambium layers do not need to be =
aligned.=20
Bud grafting is done from early July through early August. This =
method=20
uses a newly developed LATENT BUD, taken from under a live=20
leaf.
Budwood is collected from healthy =
branches that=20
grew since spring. Young trees offer good budwood because they =
produce a=20
large amounts of new growth. Use buds from the middle section of =
the=20
branch.
Remove leaves, but keep 1/4 inch of the =
leaf's=20
petiole for grasping. The bud is cut from the branch and inserted =
into a=20
T-shaped slice made in the bark of the understock. Budding should =
only be=20
done when the bark slips easily away from the tree. The bud is =
held in=20
place with special tape or wrap.
MICROPROPAGATION OR=20
TISSUE CULTURE
Each plant cell has the potential to =
grow into a=20
new plant exactly like the parent. This fact coupled with =
technical=20
advances, specialized equipment and sterile laboratory conditions =
has=20
produced modern tissue culture.
In tissue culture, individual or small =
groups of=20
plant cells are manipulated so they each produce a new plant. A =
tiny piece=20
of bud, leaf or stem can produce incredible numbers of new plants =
in a=20
small space in a short time.
The advantages of tissue culture, in =
addition to=20
speed and efficiency of propagation, include production of =
disease-free=20
plants. New plants can be made available to the public more =
quickly=20
because of tissue culture.
However, there are some problems with =
spontaneous=20
mutations which naturally occur. In tissue culture, the incidence =
of these=20
mutations is greatly increased.
Conditions for tissue culture are very =
exacting.=20
Absolutely sterile conditions must be maintained. Temperature, =
light,=20
humidity and atmosphere are strictly controlled with electronic =
sensors=20
and computerized controls. Such costly equipment rules this out =
for most=20
home gardeners.
PLANT PATENTS
Many hybridizers now patent their =
selections.=20
When a plant patent is filed, it is illegal for anyone to =
propagate the=20
plant for 17 years without written permission from the patent=20
holder.
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