Olive
trees are propagated in California several
different ways, including budding or grafting onto seedling
rootstocks,
leafy semi-hardwood stem cuttings, and hardwood cuttings. Less
commonly
used techniques locally, but somewhat more common world wide
include
truncheons, removing rooted suckers from the crown of the tree, and
ovuli.
(much content courtesy Glenn T.
McGourty
Plant Science Advisor and
County
Director UCCE
Mendocino
County)
Many cultivated olives will grow from the
seed or
pit of the olive under the right conditions.
We have been asked if the pit of an olive
in a jar
of brined olives can be grown. The answer is no; the pit has been
killed by the brine.
Growing an olive from fresh olives is
usually a
frustrating experience as very few germinate but a tree dropping
thousands
of olives over hundreds of years will produce seedlings. Trees
grown
from seeds have some interesting characteristics. The tap root
goes straight down so the tree is very drought resistant. That
also
means that it cannot take advantage of surface irrigation so
typically
grows slowly and produces fruit much later than trees grown by
other means.
It can also attain great height depending on the variety. That is a
bad trait in trees grown in orchards where dwarf trees are
preferred for
easy picking.
Oddly, the tree and fruit which grow from
the seed
will not always resemble the tree it came from. Olive pollen can
drift for hundreds of miles and olives easily hybridize with other
varieties. To get an exact replica of an olive tree, you must use
cuttings or truncheons.
|
Seedlings |
Stem
Cuttings |
Hardwood cuttings |
roots
|
Deep |
shallow |
Shallow |
Tree
Height
(depends on variety) |
25 ft |
dwarfed |
dwarfed |
first
fruit |
12-15 yrs |
3-5 yrs |
4-6 yrs |
Propagation of
Olives by Rooted
Stem Cutting
|
Mist propagation of cuttings is one of the
best
ways to propagate many olive cultivars. Being a subtropical, the
roots and
shoots of olive trees grow rapidly during late spring and early
summer when
soil moisture is relatively high, soil temperatures are warm (above
70° F),
and air temperatures are not excessively hot (between 85° and 95°
F.)
Towards the end of this rapid growth is the prime time to take
cuttings,
during the months of late June and early July. Wood should be
collected
from vigorously growing trees, and kept cool until propagated.
Pre-trim and
place in plastic bags with moist sawdust, and process the material
as
cuttings as soon as possible. It is possible to keep the wood for
several
days under refrigeration without any problems. Semi-hardwood
cuttings are
selected from healthy branches, cutting pieces about 1/4 to 1/2
inch in diameter, and 4 to 6 inches long, with the lower leaves
removed,
and 2 to 4 sets of leaves remaining. Some propagationists will
"wound" the
lower portion of the stem, making slight cuts with a sharp object,
and then
use either a hormone powder or concentrated dip to help induce
rooting. In
my experience, quick dips of 3,000 ppm indole butyric acid (IBA)
have
worked well for many of the olive oil cultivars, such as 'Lucca,' 'Frantoio,'
'Moralolo,' 'Mission,' and 'Picual.'
Hormone powders for hard to propagate
species
should be chosen, such as Root Tone #40. 1 have also gotten tip
cuttings to
root, but I only propagate those when material is very limited and
precious, as often, the wood is not mature enough to root. Some
cultivars
are just difficult to root, such as 'Sevillano.' A successful
rooting rate
of 20% would be high for this cultivar, while many of the others
are as
high as 90%.
Sterile rooting media should be used in
standard
nursery flats. A common propagation mix is 90% perlite and 10% peat
moss.
Standard nursery flats can often hold up to 70 cuttings without
much
difficulty. Some propagationists like to place cuttings in trays
that keep
root systems separate, as they find that subsequent transplanting
is easier
and less transplant shock means these trees grow more rapidly when
placed
in one gallon containers.
Intermittent mist and bottom heat are
critical for
success in rooting olive tree cuttings. The "artificial leaf"
controller
for a pressurized misting system is very effective. The controller
consists
of a rectangular piece of fine metal mesh on a counterbalanced
metallic
lever that rises as it dries, activating a mercury switch that
energizes an
electric solenoid to turn on the misting system valve. When wetted,
the
screen becomes heavy, traveling down, causing the mercury switch to
shut
off, closing the solenoid, stopping the mist. The entire cycle
usually
lasts about 5 seconds, occurring as frequently as every 3 minutes
under hot
conditions, or as infrequently as once every few hours during
cooler
conditions. Many propagationists believe this to be the best system
available. For small systems electric heating cables buried beneath
a thin
(one inch) layer of gravel controlled by an adjustable thermostat
is quite
effective. Bottom heat of 75. F is usually very helpful in getting
the
cuttings to root rapidly. The cuttings should be placed in a shaded
area in
a greenhouse or propagating structure, and not exposed to direct
intense
sunlight, as this often causes desiccation. Air temperature up to
9O° F is
acceptable. Temperatures below 7O° F often result in slow or poor
rooting.
If you don't have a mist system keep the
bed covered with plastic film,
as close to the cuttings as possible to reduce air circulation and
water
loss.
Under normal conditions, rooting becomes
obvious
after about 45 days, but may continue for up to six months or
longer (since
olive trees can live for hundreds of years, they are in no hurry!)
When
several healthy white roots are present, you can transplant into
bigger
containers. If the young rootings are going to be kept in a
greenhouse,
some growers will transplant into smaller containers such as rose
pots
(about 2 inches square,) and move into one gallon containers when
the
weather is better the following spring. Young trees need to be
protected
from heavy frosts, and dry, cold weather.
For cultivars that don't root easily,
grafting or
budding onto seedlings is used. Seeds collected and cleaned from
'Redding
Picholine' have been used in California. This small fruited
cultivar seems
to have a fairly high percentage of seeds that germinate, although
once
again, germination occurs over a long period of time (up to two
years!)
Sowing with lots of seed is a common strategy to insure that
adequate
material is available. Seedlings are grown on for one to two years,
and
then either t-budded, whip grafted, and side tongue grafted. Bark
grafting
is also used in Europe. Once successfully top worked, trees are
grown on in
the nursery for an additional year before delivery, in most cases.
Sevillano is commonly grafted onto another cultivar in California.
For a nice discussion of bud grafting on
mature hardwood, go to
Grafting Olive Trees - by Matt Starczak - pictures below are
from his
website. or go to the UC document showing how to
limb graft.
Propagation of
Olives by Rooted
Hardwood Cuttings
|
Hardwood cuttings can be made from 2 or
three year
old wood about an inch in diameter, and 8 to 12 inches long just
prior to
warm spring weather. All leaves are removed. Soaking the ends of
the
cuttings in hormone solutions, followed by storage in moist sawdust
at 7O~
F for a month to help induce callus formation is often used.
Cuttings are
then placed in the nursery to root, often being lined out in well
worked,
friable soil. The cuttings should be mostly buried, and kept moist
but not
wet. Rooting will occur over several months. Trees are then dug
bare root
and containerized or planted into the orchard.
The truncheon system is also used as a
low-tech
system for olive tree propagation. Limbs 3 or 4 inches in diameter
are
removed from trees and cut into 12 inch pieces, and then planted
horizontally
in soft, well tilled friable soil. Usually several shoots with an
accompanying root system will grow. They can be separated, and
grown for
another year before being planted in the orchard.
Rooted Truncheon used to replant
the California Mission at
Soledad - courtesy of the COOC mission project |
|
Propagation of
Olives by Rooted
Ovuli
|
Swellings found on the trunk of the olive
tree,
known as "ovuli", can be cut off and planted in early spring. These
structures contain both adventitious root initials and dormant buds
so that
new root and shoot systems can develop. This practice is damaging
to the
parent tree, and is not used very often in the US, but is used in
other
parts of the world.
Finally, suckers with a small piece of
root can be
removed from the trunk of the tree in the spring and grown in the
nursery
for a year before planting into the orchard.
SOURCE FOR SPECIALIZED PROPAGATION
EQUIPMENT:
M C Developers, located in
Ceres, Ca, telephone #
1-800-511-6151. |