The Apricot
The apricot, Prunus armeniaca L., is found in the Rosaceae, subfamily
Prunoideae. It is in the same subgenus as plums (Prunophora), and crosses
between apricot and plums have yielded "plumcots" and other
hybrids.
There are 3-10 species in the Armeniaca section of the subgenus Prunophora,
depending on who you believe. Other well-known species very similar
to P. armeniaca are P. sibirica, P. mandshurica, P. mume, and P. X dasycarpa
(a natural hybrid between P. cerasifera and P. armeniaca. While this
group presents great genetic diversity in tree size, stress tolerance,
bloom date, and fruit quality, there are very few apricot cultivars
grown commercially throughout the world, almost all of which derive
straight from P. armeniaca. Cultivars also tend to be grown in only
one region of a given country, and most would be virtually unknown outside
of that region.
For much of their history of cultivation, apricots were grown from
seedlings, and little selection took place until the nineteenth century.
Cultivars vary among countries, and in Turkey, Iran, Iraq, Afghanistan,
Pakistan, and Syria, a great deal of the production is from seedling
orchards.
Origin, history of cultivation.
The center of diversity of the apricot is northeastern China near the
Russian border (in the Great Wall area) not Armenia as the name suggests.
From there it spread west throughout central Asia. Cultivation in China
dates back 3000 yrs, and movement to Armenia, then to Europe from there,
was slow; the Romans introduced apricots to Europe in 70-60 BC through
Greece and Italy. Apricots probably moved to the US through English
settlers on the East Coast, and Spanish Missionaries in California.
Today, apricots are grow almost exclusively in California.
Folklore, medicinal and non-food uses.
Cyanogenic glycosides common in stone fruit seeds (of bitter-, not sweet-kernal
cultivars), bark and leaves are found in high concentration in apricot
seeds. The drug laetrile is derived from extracts of apricot seeds.
A controversial therapy for cancer; a few reports of tumor regression
and pain reduction. The National Cancer Institute in the USA claimed
laetrile was an ineffective cancer treatment in 1980, but it is legal
still in Mexico. Some still cross the border to seek laetrile therapy
when other cancer treatments fail. The theory behind laetrile is this:
the apricot pit extract breaks down to release CN-, but only when in
contact with ß-glucuronidase, an enzyme common to tumor cells.
The CN- is released preferentially at tumor sites, and kills cells.
Apricot seeds were used to treat tumors as early as AD 502. Apricot
oil was used against tumors and ulcers in England in the 1600s.
The apricot was used to symbolize female genitalia just like the peach
and other stone fruits. In medieval France, the word "abricot"
was slang for vulva.
Seed of Central Asian and Mediterranean apricots is generally "sweet",
such that seed can be used as a substitute for almonds, or crushed for
almond-like cooking oil.
Information provided by the University of Georgia. www.uga.edu
Growing Apricots
Young apricot trees are likely to make excessive growth, especially
trees from 2 to 5 years of age. Trees making excessive growth do not
mature early in the fall and are, therefore, more subject to injury
from low temperatures in November and early winter. Mature apricot trees
are hardier than young trees.
Trees should not make more than 2 feet of annual growth.
It is extremely important to train young trees correctly to prevent
weak crotches that are very susceptible to winter injury.
The southwest side of the trunk can become very warm on sunny days
in late fall and winter. Night temperature frequently drops to well
below freezing. This alternative freezing and thawing often injures
the bark and wood. This permits wood-destroying fungi to gain entrance,
and a large canker is likely to develop.
Paint the trunk with a latex-based, white paint. This paint is non-caustic
because it is fast-drying and does not contain turpentine or oil. It
gives good
coverage throughout the winter, and the white surface reflects the sun's
rays, preventing deep bark penetration. Brush the paint onto the trunk
from the ground line up to the first scaffold branch. CAUTION: Do not
use ordinary house paintts containing oil, turpentine or lead. These
may seriously injure or kill the trees.
Fill any holes that develop in the soil at the base of the trunk. Make
certain that the soil level adjacent to the trunk is slightly higher
so that water will drain away from the tree. Water collecting in depressions
near the trunk will form ice in late fall or winter. This ice may girdle
the tree, causing death or serious injury.
Rootstocks
Do not use apricot trees grafted on peach seedlings. Manchurian apricot
seedlings and seedlings of the Michigan apricot selection, Goldcot,
are compatible with apricot varieties. The Manchurian seedlings are
especially winter hardy and have given strong, healthy trees with minimum
tree loss.
Varieties
The standard varieties produced in the West have failed in Michigan.
Goldcot is the primary variety grown in Michigan. The cultivars listed
are reported to be hardy in the north.
Goldcot - The most dependable variety for planting in Michigan.
Early Golden Hardy Iowa - Good for fresh fruit or cooking.
Moongold - Must be planted with Sungold for pollination. Fruit suitable
for most uses.
Sungold - Must be planted with Moongold. Good fresh or in preserves.
The Use of Pollinators
Goldcot is apparently completely self-fruitful and can be planted alone.
The other varieties, while ordinarily self- fruitful, will set heavier
crops when unfavorable weather prevails during blossoming periods if
they are inter-planted with other fertile varieties.
Site and Soil
Apricot trees are sensitive to climatic conditions and require the best
possible growing sites to remain healthy and regularly productive. Some
favorable Michigan sites for apricots exist in the northwestern area
(Leelanau county) of Michigan. Apricots seem to grow and produce well
in locations where sweet cherries are productive.
Apricots blossom about a week earlier than peaches. Therefore, plant
apricots only on sites which are practically frost-free. Elevation of
the site
above the surrounding country will give added protection against loss
from frost and winter injury. Nearness to a large body of water is associated
with slow warming temperatures in the spring, which help hold back spring
bud development.
The soil must be well drained and preferably of a sandy type. Poor
subsoils of any kind will result in the death or poor growth of many
trees. Avoid heavy soils for apricots as such soils are likely to be
poorly drained.
Planting
Fall-planted trees are more subject to cold injury during the first
winter after planting. Plant the bud union 4 inches below ground level
for good anchorage. The soil should be well settled and firm around
the roots.
Training and Pruning
Train the young tree to the modified central-leader system. Select two
main scaffolds on opposite sides of the trunk, well separated so they
will not touch each other when fully grown. The first scaffold should
be about 30 inches above the ground if trees are to be mechanically
harvested. The second scaffold should be 8 to 10 inches above the first.
Select scaffolds having wide angles at the point of attachment with
the trunk.
Sharp-angled branches split badly. The leader must be left longer than
the scaffolds so that it will not be shaded out.
It is very important the second spring to remove all excess scaffolds
from the trunk, retaining just two or three. Head the scaffolds back
somewhat if they are likely to grow higher than the leader. By the third
and fourth years, the trees are beginning to produce some fruit. The
main framework of the tree has been established, and pruning is mostly
to remove additional branches that may come from the trunk, and to head
back new terminal growth if it exceeds 2 feet in length. A small amount
of thinning out may be necessary where branches are too thick or are
rubbing. Do not leave too many branches originating close together on
the trunk.
Pruning the Mature Tree
The apricot produces most of its fruit on rather short- lived spurs.
Prune mature trees to remove branches loaded with old spurs and keep
the trees producing good replacement wood. This requires a combination
of thinning out branches having many weak spurs and heading back long
branches by one-third or to a strong lateral branch. Mature trees must
make from 16 to 24 inches of new
terminal growth a year to maintain satisfactory annual production. If
less growth is made, the trees will fall into a biennial bearing habit
and produce a large crop of small apricots every other year. Prune or
head back the long branches in April. Additional pruning in June and
August will reduce excess vigor. Do not prune during late fall or mid-winter
because of drying out and the possibility of winter injury.
Grow young apricot trees slowly. They have a tendency to make excessive
growth, rendering them more susceptible to winter injury. New growth
should not exceed 2 feet in length annually.
Nitrogen is the most important nutrient in fruit production and is
usually the only fertilizer element that should be applied regularly
in Michigan. However, young apricot trees have great inherent vigor
even on relatively poor soils; therefore, nitrogen fertilizers should
not be used in young plantings on reasonably fertile land and sparingly
even on light, sandy soils. As the trees become older, start producing
and the danger of winter injury becomes less, nitrogen applications
will need to be increased sufficiently to insure an annual terminal
growth of 16 to 24 inches to maintain good production. Apply nitrogen
in late fall, after mid-November, or before growth starts in spring.
The kind of nitrogen to use should be chosen on the basis of cost of
actual nitrogen and ease of application; however, nitrogen in the form
of urea should be avoided.
Potassium is the only nutrient element, other than nitrogen, that is
likely to be needed in Michigan apricot plantings. Potassium deficiency
reduces tree
growth, yields and fruit quality. The best way to determine need for
potassium (potash) is through leaf analysis. When needed, potash may
be applied in the fall or spring. The most common potassium fertilizer
is muriate of potash (60 percent K2O).
Phosphorus is utilized in only small amounts by fruit trees compared
to either nitrogen or potassium. There is no present indication that
apricot trees will benefit from application of phosphorus. However,
in some cases, fertilizers containing phosphorus may benefit growth
of cover crop.
Fruit Thinning
If fruit set is heavy, thin the individual fruits so that they will
be 1 1/2 to 2 inches apart. Otherwise, fruits will be small, and the
trees will become biennial in bearing habit. Thinning can be done by
hand, or -- faster and easier -- by careful pole thinning. Bamboo poles
of various lengths are used. Cover the top 12 inches with a piece of
garden house to reduce injury to the branches. The excess fruits may
be removed by rubbing and tapping. Avoid hard blows, as all of the fruits
will be knocked off for a considerable distance from the point of contact.
Early thinning is recommended. Start thinning as soon as danger of frost
has passed.
Information provided by Michigan State University Extension. www.msue.msu.edu
