Doña Ana County Master Gardener Monthly Magazine—February 2017 Page 3
Olive Trees—Continued From Page 3
CURING OLIVES Botanically, the Olive is a fruit classed as a "drupe" -
a fruit with a single large pit (aka stone) inside. Green Olives and Black
Olives will be fruit from the same tree, just picked at different stages. It
is pale green when immature, darker green when it has reached its full
size, then purple or black when ripe. Green Olives have more zing and
more bitterness than Black Olives; Black Olives lack the zing, but have
a richer, mellower flavor.
The five methods of curing table Olives are:
• Dry-Cured Olives • Brine-Cured Olives
• Lye-Cured Olives • Fresh-Water Cured Olives
• Oil-Curing
It's often difficult to know what variety or cultivar of Olive you are
actually eating. Olive Oil jars almost never say what type of Olives the
oils were made from, and only rarely does a jar of Olives prove any
more helpful. The list of "types" of Olives that you can buy is actually a
mix of actual names of actual Olives, and names of various classes and
methods of preparing them for table use.
The size of an Olive depends more on the tree it is from than how
young it is picked. While the pulp of most fruit is water -- with Olives, it's
oil. Most Olives grown in the world are used for Olive Oil.
Olives are actually quite bitter when eaten straight off the tree. The
method of "curing" them to draw out the bitterness helps determine the
flavor and texture of the finished product, which is called "Table Olives"
(also referred to as "prepared Olives" or "Pickled Olives." Olives for Oil
are not cured.
How an Olive is cured actually has more impact on the taste of the
final product than what cultivar it was or where it was grown. Some
cures will produce juicier, plumper Olives than other types of curing.
After curing, Olives are then finished off in a variety of ways: brine,
vinegar, oil, etc. Spices and herbs may or may not be added. The brine
that Olives are placed in after curing is called the "mother brine." They
will ferment in this. They will also ferment a bit in any brine they are
ultimately packed in afterwards. Sometimes, Olives are pasteurized to
prevent this, which lets them be shipped more easily, but the
“pasteurization” does affect the flavor.
HISTORY Harvesting of Olives in New World countries such as
America, Australia and New Zealand is largely done with machines. The
Israelis are also big on mechanized harvesting. Producers in Southern
Europe would like to go this way, but the cultivars of Olive trees that
they grow, which produce the prized oil they are famous for, don't
always lend themselves to harvesting by machine either because the
branches grow too high, or the Olives cling too tightly to the branches.
In America, Olives are grown in California, and to a small extent in
Arizona, New Mexico and Texas. California only produces .5% to 1% of
the Olives in the world. Article Continues on Page 4
OLIVE TREE FACTS
Source: Olives, Authors: Larry Stein, Jim Kamas & Monte Nesbitt, Extension Fruit
Specialists, Texas AgriLife Extension, at link: http://aggie-
horticulture.tamu.edu/fruit-nut/files/2010/10/olives.pdf
Botany: The Olive (Olea europaea L.) is a subtropical evergreen tree or shrub
with opposite leaves. The leaves are lance-shaped, waxy green on top and
grayish green on the bottom. Young bark is green, but older bark is gray. In the
Mediterranean, Olive trees are known to live for over a thousand years. If the
top is damaged, a new tree will sprout from underground parts.
Climate: Climate is the most important limiting factor in the distribution of the
Olive in Texas and elsewhere. Temperature controls growth, reproduction, and
survival of the olive. Growth begins after mean temperatures warm to 70°F in
the spring and continues until temperatures drop below this point in the fall.
Soil Adaptation: The Olive has a wide adaptability with regard to soils; it will
tolerate a variety from sands to clays with a pH of 5.5 to 8.5. Olive trees have
fairly shallow root systems so they do not need a deep soil, but the soils must
be well-drained. Three to four feet of unstratified soils is optimum for
production.
Site Prep: Orchard sites should be prepared 12 to 18 months prior to planting
the trees. This involves killing perennial weeds and grasses and deep chiseling
or ripping down the planting rows to insure breakup of any hard layer. Soil
sample(s) should be taken from the area, and any needed amendments applied
prior to planting, so that they can be more easily incorporated around the
planting site.
Cultivation: The Olive is drought-tolerant, but grows best when it has sufficient
water. Overwatering should be avoided. Water regularly, but do not allow
waterlogging to take place. An ideal water amount to apply would be an inch of
water a week. It is critical to continue to water mature trees as the crop is
maturing. The Olive is very efficient at extracting nutrients from the soil, and
nitrogen is usually the only element that must be applied. Mature trees need
from 1/2 to 2 pounds of actual nitrogen per year, depending on tree size.
Deficiencies of potassium and boron are rare but possible. Fertilize in the spring
when new growth begins.
Pruning: Pruning should be delayed until early spring. Because the tree does
not go dormant, any increase in temperature after pruning will stimulate growth
that might be damaged by freezing temperatures. Prune Olives by thinning out
dead or otherwise unproductive wood. It should not be topped.
Pests/Disease: Stress has been the main culprit of tree death to date, as
opposed to bacterial and fungal pathogens. However, there are numerous
potential problem diseases of which cotton root rot (Phymatotricopsis omnivora)
would be one of the most important. Olive trees are quite susceptible to cotton
root rot and many trees have been lost to this soil-borne fungus in Texas. This
disease is prevalent in high pH soils in the Southwest where Olives are
climatically best adapted in Texas. Because cotton root rot more readily affects
plants that are not adequately supplied with water, it is essential to keep the
area around the tree weed-free to reduce water stress from competition.
Deer have been a serious deterrent to tree growth in many areas, making
high fences a necessity for commercial production.
See Page 4 for a list of Olive Tree varieties.